ON THE RELATIONSHIP BETWEEN STOCHASTIC LAGRANGIAN MODELS OF TURBULENCE AND 2ND-MOMENT CLOSURES

A detailed examination is performed of the relationship between stocha stic Lagrangian models-used in PDF methods-and second-moment closures. To every stochastic Lagrangian model there is a unique corresponding second-moment closure. In terms of the second-order tensor that define s a stochastic Lagrangian model, corresponding models are obtained for the pressure-rate-of-strain and the triple-velocity correlations (tha t appear in the Reynolds-stress equation), and for the pressure-scramb ling term in the scalar flux equation. There is an advantage in obtain ing second-moment closures via this route, because the resulting model s automatically guarantee realizability. Some new stochastic Lagrangia n models are presented that correspond (either exactly or approximatel y) to popular Reynolds-stress models.