AirShaper

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Rivian claims a drag coefficient of just 0.30 for the Rivian R1T. That's much lower than the typical 0.45-0.50 for cars like the Ford F150 and alike.In this video, we'll goo over the details of how they did this.

---Smooth underfloor---
On a conventional ICE (internal combustion engine) truck, many of the drive train components are exposed. This creates quite a lot of aerodynamic resistance as the air flows underneath the car. On the Rivian, they have covered almost the entire underfloor with flat, smooth panels. This greatly reduces the turbulence & drag generated.

---Smooth exterior---
Door handles have been made flush and the design in general doesn't feature many external bits of geometry sticking out. This helps to keep the flow attached to the surface.

---Air deflectors---
Ahead of both the front & rear wheels, air deflectors help to guide the air around the tires, reducing the "head on collision" of the air on the tires. They likely also help to bridge the wheel well area.

---Air curtain---
Inside the front bumper, air gets accelerated through channels which exit in the front wheel wells. This stream of air acts as an air curtain, shielding the rotating wheels. This reduces the drag generated by the wheels, which typically act as large mixers.

---Air breathers---
A slot/channel connects the rear of the front wheel wells to an open channel at the bottom of the door panels. This helps to evacuate some of the high pressure air in the wheel wells and provides a stream of air that ends up at the rear wheels.

---Cabin spoiler---
The spoiler at the cabin helps to "contract" the flow both in top view and side view. The flow lands onto the closed cargo bed, ahead of the trailing edge of the cargo bay. The spoiler also features slots which help to accelerate the flow / draw more air downward into the wake.

---Gaps---
At the top of the right A-pillar we detected more turbulence than the same area at the left A-pillar. Upon closer inspection, we found that there actually was a misalignment of panels, causing this flow problem.

A massive thanks to A2MAC1 (https://www.a2mac1.com/) for providing us with the 3D scan of the Rivian R1T. Just contact us if you want to purchase this or another analysis using their 3D scans.

Rivian R1T Aerodynamics - Is the claimed drag coefficient of 0.30 correct?

For more information, visit https://www.airshaper.com or email info@airshaper.com
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In this video we go over some of the coolest scenes of the Top Gun Maverick movie which include aerodynamics effects.

The first one is about the Dark Star, the plane in which Maverick is going for Mach 10. The plane itself is supercool and was conceptualized together with Lockheed Martin. But I was left with one question: when he is at around Mach 9, he makes a turn! Why would you make a turn when you are going for a top speed record? That would result in massive G-forces on both the plane and the pilot, only to generate extra drag and slow it down. Perhaps I am missing something, perhaps they did the same with the X-15 back in the days, but it felt like a dragster taking a corner.

The next scenes involve the F18, a fairly dated fighter jet used by the Top Gun pilots in this movie. One is where Maverick pulls up from low level flight. Pulling up like this creates massive vortices which are nicely captured by the dust on the ground.

Another scene is where the pilots are speeding up, breaking the sound barrier at Mach 1. You can hear the sonic boom and you can also visually see the planes going through some sort of white disc - or a vapor cone as they call it. It has long been thought that this cone was the actual sound barrier, but it is not. The air is first compressed and heated up by the first shockwave. Behind the shockwave is the expansion wave, lowering the pressure again. If there is enough humidity, the water vapor will condense and form the white cone you can see. After that, the air is compressed again by a second shock wave, eliminating the vapor.

And then there is the famous Cobra maneuver, or dynamic deceleration. If you are being chased by the enemy, you can abruptly raise the nose of the plane to a more or less vertical position. At such an extreme angle of attack, the plane momentarily goes into stall and will act like an air brake, slowing it down. After the chasing airplane has passed underneath you, you pull the noise back down and resume level flight, only now you are in the chasing position. 

A final remark relates to motorbikes, one of our favorite areas of development. As you may know, the rider on a motorbike creates a large wake behind him, dragging air along. Filling that void with something that is slightly smaller than the rider itself and is closely attached to it to maintain a nice flow can help to reduce the wake, boost efficiency and reduce fuel consumption. So when taking Penny for a ride on the back of his motorcycle, Maverick was probably thinking of the environment.

Top Gun Maverick Aerodynamics - Our Top Scenes Analyzed

For more information, visit https://www.airshaper.com or email info@airshaper.com
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In this fourth part of our video interview series with NASA on the X-57 Maxwell Electric Aircraft, we discuss what it will be like to fly this electric aircraft.

The high lift propellers provide extra lift for the wing, but they also produce forward thrust. This can feel a bit strange and therefore multiple control modes have been introduced.

One of them is called Air Speed Sending: as the aircraft speeds up, the high lift propellers provide more thrust and lift for take-off. Once the velocity is high enough for the wing to produce enough lift on its own, the torque on the high lift propellers is reduced again. Finally, they are shut down and folded back all together when the airplane is in cruise mode.

The other way around, as the aircraft is preparing for landing, they are first switched on at a low torque & rpm, just to know they are there. As the airplane slows down on the approach corridor, the torque is increased and more lift and thrust are generated. This increased lift helps to limit the sink rate and the extra thrust can help offset the increased drag as the airplane slows down to regions within the backside of the power curve.

In terms of scaling, the batteries don't scale so well. So this technology, using batteries, could be interesting for 10-19 seaters for example. Beyond that, the energy storage can become a problem. But the electric propulsion itself does scale well, as you can simply put more high lift propellers on a larger wing, on top of increasing their size, combined with a hybrid powertrain.

You would then not have the energy efficiency benefits of the battery, but the aerodynamic benefits of the electric propulsion are still there.

Electric Aviation - NASA interview on Maxwell X57 - Part 4: Electric Flight Experience

For more information, visit https://www.airshaper.com or email info@airshaper.com
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In this third part of our video interview series with NASA on the X-57 Maxwell Electric Aircraft, we dive into the details of cooling.

The X-57 requires around 90-100 kW in cruise versus 250 kW during take-off. This variation in loading strongly determines the sizing, the cells, the layout etc. of the battery.

Everything is directly air cooled on the airplane. The battery is passively cooled. The cooling of the inverters and motors poses quite a big challenge. They reach their operating temperature within seconds, so it's important to minimize the amount of rejected heat as well as understanding the cooling requirements across the flight envelope.

Electric Aviation - NASA interview on Maxwell X57 - Part 3: Battery and Component Cooling Design

For more information, visit https://www.airshaper.com or email info@airshaper.com
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In this second video in our series with NASA, we dive into the details of the propellers and how they compare to other propellers seen on e-VTOLs for example.

The X57 features two very distinct propellers:
- High lift propellers: these increase the local airflow speed around the wing, providing it with more lift. They aim for a uniform flow velocity to create a predictable and reliable increase in lift.
- Cruise propellers: these are aimed at maximum efficiency and feature a higher axial flow speed at the tips of the propellers

Electric Aviation - NASA interview on Maxwell X57 - Part 2: Propeller Design

For more information, visit https://www.airshaper.com or email info@airshaper.com
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In this video, we walk around the Lightyear One solar car to analyze its aerodynamic features (it has a drag coefficient below 0.20!).

We also interview Tom Selten, the Chief Business Development Officer of Lightyear. He was the team manager of the winning Eindhoven solar race team in 2015. They raced Stella Lux, which was a family car for 4 people which triggered the Lightyear adventure.

Lightyear One - Solar Electric Vehicle - Walkaround & interview

For more information, visit https://www.airshaper.com or email info@airshaper.com
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In this first out of 4 videos on our interview with NASA, we discuss the basic layout of this novel electric aircraft.

The X-57 is the latest in the famous series of X-planes developed by NASA - their experimental aircraft like the X15.

Sean Clarke and Nick Borer give their take on the design of this aircraft. We discuss the benefits if distributed electric propulsion, especially in terms of new aerodynamic concepts that are being made possible.

Electric Aviation - NASA interview on Maxwell X57 - Part 1: New Aerodynamic Concepts

For more information, visit https://www.airshaper.com or email info@airshaper.com
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F1 in schools STEM challenge is a global competition in which students can design miniature F1 cars to race in straight lines. The cars are propelled by CO2 cartridges.

In this video, the Redline Racing team of the Parramatta Marist High School in Sydney explains how the competition works and how they used AirShaper to optimize their design.

To apply for the "AirShaper F1 In Schools" package and improve your F1 in schools car design, please visit:
https://airshaper.com/f1-in-schools

F1 in schools  - Aerodynamics

For more information, visit https://www.airshaper.com or email info@airshaper.com
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Rotating Wall Boundary Condition
The simplest form is the rotating wall boundary condition. Without rotation, the velocity of the airflow is always zero at the surface because of the no slip condition. The rotating wall boundary condition simply enforces a tangential velocity onto the surface of the rotating object. This velocity is equal to the distance from the center multiplied by the rotational velocity. The further you move away from the center, the higher the velocity.
This technique is very simple and doesn’t significantly change the cost of computation, as no extra equations are introduced and the flow can be solved in a steady state manner. It’s very suitable on surfaces that are tangential to the local direction of rotation.
At AirShaper, we chose this technique to take the rotating wheels of cars into account, as it’s a very robust solution. When you click a tire, the axis of rotation will be detected automatically, the components inside will be selected as well and the rotational velocity is automatically linked to the driving speed of the vehicle

MRF – Multiple Reference Frame
For more complex geometries with a lot of non-tangential surfaces, the more advanced MRF technique can be used. It stands for multiple reference frames. In essence, you create a separate region around the rotating object. Inside this region, for each point, you calculate the relative velocity, which is a combination of the absolute velocity and the rotational velocity.
The Navier-Stokes flow equations are then built on top of this relative velocity, which results in extra terms that take the Coriolis and centrifugal forces into account. So, you end up with a set of equations for the stationary region and another set for the rotating region.
This method is a bit more expensive in terms of computational cost, but still allows for steady-state calculations and it’s able to accurately capture the “instantaneous” flow pattern around a propeller for example.
At AirShaper, we chose to use this technique when adding rotating propellers to a simulation. When selecting a propeller, the central axis will automatically be detected. The direction of rotation can be flipped and the RPM can be set by the user. And it is possible to add multiple propellers to a single simulation 

AMI – Arbitrary Mesh Interface
This instantaneous flow, however, can depend heavily on the relative position of the rotating part versus the static part, like a propeller versus a strut. So, for very advanced simulations, there’s also the AMI technique, which stands for arbitrary mesh interface. In this technique, the mesh around the rotating object is actually cut and then made to rotate. This can only be done using transient simulations, as the rotation of the mesh is now linked to the actual time step. At the sliding mesh interface, the cells of the stationary and rotating mesh exchange information on the flow.

This technique is usually the most accurate, but also very demanding in terms of computational effort. It can also be challenging in terms of stability, as the mesh interface needs to be defined very well. This type of simulation usually requires a manual approach.

Our Latest Videos Gain aerodynamic insight by watching our videos

Rivian R1T Aerodynamics - Is the claimed drag coefficient of 0.30 correct?

Top Gun Maverick Aerodynamics - Our Top Scenes Analyzed

Electric Aviation - NASA interview on Maxwell X57 - Part 4: Electric Flight Experience

Electric Aviation - NASA interview on Maxwell X57 - Part 3: Battery and Component Cooling Design

Electric Aviation - NASA interview on Maxwell X57 - Part 2: Propeller Design

Lightyear One - Solar Electric Vehicle - Walkaround & interview

Electric Aviation - NASA interview on Maxwell X57 - Part 1: New Aerodynamic Concepts

F1 in schools - Aerodynamics

How to model Rotating Elements in CFD (computational fluid dynamics) using MRF, AMI and more

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