Hydraulic jumps in turbidity currents - flume experiments

Abstract

The focus of this innovative research is on the effects of grain size and various sediment concentrations on flow dynamics, hydraulic jump characteristics and sediment deposition of experimental turbidity currents. Of special interest is the origin of structureless graded sand beds (Bouma’s Ta), supposed to be the result of an internal hydraulic jump of the high density traction carpet in a 2-phase turbidity current. In this experimental study turbidity currents of different sediment concentration and sediment grain size are created and observed in a flume at the Eurotank laboratory facility at Utrecht University. A hydraulic jump is triggered and flow dynamics and resultant deposits are analyzed. Froude numbers are calculated for 1-phase flows and partial Froude numbers for the bottom layer of 2-phase flows, to determine whether a hydraulic jump occurred. Interpretation of flow dynamics suggested the occurrence of hydraulic jumps, however measurements appeared inadequate to produce reliable Fr’ numbers to support this observation. The supposed hydraulic jump did not produce structureless sand beds; deposits observed were plane bed lamination and low shear lamination (Bouma’s Tb and Td, respectively).