An experimental and analytical study of a new flap valve for generating simulated sonic booms

Abstract

The design, operation, and performance of a sonic boom simulator, featuring a radically new dual-flap valve and electromechanical control system, are described. This new flap valve with its large maximum throat area (160 cm 2) was designed to regulate the air flow from a low pressure reservoir (up to 0·2 atm overpressure) into the apex of a large pyramidal horn (25 m long, 3 m × 3 m base), where the incoming low speed air flow (up to 150 m/s) produces a travelling simulated sonic boom or N-wave with relatively little superposed high frequency noise. As a consequence, the full scale simulated sonic boom is virtually free of superposed jet noise, a major advance over past work with such horn-type simulators. Additionally, an advanced gasdynamic analysis of the reservoir coupled with an advanced acoustic analysis of the wave motion in the horn is presented to predict the characteristics of the simulated sonic boom—wave form, amplitude, duration, and rise time. Predicted and measured overpressure signatures are shown to be in excellent agreement.