AirShaper

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.

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

For more information, visit https://www.airshaper.com or email info@airshaper.com
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Also check out Fluid Mechanics 101:
https://www.youtube.com/channel/UCcqQi9LT0ETkRoUu8eYaEkg

On Aidan's channel, you can also find the uncut, full length video of this interview:
https://youtu.be/Ntl15C2KXCQ
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For this video, we interviewed Aidan Wimshurst, who did his PhD at Oxford University (United Kingdom) on Tital Power Generation.

Concept
Tidal currents originate because of the tides: as water levels change, water flows from one area to another. When the water needs to fit through a narrow channel or move around certain coastlines, flow speeds can be quite high. These streams are very predictable, which makes it much easier to integrate the energy they produce into the grid.

The general idea is to take a typical 3-bladed wind turbine and put it under water. But there are a number of key differences to wind turbines that make tidal turbines unique.

Wing tip vortex
On an airplane, the air at the high pressure location below the wing wants to move to the low pressure location at the top of the wing via the side (the wing tip). This creates a curling motion called wing tip vortex.

On a turbine, this vortex also exists but it leaves a spiral trace instead of a linear one. And this increased vorticity & turbulence can impact turbines further downstream. It also represents efficiency losses for the turbine itself, which is why some (wind turbine) blades are equipped with winglets.

Cavitation
If pressure is reduced below the vapor pressure, you will start getting bubbles. When these implode, they can cause serious damage to the blades, structure, and so on. The risk of cavitation is reduced when the hydrostatic pressure is high, close to the sea bed. But close to the surface, this hydrostatic pressure is much lower, increasing the risk of cavitation. So the risk of cavitation varies along a single revolution.

Farm layouts
For a given plot of land, the goal is to maximize energy and thus put as many turbines as possible in place. But if you put them too close to each other, the turbulent wake of one turbine will lower the efficiency and lifetime expectancy of other turbines, so there is an optimum to be found.

With tidal energy, the orientation of the flow is always the same, only changing direction between tides. So these are typically placed in an array. The flow around a turbine is accelerated, meaning that a turbine placed in this accelerated flow will yield more power, ánd the original turbine will also perform better. This is called constructive interference. This will be analyzed in the MeyGen project.

Size trends
Compared to wind turbines, the constraints are different for tidal energy. The water depth is typically between 20 and 50 meter, so that limits the rotor size. Also, the velocity shear (difference between the velocity at the bottom and free water surface) poses strong bending loads on the rotor.

Suitable sites
Tidal energy will never be able to provide the full energy demand of a country, but it can provide a valuable contribution. And it's also very useful for remote sites, which are typically islands, as they have difficult access to other sources of energy.

Tidal Stream Turbines - Renewable Energy from the Tides

For more information, visit https://www.airshaper.com or email info@airshaper.com
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For this video, we interviewed Derek Dorresteyn, CTO at Damon Motorcycles (https://www.damon.com).

Hyperdrive platform
The case of the battery is the main stressed component of the motorcycle, which means they got rid of the traditional motorcycle frame. It has reduced mass, the stiffness can be tuned and it provided more room.
Higher top speed, faster acceleration and far less rotating mass compared to an ICE motorcycle. It’s a really simple motor-gear reduction and this reduction in rotating mass significantly reduces the apparent mass, which otherwise adds forces that resist the vehicle leaning over and changing direction. Without the added forces, the bike feels much lighter in corner transitions.

Cooling
The electric drive train is far more efficient: 85% efficiency for the electric drivetrain versus 30% efficiency for the internal combustion engine. But the threshold temperature of a battery pack is much lower than that of a combustion engine, which again increases the required size of the radiator. Both more or less cancel each other out, meaning you end up with more or less the same radiator size.

Range
There is a lot of variability in the shape and size of the people that will be on the motorcycle, but also the way they interact with the bike can be different. For the optimization work in terms of drag, they have used a standard rider in terms of height and mass combined with the SAE J2982 drive cycle.

Aerodynamics
If they made a vehicle with the lowest possible drag coefficient, it likely would not be very commercial. So they have this tension between current design trends, consumer taste and the desire to improve aerodynamic performance.
The aerodynamics are extremely important: if they wouldn’t care at all, the range would just be half of the claimed 200 miles.

Our Latest Videos Gain aerodynamic insight by watching our videos

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

Tidal Stream Turbines - Renewable Energy from the Tides

How to Design Electric Motorbikes - Interview with Damon Motorcycles

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