A NEW LOW-REYNOLDS-NUMBER NONLINEAR 2-EQUATION TURBULENCE MODEL FOR COMPLEX FLOWS

A new nonlinear, low-Reynolds-number k-epsilon turbulence model is pro posed. The stress-strain relationship is formed by successive iterativ e approximations to an algebraic Reynolds-stress model. Truncation of the process at the third iteration yields an explicit expression for t he Reynolds stresses that is cubic in the mean velocity gradients and circumvents the singular behaviour that afflicts the exact solution at large strains. Free coefficients are calibrated - as functions of y - by reference to direct numerical simulation (DNS) data for a channel flow. By using the nonlinear stress-strain relationship, the sublayer behaviour of all turbulent stresses is reproduced. The extension to n onequilibrium conditions is achieved by sensitising the model coeffici ents to strain and vorticity invariants on the basis of formal relatio ns derived from the algebraic Reynolds-stress model. The new model has been applied to a number of complex two dimensional (2-D) flows, and its performance is compared to that of other linear and nonlinear eddy -viscosity closures. (C) 1998 Elsevier Science Inc. All rights reserve d.