A Moire Pattern Technique for the Detection of Shockwaves.

摘要

An optical means of detecting and recording the structure of shockwaves formed in air is presented. The system is based upon the use of a special case of moire fringes and approaches the sensitivity usually associated with Schlieren type optical instruments. It has,in addition to a high sensitivity, a ruggedness and ease of use which makes it suitable for field-type applications. The moire pattern technique presented here is,for a specific piece of equipment,theoretically capable of sensing a 0.01% density change in air at atmospheric pressure and corresponds to a pressure differential of the order of 0.003psi (about 0.2 millibar). Pictures showing a pressure differential of the order of 0.08psi (5.4 millibars) have been made. No special attempts were made to record smaller pressures. (Author)