Some Experiments on a peripheral Jet GEM

Observation of Horseshoe Vortex and Its Influence on Drag Characteristics.

Abstract

Some experimental results are reported in this paper for a simplified peripheral jet GEM. The first phase concerns the flow pattern around the GEM, where the tuft-grid method has been used. Many instructive photographs are obtained which show a single horseshoe vortex around a GEM. The second phase contains measurements of pressure distribution on the GEM upper surface, The external drag is obtained by integrating the pressure distributions. Significant (about one-third) reduction of parasite drag has resulted from the influence of the peripheral jet over a wide speed range; inspection of the pressure distribution shows that the drag reduction occurs both at the front and rear of the GEM.