Turbulent stresses in the model of a natural eddy

A laboratory experiment was carried out with a vortex-generator model simulating a natural (atmospheric or oceanic) eddy in order to test a particular closure hypothesis for the Reynolds equations: namely the hypothesis according to which both the gradient and the convective components of turbulent transport are taken into account in the expression for turbulent stresses. A formula is obtained which provides for a good quantitative agreement between theoretical and experimental results. It is concluded that the closure of the turbulence equations using this formula correctly represents the turbulence-momentum transfer. This makes it possible to accurately describe the effect of negative eddy viscosity.