A DISSIPATION RATE-EQUATION FOR LOW-REYNOLDS-NUMBER AND NEAR-WALL TURBULENCE

Two-equation turbulence models are usually formulated for specific flo w types and are seldom validated against a variety of flows to account for near-wall and low-Reynolds-number effects simultaneously. In addi tion to low-Reynolds-number effects, near-wall flows also experience w all blocking, which is absent in free flows. Consequently, near-wall m odifications to two-equation models could be quite different from low- Reynolds-number corrections. Besides, it is known that existing two-eq uation models perform poorly when used to calculate plane wall jets an d two-dimensional backstep flows. These problems could be traced to th e modeling of the dissipation rate equation. In this paper an attempt is made to improve the modeling of the dissipation rate equation so th at it could successfully predict both free and wall-bounded shear flow s including plane wall jets and backstep flows. The predictions are co mpared with experimental and direct numerical simulation data whenever available. Most of the data used are obtained at low Reynolds numbers . Good correlation with data is obtained. Therefore, for the first tim e, a model capable of correctly predicting free and wall-bounded shear flows, backstep flows, and plane wall jets is available.