Chemical Engineering - Fluid Mechanics - Discussion

Discussion Forum : Fluid Mechanics - Section 1 (Q.No. 26)
26.
A particle A of diameter 10 microns settles in an oil of specific gravity 0.9 and viscosity 10 poise under Stoke's law. A particle B with diameter 20 microns settling in the same oil will have a settling velocity
same as that of A.
one fourth as that of A.
twice as that of A.
four times as that of A.
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
22 comments Page 3 of 3.

TANMAY SHAH said:   2 years ago
The settling velocity, and, as a result, settling time, are proportional to the diameter of the spherical particle squared.

The larger the sphere diameter, the faster the particle will settle.

The smaller the particle diameter, the longer it will stay suspended in the fluid.

So, V2/V1 = (D2)^2/(D1)^2.
V2/V1 = 20^2/10^2,
V2 = 4 V1.
So, option-D is the right answer.
(13)

May Saadoon said:   1 year ago
u(A)/u(B) = [dp(A)/dp(B)]^2.
u(A)/u(B) = [ 10 / 20 ] ^2.
u(A)/u(B) = 1/4,
u(A) = 1/4 u(B).
(2)


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