Yi Mao
James M. Sabatier
Richard Raspet
Natl. Ctr. for Phys. Acoust., Univ. of Mississippi, University, MS 38677
Previous results of a theoretical study [J. Acoust. Soc. Am. 96, 3254(A) (1994)] of the sound propagation in a cylindrical tube indicated the sound attenuation due to the evaporation-condensation process underestimated the experimental results in porous materials. Some modifications have been introduced into our theoretical model for solving the discrepancy. First, the fundamental equations in a gas--vapor mixture are resolved including relaxation processes. Again four modes---acoustical, thermal, vorticity, and mass-diffusion modes---are obtained. Second, the temperature on the wall is no longer kept constant; the wall has a finite heat capacity and heat can conduct within the wall. The sound field propagating down the tube was determined by applying the modified boundary conditions to a superposition of the newly obtained four modes. The effects of each individual modification on the sound attenuation due to evaporation-condensation are examined. [Work supported by ONR.]