On Similarity of Turbulence Statistics of a Turbulent Planar Jet Taking the Static Pressure into Account

Abstract

The pressure gradient in a jet is usually regarded as negligibly small when deriving the streamwise velocity profile from the momentum equations. In addition one assumes that the bulk streamwise momentum is conserved in the streamwise direction. On the other hand, it is known that the pressure distribution in the jet is well balanced with the square of the lateral velocity fluctuation, indicating that pressure is not negligible in the lateral momentum equation. The purpose of this study is to determine the importance of the pressure in the jet by evaluating balances in the streamwise and lateral momentum equations from experimental data measured by a static pressure tube and an X-probe. The turbulence fluctuations and the static pressure indicate similarities in their lateral distributions and are well balanced in the streamwise and lateral momentum equations. Although the contribution of the static pressure to the streamwise momentum is small, it is of the same order as that of the turbulent statistics in the lateral momentum equation.