Hindered settling velocity of sedimentation of particles using CFD-DEM

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The sedimentation process of suspended particles in a fluid can be found in many fields, e.g. the deposition of natural sediments or the many solid-liquid separation phenomena in chemical, mining and food engineering. In many applications in these fields the hindered settling process plays an important role. In this process, the particles fall at a constant velocity due to the balance of buoyancy, gravity and drag force. The local interactions of the particles and the wake effects play also an important role; the settling velocity decreases when the local particle concentration increases.

In this animation the particle-fluid flow a CFD-DEM solver is used to simulate the hindered settling velocity of solids in water with different solid concentration in a squared column. The particles are randomly distributed using volume concentrations of 10%, 20%, 30% and 40%. When the solids start to fall and reach the floor, water is pushed upwards increasing the drag forces and reducing the fall velocities of the solids that are still falling. In the animation ten percent of the simulated particles are visualized. The result of these simulations is compared to Richardson’s empirical formula. However, the CFD-DEM solver can be used to simulate more complex pipe systems in which particle-fluid flow plays an important role.