Analysis of the Fluctuating Flow Parameters in a Turbulent Jet in Mixing and Noise Formation Processes

The special features of the dynamic processes accompanying the fluctuating flow in the mixing layer of a subsonic turbulent jet are analyzed on the basis of the available experimental data. The analysis is based on the well-known relation for turbulence generation in a uniform gradient flow (without regard for viscosity) using the experimental data on dimensionless distributions of average parameters characterizing the velocities and the fluctuation intensities in a plane mixing layer. The possible determination of the mixing layer properties in a turbulent jet invoking an analysis of the jet-induced flow is also considered. It is shown that mixing layer expansion is governed by the ratio of the correlation between the fluctuations of the longitudinal and transverse velocities to the general fluctuation intensity. The determination of the main characteristics of the flow under consideration requires taking account for the dynamic interaction between the jet and the ambient medium due to a decrease in the static pressure in the mixing layer. In this case, the velocity fluctuation intensity is related with the induced inflow into the jet and can be determined. On the basis of an analysis of the decrease in the static pressure in the jet the characteristic dimensions of large-scale inhomogeneities in the fluctuating flow in the mixing layer producing acoustic disturbances are confirmed.