Modal Analysis and Flow Control on a Reduced Scale SUV

Abstract

In this work, the aerodynamic performances of a reduced scale vehicle characterized by a fully detached flow on the rear end and measured in a wind tunnel, are investigated in order to check the efficiency of active flow control using pulsed jets, implemented on the rear bumper. Here, the pressure increase on the tailgate by the optimum blowing conditions is confirmed with drag forces reduction, measured using a force balance. This flow control result is obtained using a genetic algorithm technique with a reactive loop. Integral scales of the pressure spectra and characteristics of the vortex structures enable then to propose a flow control model applied to set the amplitude and the frequency of the pulsed jets. The understanding of the pressure increase on the tailgate involves cross correlations with velocity fields on specific cut planes in the wake. Amplitudes of dynamic modes linked to the instantaneous pressure and velocity fields enable to check the most efficient blowing frequencies related to the jet location. The Dynamic Modal Decomposition (DMD) technique is used to get these modes and could be introduced in the optimisation loop in order to improve the energy efficiency of this active flow control system.