Numerical study of modeling methods and evaluation indexes for jet fans

Abstract

With the rapid development of turbulent jet technology, jet fans have been widely used in building ventilation system, especially for underground buildings. Researchers often use CFD to design the impulse ventilation system, but the study of modeling methods for jet fans have not been studied comprehensively. Because of the characteristic of jet fan, different kind of inlet boundary condition types coupled with different turbulence models lead to different flow fields. In order to find the most suitable modeling method, this paper studied the effect of the combination of 8 turbulence models and 3 flow boundary conditions on modeling accuracy of jet fans. In addition to comparing velocity and turbulence intensity, the research adopted jet core area length and diffusion angle to evaluate the pros and cons of the simulation results. Results showed that the Fan Boundary Method (FBM) integrated with the k-w SST or RSM (Stress-BSL) turbulence model; the Velocity Boundary Method (VBM) integrated with the k-w SST turbulence model; the Momentum Source Method (MSM) integrated with the standard k-ε turbulence model can represent most jet fans' performance with free jet. When the main task is to verify jet fan nozzles performance or optimize nozzles design, the RSM (Stress-BSL) and k-w SST turbulence models are recommended. When the main focus is on the fan range or the performance of the impulse ventilation system, the standard k-ε turbulence model is recommended. The choice of the final model depends on the available data and the application scenario.