Analysis of the Overtaking Process between two Ahmed body models

Abstract

The overtaking process is the common phenomena encountered in our daily life It has significant effects on the stabilities of the moving vehicles The study conducted the wind-tunnel tests with the Ahmed body models to provide available experimental data for validating the physical model and numerical method set for the simulation of the overtaking process Three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations were applied to the simulation with ANSYS Fluent The computational domain and the mesh size required for the accurate simulation are investigated by comparing with the experimental data It is found that the outlet must be located sufficient far downstream such as x/L = - 10 91 The physical model employed in the simulation such as the turbulence model was also investigated through comparison with the experimental results It is shown that the k-ω SST turbulence model can yield a satisfactory prediction of the flow field Study of overtaking process pointed out that the drag force coefficient of the overtaken car reaches its maximum at the normalized relative distance between two cars (x/L) of around - 1 while the drag force coefficient of the overtaking car reaches its maximum at 1 This study also indicated that the side force coefficient of both overtaken and overtaking cars are changed greatly during the overtaking process of x/L from – 1 5 to 1 Effects of relative velocity and transverse spacing between the overtaken and overtaking cars on the drag force coefficient and side force coefficient are examined It is appointed that greater relative velocity and narrower transverse spacing are higher drag force and side force coefficients on both overtaken and overtaking cars are

Date of Award	2019
Original language	English
Supervisor	Keh-Chin Chang (Supervisor)