Cloaking via heating: Approach to acoustic cloaking of an actuated boundary in a rarefied gas

• Published in: Physics of fluids (1994) Vol. 26; no. 6
• Main Authors: Manela, A., Pogorelyuk, L.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.06.2014
• Subjects: Acoustic propagation; Acoustic properties; Acoustic waves; Acoustics; Boundary conditions; Fluid dynamics; Gases; Heat flux; Heat transfer; Microchannels; Moving walls; Physics; Propagation; Rarefied gases; Sound generation; Sound propagation; Sound waves; Wave propagation
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.4884369

Existing studies on sound wave propagation in rarefied gases examine sound generation by actuated boundaries subject to isothermal boundary conditions. While these conditions are simple to analyze theoretically, they are more challenging to apply in practice compared to heat-flux conditions. To study the effect of modifying the thermal boundary conditions, the present work investigates the impact of replacing the isothermal with 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 prescription is demonstrated through comparison with counterpart results for isothermal boundaries. Analytical solutions are obtained for a gas at collisionless (highly rarefied) and continuum-limit conditions, and validated through comparison with direct simulation Mote Carlo predictions. Remarkably, it is found that prescription of heat flux at the walls, altering the energy balance within the medium, has a significant effect on acoustic wave propagation in the gas. In particular, when optimized with respect to the boundary acoustic signal applied, the heat flux condition may be used to achieve “acoustic cloaking” of the moving wall, a much desired property in classical acoustics.