LARGE EDDY SIMULATION OF THE INTERACTION BETWEEN WALL JET AND OFFSET JET

The interaction between a plane wall jet and a parallel offset jet is studied through the Large Eddy Simulation (LES). In order to compare with the related experimental data, the offset ratio is set to be 1.0 and the Reynolds number is 1.0×10⁴ with respect to the jet height and the exit velocity. The Finite Volume Method (FVM) with orthogonal-mesh (6.17×10⁶ nodes) is used to discretize governing equations. The large eddies are obtained directly, while the small eddies are simulated by using the Dynamic Smagorinsky-Lily Model (DSLM) and the Dynamic Kinetic energy Subgrid-scale Model (DKSM). Comparisons between computational results and experimental data show that the DKSM is especially effective in predicting the mean stream-wise velocity, the half-width of the velocity and the decay of the maximum velocity. The variations of the mean stream-wise velocity and the turbulent intensity at several positions are also obtained, and their distributions agree well with the measurements. The further analysis of dilute characteristics focuses on the tracer concentration, such as the distributions of the concentration (i.e., C/C₀ or C/C_m), the boundary layer thickness δ_c and the half-width of the concentration b_c, the decay of the maximum concentration (C_m/C_m) along the downstream direction. The turbulence mechanism is also analyzed in some aspects, such as the coherent structure, the correlation function and the Probability Density Function (PDF) of the fluctuating velocity. The results show that the interaction between the two jets is strong near the jet exit and they are fully merged after a certain distance.