Effects of expansion ratio on the calculation of parallelwalled backwardfacing step flows  Comparison of four models of turbulence
Abstract
This paper presents a numerical study of the effects of expansion ratio on twodimensional separating and reattaching flows in plane backwardfacing step geometries with parallel walls. Closure of the Reynolds equations was achieved by four different turbulence models: kepsilon, 'modified' kepsilon, algebraic stress, and 'modified' algebraic stress models. The kepsilon model relates the Reynolds stresses to the mean rate of strain through the definition of an isotropic turbulent viscosity. The more advanced algebraic stress model calculates the stresses from implicit algebraic relationships containing the stresses themselves, the mean rate of strain, and the turbulent kinetic energy and its dissipation rate. 'Modified' versions of the models employ a new dissipation rate equation whose production term was made more sensitive to streamwise curvature effects. A new nonequilibrium wall function treatment proposed by Chieng and Launder (1980) was also incorporated into each model.
 Publication:

American Society of Mechanical Engineers
 Pub Date:
 June 1983
 Bibcode:
 1983asme.confQ....S
 Keywords:

 Backward Facing Steps;
 Performance Prediction;
 Turbulence Models;
 Turbulent Flow;
 Wall Flow;
 Expansion;
 Flow Geometry;
 Flow Velocity;
 KEpsilon Turbulence Model;
 Mathematical Models;
 Reynolds Stress;
 Fluid Mechanics and Heat Transfer