Experimental Study of Unsteady Wakes Behind an Oscillating Car Model

This research focuses on the analysis of the instability of passenger vehicles associated with transient crosswind gusts. A new vehicle model, created to analyze the behavior of unsteady wakes on bluff bodies, is proposed. The tests presented here were performed on a squareback model animated by an oscillating yaw angle in a steady wind. The initial unsteady results were obtained for a yaw angle of 10°, a Reynolds number close to 10⁶, and a maximum value of the Strouhal number of 0.07. The analysis of unsteady total-pressure tomographies and unsteady particle-image velocimetry (PIV) shows the presence of phase shifting and hysteresis that evolve as a function of the Strouhal number. This work was performed in the framework of a collaboration between the Conservatoire National des Arts et Métiers, (CNAM), the Ecole Nationale Supérieure de l’Aéronautique et de l’Espace (SUPAERO) and the European automotive constructor Peugeot Citroën SA.