Author(s): Chris R. Rehmann

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Keywords: Mixing efficiency; stratification; grid turbulence

Abstract: The effect of stratification on the mixing efficiency of grid turbulence is studied with a scaling analysis that yields several regimes of behavior classified by the initial strength of the stratification, or grid Richardson number Ri0. The mixing efficiency is taken to be the ratio of the mean potential energy change during a turbulent event to the work done to create the event. For weak stratification, the scaling reproduces previous predictions and indicates when each should apply. For strong stratification, the scaling predicts a decrease in the efficiency. A feature of the analysis is that it allows transitions between regimes to be estimated. The predictions of the scaling are evaluated with results from previous analyses and towed-grid experiments.With estimates of the decay time of the turbulence and the average overturning scale, the method can be applied to other problems to estimate the variation of mixing efficiency with Richardson number.

DOI: https://doi.org/10.1080/00221686.2004.9641181

Year: 2004