Hamid Oualli

VOLUMETRIC 3-COMPONENT VELOCIMETRY MEASUREMENTS OF THE FLOW FIELD ON THE REAR WINDOW OF A GENERIC CAR MODEL

Volumetric 3-component Velocimetry measurements are carried out in the flow field around the rear window of a generic car model, the so-called Ahmed body. This particular flow field is known to be highly unsteady, three dimensional and characterized by strong vortices. The volumetric velocity measurements from the present experiments provide the most comprehensive data for this flow field to date. The present study focuses on the wake flow modifications which result from using a simple flow control device, such as the one recently employed by Fourrie et al. [1]. The mean data clearly show the structure of this complex flow and confirm the drag reduction mechanism suggested by Fourrie et al. The results show that strengthening the separated flow leads to weakening the longitudinal vortices and vice versa. The present paper shows that the Volumetric 3-component Velocimetry technique is a powerful tool used for a better understanding of a threedimensional unsteady complex flow such that developing around a bluffbody.

Experimental investigation of an actively controlled automotive cooling fan using steady air injection in the leakage gap

In an axial fan, a leakage flow driven by a pressure gradient between the pressure side and the suction side occurs in the gap between the shroud and the casing. This leakage flow is in the opposite direction to the main flow and is responsible for significant energy dissipation. Therefore, many authors have worked to understand this phenomenon in order to reduce these inherent energy losses. Up to now, most of the studies reported in the literature have been passive solutions. In this paper, an experimental controlling strategy is suggested to reduce the leakage flow rate. To this end, a fan with hollow blades and a specific drive system were designed and built for air injection. Air is injected in the leakage gap at the fan periphery. The experiment was performed for three rotation speeds, five injection rates and two configurations: 16 and 32 injection holes on the fan’s circumference. The experimental results of this investigation are presented in this article.