Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Summer 4th Sem 2141906 Fluid Mechanics Previous Question Paper

Enrolment No.___________

**GUJARAT TECHNOLOGICAL UNIVERSITY**

**BE - SEMESTER? IV EXAMINATION ? SUMMER 2020**

**Subject Code: 2141906**

**Date:29/10/2020**

**Subject Name: FLUID MECHANICS**

**Time: 10:30 AM TO 01:00 PM**

**Total Marks: 70**

**Instructions:**

**1. Attempt all questions.**

**2. Make suitable assumptions wherever necessary.**

**3. Figures to the right indicate full marks.**

**Q.1 (a)**

Define the term continuum as applied to the mechanism of flow. Is the

**03**

continuum model valid in upper atmosphere?

**(b)**

State and prove the Pascal's law and give some examples where this

**04**

principle is applied.

**(c)**

Explain the term total pressure action on a plane surface in a fluid at any

**07**

angle. Obtain an expression for this, and also for the corresponding depth

of the centre of pressure.

**Q.2 (a)**

Derive Bernoulli's equation from momentum equation.

**03**

**(b)**

Calculate the capillary effect in mm in a glass tube of 4 mm diameter,

**04**

when immersed in (1) water and (2) mercury. The temperature of the

liquid is 20 oC and the value of the surface tension of water and mercury

at 20 oC in contact with air are 0.073575 N/m and 0.51 N/m respectively.

The angle of contact for water is zero and for mercury is 130 degree.

Take density of water 998 kg/m3.

**(c)**

State and explain stability criteria of submerged and floating bodies.

**07**

**OR**

**(c)**

A cylinder 2 m in diameter x 3 m in length and supported as shown in

**07**

figure-1 retains water on one side. If the cylinder weighs 150 kN, make

calculations for the vertical reactions at A and the horizontal reactions at

B. Ignore the frictional effects.

**Q.3 (a)**

Explain absolute, gauge and vacuum pressure.

**03**

**(b)**

Sketch and describe a pitot-static probe and explain how it is used to

**04**

measure the fluid flow through a pipeline.

**(c)**

Give brief description of classification of fluid flows.

**07**

**OR**

**Q.3 (a)**

Explain the difference between a simple and differential manometer.

**03**

**(b)**

Explain

the principle of dimensional homogeneity. Is dimensionally

**04**

homogeneous equation applicable in all systems of units?

**(c)**

Prove that for a steady laminar flow between two fixed parallel plates,

**07**

the velocity distribution across a section is parabolic and that the average

velocity is 2/3rd of the maximum velocity.

**Q.4 (a)**

Explain surface tension with some examples.

**03**

**(b)**

Obtain Darcy-Weisbach formula for head loss due to friction

**04**

**(c)**

The velocity components in a two-dimensional incompressible flow

**07**

3

3

*y*

*x*

field are expressed as

2

2

*u*

2

*x*

*x y and v*

*xy*2

*y*

.

3

3

Determine the velocity and acceleration at point P(x=1m , y=3m)

**OR**

**Q.4 (a)**

What is meant by turbulence? How does it affect the flow properties?

**03**

**(b)**

Derive Euler's equation of motion along a stream line.

**04**

1

**(c)**

The water in a tank is pressurized by air, and the pressure is measured

**07**

by a

multifluid manometer as shown in Figure-2. The tank is located on a

mountain at an altitude of 1400 m where the atmospheric pressure is 85.6

kPa. Determine the air pressure in the tank if h1 =0.1 m, h2 =0.2 m, and

h3=0.35 m. Take the densities of water, oil, and mercury to be 1000

kg/m3, 850 kg/m3, and 13,600 kg/m3, respectively.

**Q.5 (a)**

Explain why air flowing at low velocities can be considered

**03**

incompressible?

**(b)**

The efficiency of a fan depends on the density , the dynamic viscosity

**04**

? of the fluid, the angular velocity , diameter D of the rotor and

discharge Q. Express in terms of dimensionless parameters.

**(c)**

Explain the terms: Mach number, Mach cone, Mach line and Mach angle

**07**

in the context of compressible flow.

**OR**

**Q.5 (a)**

Explain the term Vorticity.

**03**

**(b)**

Derive the equation for momentum thickness

**04**

*u*

*u*

1

*dy*

*U*

*U*

*o*

0

0

**(c)**

A pipe carrying oil (Sp. Gr. 0.8) changes in diameter from 300 mm at

**07**

position 1 to 600 mm diameter at point 2 which is 5 metres at a higher

level. If the pressure at positions 1 and 2 are 100 kN/m2 and 60 kN/m2

respectively and discharge is 300 litres/sec. Determine : (i) loss of head

(ii) direction of flow.

**Figure 1**

**Figure 2**

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This post was last modified on 04 March 2021