AirShaper

In this video, we will be discussing aerodynamic drag:
Aerodynamic drag is the force that you need to overcome, as you move through the air at a certain velocity. You will feel this for example when you ride a bike, because even at speeds as low as 20 km/h, the force that you need to overcome to push the air away, already accounts for more than half of the push that you need to deliver. In this video, we'll be looking at a speed skier to explain the two components of drag - pressure drag and friction drag.


Pressure drag
When the air hits the front of the skier, the pressure builds up, so that creates a force. At the back of the skier, air is dragged along, lowering the pressure, creating a wake (or draft zone) behind the object as well. If we integrate the pressure over the entire surface of the skier, we obtain the total force acting on the skier. If we want to know the drag, we just filter out the component of the total force that is directed along the wind direction: this is called the pressure drag.

Now if we want to learn more on which parts of the skier are contributing most to drag, we must zoom in and have a look at the local pressure. Clearly, the bigger the pressure, the more it can contribute to drag. But if the surface on which the pressure is acting is actually parallel to the wind direction, it doesn't impact the pressure drag. If the high pressure is, however, working on a surface that is perpendicular to the wind direction, like the front of the helmet or the hands, it does contribute a lot to drag.
To make things easier, we've multiplied this local orientation of the surface with the local pressure to give you an image that shows the direct contributions to drag. You will notice for example that the sides of the arms and the legs only show neutral green color, not contributing to drag. And that's it for the pressure drag.


Friction drag
Next to pushing and pulling on the surface, the air also slides across the surface. This generates friction forces, and although they are typically much smaller than the pressure force, they are relevant as well. In the case of the skier, they only contribute to 4% of the total drag.
If you visualize this, you again get a color map, which is called the friction map. It looks quite different compared to the pressure map. At the front of the helmet for example, where we had a lot of pressure drag, we now have almost zero friction drag, because the air comes to a complete standstill and so there is no relative velocity. On the other hand, where the air needs to curve around the sides of the object, air speeds up and there is a lot of local friction and thus a lot of contribution to the friction drag.

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

What is Aerodynamic Drag?

In this video, we will be discussing Drag Coefficients.
What are they? How can you calculate them? And most of all, how you can use them in your design process!


Theory 
Drag coefficients are used to calculate the hydrodynamic (in water) or aerodynamic (in air) force on an object, given the density Rho (ρ), the speed (u) and the frontal area (A) of an object. So if you know the force on an object at a certain speed, for example after a wind tunnel test, you can calculate the drag coefficient yourself using this formula. (0:28)

Once you know the drag coefficient for a certain geometry, you can calculate the force for different object sizes or different velocities
That is very useful for example when you need to size engines, calculate required battery capacity, etc.
But keep in mind that the drag coefficient can vary in function of the Reynolds number. So be careful with large extrapolations to other speeds, sizes or densities.


Practical use
A drag coefficient allows you to analyze the aerodynamic efficiency of an object, irrespective of its size or velocity. That makes it possible to compare a cyclist for example to a building. They are quite different, but still, they have a normalized aerodynamic coefficient.
It is also quite useful within a design process: when you are looking at different concepts for example for your new project or new vehicle, you can rank them according to their drag coefficient. Or you could get inspired by aerodynamic shapes coming from a completely different sector (Mercedes once had a car design inspired by fish!).


Typical Values
A drop shape, which is quite efficient, can have a drag coefficient as low as 0,05, whereas a building typically has one above 1. Lower means more streamlined. 
So if you are working on a drone that needs to fly as far as possible on a single charge or a cyclist that wants a higher top speed, you will want to reduce the drag coefficient as much as possible. 



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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

What is a Drag Coefficient?

In this video, we will be discussing car diffusers. How do they work? Why do car designers install them? How can you make one for your design?  

Theory - the Bernoulli effect
The Bernoulli effect states that if you follow an air particle along its path within a flow the energy density remains constant. This means that if one term goes up, another must go down. This means that for example, if the velocity increases, the pressure has to go down.

Relation to the car underbody
The car underbody is the bottom side of a car. At the front of the car, you have high pressure because the air collides with the front of the car. At the back of the car, the pressure is lower because the wake wants to pull the car backward. This pressure difference between front and back of the car is the driving force of the airflow beneath the car which is called the car underbody or car underbody aerodynamics.

Down force
Because this section is quite narrow, the air has to speed up and this is where the Bernuit effect comes in:
higher velocity, lower pressure, creating a suction effect pulling the car downwards.
For a sports car that's fantastic, it means more grip. 

Diffuser
This effect of accelerating the air below the car can be much improved by shaping the rear of the car underbody, by giving it a slight upward angle.
This improves the transition to the normal velocity of the surrounding air and it helps to fill the wake behind the car.
The result is an even bigger acceleration underneath the car with more downforce as a result. 

Design
So if you want to design a diffuser, the question is, how large should the angle be?
Too low and the effect will be too limited. Too high and the air will separate and not follow the geometry of the diffuser.
So much depends on local dimensions and aspect ratios.
An angle between 7 and 10° is considered quite a good starting point for your design. 

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

What is a Car Diffuser?

In this video, we will be discussing wingtip vortices. I will explain how wings on planes & drones generate vortices. What is causing them? How do they impact flight times? And how can you reduce them using winglets? 

Introduction
Have you ever seen those upward sharky fins at the tips of an airplane wing? 
They are called wingtips and they are there to increase the performance of the wing by reducing the vortices. And it doesn't apply just to airplanes, but also to fixed-wing drones, wind turbine propeller blades and others.

What is a vortex
Simply put, a vortex occurs when the air rotates around a line in the air, like a tornado for example. But how are they created?
To keep an airplane or a drone in the air, it needs to generate lift. This can only be done if the total pressure at the bottom of the airplane is bigger than the total pressure at the top of the airplane, generating a net force upwards. 

But as nature is always looking for balance, the air at the high-pressure side, at the bottom, wants to skip over to the low-pressure side at the top.
Luckily there is a wing in between which then captures this force and generates lift. But at the tips of the wing, the air can bend around the tip with a 180° turn to skip from the high-pressure side at the bottom to the low-pressure at the top. 

So as this airplane travels through the air, it generates a continues swirl or vortex in the air. These wingtip vortices create a loss in lifting properties of the wing as part of the crucial pressure difference between bottom and top, is lost. 

Preventing vortices
Eliminating wingtip vortices completely is quite difficult, but you can reduce them by adding a little wall at the end of the wing (a winglet).
This will prevent the air from crossing over from the bottom side to the top side. 

So how big is this effect? 
How much can you gain by adding them? We've done a project specifically on drone winglets. It was a fixed-wing drone and it already had wing tips. By analyzing and improving them, we improved the lift over drag ratio by up to 30%. 
Which is quite massive for a fixed-wing drone.

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

What is a Wing Tip Vortex?

In this video, we will be discussing Reynolds number and Turbulence. Two closely related items. 


The Reynolds Number
The Reynolds number provides the ratio between the inertia forces and the viscous forces of a flow. It is calculated by dividing the product of the flow velocity, characteristic length and density by the viscosity. You can see it in this formula (00:00:18).


Laminar flow
At low Reynolds numbers, the damping effect of the viscosity is larger than the inertia forces that want to disturb the flow: fluid particles move on steady parallel trajectories. It looks very clean, very orderly. And that's why we call this laminar flow. 


Turbulent flow
At high Reynolds numbers, the inertia forces are big enough to overcome this damping effect and you will start to see nervous movements of particles superimposed onto the main flow. The trajectories are no longer parallel but they feature many local direction variations and swirls within the flow. We call this turbulent flow.


Transition point
As the Reynolds number increases, somewhere between laminar and turbulent flow there is a transition point or transition zone. As density, viscosity and object dimensions typically stay the same within a certain case, this often happens as the velocity increases beyond a certain point, a critical point. 


Example
A well-known example of this is the flow out of a faucet. If you turn it open only slightly, you will see a stable, clear stream of water. Turn it open completely and you will see a nervous flow full of bubbles.


Practical use
So how can you use this Reynolds number in your own application?
Unless you are running a case that is exactly identical to one that has been well tested, you cannot compare directly.

Because the Reynolds number is a subjective thing, there is no clear definition of the characteristic length. It's more of a subjective method to characterize a flow rather than a real physical property. But by calculating the Reynolds number for your application, you can roughly compare to other applications, to get the first idea on whether the flow will be laminar or turbulent in your case. Using the Reynolds number you can analyze the flow of a scaled model, that you have tested in the wind tunnel for example, and extrapolate to a full size one. That's pretty useful for wind tunnel testing.


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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it? 

Check out https://airshaper.com/ and see how easy it can be!

The relation between Turbulence, Reynolds, and Wind Tunnel Testing

In this video, we will be discussing race car aerodynamics.

Frontal area
If you want to reduce aerodynamic drag as much as you can, you want to keep the frontal area as low as you can. That is why race cars are quite small & low, very close to the ground.
Click here to learn more on aerodynamic drag:
https://www.youtube.com/watch?v=DbIIw-WryHY

Front splitter
At the front, the air hits the car. This generates a high-pressure zone pushing onto the car, but also onto the front splitter. The front splitter is a flat plate in front of the car that feels and captures this high-pressure air and pulls the car downwards generating down force.

Dive planes
Dive planes are the curved planes at the front wheel arches. They make sure that the wind jumps up, pushing the front of the car downwards as a result.

Wheel arch ventilation
The front wheels rotate at a high velocity creating a high-pressure air zone. If you ventilate that high pressure air at the top of the front wheel arches, this will push down the front wheel arches, especially as this air collides with the incoming air in front of the car.

Top air intake
We want to make sure that we provide high-pressure air to the engine, because that increases the power output. We can do so by positioning the air intakes high above the car in the free stream of the air to provide good capturing of air when it hits them.

Rear wing
This wing is comparable to the wing of an airplane, only it’s flipped upside down to not pull the car upward but to push it downward onto the asphalt. You want to make sure that the wing is positioned high enough so that it is in the free stream of the air and not in the dirty, turbulent air that is generated by the air intakes or other geometry of the car upstream.

Diffuser
The diffuser is the part that improves the transition from airflow underneath the car to the wake behind the car. If done right, this can strongly accelerate the air underneath the car creating a low-pressure zone pulling the car downward onto the ground. Click here to learn more on how a car diffuser works:
https://www.youtube.com/watch?v=9UgacwMJpuk&t=64s

Aerodynamic balance
This is the ratio between the down force at the front wheels and the down force at the rear wheels. You can play with this a lot in function of the track you want to race at. It is important as it influences the car’s handling, for example understeer and oversteer.

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Race Car Aerodynamics

In this video, we will be doing High Tech aerodynamic field testing do it yourself style. We took a 1970s beetle and equipped it with little tufts. 


Tufts
Tufts are small bits of light-weight wire that can move along with the wind. They allow you to see the local orientation of the air flow.
If they stay still and stick to the surface, this indicates nicely attached air flow.
If they wiggle around in different directions, this indicates turbulence, often occuring in zones of detached air flow.


Testing on a '70s volkswagen beetle
We equiped the roof and rear window of a 1970 volkswagen beetle with tufts, all around 10 cm apart.
We're curious to learn whether the air flow will nicely follow the curvature of roof and rear window, or detach and become turbulent at a certain point.


Observations
- Front section of the roof: at the very front of the roof, just after the jump from the front wind shield, we saw a slightly more nervous movement of the first tuft.
Admittedly, the effect was not very pronounced.
The other tufts further down stream were all stable.
- Rear section of the roof: all tufts on the roof stayed nicely flat and stable.
- Rear window: intense, nervous movement of the tufts


Interpretation
We saw that at the front of the car, we had a little bit of turbulence at the first tuft. This could indicate detachment of the airflow, possibly because the flow needs to rise up and jump on to the roof. 
The sharp angle between front wind shield and the top of the roof could cause local detachment of the air flow.
Right after that first part, the flow re-attaches again and all tufts are stable until it reaches the rear window: likely, the downward angle of the rear window is too steep for the flow to stay attached. The air detaches and follows a more horizontal trajectory, somewhere above the rear window, causing flow recirculation in the area below.


With special thanks to
- My dad, for being the best Go Pro Mount alternative in the market
- https://www.bensound.com/ for providing us with royalty free music that's easier to listen to than just wind.


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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

DIY Aerodynamics #1: a '70s VW Beetle

DIY Aerodynamics #2: Vortex Generators


Volkswagen Beetle
You may remember one of our previous videos in which we analyzed the aerodynamics of a Volkswagen beetle, do it yourself style. We discovered that the airflow over the roof detached somewhere around the rear window. The theory was that the downward angle was too steep for the flow to stay attached.
Let’s dive into some theory on when this can happen.


Boundary layer
As air flows over a surface, it will stick to it, slowing down to zero. Away from the surface, air is moving at the free stream velocity.  In between the two, you’ll get a velocity profile. This transition zone is called the boundary layer.As the air in the boundary layer is moving slower, it contains less energy and less momentum than the faster air above.


Flow separation
If the curvature of the surface is too strong, the air in the boundary layer will not have enough momentum to follow it. The more energetic flow above will be dominant, wanting to continue on its horizontal course, pulling away from the surface causing the flow to detach or separate.
Locally, the velocity profile close to the surface can even feature a reverse flow, caused by an adverse pressure gradient, creating a rotating separation bubble. We saw this in our previous beetle test, where the tufts at the top of the window would move in the opposite direction, towards the roof of the car.


Drag reduction
This separated flow increases the wake behind the car, causing unwanted drag. So how can we reduce this effect? One way of doing so is by simply reducing the curvature of the roof and rear window. You can see this on modern, streamlined cars like the Mercedes CLA. Another way is to install vortex generators.


Vortex generators
Vortex generators are little devices that improve the energy and momentum transfer from the free stream air to the boundary layer, giving it more momentum to follow the curvature. A very simple example is small vertical planes, placed at a slight angle with respect to the airflow. As the air hits the front side of these planes, pressure increases. At the rear side, the pressure decreases.

As you may remember from our video on wingtip vortices, the air wants to skip from the high-pressure side to the low-pressure side, creating a vortex at the top of the planes. This will cause part of the flow above the vortex generators to dive downwards, carrying momentum into the boundary layer. It will become more turbulent, stimulating energy mixing between the free stream air and the boundary layer.


Field test on the beetle
So we installed some high-tech paper vortex generators on the beetle to see if it works. It turned out the distance between the vortex generators and the rear window was quite crucial, but after a while, we found a position that worked.


Results
By analyzing the movement range of each tuft, we were able to compare both setups.
Without vortex generators, the tufts near the top of the window featured a lot of movement and reverse flow caused by the adverse pressure gradient. With the vortex generators installed, the movement was much reduced and the reverse flow was eliminated. 


So that was it for this video! If you liked it, please click the like button and subscribe to stay tuned for more!

See ya soon!

DIY Aerodynamics #2: Vortex Generators

Drone types
Rotary wings, quadcopters, for example, use the vertical thrust of the propellers to keep the drone in the air. A fixed-wing drone, however, relies on conventional wings to generate the required lift, just like an aeroplane as it travels through the air. In most cases, this setup eliminates any hovering capabilities, but it greatly increases efficiency, giving you much longer flight times.
Fixed wing drones come in many shapes & designs. Some look just like minified aeroplanes, with a propeller at the front, a fuselage in the middle with a long slender wing at both sides and a tail with vertical and horizontal flaps. Blended wings, on the other hand, look very futuristic, with fuselage and wings morphed into a single piece, without any tail at all.

Airfoil basics
Whichever design you go for, you’ll need to choose some kind of wing section, called an airfoil, to generate lift. In more advanced designs, the size or even the shape of this airfoil can change along the width of the wing, but it’s always a good starting point to do some basic hand calculations first.
Let’s start with naming the basic parts of an airfoil. At the front, you have the leading edge, at the back you have the trailing edge. They are connected via the upper surface, also called the suction surface, and the lower surface also called the pressure surface.
The chord is the straight line connecting the leading & trailing edge. The camber line, on the other hand, runs nicely in between the upper and lower surface, showing the centre line of the wing. 
The angle of attack is the angle between the chord and the relative wind direction. The relative wind is not only composed of the wind vector but also the velocity of the drone itself.

Lift and drag
Essential to airfoils is how much lift & drag they generate. Lift is the vertical force perpendicular to the relative wind direction. Drag is the horizontal force along the wind direction. These vary in function of the angle of attack. There is a great website called http://www.airfoiltools.com/ that provides you with tons of data on different airfoils. To understand drag & lift curves, let’s illustrate this using a symmetric airfoil, where upper and lower surface are identical. An example is the NACA0012.
At zero angle of attack, the lift is zero as well. There is only drag. As soon as the airfoil rotates its nose into the air, creating a positive angle of attack, it starts generating lift. The bigger the angle of attack, the larger the lift. Beyond a certain critical angle of attack though, the lift will start to decrease again. This operating region beyond the critical angle of attack is called aerodynamic stall and is caused by a separating flow at the suction surface of the airfoil. Trying to pull up too fast during take-off, for example, is a typical scenario in which planes can go into the stall, lose lift and risk crashing. 

Another effect of increasing the angle of attack is the increase in aerodynamic drag, which could cancel out the positive effect of lift. To find the sweet spot, we can use the lift-over-drag curve, which plots the ratio of lift over drag in function of the angle of attack. The NACA0012, in this case, reaches its maximum efficiency at an angle of attack of around 8°. At this point, the lift generated by the wing is 80 times bigger than the aerodynamic drag!
This is not the best you can get through. In contrast to symmetric wings, asymmetric wings sacrifice performance at negative angles of attack to generate more lift and less drag at positive angles of attack or even at zero degrees. With airfoil tools, you can easily compare two different airfoils, like the symmetric NACA0012 versus the asymmetric NACA6412. You’ll see that the NACA6412 peaks at a lift over drag ratio of over 140!
As you may have noticed in these curves, lift and drag are expressed as coefficients Cl and Cd, rather than the real lift and drag force. This makes it easier to compare different airfoils, irrespective of their size. The coefficients are calculated by dividing the lift or drag per width of the airfoil by the product of stagnation pressure and the chord length.

Drone Design #1 - Selecting an Airfoil

In this video, we’ll be looking at what happens when we move to three-dimensional shapes.

For the full report of our Generic Drone Simulation, click here:
https://airshaper.com/assets/reports/AirShaper_sample_report_-_drone.pdf

To get started, let’s have a look at the aerodynamics of a fixed-wing drone. I have a simple 3D model that I’m uploading to AirShaper. I’ll just call it “GENERIC FIXED WING DRONE” and drag the STL file into the box. It’s a flying drone, so I’ll set it to “above the ground” and “moving” and give it a 15 m/s velocity. Now let’s rotate the nose forward and then pull it upwards, giving it an angle of attack of 15°. That’s not a very efficient flight regime, but it will allow us to see some more interesting flow results. The model was exported in meters and that’s it, now let’s order the simulation.

Ok, we’re back, 4 hours later and the simulation has finished. We’re interested in what happens at an angle of attack of 15°, which should cause a stall. But first, let’s relate to the drag & lift theory of the previous video. This drone has a lift of 21.61N versus a drag of 4.94N. That’s a lift-over-drag ratio of 4.37. Not very impressive, as we saw values of more than 100 in the previous video! Let’s have a look at some techniques to find out what is going on.
One way of finding sources of drag is to look at the total pressure coefficient. Plotting a 3D cloud of where this equals 0 is a good indication of where you have a wake or a draft zone, and thus a cause of drag. As we can see, the outer parts of the wings seem to cause quite a big wake.

To get more insight, surface streamlines & surface friction can help. Remember when we talked about flow separation and adverse pressure gradients? You can detect the edge of a separated zone by looking at low values of surface friction. Looking at the top of the drone, we can see that the outer parts of the wing feature such a separation zone. In that area, you can see the surface streamlines move in multiple directions, even opposite to the wind direction.

You can also see this reflected in the surface pressure map: for a wing to function properly, we need high pressure at the bottom surface and low pressure at the top surface. In this case, the air stays nicely attached to the centre part of the drone. High velocity, low pressure. But at the outer parts of the wing, the air separates right after the leading edge, rapidly increasing pressure and thus reducing lift.

Let’s build a few theories on why this happens. First of all, there is the airfoil that is used. At the centre, the airfoil has a high relative thickness. At the outer parts of the wing, the relative thickness is much lower. Airfoils with a high relative thickness tend to have a higher stall angle of attack. We can see this when comparing lift curves of the NACA006, NACA0012 and NACA0018, which are basically the same airfoil with a different thickness.

Another theory is the shape of this fixed-wing drone. It’s a blended wing body, with a triangular platform, the shape when viewed from above or below. The air first hits the bottom of the nose and is pushed sideways in the process. As it bends around the nose towards the top side, it is pushed back towards the centre by the surrounding air. As the left & right join at the top centre, they fill the wake that is there and prevent separation. This inward & upward pull of air towards the centre could increase the local angle of attack at the outer parts of the wings, triggering stall.

So then how do we prevent this? Well, the question could also be should we prevent this? We’ve deliberately triggered stall by setting the angle of attack to 15°, which is not a standard flight regime. We’ve also seen that stall only happened on parts of the drone, which can be a good thing: a gradual stall in function of the angle of attack will make the drone easier to fly at the limit for example, while it could still be very efficient at lower angles of attack.

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Drone design #2: 3D Flow Analysis

In this first video on aerodynamics in sports, we’ll have a closer look at how my mentor Ismaël Ben-Al-Lal is preparing for the Ironman in Hawaii in 2019, after winning the one in Taiwan in his age group in 2018.

Our partners for this video:
https://www.uantwerpen.be/en/
https://www.voxdale.aero/
https://www.linkedin.com/in/ismaël-ben-al-lal-0a55b021

Wind simulation by:
https://airshaper.com/

3D scan with:
https://www.artec3d.com/

First a short recap on the Ironman: you start off with a 3.86km swim, then you jump onto your bike for a 180.2km and you finish with a 42.195km marathon. Fair to say that every bit of reduction in resistance is appreciated during such a race.
It’s particularly important for the cycling bit: aerodynamics make up for over 80% of the total power you’re pushing through the pedals at 10 meters per second. So Ismaël got into the science behind it to go even faster. To do so, he got himself 3D scanned to obtain a 3D model for aerodynamic simulations. Here’s a short interview we did with him:

--- Interview Ismaël ---

To make the scan of Ismaël, we cooperated with engineering agency Voxdale and the product development department of the University of Antwerp. They used an Artec Eva 3D scanner that uses structured light to transfer Ismaël into the digital world. The total scan took less than 5 minutes to complete and with some post-processing, his body was isolated from the bike to focus on his body rather than his bike. Not that the bike and the body don’t interact aerodynamically, but sometimes it’s interesting to see what is possible without the bike.

So we pushed the 3D scanned model straight onto our platform for a Detailed Simulation and without revealing too much of Ismaël’s competitive advantages, we do want to provide two quick insights to get you started:
- First of all, the helmet. In the top view, we can see that Ismaël’s helmet is not oriented perfectly straight. This can cause unwanted drag, so be sure to turn your head straight into the wind. When there is a side wind, this may mean you’ll have to slightly rotate your head into the wind.
- Second of all, the upper arms: trying to keep your shoulders tucked inside could help reduce the wake just behind the top part of your upper arms. 

That was it for this first introduction to aerodynamics in sports. If you liked it, please click the like button and subscribe to our YouTube channel to stay tuned for more. And if you have any tips on other topics, just let us know in the comments!

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Sports Aerodynamics #1: Winning the Ironman Triathlon

Some say…
That motorbikes where invented by car designers on half the budget,
And that secretly, they found driving on half the number of wheels twice the fun.
All we know is, aerodynamics make them both go faster!
 
Drag
But in case of a motorbike, it’s all a bit more difficult. Let’s start with the obvious:
Motorbike drag is a disaster: apart from some laminar flow around the front fairings, turbulence is king everywhere else. With open wheels, sharp edges and a driver shifting position every two seconds, it’s a challenge to bring down drag.
 
Over time, people have come up with all sorts of clever ways to shield & streamline the driver. But sidewind sensitivity and practicality are big concerns, as you can perhaps imagine.
 

Pulling wheelies
Obviously, drag can be overcome by more power. But with acceleration and drag both trying to flip you over backwards, they add up to make you wheelie even faster. And as cool as that may sound, it’s the sign you’ve reached your maximum acceleration rate. When you’re in a race, that’s not what you want.
So imagine there is something that could push the front wheel down onto the ground, that would help a great deal. That’s exactly why over the past years, Ducati and others have been experimenting with front wings on their bikes: although not much, they create downforce on the front wheel, counteracting the torque of acceleration and drag.

Cornering
The effect of downforce on cornering is a bit more complex though, as the aerodynamic vector tilts together with the lean angle of the bike: the downforce generates more pressure and thus more grip, but it also pushes you outwards. The net effect is only positive with a tire friction coefficient of more than one, or when the rider is leaning more into the corner than the bike itself, keeping the downforce as vertical as possible.

More power
So once you’ve found a way to put more down power, it’s a matter of generating more of it. But more power means bigger cooling demands, and more cooling means bigger radiators. Unless you can use them more efficiently.
Airflow through a radiator is generated by a pressure difference between front and back. Increasing this pressure difference increases the driving forces for this airflow and thus the cooling performance. Computational fluid dynamics simulations allow you to identify or even create a suitable high and low-pressure zone for this purpose. Typically the high-pressure inlet is located at the front of the bike and the low-pressure outlet located on the sides for example.
 
Comfort
Not all bikes are designed to go as fast as possible though: some are there to enjoy miles & miles of highway cruising. Just you, the road, and perhaps a bit of unwanted wind noise. Designing the front windshield and the shape of your helmet are crucial towards reducing noise levels. This noise is in part the result of the turbulent kinetic energy of the airflow being dissipated in the form of noise energy. Simulating the sound power generated in the airflow around the rider greatly helps to understand where this noise is coming from.
 
Heat
Another effect of this turbulence is the heat transfer rate: a turbulent flow is much more capable of transferring heat between the rider and the surrounding air. That can be good when you need some chill on a hot summer day but can make you freeze on a cold winter night.

And on that bombshell, it’s time to end this second movie on sports aerodynamics!
Thanks for watching and don’t forget to click the like button and leave some comments! See you soon!

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Sports Aerodynamics #2: Motorbike Wheelies!

In this video, we’ll be looking at how to speed up the aerodynamic design process by working directly with open surface models!

Solid vs Surface models
First a few words on solid versus surface models.
In engineering, most 3D models are designed just like they are machined in real life: you start from a solid block and take away the excess material until you have the desired shape. It’s still solid on the inside and there are no gaps between the different outside surfaces.

In design or styling, however, 3d models are often built as a combination of complex surfaces: you start for example from a simple rectangular plane, which has two sides. Then you start pushing & pulling the different vertices on that plane until the shape looks good. To obtain the full 3D model, multiple surfaces are put together, sometimes overlapping, sometimes with gaps in between.

Watertight models
Now when it comes to aerodynamics simulations, it is typically required to work away all the gaps & interferences, to obtain something that is called a watertight or manifold 3D  model. In case of surface models, this often means weeks of model fixing to obtain a 3D file that is ready for simulation.
A trick to avoid remodeling is to use a wrapping method, which will literally wrap a closed surface around your model. But this can be quite tricky, as you may end up losing small details or closing holes & small gaps that weren’t supposed to be closed, like ventilation holes in a helmet for example.

Algorithms
The only proper way to avoid risky wrapping methods or weeks of remodeling is to accept the surface models as they are by treating every surface like a wall on both sides. That’s exactly what we do at AirShaper – we tuned our algorithms for months to make them work directly with open surface models. Let me show you an example of how this speeds up the aerodynamic design process:

 
In Practice
Auto Access is a company that develops & installs auto accessories, like for example hardtops for pickup trucks. In the light of more demanding emission regulations, they asked us to assess the impact on fuel consumption of adding a hard top to the Nissan NP300 pickup truck.
As you can imagine, Nissan doesn’t simply hand out their confidential 3D data. So instead we turned to a professional website for 3D car models. And as you may have guessed, these are all surface models with plenty of gaps and holes.

The results
So instead of closing all these holes, which would have required more budget and time, we just uploaded the model straight into AirShaper. Every surface was treated as a real wall on both sides. And although air leaked to the inside in some locations, these static pockets of air didn’t affect the overall behavior of the flow.
The result? Just a day after obtaining the 3D model, we were looking at the aerodynamic report. And the best news? Adding a hardtop to the Nissan NP300 doesn’t increase fuel consumption!
So that was it for this video, if you liked it, please click the like button below and don’t forget to leave your comments!

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Save weeks! Run aerodynamic simulations on open surface models.

In this video, we’ll take a look at smart mobility and the role of aerodynamics.

1. Some context:
According to the United Nations, 60% of the world’s population will live in cities by 2030. With cities already congested and polluted today, this poses a massive challenge to urban mobility.

So we’ll need to rethink the way we transport ourselves and goods, around & within cities as a whole, something called “Smart mobility”. We found many different definitions on this, so here’s our attempt to summarize it:

Smart mobility aims to use new technologies like:
1. high-speed data connections, 
2. self-driving tech, new materials & propulsion methods to create 3. sustainable mobility. And very likely, this will be a 
4. combination of different transport modes, like taking the car to the city to continue locally on the electric step, for example.

2. Weevil
To improve flexible & efficient travel between and within cities, a consortium of industry experts from around Europe have created the Weevil project.

The weevil is a highly innovative three-wheeler with two wheels at the front and one at the back. There is even room for 2 people in tandem position.

This car solves the contradiction of needing a wide wheelbase for stability in corners and a small wheelbase to maneuver in tight traffic and parking spaces. They developed a suspension mechanism that allows the front wheels to move outwards at high speed and inwards at low speeds. 

3. Aerodynamics
So practicality is covered, but what about efficiency? Of course, it’s electric, but you want to get as far as possible on a single charge. Or, make the battery smaller & lighter for a given range. In any case, reducing the energy needed to move around is key: even at intermediate speeds of 80 km/h, aerodynamic drag easily makes up for more than half of the power the battery needs to deliver.

4. The benefits
Luckily, having 2 people sit in a row rather than next to each other, greatly reduces the frontal area of the Weevil.

Another benefit of this setup is the possibility to give the car an aerodynamic drop shape, which closes behind the passenger, to reduce the wake.
 
And the rear wheel of the car is tucked away nicely at the end of this drop shape to prevent it from creating highly turbulent air as the rear wheels do on a normal 4-wheeled car. 

5. The challenges
Also challenging for small cars is the fact that some components don’t scale down like mirrors and door handles. So it’s quite a challenge to keep their relative contributions to drag low. And with variable front wheel track width, the suspension is exposed to the external air. Therefore, the Weevil team paid a lot of attention to limit the drag penalty in wide track mode.
 
6. The design
Packaging all of this together in a good looking car is not an easy task. Luckily, with Masato Inoue, the former Chief Designer of Nissan who designed the Nissan Leaf, and Hexagon Studio, transportation design & engineering experts, the Weevil team managed to turn this concept into a stunning city car.
And there is yet another cool link between the Weevil project and aerodynamics: 25 years ago, Alberto Morelli studied new ways to reduce the aerodynamic drag of ground vehicles. And today, it’s his son, Massimo Morelli, who is handling all communications concerning the Weevil project.
 
So that was it for this video! I’If you liked it, please click the like button below and if you have any questions or comments, just post them below the video!

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Smart mobility  - City Vehicle Aerodynamics

In this video, we will explain how we teamed up with Bioracer to develop the next step in individual performance clothing for athletes.
 
Golf ball dimples:
First, let’s talk about why golf balls have dimples. Euh wait, wasn’t this about athletes? Patience, we’ll get to that in a minute!

Golf balls without dimples feature a laminar flow. As the air moves over the surface, a boundary layer of slower moving air grows thicker as it sticks to this surface. As soon as the flow goes beyond the halfway point and needs to contract, it becomes more & more difficult for the flow to stay attached to the surface and eventually separates. This creates a large wake behind the golf ball, which increases drag and slows it down.

When you apply dimples to the surface, or another way of increasing the roughness, the boundary layer becomes turbulent. It will mix with the surrounding air and retain more kinetic energy. This energy allows the airflow to stay attached further down the back of the golf ball, reducing the wake created in its path. These dimples may increase the friction drag a little but reduce the pressure drag so much that the golf flies roughly twice as far!
 
So does this mean we should cover every surface with dimples to make it more aerodynamic? Hm, not quite. Increasing surface roughness to create a turbulent boundary layer only makes sense in locations upstream of a location with separation. Otherwise, you’re only increasing the friction drag!

Cyclist flow
That being said, it’s time to move on to athletes. The flow around a cyclist, for example, is a complex combination of laminar & turbulent flows, that are attached in some regions and separated in others. So the location of where increase the surface roughness is critical.
 
Bioracer, a Belgian company that is well known for its high-tech sports clothing,  already offers clothing that features a smooth surface in some areas and a rough one in others. Like increased roughness at the upper arms for example, which are comparable to cylinders in shape and where it pays off to have the flow stay attached further down the back to reduce drag. 

Individual
This is not where it ends though: every athlete is different in terms of body shape and position on the bike. This means that the locations where the flow separates are different as well! To offer a highly individual approach to drag reduction, Bioracer and AirShaper went to the Bike Valley wind tunnel to experiment with roughness increasing materials in different locations.
The test specimen of the day was Ismaël Ben-Al-Lal, triathlete, and winner of the Taiwan Iron Man in his age group in 2018 and now prepping for the one in Hawaïi. After computing Ismaël’s aerodynamics using a 3D scanned model we uploaded to the AirShaper platform, we analyzed the results together with Bioracer. We sat down to define suitable locations for increased surface roughness.

For example, we didn’t make the entire surface of the upper arms rough, as is done on existing professional jerseys. Instead, we applied rough patches tailored to specific locations on Ismaëls arms & legs and the flow around them.

Over a series of wind tunnel tests, we indeed measured drops in aerodynamic resistance and we discussed possible layouts for Ismaëls next personal outfit. This simulation-based aerodynamics approach is our path towards highly individual performance equipment.

So that was it for this episode of custom aerodynamics! I hope you liked the video and if you have any questions, just leave them in the comments or get in touch with us directly to discuss your own project.

Thanks for watching, see you soon, bye bye!

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Custom Aerodynamics - Bioracer meets AirShaper

In this video on Airplane design, someone else will do the talking. 

Some time ago I met Yong Wook Sin who works at the Peugeot design center. 

As it turns out, even during his free time, he likes to create cool stuff, like a futuristic electric airplane. 

For the full interview, check out this link: https://youtu.be/h1j7D_f0JbU

He spoke about using CAD programs to make 3D designs for his ultralight solar plane and using aerodynamics to calculate the possibility of keeping the airplane in the air indefinitely.  

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!
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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Airplane design #1 - A Peugeot Designer's Vision

In this video, we’ll be discussing the basics of flight dynamics.

1. Introduction
To fly an airplane in a straight leveled line involves a horizontal balance between aerodynamic drag & thrust force and a vertical balance between aerodynamic lift and gravity. To make an airplane take off, follow curved trajectories and land, involves a whole lot more and is the domain of flight dynamics.

2. Roll, Pitch, and Yaw
The main parameters used to describe this three-dimensional orientation are the roll, pitch and yaw axes of the plane, all running through the center of gravity.

- The roll axis, also called the longitudinal axis, runs from nose to 
  tail.
- The pitch axis, also called the transverse axis, runs from left to 
  right.
- The yaw axis, also called the vertical axis, runs from top to 
  bottom.
 

Also important is the plane’s orientation with respect to the relative wind vector, which is the combination of the velocity vector of the plane and the wind vector. Around the pitch axis, this is called the angle of attack. Around the yaw axis, this is called the sideslip angle. 

3. Leveled flight
During a leveled flight, the roll, pitch & yaw orientation stay constant. To achieve this static balance, the moments around all three axes must be zero, otherwise, the plane would start to change its orientation. 
For example, if the center of lift of the main wings is not aligned with the center of gravity, this can generate a pitch moment causing the plane to tilt its nose upward or downward. To neutralize this pitch-moment, lift or downforce can be generated at the tail. Keep in mind that the location of the center of gravity can change between flights and even during flights due to changes in cargo and fuel for example.

4. Dynamic flight
During dynamic flight maneuvers, the airplane changes its orientation.

To climb or descend, for example, the elevators at the tail can be lowered or raised. This will cause the angle of attack to change which will affect the lift and drag that are generated on the main wings for example. Mapping & understanding the correlation between angle of attack and lift is crucial to understanding & optimizing flight dynamics.
   
To achieve this, you can perform a wind tunnel test during which you monitor lift & drag values while gradually increasing the angle of attack from the lowest to the highest value of interest. Such a sweep procedure can also be performed digitally by changing the angle of attack over a series of aerodynamic simulations.

5. Horizontal sweep
The results are curves that plot the lift and drag values versus the angle of attack. This is quite similar to the 2D airfoil curves we saw in earlier videos, only now it’s the lift & drag of the full plane, taking aerodynamic effects like flow around the fuselage and wingtip vortices into account. 

Here as well, very steep curves could indicate that the plane is very dynamic but more difficult to fly. Such crucial information can then be used as input for the flight control strategy. 

6. Vertical sweep
A similar approach can be applied to a yaw maneuver, where the rudder at the tail is used to turn the plane left or right. Sweeping the sideslip angle beta again results in changes in the forces on the plane. In this case, however, the lateral force is of particular interest, as a sideslip angle will generate a sideways push on the plane.  

7.
This is only the tip of the iceberg in terms of flight dynamics: much of the airplane maneuvers involve a combination of pitch, roll, and yaw. Side winds can have a tremendous impact as well. And the speed of rolling, pitching and yawing also generates additional dynamic forces and moments that play a big role.

That was it for this short introduction on flight dynamics. Thanks for liking, sharing and leaving your comments below the video, thanks for watching and see you soon! Bye-bye.

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Airplane design #2 - Flight Dynamics

In this video, we’ll be discussing glider plane design.

This time we interviewed the people at Friendship Systems, our partner company specialized in variable geometries for flow analyses. 

They have developed an interactive 3D web app to design a glider plane. It includes a first theoretical indication on the aerodynamics after which the 3D model can be sent directly to AirShaper for a full-blown 3D flow analysis.

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Airplane design #3 - Glider plane design

Drag coefficients: https://youtu.be/bEgoZ_dAg7o

Connect with me on LinkedIn! https://www.linkedin.com/in/wouter-remmerie/

In this video, we will analyze the aerodynamic features of the Tesla Semi truck.

Emissions
First, some context. Lately, heavy-duty transport has been facing increasing pressure: in Europe, trucks, buses, and coaches together produce around a quarter of all road transport CO2 emissions.

On the power consumption side, efforts are made to reduce aerodynamic drag, as it is responsible for more than half of the power required to drive a truck at highway speeds.
Truck aerodynamics

But improving truck aerodynamics is not easy: typically, trucks and trailers are bulky objects that have been stretched to make use of every cubic centimeter that is allowed by road regulations, such as maximum length, height & width. It’s not hard to see that trucks are not exactly super streamlined, but exactly how bad is it?

Aerodynamic efficiency is expressed via the drag coefficient Cd. If you want to learn more about the drag coefficient, just watch our separate movie on this. In short, lower is better with the Tesla model 3 at 0.23 and a conventional truck between 0.5 to 1. So when Tesla claimed 0.36 for their Tesla Semi truck, we jumped up and wanted to know more.

3D model
We called Elon Musk and asked him to send us a 3D model of the truck within 2 weeks. But he’s not too good with deadlines and we didn’t want to wait, so we asked our partner engineering agency Voxdale to build a 3D model for us instead.

Results
And believe it or not, we got a drag coefficient of 0.35 for the Tesla Semi truck! You can argue that we didn’t use the exact geometry for example, but even compared to our optimistic conventional truck it featured a 20% drop in aerodynamic resistance! That’s over 10% reduction in fuel consumption or 5000 liters of fuel per year!

Let’s start at the front: the vertical frontal face of the boxy conventional truck causes a huge pressure build-up on this entire surface, as the air needs to take a 90° turn to get around the cabin, either over the top or around the sides.
To provide smoother escape routes for the air, the Tesla Semi’s cabin features a strong backward inclination angle and large smooth corners around the sides of the cabin. This allows for a much more gradual evacuation of incoming air and thus a lower pressure buildup.

On road cars, the mirrors make up 2 to 5 % of total drag. On trucks, they are much bigger and Tesla decided to simply replace them with tiny camera’s mounted on aerodynamic wing-shaped beams! It’s quite easy to spot this difference by looking at the wake caused by both mirror setups!

If the roof spoiler is too wide or too high, this can leave a large wake and create unnecessary drag, as we can see at the top of our conventional truck. If it’s too low or narrow, the air will hit the square front of the trailer, causing local pressure to build up and separation downstream. Tesla made sure the Semi cabin fits nicely with its trailer: they were able to do so by extending the side spoilers all the way to the trailer and by leaving just enough space in top view for the trailer to rotate.

The wheels. Covering the front wheels is quite difficult, as they need room to turn in corners, but the rear wheels of the Tesla Semi have been shielded to create a smoother airflow.
Should they stop there? Of course not! The trailer itself can be optimized a lot as well, with side skirts and flaps at the rear for example. There’s plenty of after-market equipment already out there. 

You can argue that in the end, it’s the CO2 emission per unit of cargo that matters and that the Semi’s longer cabin reduces the available cargo space in its wake. But then again, this depends on local regulations and it’s not a coincidence that the European Union is increasing the allowable length.
 
They have already triggered others to come up with innovative concepts, like the Ford F-Vision, for example.

Credits: 
Tesla: https://www.tesla.com/
Mercedes: https://www.mercedes-benz.com/en/
Ford: https://www.ford.com/

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Wouter Remmerie

Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Truck aerodynamics - Tesla Semi Explained

Private video

In this video, we’ll show you how aerodynamics can impact the performance, safety & environmental impact of your design!

Let’s start with aviation.
The most obvious field in aerodynamics.
Now the pinnacle of airplane performance is the Red Bull Air Race. Apart from big engines and big balls, aerodynamics determine who wins and who loses. Australian team Matt Hall Racing used AirShaper to optimize the airflow around key components of their plane. They won several races that season and nearly took the overall win!

Drones are another hot aviation topic 
Getting the aerodynamics right is crucial to fly as long and as far as possible on a single battery charge. For their latest model, the eBee X, senseFly ran several AirShaper simulations to optimize the vortex, or the corkscrew motion, of the air at the tip of the wings. By tweaking the vertical winglets together, we increased the aerodynamic efficiency by 30%! 

Aerodynamics also play a key role in performance sports, like cycling or skiing. We used a 3D scan of a speed skier to improve the aerodynamics of his stance & equipment. We helped him take his personal record from 198 km/h to a whopping 214km/h! At those speeds, aerodynamic forces dominate anything else!

But what about safety? 
Let’s have a look at the Sunfold, a free-standing container equipped with solar panels at the top to capture and store energy! Tiger Power uploaded a 3D model of their entire system into AirShaper and analyzed the forces and the moments caused by the wind to see if would tip over. 

Luckily, it didn’t!

The next step is to put all that renewable energy to good use, like efficient road transport. We benchmarked the Tesla Semi versus an optimistic generic truck and found a reduction in aerodynamic drag of around 20%! That’s over 5.000$ of fuel savings each year for a conventional truck, not to mention the reduction in emissions!

So whether you’re cycling at 30 km/h, transporting cargo at a 100 km/h or racing at 300 km/h, aerodynamics matter big time.

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Why aerodynamics matter! - Performance, Safety, Environment

In this video, we’ll be playing with the aerodynamics of the Porsche GT4 race car.

Some people are satisfied with buying a standard Porsche GT4 to go racing. And to be honest, I’d be quite ok with that as well, if I had the budget. But others get creative and start modifying their car to gain that extra bit of performance.

Volker Wawer is one of those people: he wanted to fit wider tires on his GT4 and that meant he needed to shield those tires using wider fenders. But these impact the airflow around the car, possibly blocking the air going into the side air intakes further downstream. As reduced pressure & airflow rate at the inlets translates into a loss of power, Volker wanted to check this using aerodynamic simulations.

There was one problem though: getting a 3D model from Porsche is not so trivial. As an alternative, there are near-exact 3D models made by skilled 3D drafters, which are available for purchase online. As these models are built for visualization purposes, they’re usually built using surfaces and feature quite a lot of gaps & holes. This causes aerodynamic software packages to crash, so we put a lot of effort into it at AirShaper to make our algorithms able to work directly with these so-called open surface models.

So we purchased a Porsche GT4 model and had the wider fenders modeled onto it. We launched 2 Detailed Simulations: the normal GT4 and the one with modified fenders, to clearly see the difference. And we found some interesting results.

To understand how the air flows around the side of the car, we released particles just upstream of the car’s front left fender and traced their path. This showed us that the air that eventually ends up at the side air intakes, doesn’t just come from air going around the side of the car. Part of the breathing air for the engine first rises on top of the front hood of the car, to then tumble down to the side flank of the car after the front wheel arch.

Interestingly, the new front fenders are able to sustain this high airflow on the front hood over a longer distance, reducing the amount of air that passes via the sides, where it loses momentum and gains turbulence at it passes over the front wheels. We measured the pressure at the air intakes for both cars and actually found a higher pressure for the car with the modified fenders.

It doesn’t happen too often, but in this case, Volker got both the wider fenders and a power boost for the engine. In racing, it’s impossible to fully isolate driver & car performance, but both must have been pretty good as he won his next race at the Nürbürgring.
That was it for this video on Porsche GT4 aerodynamics, thanks for watching and see you soon!

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Race Car Aerodynamics #2 - Improving the Porsche GT4

Sadly, it’s true: solar panels can really fly and about a decade ago, reports of damage to and by solar panel systems were a common thing after a storm. So what happened? 

On a small scale, you can mount perhaps 20 solar panels flush to the angled roof of your own house. On a large scale, there are vast arrays of thousands and thousands of solar panels installed on the flat or nearly flat roofs of industrial buildings.

Let’s focus on these flat roof systems. 
Penetrating the waterproof coverage for anchoring purposes isn’t always an option, many operators just put ballast of weight on the mounting system to keep things down. That avoids a possible leakage problem but adds a new one: extra weight. 

A decade ago, when no norms were available yet to determine the right amount of ballast to keep the panels down, some applied more safety than others. And with the financial crisis in full force back then, there was yet another incentive to get the total weight below the capacity limit of the roof to get projects approved and profitable. So sadly, some panels flew away.

Nowadays though, through extensive wind tunnel testing & simulations, norms have been formed and it’s clear & simple: follow the norm. Still, those norms allow for optimization, as they often take the aerodynamic behavior of the system into account. So prior to final wind tunnel testing & certification of a system, it makes a lot of sense to integrate aerodynamic simulations into the R&D phase to optimize the mounting systems.

To illustrate this, we’ve analyzed a single free-standing panel in an airflow of 40 m/s, a pretty decent storm. Under headwind, the vertical lift on the panel is around 240 kg, so the weight of the panel itself, around 20kg, is not nearly enough to keep it down.

This happens because the panel behaves like a wing with ground effect: the air hits the bottom of the panel, creating a high pressure pushing it upwards. At the top, the air separates as it jumps over the panel, creating a large suction effect again pulling the panel upwards. Even when the wind hits the panel under a large angle, the lift force can still be as high as 100kg.

If we look at the same panel receiving headwind, but now surrounded by neighbors in an array, the vertical lift force increases even further. Why? The free-standing panel had an escape route for the air on both sides. But when flanked by two neighboring panels, the only way for the air is up, increasing the pressure build up. The panels on the second, third and fourth-row feature much lower lift values, and sometimes even downforce. That is why very often the ballast for the outer panels of the array is much higher than the ballast for the inner ones.

Now if we rotate the entire array by 45°, we see some other interesting effects. As expected, the panel at the corner feels the highest vertical pull, but it’s lower than the headwind case. As we move away from the corner, the lift on the front row panels decreases significantly. Nevertheless, values are still very high and too much ballast would be needed to keep them down. So to reduce wind loading, plates are usually installed to prevent the air from entering underneath the panel, which reduces the high pressure build up at the bottom side.

We’ve added such a plate to the isolated panel. The air now hits this backplate, pushing the plate itself downwards as the air jumps up. The lift on the total system has been reduced drastically for all angles and even features downforce at some angles. The solar panel itself, however, can still feel the suction effect in the wake of the plate.

To counter that, there are some innovative systems that feature an intended opening at the top of the backplate. The suction effect, which is the largest just at the top of the backplate, will now draw air from underneath the panel. This helps to both reduce the pressure below the panel and to reduce the suction effect at the top. The effect on the vertical forces is quite clear!

Studying the behavior of a system in clean airflow is just the beginning though. In real life, complex wind flow patterns around the building itself, influenced by the surrounding terrain and featuring wind guests, add multiple layers of complexity to the problem. So complementing simulations with wind tunnel testing and adding the right safety factors is key to keep your panels from flying.

Wind tunnel image courtesy of Peutz

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Renewable Energy - Solar Panels Can... Fly?

Aerodynamic backpack ventilation – Vaude has your back

Why do we sweat when we exercise?
Well, we like to keep our body temperature constant and when doing sports, that temperature increases. To counter that, we sweat. The sweat evaporates into the air around your body and the energy needed to do so is drawn from your body, cooling it down.

But what if you’re blocking the air? Then the sweat piles up and you’ll need to sweat even more in other places to get enough cooling. It leaves commuters with a soaked T-shirt on the back and athletes with decreased performance.

So Vaude turned up the technology level on their newest backpack to come up with a solution for this. In a first step, they ran several airflow simulations on a digital mountain biker without a backpack, simply to understand how the air moves around the body and find sources of cooling. They saw that the airflow around neck & shoulders re-joins at the higher part of the back, to then channel down at relatively high speed before letting go somewhere lower down the back.

At some point, the air going around the torso was also considered to help drive air underneath the backpack. But with the air being too turbulent after going around the torso and the backpack hidden in the wake of the rider’s back, this turned out to be less efficient.

So together, we figured it would be quite nice to use the central airstream at neck & shoulders to help cool down the rider’s back in the locations where it matters most: the central part of the lower back. Multiple concepts were thought of, all with the aim to capture this airstream and channel it between the rider’s back, and the backpack itself.

Aerodynamically optimized channels were carved out of the padding between rider and backpack and after numerous checks via simulation, we ended up with a design that outperforms anything that is currently out there in the market.

And that’s not just us talking: Vaude performed multiple wind tunnel tests, with riders going at it in well-controlled conditions, like the temperature, seating position, produced power and so on. They even went to the Sports Tech Research Centre, who operate a specialized wind tunnel, to put their new backpack design to the test.

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Wouter Remmerie
Wouter is the Founder of AirShaper, an online, virtual wind tunnel. With this tool and these videos, we want to make aerodynamics accessible to everyone! Interested in more content like this on the field of aerodynamics? Make sure to click that subscribe button, we post new videos every week!

Looking for a way to test your Aerodynamics projects without all the hassle and the huge costs coming with it?

Check out https://www.AirShaper.com and see how easy it can be!

Sports Aerodynamics #3 - Aerodynamic backpack ventilation

In this video, we’ll explain the basic principles of CFD or computational fluid dynamics.

Let’s start with computational: this means that in contrast to physical flows, CFD flows are simulated using computers. For simple problems, this can be done on your laptop. For bigger problems, in automotive or aviation, for example, huge clusters with thousands of cores and terabytes of memory are often used.

Secondly, it involves a fluid, which can be a liquid or a gas. When you’re working with water, it’s called hydrodynamics. When you’re working with air, it’s called aerodynamics.

Last but not least, it involves dynamics, which relates to the fluid movement.

So how does one compute a flow? 

Modeling involves the continuous mathematical functions that you use to describe the real flow. In reality, that flow is the result of many different laws of physics working together. To limit computational effort, it’s a matter of selecting only the ones that have a substantial impact on your flow topic: if you’re calculating the aerodynamic force on a wing, for example, there’s little use in taking the gravitational pull of the moon into account, as the effect is negligible. So, defining correct & relevant models is important to limit the modeling errors:

In case of fluid mechanics, the most important model is a set of partial differential equations called the “Navier Stokes” equations. These basically apply the laws of Newton for every small bit of the fluid, stating the dynamic balance between the forces acting on it and the change in its momentum. This conservation of momentum, together with the conservation of mass, allows you to describe the flow field.

For some very simple cases, like laminar flow through a pipe, there are analytical solutions: the entire flow field can be described using continuous mathematical functions. These allow you to calculate the exact velocity & pressure for any given location in the flow field at an infinite resolution.

But for anything more complex than these very simple cases, we don’t have such an analytical solution. That means we need to break down reality into small blocks for which we do have a solution. These blocks can be finite elements or finite volumes, also called cells. Think of it as the difference between analog and digital photography, where a complex image is described by simple pixels, each having just one color.

This process of breaking down a large continuous flow field into small cells is called meshing. For each of these cells, we can approximate the continuous Navier-Stokes equations by discrete algebraic equations. These allow us to calculate the pressure & velocity at the center of each cell, which is called the node, based on the values of velocity & pressure of the surrounding nodes.

The higher the order of these discrete approximations, the more surrounding nodes are included. This “reach” is called the computational molecule, resulting in a set of algebraic equations for each node. As the value of one node depends on the value of neighboring nodes and vice versa, the equations are connected. This means you need to solve them simultaneously by putting them together in a big matrix.

But before we discuss how to solve this matrix, we need to talk about the discretization error: “The difference between the exact solution of the governing equations and the exact solution of the discrete approximation”. The more cells you apply, the smaller this error. But this also increases the number of equations you need to solve, and with meshes typically containing millions of cells, this quickly becomes very expensive. So you’re best off applying small cells to locations where the flow is complex, and large cells where the flow is less curvy, typically further away from the object.

Once you have defined your mesh and your matrix of equations, it’s time to solve them. It’s possible to find the exact solution of this matrix problem through a direct method like Gauss elimination or LU decomposition. But this is very costly in terms of computational power and why bother solving the equations down to computer accuracy level, when your discretization error is much bigger anyway?

This is where faster iterative methods come in: they start by “guessing” an initial solution, which could even just be a standstill flow field, or “zero velocity” for every point. Then they linearize the equations around that point and improve the solution through iteration. If you iterate long enough, the flow field will converge to a stable solution, reducing the iteration error. The difference between this solution and the direct solution of the equations is called the iteration error.

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