2D CFD study of cross-section foils performances in cycling aerodynamics

Abstract

In cycling aerodynamics the NACA airfoil and teardrop shape have been widely used on bicycles recently However both of their aerodynamic performances are still being questioned in low Reynolds number range (30 000-80 000) due to early flow separation and vortex generation The aim of this project was to find a new geometric design providing better aerodynamic performance compared with the traditional symmetric NACA airfoil and teardrop shape at a certain Reynolds number range using 2D Computational Fluid Dynamics (CFD) By studying the flow separation point aerodynamic coefficients and flow development on many different foils having the same chord length and thickness we defined all the important geometric parameters influencing the performance Our final CFD results gave us a new geometry called TE (Truncated Ellipse) which follows most of the Kammtail principles The TE shows a much lower drag coefficient along the chord direction of the foil compared with the symmetric NACA airfoil and the teardrop shape At low yaw angles (? 10 degrees) the performance is better the TE foil is acting as a bluff body and thus the flow separation is delayed At higher yaw angles (>10 degrees) the aerodynamic drag coefficient combined with an extremely high aerodynamic lift coefficient give a much lower drag coefficient along the chord direction This high aerodynamic lift is given by the separation bubble found on the TE at a high yaw angle This research has implications on the future prospects of aerodynamic bicycle design Keywords: Cycling aerodynamics CFD Flow separation Aerodynamic coefficients Streamlining

Date of Award	2014 Jul 25
Original language	English
Supervisor	Jiun-Jih Miau (Supervisor)