Abstract:
We show that meaningful turbulence statistics can be obtained for gravity currents, in particular turbidity currents, by applying streamwise and spanwise spatial averaging over a carefullychosen region of the current’s head. The current structure is generally depicted as having a compact head, followed by a decaying body and an almost non-turbulent tail. Due to the transient nature of turbidity currents, it is difficult to quantify the turbulence of the inner current, since the inability to calculate temporally averaged statistics prevents the quantification of the mass and momentum flux exchanges in this region. For a Reb = 60,000 lock-exchange current, we demonstrate that spatial averaged statistics from a single run are consistent with those from an ensemble average of 200 runs. Slight discrepancies are observed, showing the limits of the hypothesis of spatial homogeneity considered.