Evaluation of biomimetic approach to drag reduction of time trial helmet using computational fluid dynamics

Abstract

Computational fluid dynamic (CFD) using OpenFOAM are performed to investigate aerodynamics of a time trial bicycle helmet. Mesh generation by the two softwares OpenFOAM and Pointwise are compared, to detect differences between them. A new type of helmet, inspired by the shell of an armadillo is presented. Results are compared with earlier wind tunnel experiment to validate if simulations without the cyclist is feasible. Simulations have focus on drag force and how mesh influence the results. Results indicates the same tendencies as wind tunnel experiment performed with a helmet attached to human. Computational time will be saved running simulations with only the helmet. Quality check gave better results for the mesh created with Pointwise than for OpenFOAM. Pointwise’s properties converged with half of the amount of cells compared to OpenFOAM’s, and were less time consuming. Pointwise generated proper layers despite coarse far field, while OpenFOAM require finer far field to properly generate layers. The original helmet were modified by inverse kinematics, forcing a smaller frontal area. Results showed an reduction in air resistance at 22% and 13%.