Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech II FLUID MECHANICS AND HYDRAULICS Previous Question Paper (March - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
The right limb of a simple U-tube manometer containing mercury is open to the atmosphere while the left limb is connected to a pipe in which a fluid of sp. Gr. 0.9 is flowing. The centre of pipe is 12 cm below the level of mercury in the right limb. Find the pressure of fluid in the pipe if the difference of mercury level in the two limbs is 20 cm.
Answer
To find the pressure of the fluid in the pipe, we apply the principle of hydrostatic equilibrium, which states that the pressure at any two points at the same level in a continuous static fluid is equal. Let the datum line be the level of the lower mercury surface in the left limb.
Given data:
- Specific gravity of fluid in pipe (S1) = 0.9
- Specific gravity of mercury (S2) = 13.6
- Difference of mercury level in the two limbs (h2) = 20 cm = 0.2 m
- Height of the centre of the pipe above the datum line (h1) = (20 cm - 12 cm) = 8 cm = 0.08 m
Equating the pressure at the datum line in both limbs:
Substituting the values where ρ1 = 900 kg/m3, ρ2 = 13600 kg/m3, and g = 9.81 m/s2:
Thus, the pressure of the fluid in the pipe is 25.98 kPa.
Find the kinematic viscosity of an oil having density 981 kg/m3. The shear stress at a point in oil is 0.2452 N/m2 and velocity gradient at that point is 0.2 per second.
Answer
To find the kinematic viscosity, we first determine the dynamic viscosity using Newton's law of viscosity, which states that shear stress is proportional to the velocity gradient:
Given values:
- Shear stress (τ) = 0.2452 N/m2
- Velocity gradient (du / dy) = 0.2 s-1
- Density (ρ) = 981 kg/m3
First, calculate the dynamic viscosity (μ):
Next, calculate the kinematic viscosity (ν) using the relation:
Thus, the kinematic viscosity of the oil is approximately 1.25 × 10-3 m2/s.
A 25 cm diameter pipe carries oil of sp. Gr. 0.9 at a velocity of 3 m/s. At another section the diameter is 20 cm. Find the velocity at this section and also mass rate of flow of oil.
Answer
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Define the equation of continuity. Obtain an expression for continuity equation for a three-dimensional flow.
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A pipe of diameter 400 mm carries water at a velocity of 25 m/s. the pressure at the points A and B are given as 29.43 N/cm2 and 22.563 N/cm2 respectively while the datum head at A and B are 28 m and 30 m. Find the loss of head between A and B.
Answer
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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. Calculate the discharge of oil through the horizontal venturimeter. Take Cd = 0.98.
Answer
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Define displacement thickness. Derive an expression for the displacement thickness.
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Explain the working principle of centrifugal pump.
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Define turbo machine. Explain the principal components of turbo machine.
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