Bulk Viscosity, Thermoacoustic Boundary Layers, and Adsorption Near the Critical Point
Keith A. Gillis, Iosif I. Shinder, Michael R. Moldover
We measured the resonance spectrum of an acoustic resonator filled with xenon near its critical temperature Tc. We reduced the effect of gravity on the xenon by convective stirring to achieve a temperature resolution of (T-Tc)/Tc 7 10-6. The data yield accurate values of xenon s speed of sound, acoustic dissipation, and thermal conductivity. Linear acoustics, including the frequency-dependent bulk viscosity from renormalization-group theory, predicts the dissipation within the thermoacoustic boundary layer peaks at characteristic temperatures. The peak was not observed. We show that critical-point adsorption is one mechanism that can suppress the peak.