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Case Study

One, two, three, GO! Reduction of aerodynamic drag by using surface structures

Branche

Sports

Customer

Austrian Bobsleigh & Skeleton Federation

Service

External Aerodynamics

Task

Reduction of aerodynamic drag. Time gain of a few hundredths in Olympic racing sports.

Solution

Re-design of racing suits by applying surface structure modifications at pre-defined areas of the suits.

Benefit

A tremendous reduction of aerodynamic drag by 4,2 percent achieved by using the tear-off edge effect.

Project details

Just imagine a steep ice channel, an athlete lying down, blazing down the track, headfirst, face down, only inches from the ice. The skeleton sled reaches a speed up to 150km/h (about 93mph) and a gravitation force of up to 5G. So, maybe you are familiar with that thrill-inducing pressure from rollercoasters but for skeleton athletes this is a daily routine. Skeleton sliders are looking for a maximum of acceleration while athletes sustain an enormous pressure on their bodies, competing for centesimals and medals. Being a gifted high-performance athlete steering the sled down a sheet of ice using only small shoulder and knee shifts is the one thing for medal-winning chances, but after all, technical ability is never the only defining factor in top performance. If you don’t get the maximum out of your equipment, you’re missing out on a massive competitive advantage. Over time, sporting equipment has evolved because for a peak performance you must push the envelope. That’s why we at bionic surface technologies GmbH (BST) in cooperation with GRDXKN got the mission assigned by the Austrian Bobsleigh & Skeleton Federation (IBSF) to improve the racing suits for the bobsleigh and skeleton team.

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Figure 1: Dimples on textile . Photo ©GRDXKN

 

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Figure 2: Mesh Detail

Functional surfaces are of paramount engineering importance as they allow us, for example, to modify the surface of a material to improve its properties or to achieve new functionalities that the base material does not have. Positive effects can be reached by dimples or by the tear-off edge effect. Edges in surfaces of blunt bodies cause flow separation at certain points. Intentionally produced changes of the direction and position of the detachment of the boundary layer from the surface into a wake can have positive or negative effects. The scope is to reduce the air resistance by achieving that the flow around the object changes propitiously. Whether an earlier or later separation on a certain area is favorable can be determined by conducting numerical simulations. We calculated the applicable flow dynamics for the racing suits and minimized the separation zone by adding a concave structure that induced a flow separation in the area. Finally, GRDXKN printed the concave surface structure on the racing suits. The optimized surface structure reduced the air resistance and enhanced the aerodynamic performance considerably. This aerodynamically effective tear-off edge yielded an incredible reduction of 4,2 percent.

Outcome

Bionic surface technologies GmbH and GRDXKN, created in close co-operation specialized racing suits, designed to support the aerodynamic properties. We optimized the contours of the racing suits on certain, pre-defined areas reaching a positive effect by minimizing the separation. Amazingly the change yielded a reduction of 4,2 percent giving the athletes a technical advantage over the competitors.

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Figure 3: Flow Visualization