Energy spectrum and interscale transfer in non-homogeneous rotating flow: the case of a mixer

Time-resolved 2D2C PIV measurements are carried out in a water tank agitated by four blades rotating at constant speed. Different blade geometries with rectangular and fractal-like shapes are tested in order to change the turbulence properties. In some runs, vertical bars (baffles) on the walls are used to break the rotation of the flow and see the impact on the results.

A classical energy spectrum slope close to -5/3 is identified in the configurations with baffles. On the other hand, a steeper slope (between -2.3 and -1.9) is found for the configurations without baffles where the flow is strongly rotating. The analysis of the second order structure functions gives similar trends with a close to r^2/3 dependence on two-point separation r for the baffle configurations and a close to r evolution for the configurations without baffles.

Estimates of average interscale transfer and interspace transport rates are also evaluated from the data. These rates, defined from the Kármán-Howarth-Monin-Hill equation (KHMH), are used to quantify the impact of the rotation and non-homogeneity on the interscale transfer. A complementary equation to the KHMH one is also analysed and provides additional information for these flows.