Investigations of Transonic Ludwieg Tubes Part 2 Starting Process in the Case of a Downstream Valve

Abstract

Among many types of transonic wind tunnels, transonic Ludwieg tube is the most suitable facility for very hiqh Reynolds number transonic testing. However, its starting process is quite complicated and the flow mechanism is not yet understood. In the present paper, the starting process of a transonic Ludwieg tube with a downstream quick-opening valve and a plenum exhaust system was experimentally investigated over a wide range of plenum chamber volumes and flow rates. The result shows that a steady and uniform flow in the test section is established when the mass flow rate through the porous wall of the test section becomes equal to that through the plenum exhaust system. Although this is the same as in the case of an upstream valve system, it has been also shown that the flow mechanism of both cases is quite different between the two.