Abstract:

The fundamental problem of thermoacoustic streaming in the presence of a rigid sphere in a strong standing acoustic field has been treated analytically. As a first step the compact sphere assumption is made, and the corresponding governing equations developed in dimensionless form to allow for a consistent treatment of all the energy-exchange mechanisms. It is found that the interaction of the strong acoustic field with the rigid boundaries of the sphere is capable of inducing a second-order time-averaged temperature distribution, in addition to the well known second-order time-averaged fluid motion. The associated temperature gradients cause localized heating and cooling effects on the surface of the sphere, even in the complete absence of any externally applied temperature potential. The role of a little known second-order thermal expansion coefficient is pointed out. A careful analysis of this conjugate problem coupling the solid--fluid time-averaged transport effects could help in the measurement of this second-order thermodynamics modulus. [Work supported by NASA.]