Flow Properties of Slotted Walls for Transonic Test Sections.
AERONAUTICAL RESEARCH INST OF SWEDEN STOCKHOLM AERODYNAMICS DEPT
Pagination or Media Count:
A theoretical and experimental study is in progress of the flow through slotted walls under a variety of conditions. The ultimate objective is to make possible accurate numerical computation of transonic flows around models in slotted test sections. This paper is concerned with a slot flow configuration typical of two-dimensional, low lift tests at high subsonic free stream Mach numbers. With the test section empty the slot flow is outwards, into the plenum chamber, and this remains true over a large part of the test section when the model is introduced. From oil flow pictures and pressure measurements in and around the slots it is concluded for the configurations investigated that the slot flow is slightly influenced by the presence of the wall boundary layer, that the flow within the slot is attached and approximately inviscid although influenced by boundary layer formation, that the flow enters the plenum chamber as a thin free jet and that the transverse velocity in the jet and slot is too large for a linear pressure drop equation to be sufficently accurate. When the slot flow turns back over the rear end of the model it may admit stagnant air from the plenum chamber into the test section the ability of the slot to maintain a pressure difference across the wall is then necessarily reduced. Based on these observations a tentative flow model is proposed, yielding a relationship between the pressure difference across the wall and the transverse velocity through the slots. Improved expressions for the coefficient of the streamline curvature term are obtained, accounting for the depth of the slot and the presence of a jet.
- Test Facilities, Equipment and Methods
- Fluid Mechanics