Flow features of the Ahmed body at a low Reynolds number

Abstract

This study investigates a low Reynolds number flow over the Ahmed body using the unsteady IDDES simulations at a low Reynold number of 1.4×104 based on the model height. The study is motivated by the lack of information in the literature on the Ahmed body for slant angles between 25° and 30°, especially for low Reynolds numbers. Therefore, the present study documents for the first time the basic flow characteristics in the transition angle range (TAR) for slant angles from 25° to 30° using time-averaged and instantaneous flow velocities. The results show that the width of the recirculation region on the slant surface decreases with increasing slant angle. Additionally, the length of the recirculation region on the slant surface increases with the slant angle, such that at 30°, it is 95 % of the slant length compared to 76 % at 25°. Furthermore, the vortex identification documents the complex system of the vortical structures and the changes due to the slant angles. Overall, the results confirm that low Reynolds number flows can reproduce the basic flow features of the Ahmed body for slant angles from 25° to 30° and help elucidate the mechanism of flow transition at a lower cost compared to that at high Reynolds numbers.