Invariant Sets and Explicit Solutions to a Third-Order Model for the   Shearless Stratified Turbulent Flow
  We study dynamics of the shearless stratified turbulent flows. Using the method of differential constraints we find a class of explicit solutions to the problem under consideration and establish that the differential constraint obtained coincides with the well-known Zeman--Lumley model for stratified flows. 
V.N. Grebenev, B.B. Ilyushin