Correct Answer - Option 1 : equal to self-cleansing velocity
Explanation:
Self-cleansing velocity:
- It is the minimum velocity maintained in a sewer line that prevents the deposition or settlement of solids inside the sewer line.
- So that the sewer gets cleaned by the action of gravity only and without the use of any other energy.
- it is designed like this so that at once in a day the sewer gets totally cleared.
Self-cleansing velocity (V) = \(\sqrt {\frac{{8g}}{f}\left( {1 - n} \right)sinθ \left( {G - 1} \right)d} \)
f = Friction factor
g = acceleration due to gravity
n = Porosity
θ = angle of sewer with a horizontal line
G = Specific gravity of solid
d = average size of solid
So, The minimum velocity of flow in a sewer should be ideally equal to self-cleansing velocity.
