A TWO-SCALE SECOND-MOMENT ONE-POINT TURBULENCE CLOSURE

摘要

We report on progress in the development of a two-scale second-moment closure model, based on wave-number-weighted spectrum integrals, which allows one to distinguish between the turbulence scales associated with the energy containing and dissipative parts of the energy spectrum. In contrast to the split spectrum approach, where the dynamics of each spectral slice is modelled with a separate set of transport equations - be it at the eddy-viscosity or second-moment level, the approach presented here retains the equations for the total turbulent stresses (or the kinetic energy). We present some results of model testing in several homogeneous and inhomogeneous non-equilibrium and unsteady flows: in an axisymmetric contraction with a high (1:4) contraction ratio, flow subjected to a successive plane strains, in a flow behind a backward facing step subjected to periodic perturbations. Improvements have been noted in most cases tested, though further tuning may be required. However, visible differences have been noted in the response of the two scale-providing variables, indicating that the approach has a potential for capturing effects of the spectral nonequilibrium and the dynamics of two turbulence scales.