Numerical and Experimental Analysis of Unsteady Separated Flow behind an Oscillating Car Model

The objective of this research is to improve the understanding of unsteady three-dimensional separated flows on bluff bodies. This research focuses on the analysis of the instability and safe maneuverability of passenger vehicles associated with unsteady atmospheric crosswind conditions. Experimental and numerical analysis were performed on the squareback Willy car model animated by an oscillating yaw angle in a steady wind. Experiments were carried out at a Reynolds number of 0.9 10(6), a frequency of 2 Hz, with an amplitude of Delta beta = 10 degrees at the Conservatoire National des Arts et Metiers (CNAM). Unsteady wall pressures were obtained with sensors located inside the model. Computations were performed at the Ecole Centrale de Nantes (ECN). The ISIS-CFD flow solver, developed by the CFD Department of ECN, used the incompressible unsteady Reynolds-Averaged Navier-Stokes equations. Experimental and numerical comparisons are completed with numerical simulations at a larger yaw angle. The analysis of the physics of the unsteady flow around the model is done through the calculation of aerodynamic forces and moments, and cross flow velocities.