Local and gross parameters of air distribution in a room with a sidewall jet: CFD validation based on benchmark test

Abstract

The mixing ventilation system with diffusers placed on the side walls, above the occupied zone, is the most popular indoor air distribution system. Computational fluid dynamics (CFD) can support the design and optimization of this system, however the uncertainty of CFD results should be estimated. The CFD benchmark test of a room with a sidewall jet was proposed in 2015, and in the present work, this benchmark test was used to evaluate the quality of CFD predictions that used two turbulence modeling techniques: vortex-resolving large eddy simulation (LES) and unsteady Reynolds-averaged Navier–Stokes (URANS). Local data were used to determine the gross and integral parameters characterizing the velocity distribution in the jet at a certain distance from the inlet, like: maximum mean velocity, jet width, volume flux and momentum flux. The velocity distributions in the quasi free jet region were approximated with the model of a jet from the point source of momentum, its parameters were also established. The URANS approach did not improve the simulation results relative to the previous steady-state RANS modeling procedure. In terms of the gross and integral parameters the results of LES with refined mesh were more consistent with the measured results. In the jet zone and occupied zone, the gross parameters obtained from LES calculations differed by less than 15% from the measured values. The accuracy requirements for CFD predictions for the conceptual design of ventilation systems were therefore satisfied.