Scaling the Velocity Gradients in a Vessel Agitated by a Rushton Turbine

Abstract

Scaling of fluctuation velocity gradients was investigated in a vessel agitated by a Rushton turbine. By using turbulence spectrum analysis, it was derived that, for high Reynolds numbers, the squared dimensionless local fluctuation velocity gradient is proportional to the squared impeller Reynolds number. This theoretical prediction was tested on experimental data in the range Re = 50 000 – 110 556. The calculated isotropy ratios are independent of the impeller Reynolds number, and their inter‐ratios depend on the ratio of the axial and the radial components of the fluctuation velocity. The experiments also support the idea that the isotropy ratios differ from zone to zone in an agitated vessel.

Effect of Particle Image Velocimetry Setting Parameters on Local Velocity Measurements in an Agitated Vessel

“…Nevertheless, many PIV studies do not take the spatial resolution effect into account. In our previous work , we found that the fluctuation velocity gradients are also affected by PIV resolution. The recording time is another crucial factor that influences the relevance and accuracy of measured data.…”