Abstract Particle-laden flows or turbidity currents along the seafloor are important to the formation and erosion of submarine topography. To understand the mass-transport process, flume tests were carried out with a continuous supply of quartz-laden suspension. The vertical and horizontal velocities were extracted by two pairs of ultrasound Doppler velocity profilers installed at different angles with respect to the bed-normal direction. Due to the head intrusion into the ambient water, the sediment in the suspension was continuously lifted up and mixed, leaving lobes and clefts. The velocity-maximum layer acted as the main sediment conveyor and divided the body into wall and jet regions. The concentration distribution was also quantified based on the relationship between the fluid density and the intensity of light attenuation obtained using a video recording. An area of high sediment concentration was observed just behind the head frontal area. Analysis of the velocity and concentration distribution demonstrated that sediment in the turbidity current was transported mainly by head movement and that continuous sedimentation took place in the wall region. The results indicate that a turbidity current proceeds while maintaining an ordered inner dynamic structure.

Abstract Turbidity currents occur widely in submarine environments, but field-scale numerical simulations of the flow features have not been applied extensively. Here, we present a two-dimensional layer-averaged numerical model to simulate turbidity currents over an erodible sediment bed, and taking into consideration deposition, entrainment and friction. The numerical model was developed based on the open-source code, Basilisk, ensuring well-balanced and positivity-preserving properties. An adaptive spatial discretization was used, which allows multi-level refinement. The adaptive criterion is based on the dynamic features of the flow and sediment concentrations. The numerical scheme has a relatively high computational efficiency compared with models based on the Cartesian mesh. A hypothetical case based on a true large-scale landform (the Moroccan Turbidite System, offshore NW Africa) was studied. Compared with previous models, the current model accounted for the coupling between flow, sediment transportation and bed evolution. This approach may improve simulation results and also allow the simulation of complex field-scale landforms, while preserving the flow details.