Effect of molecular rotations on acoustic properties of a two-fluid medium

The effect of molecular rotations on the dispersion of the speed of sound and the absorption factor is theoretically analyzed for mixtures of diatomic and monatomic gases with disparate molecular masses. Two types of mixtures are considered: 1) the molecules of the diatomic component are significantly lighter than the molecules of the monatomic gas, and 2) the monatomic molecules have a smaller mass. The calculations show that the effect of rotational relaxation on acoustic characteristics in the range of frequencies close to the critical value can by ignored in the first-type mixtures, whereas the energy exchange between the rotational and translational degrees of freedom of molecules has a considerable effect on the propagation of forced acoustic oscillations in the second case.