Approach to Acoustic Cloaking in Rarefied Gases

We consider the effect of modifying the thermal boundary conditions on an acoustically excited boundary, from commonly used isothermal conditions to heat-flux conditions, on propagation of acoustic waves in a microchannel. The linearized problem is formulated for an ideal hard-sphere gas, and the effect of heat-flux conditions is demonstrated through comparison with counterpart results for isothermal boundaries. Analytical solutions are obtained for a gas at collisionless and continuum-limit conditions, and validated through comparison with direct simulation Mote Carlo predictions. It is found that prescription of heat flux at the walls has a significant effect on acoustic wave propagation. in particular, when optimized, heat flux conditions may be used to achieve "acoustic cloaking" of a moving wall, a much desired property in classical acoustics.