Spalart, P.R. and Coleman, G.N.
Numerical study of a separation bubble with heat transfer
European Journal of Mechanics - B/Fluids, 16, (2), .
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We present a Direct Numerical Simulation of the rapid separation and reattachment of the turbulent boundary layer on a flat wall. The temperature is a passive scalar, with an isothermal wall. Prescribed suction and blowing along an inviscid boundary opposite the layer create the required pressure gradients. The transpiration profile is defined analytically, inflow profiles are given, and outflow conditions are non-critical; this allows duplication of the flow. The incoming boundary layer is turbulent, but unfortunately not perfectly developed, primarily due to Reynolds-number constraints. These constraints come from the high computing cost and are also the reason for making the bubble unusually short. The mean quantities and Reynolds stresses reveal that the severe distortion of the turbulent layer associated with separation defeats not only the boundary-layer assumptions, but also several assumptions convenient in turbulence modelling; negative production of turbulent kinetic energy and counter-gradient heat transfer are observed locally. The Reynolds analogy between velocity and temperature fields weakens to the extent that the wall heat transfer increases just where the momentum transfer collapses.
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