Acoustic fields in binary gas mixtures: mutual diffusion effects throughout and beyond the boundary layers.
The acoustic behavior in thermo-viscous gas mixtures, both in proximity of walls and far from them (outside the boundary layers), involves deviations from the adiabatic and laminar movements in pure gases, which result from the influence of several diffusive fields, namely, shear, entropic, and concentration variation fields (their energy being provided by the acoustic field itself). Owing to the boundary conditions, that are slip condition, isothermal condition and concentration flux vanishing on the walls, a strong coupling between these fields occurs inside the boundary layers while their effects appear to be simple additive processes in the bulk of the medium. Although recent literature on this subject leads to interesting results, opening the way to several new issues [R. Raspet et al., J. Acoust. Soc. Am. 105, 65-73 (1999); R. Raspet et al., J. Acoust. Soc. Am. 112, 1414-1422 (2002); G. W. Swift and P. S. Spoor, J. Acoust. Soc. Am. 106, 1794-1800 (1999); D. A. Geller and G. W. Swift, J. Acoust. Soc. Am. 111, 1675-1684 (2002)], the results available still have limitations because they do not provide complete solutions for the propagative and diffusive fields throughout and beyond the boundary layers. The present work aims at providing these solutions in the whole domains considered. The results allow interpreting analytically the behavior of the fields above mentioned in closed cavities and ducts, and particularly in spherical cavities which are best suited to develop metrological applications.
Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91 10135 Torino, Italy. c.guianvarch@inrim.it
Cécile
C
Guianvarc'h
Michel
M
Bruneau