A comparison of accelerometer and piezofilm-based force balances for hypersonic shock tunnels

Abstract

A blunt double-cone model, equipped with a three-component accelerometer or piezofilm-based force balance system, is tested in the IITB-Shock Tunnel at 0 º and 10 º angle of inclinations during force measurement experiments. Conventional accelerometer force balance theory and soft computing-based adaptive neuro fuzzy inference system have been adopted to recover the axial and normal forces. In order to arrive at the time varying forces, these balances are calibrated using impulse hammer tests at single or multiple points. Necessity of multipoint calibration has also been demonstrated during recovery of forces for both the balances. Genetic algorithm in conjunction with adaptive neuro fuzzy inference system has been implemented herein to train the system for force prediction. Encouraging agreement has been noted between the predictions made using accelerometer force balance theory and adaptive neuro fuzzy inference system-based recovery of forces from accelerometer and piezofilm balances. Thus, present studies not only provide the methodology for calibration and implementation of piezofilm based force measurement, but also recommend its usage in short duration impulse facilities.

Assessment of drag measurement techniques in a shock tunnel

“…This can be achieved by performing the comparative assessment of the techniques under the specific test environments, based on the rigorous understanding of each technique's characteristics and experimental application. Although comparative studies between two of three force measurement techniques have been conducted [22][23][24][25], the direct comparisons and discussions of all three techniques regarding the system setup's key factors and the appropriate range of test model sizes for the technique's application are insufficient.…”