An Algebraic Turbulence Model for Flow Separation Caused by Forward and Backward Facing Steps

An Algebraic Turbulence Model for Flow Separation Caused by Forward and Backward Facing Steps
Author: James E. Danberg
Publisher:
Total Pages: 34
Release: 1989
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ISBN:

The Baldwin-Lomax algebraic turbulence model is currently widely used in numerical Navier-Stokes codes primarily because it avoids the problems of calculating a boundary layer thickness. However, two of its disadvantages are: 1) it requires the evaluation of a maximum in the moment of vorticity with respect to the surface which is ambiguous under certain conditions and, 2) its applicability to some separated flows is unclear. The basis for the Baldwin-Lomax method is reviewed in detail particularly as it applies to locally separated flows. This leads to a reformulation of the Baldwin-Lomax method. The modification uses a velocity scale, at each separated flow station, which is the difference between the maximum velocity and the minimum velocity (considered negative in separated flows with recirculation regions). The length scale is defined in terms of the ratio of this velocity scale to the maximum vorticity. Other modifications are included which adapt the model to forward and rearward facing step applications. Keywords: Fluid mechanics; Turbulent flow; Forward and backward steps; Separated flow; Supersonic flow; Turbulence modeling; Algebraic model. (JHD).