APPLICATION OF DIGITAL FOURIER-ANALYSIS IN PROCESSING DYNAMIC AERODYNAMIC HEATING MEASUREMENTS

A PRACTICAL application of a digital Fourier analysis (fast Fourier transform) in processing fluctuating heattransfer data was utilized in a wind-tunnel test program at Mach number 8. A 4-deg, half-angle cone instrumented with conventional heat gages was oscillated in pitch at an amplitude of 2 deg and frequencies up to 15 Hz. The gages had a time constant of approximately 120 ms, which was not sufficiently responsive to follow the motion, and the Fourier analysis was used to correct the gage outputs. These measurements were used to map the location of the boundarylayer transition front. The purpose of this paper is to describe in some detail the technique used in processing these transient heat-transfer measurements. A more detailed presentation may be found in Ref. 1. The results indicate that the Fourier analysis was a very powerful method for correcting dynamic heat-transfer measurements. © 1979 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.