Investigation of the flow past finite wedges of 20 deg. and 40 deg. apex angle at subsonic and supersonic speeds, using a Mach-Zehnder interferometer with appendix: sensitivity and accuracy of the interference method applied to pressure measurements

Abstract

An investigation has been made in the high-speed wind tunnel A 7 of the Luftfahrtforschungsanstalt. Brunswick, of the flow past finite wedges of 20 deg. and 40 deg. apex angle at both subsonic and supersonic speeds, the Mach numbers lying between 0.6 and 0.85 on the one hand, and between 1.4 and 2.8 on the other. The pressure distributions on the models have been evaluated from photographs of density contours obtained by the use of a Mach- Zehnder interferometer. The interferometer technique is briefly described, and also the method of evaluation of the photographs. The results are discussed in detail, and are compared with the theoretical predictions of Maccoll and Codd. A selection of photographs, and a number of diagrams showing the pressure distribution, are included. In the Appendix, the sensitivity and accuracy of the interference method applied to pressure measurements are discussed. It is shown that requirements for both, in the particular case of the A 7 tunnel, are satisfied in a range of Mach numbers between 0.5 and 3.0.