Numerical Simulation of Unsteady Separated Flow and Convective Heat Transfer

Flow separation with reattachment is a phenomenon characterized by unsteadiness and complex turbulence that occurs in a large variety of environmental situations and engineering devices. Separated flows have been particularly challenging to predict using classical turbulence models which rely on time-averaging of the turbulent motion and its parameterization with semi-empirical models. In this paper we present two and three-dimensional time-dependent simulations using the Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) techniques. The prototype separated-reattaching flow configuration considered is the flow over a bluff rectangular plate. Simulations are presented and discussed with a focus on the large scale dynamics and on the behaviour of the surface heat transfer coefficient—the parameter of prime interest in the design and optimization of heat transfer device. Unsteadiness and three-dimensionality are shown to play a central role in determining the structure of the thermal field and wall heat transfer rates. Simulations with long integration times are required to obtain reliable flow statistics.

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