A two-scale second-moment one-point turbulence closure

Abstract

A major deficiency of all the conventional single-point turbulence models is associated with the use of a single turbulence scale to model all turbulence interactions. This chapter examines 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 modeled with the help of a separate set of transport equations, be it at the eddy-viscosity or second-moment level, this two-scale approach retains the equations for the total turbulent stresses or kinetic energy. Furthermore, the chapter presents some results of model tested in several homogeneous and inhomogeneous nonequilibrium and unsteady flows. Visible differences noted in the response of two scale-providing variables significantly indicate that this approach has a potential for capturing effects of the spectral nonequilibrium and the dynamics of twoturbulence scales.