Fluid Mechanics MCQ Questions & Answers

41

The Stoke's stream function applies to the

A) Irrotational flow only B) Ideal/non-viscous fluids only C) Cases of axial symmetry D) None of these

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Answer & Solution

Answer: Option C

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42

In case of turbulent flow of a Newtonion fluid in a straight pipe, the maximum velocity is equal to (where, V_avg = average fluid velocity)

A) V_avg B) 1.2 V_avg C) 1.5 V_avg D) 1.8 V_avg

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Answer & Solution

Answer: Option B

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43

For Laminar flow through a packed bed, the pressure drop is proportional to (V_s is the superficial liquid velocity and D_p is the particle diameter)

A) $$\frac{{{{\text{V}}_{\text{s}}}}}{{{{\text{D}}_{\text{p}}}^2}}$$ B) $$\frac{{{{\text{V}}_{\text{s}}}^2}}{{{{\text{D}}_{\text{p}}}^2}}$$ C) $$\frac{{{{\text{V}}_{\text{s}}}^2}}{{{{\text{D}}_{\text{p}}}^3}}$$ D) $$\frac{{{{\text{V}}_{\text{s}}}}}{{{{\text{D}}_{\text{p}}}^3}}$$

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Answer & Solution

Answer: Option A

Solution:

For laminar flow in a packed bed (imagine a pipe filled with small balls), the pressure drop (how much the pressure decreases as the fluid flows) depends on how fast the fluid is moving and the size of the balls.
Ergun Equation describes this relationship. For laminar flow, a simplified version of the Ergun equation is used.
This simplified version shows that the pressure drop is directly proportional to the superficial velocity (Vs) and inversely proportional to the square of the particle diameter (Dp).
Superficial velocity (Vs) means the velocity of the fluid if the bed were empty.
Particle diameter (Dp) is the size of the balls in the packed bed.
Therefore, if the superficial velocity increases, the pressure drop increases. If the particle diameter increases, the pressure drop decreases (because bigger particles offer less resistance to flow).
Looking at the options, only option A shows this direct proportionality to Vs and inverse proportionality to the square of Dp (Dp²).
Option A: Vs/Dp² correctly represents this relationship for laminar flow in a packed bed.

44

The equation given below is called the __________ .
$${{\text{f}}^{ - 0.5}} = 4.07\,{\log _{\text{e}}}{\left( {{{\text{N}}_{{\text{Re}}}}\sqrt {\text{f}} } \right)^{ - 0.6}}$$

A) Colebrook formula B) Von-Karman equation C) Fanning equation D) None of these

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Answer & Solution

Answer: Option B

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45

The fluid velocity varies as the square root of the cylindrical pipe diameter in case of steady state laminar flow at constant pressure drop fo __________ fluid.

A) Dilatant B) Pseudo-plastic C) Bingham plastic D) Newtonion

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Answer & Solution

Answer: Option A

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46

Permanent loss in a venturimeter is about __________ percent of the pressure drop in theupstream cone.

A) 1 B) 10 C) 40 D) 70

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Answer & Solution

Answer: Option B

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47

The pressure drop per unit length of pipe incurred by a fluid 'X' flowing through pipe is $$\Delta {\text{p}}.$$ If another fluid 'Y' having both the specific gravity & density just double of that of fluid 'X', flows through the same pipe at the same flow rate/average velocity, then the pressure drop in this case will be

A) $$\Delta {\text{p}}$$ B) $$2\Delta {\text{p}}$$ C) $$\Delta {{\text{p}}^2}$$ D) $$\frac{{\Delta {\text{p}}}}{2}$$

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Answer & Solution

Answer: Option B

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48

The simple pitot tube measures the __________ pressure.

A) Static B) Dynamic C) Total D) None of these

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Answer & Solution

Answer: Option C

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49

The peripherial velocity at inlet of a centrifugal pump having inlet diameter of 25 cms and rotating at 950 rpm is __________ m/sec.

A) 1.8 B) 12.4 C) 186.2 D) 736.4

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Answer & Solution

Answer: Option B

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50

Which of the following is not a dimension-less parameter?

A) Euler number B) Specific gravity C) Fanning friction factor D) None of these

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Answer & Solution

Answer: Option D

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Fluid Mechanics MCQ Questions & Answers | Chemical Engineering