Numerical and Experimental Investigation of the Influence of the Wake Behind an Injector Frame on Jet Dilution in a Crossflow

In this paper, a mixing of gases through square Jets issuing normally Into a CrossFlow (JICF) is investigated by means of both numerical simulation and experiment. The jets are emitted by two injectors mounted at the top and bottom of an Injector Frame (IF) which is installed at the center of an Eiffel type wind-tunnel. This jet configuration makes it possible to approximate an industrial gas mixer placed at the center of a pipe. Large Eddy Simulation based on the Smagorinsky model is used, enabling characterization of the mean and fluctuating velocities as well as the oscillating flow frequencies. Different diagnostic techniques, such as Laser Doppler Anemometry and Particle Image Velocimetry are employed for validating the numerical models, and a good agreement between prediction and experiment is obtained. In the numerical simulation, introduction of a passive scalar through the jet makes it possible to show three dilution phenomena. They are generated respectively by the wake of the IF, the jet/wake assemblage and the jets alone in function of the momentum flux ratio between jet and crossflow. Influence of the various parameters on the mixing process between the jets and the crossflow is identified. The numerical results show that if the IF wake is suppressed with the presence of a trailing edge behind the IF, classical formation of Counter-rotating Vortex Pair is found.