Experimental verification of the opposite effect of fluid loading on the velocity of dilatational waves in thin plates and rods

Abstract

In a recent paper [J. Acoust. Soc. Am. 102, 3478 (1997)], it was demonstrated by analytical means that radiation loading increases the velocity of dilatational waves in immersed thin plates, but decreases it in thin rods. The main goal of this paper is to verify experimentally the predicted opposite effect, which is particularly interesting because in almost every respect, the lowest-order dilatational modes of wave propagation in thin plates and rods are very similar. Experimental verification of the predicted small radiation-induced velocity change is rather difficult, partly because of the accompanying strong attenuation effect caused by radiation losses, and partly because of the presence of an additional velocity change caused by viscous drag even in low-viscosity fluids like water. In spite of these inherent difficulties, the presented experimental results provide unequivocal verification of the earlier theoretical predictions.