PROJECTS

Sport Aerodynamics

A skijumper with V-style

The interaction between a performing athlete and the surrounding atmosphere is termed sport aerodynamics. Various forces will come into action and it is convenient to categorize these into the following three groups:
A – Human power, drag force and friction (skater, biker, runner etc.)
B – Gravity, drag force and friction (downhill skier, toboggan, bob etc.)
C – Lift force, drag force and gravity (ski jumper, golf ball etc.)

In category A, an athlete can produce about 700 W over a time period of 40 seconds (500 m skater) or 300 W during 14.5 minutes (10 000 m skating). The drag force consumes 85% of the power output and the latter skater can reduce his running time by 1 second if he reduces the aerodynamic drag by 3.2 gram.
The speed skier e.g. can represent category B and the world speed record is around 250 km/h. The weight and the drag force are the dominant factors, whereas the friction between the snow and the skis is of minor importance. A downhill racer, however, attains lower speeds due to large variations in body position.
A ski jumper with V-style (category C) has a lift force of approximately 40 kilo during a flight in a 120 m ski jump arena of which half comes from the jumpers body. A reduction of 1 kg bodyweight will yield 2.4 meter more in jumping length.
Computer model of V-style ski jumper (see figure) where pressure distribution shows areas of suction (blue) which provides lift. White color denotes stagnation pressure. The close-up of the ski tip illustrates the vortex-generated lift on the skis due to optimum opening angle between the skis.