A Study of Radial Underexpanded Jet by Shadow and Schlieren Photography

When an underexpanded jet impinges normally on a flat plate, the so-called plate shock forms in front of the plate and downstream of the shock the flow spreads radially on the wall. The flow field of underexpanded impinging jet has been studied elsewhere and the shock wave patterns, different modes of oscillation etc, were examined so far. Compared to these studies, the flow on the wall, i.e. the wall jet, are investigated less because of the complicated nature of the flow field where it includes the oblique shock waves with various modes of shock oscillation, asymmetric flow patterns under certain conditions, etc. In the present paper a study on the flow pattern of the wall jet has been carried out. Mainly the optical techniques such as schlieren and shadow photography are applied in the experiment to visualize the flow field.