Turbulence energetics in an axisymmetric impinging jet flow

Abstract

Turbulence energetics is investigated in the impingement and wall jet regions of an axisymmetric impinging jet flow, by using the two-dimensional particle-image velocimetry measurement technique. The inlet-based Reynolds number is equal to 5200, and the height to the diameter ratio is equal to 5.95. This study shows that turbulence kinetic energy balances in outer, middle, and inner layers of the impingement region differ greatly from each other. The balances in near-field and far-field wall jet regions differ, as well. This study also provides various useful insights into the directional characteristics of the energy transports. For example, it has revealed that the turbulence diffusion process transports energy in the upstream direction in the jet core, but obliquely in the mixing layers. The balance terms are decomposed into physically meaningful spatial components, which, among various other insights, show that the negative production rate that is earlier reported in the stagnation region is caused by the negative work contributions of the radial and the tangential Reynolds stresses. This study, overall, lets us have a thorough understanding of the turbulence production, the convection, the turbulence diffusion, and the viscous diffusion processes, while the turbulence dissipation and the pressure diffusion terms are clubbed together and obtained as the residual of the energy balance equation. Information that is extracted from the residual has demonstrated the failure of Lumley's model to estimate the pressure diffusion rate near the impingement surface.