SOME RECENT EXPERIMENTAL STUDIES ON THE AEROELASTIC STABILITY OF THIN CYLINDRICAL SHELLS. PART I. AN EXPERIMENTAL STUDY OF THE SUPERSONIC FLOW FIELD OVER AN AEROELASTIC OGIVE CYLINDER MODEL WITH BOUNDARY LAYER CONTROL

Abstract : An experimental study was conducted as the first phase in a program to determine the influence of a compressible viscous boundary layer on cylindrical shell panel flutter. In the first part of the experiment, a study was conducted to provide data on the uniformity of the surface pressure distribution over the region of the flutter model where the thin cylindrical shells were mounted for the flutter experiments. The measured data confirmed that for all flow conditions above Mach Number 1.2, no significant pressure gradient existed over the region of the model where the flutter shells were mounted for testing. A study was then conducted to determine the effectiveness of the boundary layer control system for increasing the boundary layer thickness over the region of the model where the flutter shells were mounted. The boundary layer control system proved to be quite effective and under optimum conditions could increase the displacement and momentum thicknesses by a factor of 10. In general, the displacement and momentum thicknesses could be increased by at least 50% for most of the operating conditions of the wind tunnels by maximum activation of the boundary layer control systems. Finally boundary layer transition and profile similarity studies were conducted to determine the range of free stream flow conditions and boundary layer control activation rates where boundary layer profile similarity could be achieved over the test shell area of the model. The results indicate that similar laminar or turbulent boundary layer profiles can be maintained over the test region of the model for flow conditions where panel flutter can be expected to occur. (Author)