Force Measurement Using an External Drag Balance in a Shock Tunnel

Abstract

An external force balance was considered as a system to measure aerodynamic drag in an impulse facility, and was then calibrated, and tested. The stress wave force balance technique was employed to measure aerodynamic drag because, in an impulse facility, the test time is on the order of milliseconds. Using a system impulse response function, which was obtained by conducting dynamic calibration processes with impulse loads, the aerodynamic drag of a test model was reconstructed from strain gauge signals. Inertial forces caused by a test model support exposed to the flow were compensated using filtered acceleration signals, and the effective vibrating mass of the system. Experiments were conducted in a shock tunnel at a nominal freestream Mach number of 6. The test model was a simple sharp cone. The measured force characteristics were then compared with a numerical simulation and found to agree well within a margin of error.