Comparing Turbulence Models for Buoyant Plume and Displacement Ventilation Simulation

Abstract

Computational fluid dynamics may be used to predict the details of airflow in rooms served by displacement ventilation systems, provided a suitable turbu lence model can be found. Since buoyant plumes are central to the displace ment ventilation strategy, four turbulence models - three eddy-viscosity mod els (the 'standard' k-ε model, a modified k-ε model, and an RNG k-ε model) and the Reynolds stress model - were applied to simulate airflow in a turbu lent buoyant plume. Corresponding experimental data from the literature were used for validation, although for a plume stronger than expected in rooms as no reliable plume data for room air flow were found. The Reynolds stress model predicted velocity, temperature, and turbulence quantities satis factorily while the eddy-viscosity models performed poorly. The eddy-viscosi ty models were then applied to predict airflow in a furnished room with dis placement ventilation. The computed airflow patterns, mean velocities, tem peratures, and contaminant concentrations agree reasonably well with the experimental data obtained from a full-scale test chamber, but the discrepan cies in some locations were large.