Bicycle Aerodynamic Performance

HEEDS and Simcenter STAR-CCM+ help Trek discover better design solutions faster. Design space exploration enables optimization of bicycle aerodynamics and ride quality. Attacking this challenge in developing its Madone road bike, Trek applied computational fluid dynamics (CFD) together with finite element analysis (FEA) to set a new benchmark for aerodynamics in a bicycle that’s also comfortable to ride and handles smoothly. Aerodynamic performance is most influenced by the geometry of a bicycle’s tubular frame. Aerodynamic tube shapes typically have high aspect ratios, where the depth of the tube is two to three times greater than the width. This provides for a very aerodynamic profile, but the large section properties resist bending, like an I-beam, creating a harsh and unforgiving ride. To overcome this conflict, Trek engineers hit on the solution of separating the aerodynamics from the comfort with a tube-in-tube construction. This new way of designing a frame allowed them to design an outer tube structure optimized for aerodynamics with Kammtail Virtual Foil (KVF) tube shapes – an aerodynamic airfoil design that originated in the auto racing world. Meanwhile, an inner tube structure was optimized for ride comfort by FEA-based tuning of deflection and vertical compliance. These are the properties by which the frame cushions the rider from vibration and road surface irregularities.