Comparative Study of Porous Media and Physically Modelled Perforated Plate Approaches for Flow Conditioning in a Low-Speed Water Tunnel Using CFD

Flow straighteners or conditioners such as perforated plates are devices capable of eliminating swirl and providing uniform flow in high turbulence environments. However, using traditional computational fluid dynamics (CFD) methods to analyze flow across perforated plates are computationally expensive due to the wide range of flow scales produced by the perforations, requiring refined modelling. This study aims to determine the efficacy of the porous media approach in OpenFOAM to mimic the effects of a perforated plate, offering a potentially less computationally intensive method compared to traditional CFD analysis. The study also assesses the capability of the porous media approach to produce the desired flow conditioning in a simplified low-speed water tunnel. Results show that the percentage difference in pressure drops between the actual perforated plate and the porous domain in the water tunnel is less than 12%. The flow uniformity index at the middle of the test section is 0.9694 for the perforated plate and 0.9711 for the porous domain, compared to 0.9255 without a flow straightener. In terms of average turbulent kinetic energy (TKE), maximum reductions of 73.3% and 92.1% are achieved by the perforated plate and porous domain, respectively. This study demonstrates the feasibility of the porous media approach to provide reasonable flow characteristics produced by perforated plates with efficient computational effort, using approximately two million cells compared to three million cells with the physical plate approach.