Low Reynolds number suspension gravity currents.

Area of Science:

• Fluid dynamics
• Sediment transport
• Computational physics

Background:

• Gravity currents spread via viscous-buoyancy forces, following a square root of time relationship.
• Particle sedimentation significantly alters gravity current behavior, reducing the driving force and causing premature halting.

Purpose of the Study:

• Investigate the dynamics of low Reynolds number suspension gravity currents.
• Model particle settling and its impact on current propagation.
• Identify distinct phases and features of suspension gravity currents.

Main Methods:

• Utilized the Lattice-Boltzmann (LB) method for numerical simulation.
• Modeled suspensions as continuous media with concentration-dependent viscosity.
• Simulated particle settling using a drift flux function, capturing kinematic shock waves.

Main Results:

• Observed the formation of two new fronts: a descending horizontal front and a growing sediment layer.
• Identified three spreading phases: constant rate, decreasing rate, and a final halt.
• Demonstrated that suspension currents stop before all particles settle, contrary to simple predictions.

Conclusions:

• Particle sedimentation fundamentally changes gravity current dynamics, introducing new structures and halting mechanisms.
• The LB method effectively captures complex phenomena like kinematic shock waves and wall layer effects.
• Experimental validation supports the numerical findings on suspension gravity current behavior.