STEADY AND UNSTEADY COMPUTATION OF A 2-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 an d an unsteady numerical approach were taken. For the steady computatio n, we adopted various eddy viscosity models(the standard k-epsilon mod el, the RNG k-epsilon model and the Bardina's model) and the Reynolds stress transport model with various diffusion term closures. Results o f the steady computation indicated that the jet halfwidth was very muc h underpredicted, and hence the velocity profiles of the upwash jet we re in very poor agreement with the experimental data. We found, howeve r, that the velocity profiles nondimensionalized by the jet half width and the maximum velocity appeared to be in good agreement with the ex perimental data, which could be misleading. When an unsteady approach with an unsteady version of the standard k-epsilon eddy viscosity mode l was taken, a periodic oscillation of the jet was observed. The jet h alf-width distribution obtained by taking the time average of the peri odic velocity profiles was found to be in much better agreement with t he experimental data.