Entrainment into a fully developed, two-dimensional shear layer

It is observed experimentally that a spatially growing shear layer entrains an unequal amount of fluid from the each of the free streams, resulting in a mixed fluid composition which favors the high speed fluid. An ansatz is proposed, based on the geometrical properties of the large scale flow structures of the sub-sonic, fully developed, two-dimensional mixing layer, which yields the entrainment ratio and growth of the turbulent mixing layer. The predictions depend on the velocity and density ratio across the layer and are in good agreement with measurements to date.