Organisation Et Depouillement Automatique Des Mesures Dans Les Deux Soufflerier a Arc De L'Onera

Abstract

Several unique conditions are imposed upon measurements made in ONERA hotshot wind tunnels: the duration of flow; the environmental conditions; the circumstances under which the tunnels are used. Flow durations between 40 and 100 milliseconds are produced, and this imposes demands upon transducer performance. Instantaneous power consumed by the tunnels is of the order of 200 megavolt-amperes, and this places the transducers and portions of the readout system in an electrical environment wherein elaborate shielding precautions are required. The contract arrangement under which the tunnels are operated necessitates their use in testing for an optimum number of runs within a half-day of operation, and this necessitates the use of highly automated readout apparatus. This paper describes the solutions to these and other hotshot instrumentation problems. Methods of measurement and readout of pressure, forces, and rates of heat transfer are discussed, and systems for calibration are presented. Many elements of the calibration and readout processes have been made largely automatic. Errors contained among data representing the measurement of forces are sufficiently small as to be considered negligible in the face of minor uncertainties in readout constants. Measurement of pressures is conducted to an overall accuracy (including calibration and readout) of 2.5%. Heat transfer calibrations of 5-10% accuracy are imposed, and overall accuracy of heat transfer data ranges between 15 and 20 percent.