Computational Fluid Dynamics (CFD) was applied to investigate blockage effects (or velocity correction) in a climatic wind tunnel (CWT) test environment. Different blockage effects in the CWT ware modelled using tour simplified vehicles that approximated a sedan, an SUV, a pickup truck, and a minivan. Blockage dependence on nozzle size and spacing between the nozzle exit plane (NEP) and the vehicle ware also investigated. The study quantified the blockage effect using different correction methods based on vehicle frontal velocity profiles and upper surface pressure traces. The blockage-free solution was also simulated for each vehicle in an 'open road' or free air condition. The CFD study revealed that all the test cases resulted in blockage correction factors, defined by V'actual'/V'simulated' greater than 1.0. This is a condition in which the uncorrected wind tunnel velocity was higher than the 'open road' condition. It was determined that vehicles with higher COAF values induced higher blockage correction factors. The blockage correction factor increased exponentially as the vehicle was positioned Glaser to the NEP. Small differences in the blockage factor between the frontal velocity profile method and the upper vehicle surface pressure trace method ware found. These results led to two unified CWT blockage correlations based on the vehicle frontal velocity profiles and the upper surface pressure traces. Each correlation is valid across a range of vehicle frontal areas, drag coefficients, and separation distances between the nozzle exit plane and the vehicle.
Determining blockage corrections in climatic wind tunnels using CFD
Bestimmung von Versperrungs-Korrekturfaktoren in Klimawindkanälen durch numerische Strömungssimulation
2003
11 Seiten, 14 Bilder, 3 Tabellen, 6 Quellen
Conference paper
English
Determining Blockage Corrections in Climatic Wind Tunnels Using CFD
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