Abstract
We report measurements of the second-order Lagrangian structure function and the Lagrangian velocity spectrum in an intensely turbulent laboratory flow. We find that the asymmetries of the large-scale flow are reflected in the small-scale statistics. In addition, we present new measurements of the Lagrangian structure function scaling constant C0, which is of central importance to stochastic turbulence models as well as to the understanding of turbulent pair dispersion and scalar mixing. The scaling of C0 with the turbulence level is also investigated, and found to be in agreement with an existing model.
Highlights
Due to the complexity of the fluid equations of motion, we are forced to turn to phenomenological modelling to gain insight into the behaviour of turbulent flows
Timescales that are small compared with the injection of energy into the flow. If these small-scale statistics are to be universal, they must be independent of the large-scale flow structure
Careful study of the effects of large-scale anisotropy on the small-scale turbulent fluctuations is very important for understanding the behaviour of turbulent flows in nature
Summary
Due to the complexity of the fluid equations of motion, we are forced to turn to phenomenological modelling to gain insight into the behaviour of turbulent flows. We see very short plateau regions for all three diagonal components of the structure function tensor, consistent with the K41 scaling prediction, though without a fully developed Lagrangian inertial range. We note that the difference in magnitude between the radial spectra and the axial spectrum reflects the large-scale structure of our flow.
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