A Computational Study on X-33 Engine Noise

Prof. Kader Frendi

Department of Mechanical and Aeroospace Engineering
University of Alabama in Huntsville

September 29, 2000

Abstract

Experimental and computational results on the X-33 linear aerospike engine noise are presented. The experimental setup is such that the engine, located 18.3 m above the ground, has its exhaust plume diverted from a vertical position to a nearly horizontal position located 3 m above the ground using a J-deflector. Experimental measurements are made at several locations in the nearfield and midfield. An empirical model is derived that accounts for the non-axisymmetry of the engine exit plane. The model uses mean flow quantities obtained from a CFD computation using a turbulence model. Nearfield and midfield results obtained using the empirical model are in reasonable agreement with the experimental measurements. The empirical model was able to explain the source of a low-frequency peak observed in the nearfield spectra (near 10 Hz). In addition, the midfield directivity pattern and overall sound pressure levels given by the empirical model are in reasonable agreement with the measurements.