Gujarat Technological UniversitySummer 2026 examination

GTU BE04000161 Fluid Mechanics Summer 2026 Question Paper & PDF

B.E. · Mechanical Engineering · Semester 4 · Subject code BE04000161
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Total
70 marks
To pass
23 marks (33%)
Duration
2.5 Hours 10:30 AM – 1:00 PM
Questions
5 with internal choice
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Q.1

14 Marks
(a)
3 marks
The surface tension of water in contact with air at 20∘C20^\circ\text{C} is 0.0725 N/m0.0725\text{ N/m}. The pressure inside a droplet of water is to be 0.02 N/cm20.02\text{ N/cm}^2 greater than the outside pressure. Calculate the diameter of the water droplet.
(b)
4 marks
Explain the terms: Compressibility and Bulk Modulus.
(c)
7 marks
Find the magnitude and direction of the resultant force due to water acting on a roller gate of cylindrical form of 4.0 m4.0\text{ m} diameter, when the gate is placed on the dam in such a way that water is just going to spill. Take the length of gate as 8 m8\text{ m}.

Q.2

14 Marks
(a)
3 marks
Differentiate between: (i) Uniform and Non-Uniform flow (ii) Compressible and incompressible flow (iii) Rotational and Irrotational flow.
(b)
4 marks
A fluid flow field is given by V=x2yi+y2zj−(2xyz+y2z)kV = x^2 y i + y^2 z j - (2xyz + y^2 z)k. Prove that it is a case of possible steady incompressible fluid flow. Calculate the velocity at the point (2,1,3)(2, 1, 3).
(c)
7 marks
State Euler’s equation. Derive Bernoulli’s equation from Euler’s equation. What are the limitations of Bernoulli’s equations?
(c)
7 marks
Derive continuity equation in three dimensional Cartesian coordinates with usual notation and reduce it for steady incompressible flow.

Q.3

14 Marks
(a)
3 marks
Explain Hydraulic Grade Line and Total Energy Line. State their physical significance.
(b)
4 marks
Show that the value of co-efficient of friction for viscous flow through a circular pipe is given by, □ = 64/□□ where Re = Reynolds number.
(c)
7 marks
Derive Hagen–Poiseuille equation for laminar flow through a pipe. A pipe of diameter 150 mm150\text{ mm} carries oil (μ=0.9 Ns/m2\mu = 0.9\text{ Ns/m}^2). Calculate discharge when pressure drop over 10 m10\text{ m} length is 50 kPa50\text{ kPa}.
(a)
3 marks
Explain Darcy–Weisbach equation for head loss due to friction in pipes.
(b)
4 marks
Explain Moody diagram and its practical importance.
(c)
7 marks
An oil of viscosity 0.1 Ns/m20.1\text{ Ns/m}^2 and relative density 0.90.9 is flowing through a circular pipe of diameter 50 mm50\text{ mm} and of length 300 m300\text{ m}. The rate of flow of fluid through the pipe is 3.5 litter/s3.5\text{ litter/s}. Find the pressure drop in the length of 300 m300\text{ m} and also the shear stress at the pipe wall.

Q.4

14 Marks
(a)
3 marks
Explain Reynolds, Froude and Mach numbers with physical significance
(b)
4 marks
If power PP required to transport a fluid through a pipe depends on length of pipe LL, diameter DD, surface roughness KK, discharge QQ, density ρ\rho and coefficient of dynamic viscosity μ\mu. Using Buckingham-Pi method, find the desired expression.
(c)
7 marks
The inlet and throat diameter of the horizontal venturi meter is 30 cm30\text{ cm} and 10 cm10\text{ cm} respectively. The water is flowing through the meter. The pressure at the inlet is 13.734 N/cm213.734\text{ N/cm}^2 while the vacuum pressure head at throat is 37 cm37\text{ cm} of mercury. If the 4%4\% of the differential head is lost between inlet and throat, find coefficient of discharge and volume flow rate.
(a)
3 marks
Differentiate the term dimensional analysis and model analysis
(b)
4 marks

Using Buckingham’s π\pi-theorem, show that the velocity through a circular orifice is given by

V=2gH ϕ[D/H,μ/ρVH]V = \sqrt{2gH}\ \phi[D/H, \mu/\rho V H]
Where, H=Head causing flowH = \text{Head causing flow}, D=Diameter of the orificeD = \text{Diameter of the orifice}, μ=Co-efficient of viscosity\mu = \text{Co-efficient of viscosity}, ρ=Mass density\rho = \text{Mass density}, and g=Acceleration due to gravityg = \text{Acceleration due to gravity}.

(c)
7 marks
A nozzle of diameter 20 mm20\text{ mm} is fitted with the pipe of diameter 40 mm40\text{ mm}. find the force exerted by the nozzle on the water which is flowing through the pipe at rate of 1.2 m3/min1.2\text{ m}^3\text{/min}.

Q.5

14 Marks
(a)
3 marks
Explain laminar and turbulent flow with velocity distribution diagrams.
(b)
4 marks
Explain surface tension and capillarity with two engineering applications each.
(c)
7 marks
Derive an expression for velocity for the sound wave in a compressible fluid in terms of change of pressure and change of density.
(a)
3 marks
Explain the term co-efficient of friction. On what factors does this co-efficient depends?
(b)
4 marks
Differentiate between stable, unstable, and neutral equilibrium of floating bodies with neat sketches.
(c)
7 marks
Prove that the velocity of sound wave in compressible fluid is given by c=Kρc = \sqrt{\dfrac{K}{\rho}}, where K=Bulk modulus of fluid\text{K} = \text{Bulk modulus of fluid} and ρ=Density of fluid\rho = \text{Density of fluid}.

Other Semester 4 subjects

BE Mechanical

2141905
Complex Variables and Numerical Methods
3141901
Mechanical Measurement and Metrology
3141906
Fluid Mechanics and Hydraulics Machines
3141907
Fundamentals of Machine Design

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Official Gujarat Technological University (GTU) examination paper for Fluid Mechanics (Summer 2026, B.E. · Mechanical Engineering, Sem 4). Features complete 70-mark regular & remedial examination pattern, official marking distribution across all 5 questions, and direct 1-click official PDF download.

Transcribed for student exam preparation from Gujarat Technological University official examination archives. Questions, syllabus guidelines, and curriculum marking schemes remain the intellectual property of Gujarat Technological University.

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