REYNOLDS STRESS CALCULATIONS OF HOMOGENEOUS TURBULENT SHEAR-FLOW WITHBOUNDED ENERGY-STATES

Reynolds stress calculations of homogeneous turbulent shear flow are c onducted with a second-order closure model modified to account for non -equilibrium vortex stretching in the dissipation rate transport equat ion as recently proposed by Bernard and Speziale [J. Fluids Engng 114, 29 (1992)]. As with the earlier reported K-epsilon model calculations incorporating this vortex stretching effect, a production-equals-diss ipation equilibrium is obtained with bounded turbulent kinetic energy and dissipation. However, this equilibrium is now not achieved until t he dimensionless time St > 60 - an elapsed time that is at least twice as large as any of those considered in previous numerical and physica l experiments on homogeneous shear flow. Direct quantitative compariso ns between the model predictions and the results of experiments are qu ite favorable. In particular, it is shown that the inclusion of this n on-equilibrium vortex stretching effect has the capability of explaini ng the significant range of production to dissipation ratios observed in experiments.