Comparison of stationary and transient RANS modelling Spatial velocity field of a ceiling integrated fan

摘要

Ceiling fans allow an increase of the local air velocity on the human body. The associated heat transfer increases user's temperature tolerance in warm environments. In the presented study, the differences in the application of sta-tistical turbulence modeis (RANS) for modelling the air flow in-duced by a ceiling integrated fan is outlined with particular focus on comparing steady and transient simulations. Results of a CFD Simulation (Fluent) are shown and compared with measured data of the horizontal velocity distribution. The study shows that especially the transient Simulation using the Realizable k-ε model shows a stable convergence behav-iour regarding the residuals as well as target values. But at 1.1m above the floor, the mean absolute error of the transient Simulation is larger compared to the stationary model using the Multiple Reference Frame (MRF) approach. Despite the stationary model produces an unrealistic velocity distribution in the immediate vicinity of the fan, if the moving zone needs to be small due to obstacles. For a freely suspended ceiling fan, the moving zone can be adjusted accordingly and the flow pattern can be improved. But modelling a ceiling integrated fan with a fan housing and obstacles in the near region, transient simulations using rigid body motion are required for accurate results.