V shape

Probably you already have seen it, during the start of the good weather and at the end of the summer birds travel with the nice weather. Birds that migrate in a flock often fly in a V shape. The reason for this is caused by the same effect that is also the reason why aiplanes have winglets.

Due to a pressure difference between the top side and the bottom side of the birds wings there will be a vortex generated at the end tip of the wings. This will create a down and up wash behind the wing tips. Birds flying in a v shape use this as an advantage during long flights. The second row birds will fly behind the leadings bird wing tips at a certain distance. The distance will be at a position where they are at the up wash region in the wingtip vortices. Because of this, the birds after the leading bird use less energy, because they can hover more due to the lift generated by the up wash. For example, when birds are flying in a flock of 25 birds, it will reduce the drag by 65%, as result that they can extend their range by 71%.

Because it is energy saving and to avoid the wake of the other planes, it is also used by fighting jets.

Streamlining principle

A company in California has been developing air and fluid movement products based on several natural designs like the Fibonacci sequence, logarithmic spirals and the Golden Ratio. If we look to these shapes, we can concluded that they will have lower resistance than common shapes that are used. These shapes align with the observation that the path of least resistance in this universe isn’t a straight line. This is also called the “Streaming Principle” and is being applied to fans, mixers, impellers and such that move air and liquids around in systems. Such fans on motors, compressors and pumps of all sizes and in all applications could save at least 15% of all the electricity consumed in the US. By using this kind of products, it will reduce electricity consumption massively and it will reduce the exhaust of CO2. So this is a benefit for nature and people too.

Here you can find an example company, who make parts based on this theory. http://www.triplepundit.com/2008/07/the-nature-of-efficiency-innovation-in-action-part-3-pax-scientific-extracting-the-mathematics-of-nature/

Termite shopping center

Another day, another interesting biomimicry example.

In Harare, Zimbabwe, you can find the Eastgate Centre building, a large shopping center. This building is quite fascinating because it has a self-regularting ventilation system that keeps the temperature at a comfortable level.

This passive cooling, without any fuel-based air conditioning, is inspired by thermal control found in termite mounds. Through tunnels, chimneys and using wind creating pressure fields, these macrotermitine termites maintain a constant internal temperature in the mounds. They control the air flow in such a way that the warm air generated in the core of the nest leaves the nest through narrowing shafts rising through the mound channel which accelerates the release of the warm air. Through openings at the base, cool air is drawn inside as the warm air flows up through the chimneys.

This isn’t an example that would come to mind when talking about aerodynamics, but here you can see that air flow doesn’t necessarily have to be related to mechanical stuff. It can also be an impressive technique to control the air flow while keeping a constant temperature.

Tubercle Technology

I found another example of biomimicry which improves the flow of air: wind turbines inspired by whales.

The flippers of the humpback whales have non-smooth leading edges which contradict the smooth leading edges of all our man-made aerodynamic blades.  The large, irregular looking bumps across the leading edges are called tubercules and maintain even channels of fast-moving water when it passes them. If smooth flippers would be used, the water flowing over those would break up into myriad turbulent vortices.

Wind tunnel tests of model humpback flippers with and without those tubercules across the leading edge proved that the tubercules were responsible for a reduction of 32% in drag, of 8% in lift and an increase of 40% in the angle of attack.

A company called WhalePower uses this technology for their fans and turbine blades. Their motto is also a nod to nature with the ‘A Million Years of Field Tests.’-part, which can also be read at the bottom of their website.

Winglets

Some more biomimicry from aerodynamic solutions that engineers got out of nature. When we look at the evolution of airplanes, they had to become always bigger and bigger, because more and more people wanted to travel with this transportation method. So more weight has to be kept in air. This is only possible when more lift will be generated. Because the lift is generated by the wings of the airplane, the wing span has to become wider. This has some disadvantages. First of all it will add more weight. Second it will be more difficult to keep the mechanical strength, because the wings become longer and more forces are induced on the wings. The last point is that airplanes will become too large to fly to airports, because the infrastructure is not adapted to the planes. So engineers looked for a solution and they found it by studying an eagle.

An eagle has the capacity to glide through the air without flapping with its wings. They also observed that, on a high altitude, the eagle curved its wing tips. When testing and simulating the curved wing tips, they learned that this reduces the drag that is induced by the lift and that is will increase the lift. Winglets were invented. The winglets prevent that a vortex that is generated under the wings, travels down to the side of the wing and curve on top of the wing. This is what reduces the lift. So by preventing that this will happen, the efficiency is increased and the wing span of the airplane can be less.

Karman Vortex

When designing and simulating an aerodynamic part, it is possible that you have to do with Karman Vortices. This is a phenomenon caused by an unsteady separation of the flow of a fluid around a part. The effect is only induced in a certain velocity range. It will create a repeating swirl behind the body. Like every swirl that is generated, it will cause drag and will then reduce the efficiency of the aerodynamic part.

This phenomenon can also be seen in nature. If you have wind to an isolated island with a high mountain, you can observe this vortex pattern in the clouds. Also you may observed this effect already somewhere else. This effect is the cause that a car antenna is vibrating at a certain speed of the car. A vibration of a cable that is hanging in the wind and generates a ‘singing’ noice, is also caused by this effect. To reduce the generation of the vortices, helical projections, like a big screw thread, can be placed on the part, like is done with some car antennas.

Some insects use the vortices to reduce their energy consumption. After the down stroke they turn their wings and the up stroke is done by the vortices that are induced. 

Bionic fish car

To give another biomimetic development in the automotive industry, DaimlerChrysler has designed a new concept car from Mercedes-Benz based on the shape of an odd tropical fish. A new bionic car is born. The car has such streaming lines, that it will also have the looks of the fish. Using the shape of the tropical boxfish, designers achieved an aerodynamic ideal that leads to 20% less fuel consumption and as much as an 80% reduction in nitrogen oxide emissions. The diesel powered car will get about 70 miles per gallon that is equal to 3.36 l/100km. The motor is so advanced that it has no problems with running on biodiesel. It’s been a few years since development, so we can hope this car will be produced in the future. It will give a much more clean transportation method.

Here you can find more information about it: http://news.mongabay.com/2005/0710-DaimlerChrysler.html

Kingfisher and owl train

Everyone has probably heard the story of the Shinkansen Bullet train that produced too much noise when it travelled through a tunnel due to an atmospheric pressure wave forced in front of the train. This happened because of the bullet shaped nose of the train. The solution to this problem was inspired by the Kingfisher birds and their streamlined beak which reduces the impact and allows the air and water to flow past the beak rather than being pushed in front of it.

However, another noise source was the pantograph above the train which is needed to receive electricity from the wires overhead. The solution to this problem was inspired by the primary feathers of owls. They have serrations which create small vortices instead of one large one. Similar structures were added to the main part of the pantograph, thus reducing the noise.

This is an example of how improving the flow of air has a positive effect on the environmental standards, since the train didn’t exceed the sound levels anymore after these changes were made.

Morphing wings

Using inspiration from both birds and fish, scientists developed a kind of morphing airplane wings that change shape depending on the speed and duration of flight. Different birds have differently shaped wings useful for the speeds at which they fly, as well as for sustaining flight speeds over long distances using the least amount of energy. The scientists built a compliant, shape-changing truss understructure for the wings, then covered it with scales that can slide over one another to accommodate the in-flight shape changes. When deployed in new aircraft (and drone) models, the wings are expected to conserve fuel and enable faster flights over longer distances. This technique can be used on planes that sometimes have to travel at a high speed and sometimes slow. For fast flying the wings has to be narrow, for slow flying long and thin.  The information about the experiment you can find here: http://www.sciencedaily.com/releases/2004/04/040422000037.htm

Like a shark through water

I don’t know if you have ever heard of biomimicry. Wikipedia describes it as the imitation of the models, systems and elements of nature for the purpose of solving complex human problems.

However, the thing I would like to share with you today isn’t about air, but about water.

For a long time now, scientist try to recreate nature in their lab, they tried it with spider silk, but they also tried it with shark skin. As can be read in this article, shark skin is a multifunctional marvel, which makes it possible for the animals to move efficiently through water. Their “smooth” skin doesn’t only reduce the friction drag, it also auto-cleans ecto-parasites from its surface so it stays “smooth”.

The 3D-printed shark skin nose of Formula Group T’s first car Areion

This engineered surface proved to be helpful in the medical and healthcare environment, where they are always looking for manners to reduce the number of microorganisms, and the correlated hospital-aquired infections. Since it is the shape of the surface preventing the attachment of organisms and not any chemical substances, there is a minimal risk of allergic reactions.

There are also surface coatings for boat hulls which emulate shark skin texture, which keeps the surface clean and thus the boat will be more energy efficient. One of positive consequences is that there are no longer toxic, biocidal chemicals necessary to clean the hull. And another consequence is that, because organisms have trouble attaching themselves to the boat, the transportation of invasive aquatic species from one place to another is greatly reduced.

Another example are swimsuits, but since not everyone agrees on their effect, I’m not going further into this.

In my opinion, sharks have become a lot cooler now.  I never knew their skin was so versatile. Here you can clearly see that an enhanced surface has more benefits than just a more energy efficient way of moving. I also think it is wonderful how we can look at nature and try to copy its solutions to solve our own problems and I will definitely be looking for more similar stuff about nature’s way of enhancing a fluid’s flow.