Modal Acoustic Impedance of an Infinite Cylindrical Source Immersed in an Unbounded Thermoviscous Fluid

A modal impedance matrix is formulated for an infinite cylindrical source undergoing axi-symmetric oscillations in a thermoviscous acoustic medium. A matrix based method is used to gen-erate the surface-force curves. At first governing equations of the acoustic fields in the thermovis-cous fluid are manipulated to yield the well-known Helmholtz equations and corresponding wave numbers. Equations of radial and meridional velocities and the excess temperature are also derived. In addition, the classical relations for radial and meridional stresses and the heat flux are written as potential based equations. Velocities and the excess temperature as well as the stresses and the heat flux at the surface of the source are expressed as Bessel series with unknown coefficients. The gen-eralized Fourier series solution for the field equations with unknown coefficients are substituted in the potential based equations to find the matrix relations between the coefficients. Eventually the modal impedances for three first modes are calculated and plotted as a function of distance from the source surface. Numerical results for immersion in glycerol and olive oil are obtained as examples. Considering the thermoviscous effects (i.e. thermal waves) in cylindrical coordinates can be re-garded as the main contribution of the present work to the previous ones

کلیدواژه ها:

thermoviscous fluid ، acoustic impedance ، cylindrical source