The damping coefficient of a pressure wave under conditions of pulsating turbulent flow of gas in a channel

The available results of experimental and prediction studies of the damping coefficient and phase propagation velocity of waves under conditions of pulsating turbulent flow in a narrow channel are reviewed and analyzed. It is demonstrated that the concept of complex damping coefficient may be introduced strictly on condition of certain restrictions imposed on an oscillating and time average flow. The dependences of the complex damping coefficient on the oscillation frequency and on the Reynolds and Mach numbers of time average flow are analyzed. The calculations are performed using the data on the relative amplitude and phase of oscillation of the tangential wall stress, obtained with the aid of the turbulence model including the relaxation equations for turbulent viscosity and tangential stress. It is demonstrated that quasi-stationary models of turbulence are invalid in the region of relatively high frequencies. Numerical simulation based on the difference solution of a set of channel cross section-averaged equations of motion, continuity, and energy is performed with due regard for the experimental conditions and measuring techniques. The calculation results agree well with the experimental data.