The Mako shark is one of the fastest animals on the planet. Thanks to evolutionary adaptations acquired over millions of years, it can move between 60 and 80mph through water.
This is possible thanks to its skin, which is not smooth, but rather made up of small tooth-like scales, just 0.2mm long. These scales can bristle, or flex backwards while swimming if the water flow changes. This allows them to control what’s known as flow separation, and reduce drag.
Flow separation is an effect that takes place when a solid object moves through liquid. The object acquires a boundary layer of liquid around it, resulting in increased drag. The Mako shark’s scales, known as denticles, can change direction to disperse the forces around it. They can move as much as 40 degrees, and are being replicated through 3D printing.
This is not the first instance of research into flow separation: the fur on a tennis ball and the dimples in a golf ball are both examples of innovations which delay flow separation, allowing the objects to travel further and faster through the air.
This phenomenon is now being applied to the field of aviation, helping to make planes that can fly faster thanks to improved drag-resistant coatings. The practice of taking inspiration for technical innovations from nature is known as biomimicry.
The scales can not only decrease drag, but increase lift. This has exciting potential for the aviation industry.
The research team printed denticles and applied them onto an aerofoil, testing it inside a water flow tank. Twenty different arrangements of sizes and positions were used, trying to find the optimum design and layout. They found that arranging them to act as low profile vortex generators dramatically increased lift.
Applying this principle in the design of an aerofoil on a plane could in theory increase performance by 300%, and cut fuel costs by 1%, which would translate to around $1.5 billion annually for the commercial aviation industry.
This research is being funded by Boeing and the US Army. Airbus tested something similar back in the 1990’s, but it wasn’t replicable at scale. However, thanks to new manufacturing technology, the denticles can now be produced faster.
One of the main problems with this technology is that the texture on the plane would need to be kept clean in order to get the desired result. A buildup of dirt would damage the scales’ ability to move. Washing a plan every time it lands takes a lot of time, and would impact how many flights could take off each day.
The texture must also maintain structural integrity, avoiding erosion or abrasion from dust and sand. Planes are routinely assaulted by tiny particles moving through the air at great speed, and over time this can wear away elements of the outer layer of the aircraft.
This technology may well change the future of the industry, creating planes that fly faster using less fuel.
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