Theoretical pressure–strain term, experimental comparison, and resistance to large anisotropy

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Abstract
Although models of the pressure–strain term explain many features of nearly uniform homogeneous shear flows, a discrepancy remains (Leslie 1980). It is suggested that the discrepancy is caused by use of an empirical expression for the fluctuation part of the pressure–strain term, the part usually denoted by ϕij,1. The discrepancy is eliminated by replacement of the empirical ϕij,1 with a recent theoretical expression. Relatedly, the Launder, Reece & Rodi (1975) model for the mean-field part ϕij,2 is shown to be a good approximation for both a strongly and weakly sheared flow. This model of ϕij,2 when combined with the theoretical ϕij,1 is found to provide an explanation for experiments of both Champagne, Harris & Corrsin (1970) and Harris, Graham & Corrsin (1977). Full correction requires that deviations from local isotropy be accounted for. Special emphasis is given to a theoretical demonstration that the pressure–strain term does not cause a retun to isotropy but, rather, it resists large anisotropy – a weaker effect.