Pressure Oscillations Produced in a Wind Tunnel by Hinged Plates in the Walls of the Test Section

摘要

For a study of the feasibility of producing suitable pressure oscillations in a supersonic wind tunnel for testing inlets under gust conditions, the linearized partial differential equation for the perturbation velocity potential was solved for the unsteady flow downstream of oscillating wind tunnel walls. The boundary conditions were satisfied on the mean position of the walls which were assumed to be rotating sinusoidally through small angles about the upstream edges. The amplitude of the pressure and density oscillations in the test rhombus was computed for several values of the reduced frequency, defined by the product of the angular frequency of oscillation and of the time for the fluid to travel a distance equal to one half the wind tunnel height. The pressure amplitude was found to be fairly uniform in the test section when the reduced frequency was less than about 1/4 at a free stream Mach number of 2.4. For larger values of the reduced frequency, the pressure amplitude varied throughout the test rhombus, the degree of variation increasing with the reduced frequency. (Author)