The transient cavity flow

The use of cavity reveals many problems related to the application of weapons storage mechanisms, as the opening of doors at subsonic and supersonic speeds produces high intensity noise which could damage the internal stores and surrounding cavity structures. Furthermore, the flow inside the cavity could cause a considerable drag force on the object. The objective of this thesis is to explore experimentally the effect of the door kinematics in the transient phase of the cavity flow. Transient wall pressure at 12 pressure taps which are arranged in a line along the centreline of the cavity floor are measured in a very low-speed wind tunnel facility. Data were acquired for two opening door mechanisms – one appliance has a vertical doors opening mechanism with a longitudinal hinge, and the other one is a lateral sliding opening mechanism. In both cases, the door movement has been observed to affect cavity pressures over a long period of time, before reaching steady levels. A passive flow control (cylinder) was also demonstrated to act effectively in the shortening of the transient phase. These studies have been supported by the flow visualisation, and a preliminary use of Particle Image Velocimetry (PIV)