Time-resolved X-ray measurements of lock-exchange turbidity currents

Turbidity currents are gravity-driven flows where a dense mixture of sediment and fluid moves into lighter ambient fluid due to density differences. These types of flows occur in oceans, avalanches, and volcanic flows. Experimental measurements of the spatiotemporal evolution of density fields during current propagation are essential to understanding mixing dynamics at different density ratios. This study uses time-resolved X-ray densitometry to investigate turbidity currents in a two-dimensional lock-release system. The experiments involve two sand particle sizes (60 microns and 120 microns), four water depths (25 mm to 100 mm), initial particle concentration ranging from 30 g/L to 490 g/L. The density ratio in the experiments varies from 0.77 to 0.98, encompassing both Boussinesq and non-Boussinesq limits. Acceleration, slumping, and deceleration phases of currents with different sand sizes and column heights are presented. X-ray densitometry-based evolution of density fields is discussed for the three phases and a range of density differences. The entrainment and evolution of the current head density profile are discussed from the time-resolved X-ray-based density field measurements.