Bending the Limit Part 3

Some techniques have been discussed so far as to how to possibly lower the drag of a car. One without a lot of adaptions and one that requires a more intellectual approach. However, there is one more adaptation one can make without too many changes that has been the topic of a lot of discussions. Namely removing the side view mirrors and replacing them with side view camera’s.

 

The principle behind this is fairly easy to understand. The side view mirrors cause a (small but noticable) increase in frontal area and actually has quite a lot of drag. This drag force has a quadratically proportional to the speed, thus 2 highly energy consuming elements at high speeds. On the other hand, rear view camera’s and LCD’s are very cheap nowadays and don’t consume a lot of energy. Having that said, installing and implementing the camera’s is not as simple and should be left for those who have a lot of knowledge on how to do this. For example, the camera should be lag free, shouldn’t be influenced by noise, isn’t allowed to fail (dangerous to drive without being able to see next to you)

 

A lot of pro’s and cons should be weighed against eachother to see if it can be done safely and if it’s beneficial. Below,  you can find an article where a calculation is done to show how the differences.

 

Source: http://gas2.org/2013/08/23/learning-from-elon-what-if-ford-went-mirrorless/ 

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Theory vs practice

Back in the first post on this blog, I posted a video regarding misconceptions in aerodynamics. Somewhere around the second half of the video, a device is discussed that could ‘eat away’ the vorticity at the wingtips to prevent vortices from forming. The creation of these vortices is caused by induced drag and is happens when air flows from the low pressure area to the high pressure area over the wingtip, creating a circular motion, causing the air to spiral.

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However, in the video itself, the lector is vague around the design of such device. A few weeks ago at the JEC fair in Paris, I actually came across a company that had developed such a device and claimed to have gotten significant results of up to 6% net gain usage of the entire plane. It is interesting to see that, a technology that was deemed useless, suddenly shows up with pretty good results. There are some remarks that have to be made when looking at the results.

For example, the pathlines shown on their website are only the ones closest to the wing, so it’s not certain if the entire vortex has been eliminated or only the small part directly at the wingtip. So it’s hard to draw conclusions from this. Secondly, the technology was shown on many fairs, starting from 2003. More than 10 years later, the technology still hasn’t been applied to modern airplanes. If this technology is really that good, why hasn’t it been used already?
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Source: http://www.aviationpros.com/press_release/10779593/minixcr-solution-for-energy-efficiency

A small step forward

More and more car companies are focussing their attention to greener technologies to sustain a better tomorrow. One of such technologies is electric actuators instead of fuel engines. Not only do fuel engines pollute (a lot), their efficiency is remarkably low while compared to electrical motors, who have been noted to have efficiencies of up to 97.5%. However, to be really effective, EV’s should have to happen on a large scale.

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This idea led Kia to the development of the Kia Ray EV. The target was to develop a mass producible EV to launch in a highly populated country, being Korea. Despite having pretty good specs (click the link below), the vehicle didn’t really break trough. After the first batch in 2012, not a lot of these cars have been sold. This was because the Ray was sort of the predecessor of the KIA Soul which was planned to be distributed mid 2014 in Korea as well. If we compare the two, one thing immediately catches the eye. The KIA Ray looks like a cube, meaning it’s not aerodynamic … at all. If we compare this to the KIA Soul or the Renault TWIZZY, we can see that these EV’s have spent a lot more attention on this aspect, which is still one of the major losses in a car.

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Since the car is about to be released in a few months and it’s goal is to sell 5000 pieces by the end of this year in Korea alone. We’ll have to wait and see if they’ll succeed in their plans.

 

Source: http://www.engadget.com/2011/12/22/kias-ray-ev-hasnt-heard-about-aerodynamics-sets-out-to-defy-n/

Biomimicry at its best.

These days, the human mind has been conditioned in a number of ways. If one talks about aircraft, one automatically thinks about airplanes, helicopters, military fighter aircraft, … However, what this basically comes down to is people automatically think about either ‘stationary’ wings, turbines and propellers. Stationary wings do have a few moving parts to influence the created amount of lift, but are not what causes lift to happen. This is normal, because when we look up in the sky, this is exactly the only things we see.

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However, if we look up, we actually see another type of aircraft: the birds. What is special about them is the way they propel themselves through the air. Instead of stationary wings, they flap their wings to propel them forward. This of course is nothing new, everybody knows how birds transport themselves. however, one might wonder if this could also be applied to manmade machines that mimic the their way of transport.

As the video below already might suggest, this was indeed possible. With the help of Festo, which is specialized in electric and pneumatic transducers, a team of engineers made a robotic bird which can fly around the same way real birds do. This just goes to show that nature indeed holds a lot of answers to certain problems we are faced with and that it’s definitely worth looking into. The industrial applications of this are probably nonexistent, it’s hard to imagine an airplane that flies around using this as propulsion. However, this indicates that there are still other possibilities than what the modern day has already discovered. You can watch the entire video below:

Bending the Limits Part 2

As stated in the previous post, aerodynamical adaptions are a very efficient way of boosting a vehicles performance. The following technique is a lot more complicated than the bio-mimicry discussed before, however this method holds great promise. The biggest difference is that one should make a whole lot of adaptions and is not something just anyone can accomplish. The technique is called ‘Boundary layer suction’.

Without going into too much detail, the boundary layer is the region closest to an object wherein the speed internally differs. In other words, one ‘layer’ of air has a different speed than the layer immediately above or below it, which results in viscous friction. This flow in general is closely attached to the surface and doesn’t let go, however, this layer can separate from the surface and causes a large increase in drag. This happens for example when the angle of attack of a wing becomes too high and stall occurs.

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The idea behind boundary layer suction is that one sucks away this layer before it has the chance to separate. This not only increases the extent to where the flow stays attached, one also is able to extend the range of the laminar flow, decreasing the drag even more. However, this suction also costs energy, so one should try to calculate the net gain in energy before considering this technique. It holds great opportunities for aerospace, but would it be something also applicable to cars as well?

Bending the Limits Part 1

If one wants to boost the performance of their vehicle, improving the aerodynamics is a very good way to do it. However, people who are not well known with the principles of aerodynamics don’t know that, even if they don’t wish to alternate the initial shape of their car, they are still able to improve their performance without alternating the shape of their car.

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Without going too much into the details, when a car moves forward (or backwards), the air has to flow around the car so that the car can move through. This causes viscous friction between the car and the air which causes a force working against the movement of the car, thus slowing it down. This friction force is dependent on the surface the air is flowing over and therefore you can improve this drag force by alternating the surface.

In general, a rough surface is considered to be bad for the performance. However, there are some exceptions. If bio-mimicry has taught me anything, it is that looking at nature often has a lot of answers to a lot of the nowadays questions. Just by looking at animals who have to live in similar conditions, on might find how these animals deal with such problems. The one that have gotten a lot of attention lately are sharks. Sharkskin has a special pattern that improves the flow around them, meaning they have to use less energy to move around.

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These days, this pattern is also adapted  to swimsuits of competitive swimmers in order to boost their performance. So in theory, this should also be applicable to cars. These days, a few are experimenting with applying this technique on vehicles and are getting good results. This way, a relatively simple coating could easily reduce the drag forces working upon cars and make them more efficient. So within a few years, you might be able to buy one of these with a coating already on it.

Made in Belgium

Since the start of our thesis, it became very clear to us that if you wanted to study something in the area of fluid dynamics, CFD software would almost always be a necessity. CFD stands for Computational Fluid Dynamics and indicates the branch of fluid dynamics where one uses numerical methods and algorithms to solve problems instead of a practical approach in windtunnels. Mostly when studies are conducted, a CFD study is done as a start or means for optimization with an actual case study in a windtunnel for verification of the results.

When it comes to CFD software, there are 2 main names you come by very often, being ‘Ansys Fluent’ and ‘OpenFOAM’. Although both do a very good job, there are some key differences. For example, Ansys works with a license based package, has a very good GUI and is fairly easy to use. OpenFOAM however is an open source software, has a very limited GUI, mostly runs on scripts and runs on Linux, which makes it harder for starters to work with the software.

However, a third player is slowly but surely making its way into the market: Numeca. It’s a Belgian company located in Brussels which was founded in the 1992. They are nowadays present on a broad spectrum of industries, going from Aerospace to even Healthcare. The company started off as a Spin-Off of the Vrije Universiteit Brussel and now has offices worldwide. One of the software’s that caught my eye was the ‘AutoGrid’ which is capable of applying a high quality mesh for a number of application. Since the results of CFD are highly dependent on the quality of the mesh, this tool is very helpful to increase the accuracy of the results, if used properly of course. A quick example can be seen below:

Chances are you will hear a lot more of this company in the coming years.