Chemical Engineering - Fluid Mechanics - Discussion
Discussion Forum : Fluid Mechanics - Section 3 (Q.No. 47)
47.
Which of the following quantities are computed by using the hydraulic radius for non-circular ducts ?
Discussion:
3 comments Page 1 of 1.
Sujit said:
9 years ago
Please, explain how?
Per said:
8 years ago
Why not Friction factor?
Yogesh Makwana said:
2 months ago
The correct answer is: Reynolds number and friction factor.
Explanation:
For non-circular ducts (like rectangular or annular cross-sections), flow calculations use the concept of hydraulic radius to account for the geometry.
Hydraulic radius ( ) is defined as:
R_h = \frac{A}{P}
Where:
= Cross-sectional area of flow
= Wetted perimeter
Quantities that use hydraulic radius:
1. Reynolds number:
Re = frac{ρ u D_h}{mu}
= frac{ρ u cdot 4R_h}{mu}.
2. Friction factor (f):
Used in the Darcy-Weisbach equation for head loss.
Depends on the Reynolds number and relative roughness, where;
Other options:
Velocity: Can be computed using continuity or energy equations, not directly dependent on hydraulic radius.
Head loss: While indirectly related through the friction factor, it’s not computed by hydraulic radius itself.
So, Final Answer is Reynolds number and friction factor.
Explanation:
For non-circular ducts (like rectangular or annular cross-sections), flow calculations use the concept of hydraulic radius to account for the geometry.
Hydraulic radius ( ) is defined as:
R_h = \frac{A}{P}
Where:
= Cross-sectional area of flow
= Wetted perimeter
Quantities that use hydraulic radius:
1. Reynolds number:
Re = frac{ρ u D_h}{mu}
= frac{ρ u cdot 4R_h}{mu}.
2. Friction factor (f):
Used in the Darcy-Weisbach equation for head loss.
Depends on the Reynolds number and relative roughness, where;
Other options:
Velocity: Can be computed using continuity or energy equations, not directly dependent on hydraulic radius.
Head loss: While indirectly related through the friction factor, it’s not computed by hydraulic radius itself.
So, Final Answer is Reynolds number and friction factor.
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