While applying Stoke's law, the concept of equivalent diameter is used. The equivalent diameter of a soil particle is defined as the diameter of an imaginary sphere which has the same specific gravity as the soil particle and settles with the same terminal velocity as that of the soil particle. It is assumed that every particle settles independently without interference from other particles as well as from the sides of the jar.
To minimize error due to this assumption, it is recommended that not more than 50 gms of soil particles be taken in ml of soil suspension. The soil particles in the soil suspension may have different values of specific gravity. But in the computations, an average value of G is used. The lower limit of particle size for the validity of Stoke's Law is 0. However, the upper limit for the same is 0. For particles of size less than 0. Stokes's law is valid upto a maximum Reynolds number of 1. Start Learning English Hindi.
This question was previously asked in. Answer Detailed Solution Below Option 2 : 1. Know more about Water Treatment and ace the concept of Sedimentation. Start Now. Get Started for Free Download App. More Sedimentation Questions Q1. In a sedimentation tank design, surface overflow rate S. R is calculated as. The Percentage of bacterial load that is removed through plain sedimentation is about. A sedimentation tank removes kg of suspended solids per day.
What is the detention period and overflow rate for plain sedimentation tank compared to sedimentation with coagulation? The detention time for the tank is:. The second stage of water treatment is For a given discharge, efficiency of sedimentation tank can be increased by.
This results in floatation or creaming most commonly seen in emulsion systems. High solid content imparts additional viscosity to the system, which must be taken into consideration if the correct rate of settling is to be determined.
The equation contains only the viscosity of the medium. The electrical potential between two charges has an inverse relationship with the dielectric constant of the medium.
Therefore, zeta potential is dependent on the dielectric constant of the medium. The implication is that if a vehicle has low dielectric constant, the double layer is many times thicker than in an aqueous medium resulting also to a different zeta potential and, thus, the settling will be different. These factors are important when nonaqueous vehicles, e. Brownian movement counteracts sedimentation to a measurable extent.
As the particle size is reduced, Brownian movement becomes significant. Below a critical radius, the movement will be sufficient to keep the particles from sedimentation. Differences between Flocculated and Deflocculated Suspensions.
Since the sphere is falling with constant velocity there is a balance of forces that result in no acceleration. We can determine this smoothness by calculating Reynolds number:. The uncertainty for such calculations will be determined using standard uncertainty propagation equations.
A rotational viscometer uses the principle behind the ideal model of shear stress being produced between a stationary plate and a moving one under non-slip conditions. Rather than using a moving plate, a rotational viscometer employs a rotating disc submerged into the fluid in question. This shear stress at a position r along the radius, R, of the disc can be described as:.
The tools required for this experiment included a set of dial calipers, 2 spheres, a Mettler-Toledo balance, a stop-watch, a meter stick, a flexible pick-up tool, and a 2L graduated cylinder filled with liquid glycerin. The temperature of the room was noted for later use in finding the tabulated values of viscosity and density of the glycerin. For each sphere, the diameter was measured using the dial calipers, and their mass found using the Mettler-Toledo balance.
After filling the graduated cylinder with glycerin, the distance between two positions sufficiently far enough away from the top was measured.
Using the pick-up tool and stop watch, each sphere was dropped into the liquid glycerin and the time to travel the measured distance recorded. This distance covered divided by the time of travel gave us the approximate terminal velocity of each sphere. The set-up for this experiment consisted of a rotational viscometer and the included set of spindles, as well as a beaker filled with glycerin. First, the viscometer had to be leveled, centered within the beaker, and the auto-zeroing function run to completion.
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