Numerical evaluation of 2D and 3D parallel unsteady confined dual air jets

A numerical investigation was performed at two Reynolds numbers to compare the flow and heat transfer characteristics for a pair of parallel impinging slot jets in 2D and 3D. The present study continues the authors\´ earlier work [1], and identifies the main similarities and differences arising from the expansion to the third dimension. For comparison purposes, a couple of slot jets impinge on two constant heat flux sources. Two Reynolds numbers have been selected, namely 100 and 300, such that the jets are steady at the lower Reynolds number flows for both the 2D and 3D models, and unsteady for the higher Reynolds number flow simulations. As before, both simulations are in the laminar regime. The steady cases at Re =100 show that the 3D slot jets produce similar values as the 2D case, and the flow indicates a symmetrical, steady flow hydrodynamic pattern with the jets being deflected laterally. By further increasing the Reynolds number to 300, a complex and highly unsteady flow develops for both the 2D and 3D simulations. The complex flow patterns reveal the vortex pairing effects observed before for the 2D flows, leading to the jets "buckling and sweeping" behavior. However, the 3D unsteady jets produce results that deviate from the 2D unsteady case due to the 3D effects, which are more pronounced than for the steady flow. The relevant differences between the 3D spatial behavior versus the 2D planar behavior occurring for the unsteady flows are documented by comparing field plots and the Nusselt number on the target wall for the cases under evaluation. Plots of the velocity, vorticity and temperature fields for both 2D and 3D cases are provided together with a discussion of the results.