Turbulence structure of a counter-flowing wall jet

Although several studies have been carried out to analyze the characteristics of counter-flowing wall jets (CFWJs), their internal turbulence structure is yet to be fully understood. In this paper, a CFWJ issuing into a main flow is numerically examined using a three-dimensional, unsteady, improved delayed detached-eddy simulation. The results of the simulation are validated with the experimental results and are presented with pertinent discussions. The interaction of the jet with the wall and the main flow leads to the oscillation of the stagnation point (SP), further enhancing the turbulence. The analysis of the instantaneous flow field reveals the presence of a feedback mechanism between the stagnation region and the shear layer of the counter-flowing wall, resulting in the excitation of the jet. This feedback mechanism is responsible for the oscillation of the SP. To further evaluate the internal structure of turbulence, the coherent structures within the flow are identified using a vortex identification criterion. These structures are also quantitatively evaluated using proper orthogonal decomposition. The analysis of the coherent structures revealed the presence of large-scale structures in the vicinity of the SP. The complex dynamics of these structures and their interactions is presented with pertinent discussions. Published under license by AIP Publishing.