On a Hybrid RANS/LES Approach for Indoor Airflow Modeling (RP-1271)

Abstract

Airflows in an enclosed environment are a wall-bounded unstable flow, which is difficult to simulate using either a RANS or an LES model. The hybrid RANS/LES simulation, which uses a RANS model for the near-wall attached boundary layers to avoid an excessively fine grid, and an LES for the separated turbulence region to resolve unstable eddies, is promising for this type of flow. However, the available hybrid RANS/LES models have not performed well for indoor airflows due to the RANS model they used. This investigation developed a new RANS/LES model for indoor airflow modeling using a semi-v2f model. This model correctly predicted near-wall flows by taking into account the wall normal stress, which was calculated by an algebraic equation. By applying the new model to a mixed-ventilation flow in a room and a strong buoyancy-driven flow with a high temperature gradient in a room, the predicted results are accurate and the model seems robust.