Aero Theory with Wouter Remmerie

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!

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.

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.

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.

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.

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 occurring in zones of detached air flow.

Testing on a '70s Volkswagen Beetle

We equipped 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 re-circulation 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.

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.

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! If you liked it, please click the like button below and if you have any questions or comments, just post them below the video!

In this video on drone design, we will be discussing air foils, the basic principles and how they apply to fixed-wing drone design. 

Drone types

Rotary wings, quad-copters, 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 airplane 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 airplane, 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 center 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.

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

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.

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.

Description is coming!

- For the full interview check out https://www.youtube.com/c/airshaper

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!

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!

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-be

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!

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!

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!