I. Design and application of piezoceramic transducers to transient pressure measurements. II. Some measurements of curvature and thickness of reflecting normal shocks at low initial pressures

摘要

A small pressure transducer, using the piezoelectric properties of a manufactured ceramic, was designed, constructed and installed in the end plate of the GALCIT 17-inch shock tube to obtain high-speed measurements of the pressure field behind a reflecting shock.The design problem for piezoceramic pressure transducers and some possible solutions are discussed in detail. Results of transducer calibration and recommendations for improvement of the instrument are presented.An initial program to determine the curvature of a shock at low initial pressures was run concurrently with calibration of five of the above pressure transducers. The results of this program are described in as much detail as the data obtained to date will permit.At an initial pressure of 30 microns in the GALCIT 17-inch tube, the shock obtained at a Mach number of about 7.5 in argon is observed to have a total curvature of approximately 10 millimeters, or approximately two per cent of the tube diameter. The shock thickness observed under these conditions is approximately 5 millimeters. These results indicate that it may be entirely possible to obtain good optical measurements inside the shock, but that it may be necessary to resort to special techniques to avoid optical distortion caused by curvature.