Flow dynamics and mixing of a turbulent gaseous jet into oscillating crossflow

The flow dynamics and mixing a gaseous jet into a crossflow is numerically investigated under conditions with externally imposed oscillations from the crossflow upstream region. A broad range of forcing frequencies and amplitudes are considered. The analysis is based on a large-eddy-simulation (LES) technique, with special attention given to the near-injector and near-wall turbulence treatment. Detailed information about the flow structures and mechanisms that dictates the flow evolution is obtained by means of the proper orthogonal decomposition (POD) analyses. Results reveal that the dominant structures in the stationary crossflow case, with jet Strouhal numbers around 0.1 and 0.7, have been suppressed by the excitations. The flapping and detaching movements, bearing the forcing frequencies and their subharmonics, become the dominant phenomena as the forcing amplitude increases. These induced motions lead to a longer and narrower jet plume in any transverse plane and a lower "center of gravity" within the scalar field, which substantially modify the mixing efficiency.