Mixing of impurities by two dimensional turbulence

Collaborators: Jerry Gollub, Ben Williams, Troy Sheaffer
When a weakly diffusing passive impurity is introduced into a turbulent flow, regions of high concentration are stretched and folded repeatedly. This process creates thin striations with large concentration gradients that enhance diffusion, so that uniformity is achieved at the smallest scales. More than 30 years ago, Batchelor predicted that the spatial power spectrum of the impurity should show a region proportional to the inverse of the wavenumber k. We studied the mixing of a passive scalar in two dimensional turbulence in part to test this prediction. The flow is established in a thin buoyant layer that is electromagnetically forced by an array of permanent magnets. Mixing is studied by introducing a dye solution on one side and extracting the mixed solution at the other. An image corresponding to the dye mixing is shown.

Strong deviations are observed from the predicted 1/k scaling.

Ben Williams won the Apker Award of the American Physical Society for his work on this problem. A long paper has appeared in Physics of Fluids 9, 2061-80 (1997).

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Last updated 10/31/98