DNS OF SEPARATED FLOW AND HEAT TRANSFER AND AN EXPLORATION OF TURBULENCE MODELING

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The Direct Numerical Simulation (DNS) of a separated flow around a blunt flat plate and heat transfer has been conducted. Further, the Large Eddy Simulation (LES) With the Dynamic Smagorinsky Model (DSM) are made at Re = 11600 and 50000. A three-dimensional unsteady flow and heat transfer around a surface-mounted hexahedron was analyzed using the DNS.Main results obtained are summarized as follows.In the case of a two-dimensional flow, DNS was carried out for Re = 1000 and Pr 0.7. The separated shear layer rolls up as forming the vortices, and they coalesce into a large scale vortex, which is almost periodically shed from the reattachment region to the downstream.The time averaged Nusselt number reaches the maximum a little upstream of the reattachment point.The maximum of Nusselt number is formed under the large scale vortex, where the heat transfer is instantaneously promoted.In the case of a three-dimensional flow, the DNS results agree well with the previous measured data.LES results for Re = 11600 and 50000 predict well the detailed mechanisms of the separated flow and heat transfer described above. They also agree well with the measured data.The DSM predicts well the complicated flow and heat transfer mechanism of the separated flow.The separated flow and heat transfer around a surface mounted hexahedron were analyzed using the DNS method. The results clarified an important role of the horseshoe vortex formed around the hexahedron.