Decreasing the action of a flow behind a weak shock wave emerging from a channel upon an obstacle

It is experimentally demonstrated that, if the flow behind shock waves outgoing from a channel is subsonic, the action of this flow upon an obstacle can be decreased by changing the shape of the output channel cross section. The results of numerical modeling of the experimental oscillograms show that, by replacing a round channel with a cross-shaped one, the excess action upon the obstacle in a quasi-stationary stage can be reduced by half. This decrease is related to energy dissipation in a three-dimensional flow as a result of the interference of rarefaction and compression waves. The interference arises due to mass redistribution between various symmetry axes in the gaseous medium and due to the flow energy losses for the vortex formation at the channel edges, which are revealed by schlieren photographs. (C) 2005 Pleiades Publishing, Inc.