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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER-III EXAMINATION WINTER 2018
Subject Code:X31901 Date: 17/11/2018
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

Define the following terms:1)Viscocity,2)Surface tension,3)Capilarity.4)Vapour pressure,5)Cavitation,6)Specific weight,7)Specific Density
07

State and prove Pascal's law with usual notations.
07
Q.2

Define total pressure and centre of pressure and derive the equations for vertical plane surface submerged in liquid.
07

Calculate the capillary rise in a glass tube of 2.5 mm diameter when immersed vertically in water and mercury. Take surface tension σ 0.0725 N/m and σ=0.52 N/m for mercury in contact with air. The specific gravity of mercury is given as 13.6 and angle of contact =130o .
07
OR

A simple U-tube manometer containing mercury is connected to a pipe in which a fluid of specific gravity 0.8 and having vacuum pressure is flowing. The other end of the manometer is open to atmosphere. Find the vacuum pressure in pipe, if the difference of mercury level in the two limbs is 40 cm and the height of fluid in the left from the centre of pipe is 15 cm below.
07
Q.3

Explain Buoyancy, centre of pressure, metacentre and metacentric height in details.
07

A uniform body of size 3m long x2m wide x 1m deep floats in water. What is the weight of the body if depth of immersion is 0.8m? Determine the metacentric height also.
07
OR
Q.3

Explain types of fluid flow in details.
07

A 25 cm diameter pipe carries oil of sp.gr.0.9 at a velocity of 3m/s .At another section the diameter is 20 cm.Find the velocity at this section and also mass rate of flow of oil.
07
Q.4

Derive Euler's equation of motion.
07

An oil of sp.gr.0.8 is flowing through a venturimeter having inlet diameter 20 cm and throat diameter 10 cm.The oil-mercury differential manometer shows a reading of 25 cm.Calculte the discharge of oil through the horizontal venturimeter.Take Cd=0.98
07
OR
Q.4

Explain Notches and Weirs and classify both.
07

Derive an expression for the velocity distribution for viscous flow through a circular pipe. Also sketch the velocity distribution and shear stress distribution across a section of the pipe.
07
Q.5

State and explain Buckingham's π-theorem
07
2

A gas is flowing through a horizontal pipe which is having area of cross section as 40 cm2, where pressure is 40 N/cm2 (gauge) and temperature 15o C.At another section the area of cross section is 20 cm2 and pressure is 30 N/cm2 (gauge).If mass flow of gas through the pipe is 0.5 find the velocities of gas at these sections, Assuming an Isothermal change. Take R=292 N-m/kgoK, and atmospheric pressure =10 N/cm2.
07
OR
Q.5

What power is required per kilometer of a line to overcome the viscous resistance to the flow of glycerin through a horizontal pipe of diameter 100 mm at the rate of 10 liters/s?Take poise and kinematic viscosity(v)=6.0 stokes.
07

Derive an expression for velocity of sound wave for a compressible fluid when the process is assumed as: Isothermal Adiabatic.
07