NONLOCAL TURBULENT TRANSPORT OF MOMENTUM IN FLOWS WITH SIGN-CHANGING VELOCITY SHEAR

The paper is a further development of the author's work 1!. A simplif ied stationary model is formulated, based on the third-order closure s cheme, and including a set-of two ODE for Reynolds stresses and vertic al velocity dispersion. Analytical expressions for considered quanitit es are obtained, which reflect non-local nature of the turbulent trans port and connection with the concept of the so-called transilient turb ulence 5!. An analysis of the obtained solution with respect to param eters and configuration of the mean velocity shear is presented. It is shown that counter-gradient transport of the momentum can take place, probably, only in sign-changing shear flows.