Observations on the Distribution of Energy Dissipation in Stirred Vessels

The distribution of the rate of dissipation of the turbulence energy, ɛ , in a vessel stirred by a Rushton turbine has been obtained from CFD predictions of the flow employing a sliding mesh technique. Volume-weighted average values of ɛ for different regions in the vessel have been calculated, and are compared with values previously reported in the literature obtained from CFD predictions and/or LDA and other measurements. It is shown that in general values of ɛ obtained from estimates of the macro length scales of turbulence from measurements may overestimate the amount of energy dissipated in the impeller swept region and in the impeller stream, while the present CFD results, as well as recent LDA experiments where ɛ has been measured directly, indicate that a substantial amount of energy might be dissipated in the bulk of the flow and near the wall and baffles.

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