The Effect of Boundary Conditions on Numeric Simulations of Wind Tunnel Experiments*

Computational simulations are often performed in conjunction with wind tunnel experiments. The choice of boundary conditions in simulations are the choice of the user. The boundary conditions in a wind tunnel, however, are prescribed by the experimental facility. In this work we look at a study aimed at reducing drag on Olympic luge sleds. This study combines computation simulation and optimization using numeric tools with experimental drag measurements to design luge sleds. We compare the computational results, and more importantly the trends in the drag values, for several different computational domains. The domains included an "open" computational domain with a ground plane, an enclosed domain matching the test section of the wind tunnel, and a domain defined by the wind tunnel contraction, test section and diffuser. These results are also then compared to the results from the wind tunnel experiments. The results indicate that the choice of computational domain and boundary conditions affect the trends in the drag value. In some cases the choice in computational domain showed decreases in drag in the computational domain while the experiments resulted in drag increases. The results highlight the importance of simulating the wind tunnel domain when comparing computation and experimental results.