Effects of Viscous and Thermal Losses on Radiation from an Infinite Plate

Abstract

This paper is concerned with the behavior of sound radiation from bending waves of an infinite plate in a fluid with viscous and thermal losses. The radiation field variables are obtained through a solution of the equation of motion for viscothermal fluids. Acoustic energy flux in the fluid is investigated, with particular emphasis on its behavior near the plate surface. Energy flux is shown to change direction in a region near the plate. The motion of the particles orbiting in elliptical patterns also exhibits a similar change of direction as a result of viscous and thermal losses. A notable effect of the viscothermal losses is the radiation of acoustic power from the plate below the critical frequency.