Steady and unsteady computation of a two-dimensional upwash jet

Computational procedures and results of an upwash jet arising from two opposing plane wall jets based on the Reynolds averaged Navier-Stokes equations are discussed. For the calculation of the flow, a steady and an unsteady numerical approach were taken. For the steady computation, we adopted various eddy viscosity models(the standard k-epsilon model, the RNG k-epsilon model and the Bardina's model) and the Reynolds stress transport model with various diffusion term closures. Results of the steady computation indicated that the jet halfwidth was very much underpredicted, and hence the velocity profiles of the upwash jet were in very poor agreement with the experimental data. We found, however, that the velocity profiles nondimensionalized by the jet half width and the maximum velocity appeared to be in good agreement with the experimental data, which could be misleading. When an unsteady approach with an unsteady version of the standard k-epsilon eddy viscosity model was taken, a periodic oscillation of the jet was observed. The jet half-width distribution obtained by taking the time average of the periodic velocity profiles was found to be in much better agreement with the experimental data.