Engineering Models for Aerodynamic Noise Environments

Abstract

Engineering models have been constructed for several aerodynamic noise environments typical of those exciting random vibratory response on aerospace vehicles during subsonic, transonic, and low supersonic flight. Data for these models were obtained from the publications of various investigators. The data are nondimensionalized with respect to common parameters, so that statistical properties of the various environments may be compared directly and some insight into the physical phenomena producing differences between the environments may be obtained. The specific models presented describe the fluctuating wall pressures produced on smooth surfaces by subsonic turbulent boundary layers with zero, mild-adverse, and mild-favorable mean-pressure gradients; supersonic turbulent boundary layers; and oscillating shock interaction with separated flow in the vicinity of compression corners at supersonic speeds. Nondimensional statistical properties used to describe the models are fluctuating pressure coefficients as a function of free-stream Mach number, pressure spectral densities, stream-wise and transverse root-coherence and phase, and convection/free-stream velocity ratios. [This work was performed under contract for NASA, Manned Spacecraft Center.]