Scientico

Settling of sedimentation is the separation of solid particles from fluids under the gravitational force. When a solid particle moves in a fluid. Then a number of forces are acting on it:
•The gravitational force, acting downward.
•The buoyant force, acting upward.
•The drag force, acting upward.
When a particle falls in a fluid under constant force, e.g. force of gravity, then particle accelerates for some time, but when the accelerating force equals to retarding force (Buoyant force and Drag force) then the resultant force acting on the particle will be zero, and particle quickly reaches velocity, which is the maximum attainable under the circumstances and which is called the terminal velocity. When slurry is prepared in a container and then allowed to remain undisturbed for some time, four settling zones will appear as below: