スパコンによる大規模計算に基づいた自転車の集団走行の空力評価

抄録

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.