it is desired to formulate an expression to predict the mixing generated by wind blowing over a stratified body of water. specifically the wind transfers energy into the water by a surface shear stress which maybe characterized by a friction velocity u$*=$sqrt$($tau$/$rho$0).$ part of this energy is used to mix fluid across the density interface, resulting in the deepening of the upper layer. Formulate a non dimensional expression that could be used to relate the entrainment velocity Ue$=$dh$/$dt to other variables of the problem $($remember to include g$).$ The result should be written in terms of the bulk Richardson number Ri$=$g$\text{'}*$h$/$u$*^2$