An Experimental Study on an Underexpanded Annular Impinging Jet

Abstract

An underexpanded annular impinging jet is studied experimentally and it is shown that the aerodynamic characteristics of the impinging jet depend significantly on the distance H between the nozzle exit plane and the impinged flat plate. The annular impinging jet diverges in the downstream direction provided H is smaller than a critical value H_C. The feature of the jet changes significantly at H=H_c. The stream lines issuing from the inner edge of the annular nozzle join at a point upstream of the impinged plate. However, a vortex ring may appear on the plate even for H>H_c depending on the magnitude of loss in the stagnation pressure at the jet axis.