An evanescent wave array for wavenumber calibration
Harvey Charles Schau, L. Dwight Luker, Sarah E. Petrie, Arnie Lee Van Buren · The Journal of the Acoustical Society of America · 1986
A transmitting array that is designed to generate specified evanescent pressure fields near the array is described. The pressure fields are convective in nature, moving parallel to the plane of the array with a phase velocity that is slow, i.e., less than the speed of sound in water. A slow phase velocity corresponds to a spatial wavenumber k which is greater than the corresponding acoustic wavenumber in water. Such an array can be used to obtain the response of extended acoustic sensors to high-wavenumber pressure components such as exist in turbulent flow fields. Two small prototype planar arrays have been designed and constructed. The first one utilizes the piezoelectric polymer (PVDF) as its active material while the other one utilizes a Neoprene-lead titanate composite material. The positive electrodes on both arrays are segmented into independently driven areas by use of equally spaced stripes. Experimental results obtained for the prototype arrays are compared with computer model predictions. [Work partially supported by ONT.]