Numerical Investigation of Flow Induced Noise in a Simplified HVAC Duct with OpenFOAM

Abstract: Due to the growing demand for comfort, the noise generated by HVAC components should be considered by the designers. Flow induced noise is one of the major contributors to the noise in HVAC systems. By means of computational aero-acoustics(CAA), the mechanism of noise generationis able to be studiedin the design phase. This research has been conducted based on a simplified HVAC duct, aiming to validate a hybrid method in CAA. The hybrid method is an affordable and promising approach for industrial applications. CFD simulation, as the first step of the hybrid method, has been performed. Due to the deficiency of RANS and high computational cost of LES, hybrid RANS-LES approaches are employed to combine sufficient accuracy and reduced cost. Delayed Detached Eddy Simulation (DDES) and Scale Adaptive Simulation (SAS), as the representative hybrid RANS-LES approaches, are performed and compared. CFD results are shown in detail and compared with the experimental measurements available in the literature. The comparison shows a good agreement for the time averaged flow field and a fairly good agreement for uns teady flow phenomena. Discrepancies between numerical results and measurements can be observe dregarding mainly unsteady pressure fluctuations.The influence study of grid, discretization schemes, time step as well as other parametersis also conducted. The insights gained here can serve as a guideline for future complex applications.