抄録
A jet with higher stagnation pressure than a certain critical value becomes underexpanded. It is known that underexpanded jet can produce a high-frequency sound known as screech, which has been studied so far. However its mechanism has not fully explained yet. Impingement of such a jet on an object can be found in various fields in industry. Impingement on a flat plate has been much studied, but the study has been mostly focused on the jet immediately downstream of the nozzle and not the wall jet on the plate. The disturbance generated at the wall jet is very much likely to affect the main jet. Thus it is necessary to examine and discuss the flow pattern and the behavior of the wall jet for the mechanism of the screech in the main underexpanded jet. In the present study in order to simplify the flow field of wall jet downstream of the main underexpanded jet, two colliding jets under equal condition are used. The flow field is visualized with schlieren and shadow graph technique.
