Aerodynamics Study on a Bicycle Configuration for Group Race Using Large-scale Simulations by a Supercomputer

Abstract

The drafting is a main strategy to reduce aerodynamics drag in bicycle race, and the effect of the drafting is drastically affected by a positioning of the cyclists in the running group. We perform aerodynamics simulations to study a bicycle configuration for group race. The simulations adopt locally mesh-refined lattice Boltzmann method (LBM) with coherent-structure Smagorinsky model (CSM) to calculate the turbulent flow around the bicycles as a large eddy simulation (LES). Each calculation took 1 or 2 day(s) to get a result of 4 seconds in physical duration. First, we calculate an isolated cyclist test for a validation. The results of drag area show good agreements with experiments in both of the cyclist with the upright and the drop posture. Second, we evaluate the drafting effect in a group 4 cyclists. We revealed that the drafting effect on the trailing cyclist is enough gained when the longitudinal distance from the leading 3 cyclists to the trailing cyclist is less than 1 meter. We also found that the drafting effect on the trailing cyclist is strictly affected by the lateral distance rather than the longitudinal distance in such small gap. Finally, we execute a large-scale simulation of the group of 72 cyclists.