Evaluation of a Fast, Simplified Computational Fluid Dynamics Model for Solving Room Airflow Problems.
Evaluation of a Fast, Simplified Computational Fluid
Dynamics Model for Solving Room Airflow Problems.
Musser, A.; McGrattan, K. B.; Palmer, J.
NISTIR 6760; 65 p. June 2001.
computational fluid dynamics; air flow; convection;
This report investigates the use of the Fire Dynamics
Simulator (FDS), for coarse grid modeling of non-fire
and fire situations. FDS is a large eddy simulation
computational fluid dynamics program that was developed
to model fires in enclosures. One goal of this study was
to compare its predictions with experimental data and
other published CFD studies of test rooms without tires
in them. Four such experiments are considered. The first
three are idealized test rooms designed to demonstrate
forced, natural, and mixed convection. The fourth is a
more realistic room setup with furniture, a displacement
ventilation system, and a contaminant release. The
results of these simulations agree reasonably with the
experimental data, provided that care is taken in
defining boundary conditions and inputs in a way that is
consistent with the intention and capabilities of the
model. In particular, some care is needed to define
convection coefficients for heated or cooled surfaces. A
second goal of this study WAS to determine the effects
of using very coarse grids on both the computational
results and computing time. The results of this
comparison show that non-fire simulations are generally
much faster than fires because the simulation times step
is limited by the convection motion. In many cases, the
coarse grid solutions agreed with the experimental data
nearly as well as could be accomplished with a much
finer grid and could be modeled in real time or faster.
However, accurate contaminant dispersal modeling did
require a significantly finer grid.