JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II FLUID MECHANICS AND OPEN CHANNEL HYDRAULICS Previous Question Paper (March - 2022 - R13)
Answer any five questions
All questions carry equal marks
Main
Explain briefly the following mechanical gauges:
Bourdon tube pressure gauge
Answer
A Bourdon tube pressure gauge is a mechanical device used to measure gauge pressure by utilizing the elastic deformation of a curved metal tube. The gauge consists of a thin-walled, hollow, C-shaped tube closed at one end and connected to the pressure source at the other. When fluid pressure is applied, the tube tends to straighten out due to the difference in force acting on its inner and outer surfaces. This small mechanical displacement is transmitted through a linkage and gear mechanism to a pointer, which rotates across a calibrated scale to indicate the pressure value.
Diaphragm gauge
Answer
A Diaphragm gauge measures pressure by sensing the deflection of a flexible, thin circular metallic plate or membrane. The diaphragm is clamped at its edges, and one side is exposed to the pressure being measured, while the other side is typically open to the atmosphere or a reference pressure. As the pressure acts on the diaphragm, it undergoes elastic deformation or bulging. This deflection is proportional to the applied pressure and is converted into a readable measurement using a mechanical linkage, gear train, or electrical transducer. These gauges are particularly useful for measuring low to medium pressures and are often used in applications where the process fluid must be isolated from the internal mechanism.
A U-tube manometer is used to measure the pressure of oil of specific gravity 0.85 flowing in a pipe line. Its left end is connected to the pipe and the right limb is open to the atmosphere. The centre of the pipe is 100mm below the level of mercury (specific gravity=13.6) in the right limb. If the difference of mercury level in the two limbs is 160mm, determine the absolute pressure of the oil in the pipe?
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Explain the characteristics of Boundary Layer.
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A pipe 200 m long slopes down at 1 in 100 and tapers from 600 mm diameter at the higher end to 300 mm diameter at the lower end, and carries 100 liter/sec of oil (sp. Gravity 0.8). If the pressure gauge at the higher end reads 60 KN/m2, determine:
Velocities at the two ends
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Pressure at the lower end. Neglect all losses.
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A discharge of 0.06 m3/s was measured over a right-angled notch. While measuring the head over the notch, an error of 1.5 mm was made. Determine the percentage error in the discharge, if the co-efficient of discharge for the notch is 0.6.
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A wooden block of specific gravity 0.75 floats in water. If the size of the block is 1m × 0.5m × 0.4m, find its metacentric height.
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Derive Darcy-weisbach formula for calculating loss of head due to friction in a pipe.
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A rectangular channel of 0.5 m width, a hydraulic jump occurs at a point where depth of water flow is 0.15 m and Froude number is 2.5. Determine:
The specific energy
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The critical and subsequent depths
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Loss of head.
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