kth_logo.gif

Article

Large Eddy simulation of a forced semi-confined circular impining jet.

Authors: Olsson, M., Fuchs, L.F.
Document Type: Article
Pubstate: Published
Journal: Phys. Fluids
Volume: 10   476-486
Year: 1998

Abstract

Large eddy simulations (LES) of a forced semiconfined circular impinging jet were carried out. The Reynolds number was 10/sup 4/ and the inflow was forced at a Strouhal number of 0.27. The separation between the jet inlet and the opposing wall was four jet inlet diameters. Four different simulations were made. Two simulations were performed without any explicit sub-grid-scale (SGS) model using 128/sup 3/ and 96/sup 3/ grid points, respectively. Two simulations were performed with two different SGS-models using 96/sup 3/ grid points; one with a dynamic Smagorinsky based model and one with a stress-similarity model. The simulations were performed to study the mean velocity, the turbulence statistics, the SGS-model effects, the dynamic behavior of the jet with a focus on the near wall region. The existence of separation vortices in the wall jet region was confirmed. These secondary vortices were found to be related to the radially deflected primary vortices generated by the circular shear layer of the jet. It was also shown that the primary vortex structures that reach the wall were helical and not axisymmetric. A quantitative gain was found in the simulations with SGS-models. The stress-similarity model simulation correlated slightly better with the higher resolution simulation than the other coarse grid simulations. The variations in the results predicted by the different simulations were larger for the turbulence statistics than for the mean velocity. However, the variation among the different simulations in terms of the turbulence intensity was less than 10%.