JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year HYDRAULICS AND HYDRAULIC MACHINERY Previous Question Paper (November/December - 2020 - R15)
Answer any Five Questions. All Questions Carry Equal Marks.
Main
Find the bed slope of the trapezoid channel of bed width 6 m, depth of water 3m and side of slop 3 horizontal to 4 vertical, when the discharge through the channel is 30 m3/s. Take Chezy’s constant C = 70.
Answer
Given parameters for the trapezoidal channel are:
- Bed width (b) = 6 m
- Depth of water (y) = 3 m
- Side slope (n) = 3 horizontal to 4 vertical, so n = 3/4 = 0.75
- Discharge (Q) = 30 m3/s
- Chezy's constant (C) = 70
First, calculate the area of flow (A) and the wetted perimeter (P):
Next, determine the hydraulic radius (R):
Using the Chezy formula for discharge Q = A × C × √(Ri), where i is the bed slope:
Squaring both sides to solve for i:
The bed slope of the channel is approximately 1 in 6116.
Explain about hydraulic jump and energy dissipation for varied flow phenomena.
Answer
A hydraulic jump is a localized phenomenon occurring in an open channel flow when liquid at a high velocity discharges into a zone of lower velocity, resulting in a sudden rise in the liquid surface. It represents a transition from supercritical flow (Froude number > 1) to subcritical flow (Froude number < 1).
The jump is characterized by a turbulent roller, significant surface agitation, and a rapid increase in flow depth. The relationship between the depths before (y1) and after (y2) the jump is given by the Belanger equation:
where Fr1 is the Froude number at the supercritical section.
Energy dissipation is the primary functional purpose of a hydraulic jump in hydraulic engineering. As the flow transitions, a substantial portion of the kinetic energy is converted into heat due to intense turbulence and eddy formation. The energy loss (ΔE) is calculated as:
Key aspects of energy dissipation include:
- Stilling Basins: Engineers design hydraulic structures such as spillways and sluice gates to force a hydraulic jump within a controlled area called a stilling basin. This prevents downstream erosion by dissipating excess energy before the water enters the natural channel bed.
- Flow Control: By managing the jump location through baffle blocks or end sills, the velocity is reduced to a non-erosive level.
- Efficiency: The efficiency of the jump is defined as the ratio of energy after the jump to energy before the jump. Higher Froude numbers result in greater energy dissipation, making the jump more effective at higher supercritical velocities.
Derive an expression for the drag force on smooth sphere of diameter D, moving with a uniform velocity V in a fluid of density ρ and dynamic viscosity μ.
Answer
Sign in to view the complete answer paper.
A pipe of diameter 1.5 m is required to transfer an oil of sp.gr. 0.90 and viscosity 3 × 10-2 poise at the rate of 3000 litre/s. Tests were conducted on a 15 cm diameter pipe using water at 20°C. Find the velocity and rate of flow in the model. Viscosity of water at 20°C = 0.01 poise.
Answer
Sign in to view the complete answer paper.
A nozzle of 50 mm diameter delivers a stream of water at 20 m/s perpendicular to a plate that moves away from the jet at 5 m/s. Find the force on the plate, work done/sec, and the efficiency of the jet.
Answer
Sign in to view the complete answer paper.
Draw the layout of a typical hydropower installation and explain its components.
Answer
Sign in to view the complete answer paper.
A Kaplan turbine runner is to be designed to develop 9100 kW. The net available head is 5.6 m. If the speed ratio = 2.09, flow ratio = 0.68, overall efficiency = 86% and the diameter of the boss is 1/3 the diameter of the runner. Find the diameter of the runner, its speed and the specific speed of the turbine.
Answer
Sign in to view the complete answer paper.
A centrifugal pump rotating at 1000 r.p.m. delivers 160 litres/s of water against a head of 30 m. The pump is installed at a place where atmospheric pressure is 1 × 105 Pa (abs.) and vapour pressure of water is 3 kPa (abs.). The head loss in suction pipe is equivalent to 0.2 m of water.
Answer
Sign in to view the complete answer paper.
Answer
Sign in to view the complete answer paper.