A Comparison of LES and RANS in a Simulation of Colliding Plane Jets
|Forfattere||Tomas Brockmann, Hannu Koskela, Panu Mustakallio, Timo Siikonen|
|Redaktør||Vojislav Novakovic, Sten Olaf Hanssen, Hans Martin Mathisen|
AbstraktThe collision of plane jets between ceiling-mounted active chilled beams is studied in the present paper. Draught problems are often caused by the deflection of an attached ceiling jet downwards into the occupied zone. As computational fluid dynamics is utilized, a correct simulation of these jets is important for the estimation of thermal comfort. RANS (Reynolds-averaged Navier-Stokes) simulations tend to overestimate the maximum flow velocities and the thermal discomfort in the occupied zone. In order to improve the prediction, LES (large-eddy simulation) models are studied in comparison with RANS using different turbulence models. Subgrid-scale turbulence modeling is based on dynamic Smagorinsky or turbulence kinetic energy equation models. The desirable symmetric flow state was found to be negatively stable with LES when applying non-turbulent inlet boundary conditions. As a remedy, turbulent time-dependent flow distributions are applied. Simulations are made using the OpenFOAM 1.5 -code. The beams were installed in a laboratory test room and the flow pattern between the units was measured for validation. The flow pattern after the collision of the jets was found to be fluctuating.
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