Numerical Simulation of the Flow Field of a Confined, Submerged Slot Jet Impinging on an Oscillating Surface: A Parametric Study

Impinging jets are an attractive option for spot-cooling of high heat flux devices because of the stagnation region surrounding the point of impingement and the resulting high heat transfer. In small devices with a small jet (microjet) , however, the cooled region due to just a single jet is small. One way to potentially increase this area exposed to the impinging jet is by oscillating the heated surface. In the current paper, the flow structure and transport in a confined and submerged jet impingement arrangement impinging on a wall oscillating horizontally is numerically studied with respect to both parameters governing jet impingement :Jet Reynolds Number (from 40 to 200), distance from the jet inlet to the impinging wall (z/d ratios of 2 and 5) and an oscillation parameter (oscillatory peak Reynolds Numbers of 55 and 110). OpenFOAM v 2.2.2, an open-source CFD code based on the finite volume method is used to solve the problem. The Grid Convergence Index (GCI) is used to estimate discretization uncertainty and error bars on all of the parameters calculated. The flow structure in a confined submerged jet is made up of a double recirculation zone (mostly attributed to the confining top wall) the reattachment regions are associated with a secondary peak in the Nusselt Number. Heat transfer is not studied in this paper. The effect of the oscillating lower wall on the locations of the primary and the secondary recirculation zones are studied with respect to all the parameters mentioned above over a complete oscillation cycle. The local skin friction coefficients along different sections on the lower wall are computed along sections of the oscillating wall and compared to the case where there is no oscillation.The results are anticipated to have significant impact on the heat transfer enhancement possible in such an arrangement.