Fluid Properties and Flow Regimes - Classification of Flows - Engineering Sciences Previous Year Questions

1

2007 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2007

For a two-dimensional turbulent boundary layer, the wall shear stress can be expressed as \(\tau_w = \mu \left.\frac{\partial u}{\partial y}\right|_{wall}\) where \(u\) is the velocity parallel to the wall and \(y\) is the coordinate perpendicular to the wall. In the above expression, \(\mu\) denotes

A

the molecular viscosity of the fluid

B

the turbulent eddy viscosity

C

an effective viscosity which is greater than the molecular viscosity

D

an effective viscosity that is less than the molecular viscosity

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2

2007 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2007

Consider a constant pressure boundary layer over a flat plate of length L = 3 m. The freestream velocity is U = 60 m/s and the density and viscosity of the fluid respectively are ρ = 1.23 kg/m³ and μ = 1.79 × 10⁻⁵ Ns/m². Transition occurs at a distance x_cr = 0.1m from the leading edge. If the free stream velocity is changed to U = 120 m/s, x_cr becomes

A

0.2 m

B

0.1 m

C

0.05 m

D

0.005 m

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3

2008 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2008

A cubical block of melting ice (20 cm x 20 cm x 20 cm) rests on a smooth horizontal floor over a layer of water of 0.1 mm thickness. To pull the block at a speed of 1 m/s a force of 1 N is required. What is the force required to pull the block at a speed of 2 m/s?

A

0.5 N

B

1 N

C

2 N

D

4 N

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4

2009 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2009

An oil droplet (density = 800 kg/m³) is rising in still water at a constant velocity of 1 mm/s. Its radius is approximately

A

21 micron

B

24 micron

C

34 micron

D

47 micron

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5

2009 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2009

Which of the following statements are true ?
P : In Case 1, the velocity at section A is twice the velocity at section B
Q : In Case 1, the velocity at section A is half the velocity at section B
R : In Case 2, the flow rate at section A is twice that at section B
S : In Case 2, the flow rate at section A is half that at section B

A

P, R

B

P, S

C

Q, R

D

Q, S

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6

2010 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2010

Water at 20°C is pumped from a base tank to an elevated tank, 15 m above the base tank. Water flows at a rate of 5.0 × 10^-3 m³ s^-1 through a pipe having internal diameter of 0.1023 m. Frictional energy loss in the pipe is 6.837 J kg^-1. The pump has an efficiency of 63%. Density and viscosity of water are 998.2 kg m^-3 and 1.005 × 10^-3 Pa s, respectively.
Reynolds number for water flowing through the pipe is

A

5.286 × 10⁴

B

6.180 × 10⁴

C

2.285 × 10⁴

D

1.252 × 10⁵

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7

2011 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2011

For a fully developed flow between two parallel flat plates, the velocity gradient at a point is found to be 1000 s⁻¹. If the density of the fluid is 880 kg/m³ and the kinematic viscosity of the fluid is 7.4 × 10⁻⁷ m²/s, the shear stress at the same point is approximately

A

0 Pa

B

1.30 Pa

C

0.32 Pa

D

0.65 Pa

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8

2014 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2014

A Bingham plastic fluid is flowing under gravity, down a vertical plate, as a film. Find the appropriate match for the fully developed velocity profile of the fluid in the film, from among those shown below.

A

[Image]

B

[Image]

C

[Image]

D

[Image]

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9

2015 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2015

Milk is flowing at 0.12 m³/min in a 2.5 cm diameter pipe. The temperature of the milk is 21 °C and the corresponding viscosity and density are 2.1 x 10⁻³ Pas and 1029 kg/m³, respectively. If the flow is found to be turbulent under the given conditions, the Reynolds number is __________

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10

2017 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2017

Two infinite parallel horizontal plates are separated by a small gap ($d = 20$ mm) as shown in figure. The bottom plate is fixed and the gap between the plates is filled with oil having density of 890 kg/m³ and kinematic viscosity of 0.00033 m²/s. A shear flow is induced by moving the upper plate with a velocity of 5 m/s. Assume, linear velocity profile between the plates and the oil to be a Newtonian fluid. The shear stress (N/m²) at the upper plate is __________

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11

2017 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2017

A 50% sucrose solution at 20 °C is flowing at a rate of 3.5 m³/h through a pipe with an inside diameter of 0.0475 m and length of 12 m. The viscosity and the density of the solution are 15.43 cp and 1232 kg/m³, respectively. The Reynolds number of the flow is ______.

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12

2018 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2018

Identify the correct statement related to the viscosity of Newtonian fluids from the following

A

It is not influenced by temperature

B

It increases with shearing rate

C

It decreases with shearing rate

D

It is not influenced by shearing rate

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13

2018 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2018

On a flat plate, transition from laminar to turbulent boundary layer occurred at a critical Reynolds number (Re_cr). The empirical relations for the laminar and turbulent boundary layer thickness are given by \frac{\delta_{lam}}{x} = 5.48 Re_x^{-0.5} and \frac{\delta_{turb}}{x} = 0.37 Re_x^{-0.2}, respectively. The ratio of laminar to turbulent boundary layer thickness, at the location of transition, is 0.3. The value of Re_cr is ______.

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14

2018 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2018

The plot shows apparent viscosity versus shear rate of Newtonian, Dilatant and Pseudoplastic fluids. Based on this plot and the fluid behaviour as mentioned below, find out the correct combination.

A

P-1; Q-2; R-3

B

P-3; Q-1; R-2

C

P-2; Q-3; R-1

D

P-2; Q-3; Q-1

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15

2020 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2020

The variation of shear stress (τ) against strain rate (du/dy) is given in the Figure. Identify the line/curve among P, Q, R and S, that represents an ideal fluid.

A

S

B

P

C

Q

D

R

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16

2020 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2020

The whole milk at 22 °C is pumped through a stainless steel pipe at a flow rate of 3 L s⁻¹. The length and inner diameter of the pipe are 40 m and 4 cm, respectively. If viscosity and density of the milk at the pumping temperature of 0.2 Pa s and 1032 kg m⁻³, respectively, the Reynolds number (rounded off to nearest integer) will be ______.

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17

2021 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2021

Which of the following expressions represent the Reynolds number of a fluid flowing through a uniform circular cross section pipe?

A

\(\frac{\text{(density of the fluid)}\times \text{(average velocity of the fluid)}\times \text{(internal diameter of the pipe)}}{\text{(dynamic viscosity of the fluid)}}\)

B

\(\frac{\text{(average velocity of the fluid)}\times \text{(internal diameter of the pipe)}}{\text{(kinematic viscosity of the fluid)}}\)

C

\(\frac{\text{(dynamic viscosity of the fluid)}}{\text{(average velocity of the fluid)}\times \text{(density of the fluid)}\times \text{(internal diameter of the pipe)}}\)

D

\(\frac{\text{(kinematic viscosity of the fluid)}}{\text{(average velocity of the fluid)}\times \text{(internal diameter of the pipe)}}\)

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18

2021 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2021

The general relationship between shear stress, $\tau$ , and the velocity gradient $\left(\frac{du}{dy}\right)$ for a fluid is given by $\tau = k \left(\frac{du}{dy}\right)^n$ , where $k$ is a constant with appropriate units. The fluid is Newtonian if

A

$n > 1$

B

$n < 1$

C

$n = 1$

D

$n = 0$

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19

2022 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2022

As temperature increases

A

the dynamic viscosity of a gas increases.

B

the dynamic viscosity of a liquid decreases.

C

the dynamic viscosity of a liquid does not change.

D

the dynamic viscosity of a gas decreases.

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20

2023 · Engineering Sciences · Classification of Flows · Fluid Properties and Flow Regimes

Engineering Sciences (XE) 2023

Among the shear stress versus shear strain rate curves shown in the figure, which one corresponds to a shear thinning fluid?

A

P

B

Q

C

R

D

S

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