JNTU
JNTU B.Tech II HYDRAULICS AND HYDRAULIC MACHINERY Previous Question Paper (December - 2018 - R15)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
PART-A
Derive an expression for the discharge through a channel by Chezy’s formula.
Answer
Chezy's formula is derived from the balance of forces on a fluid element in uniform flow. The force due to gravity component along the flow is equal to the shear force at the boundary. The expression is:
Where V is mean velocity, C is Chezy's constant, m is hydraulic mean depth (Area/Wetted Perimeter), and i is bed slope. The discharge is given by:
Define the term most economical section of a channel.
Answer
A channel section is considered most economical when it provides the maximum discharge for a given amount of excavation and lining, or conversely, when it requires the minimum wetted perimeter for a given discharge and slope. This minimizes the cost of construction and friction losses.
Explain different types of hydraulic similarities that must exist between a prototype and its model.
Answer
Sign in to view the complete answer paper.
What is meant by geometric, Kinematic and dynamic similarities? Are these similarities truly attainable? If not why?
Answer
Sign in to view the complete answer paper.
Derive the force exerted by a jet of water on a fixed vertical plate and moving vertical plate.
Answer
Sign in to view the complete answer paper.
Derive the force exerted by a jet on a single curved moving plate and a series of curved moving plate.
Answer
Sign in to view the complete answer paper.
Differentiate between the turbines and pumps.
Answer
Sign in to view the complete answer paper.
Explain the different types of the efficiency of a turbine.
Answer
Sign in to view the complete answer paper.
Differentiate between the volute casing and vortex casing for the centrifugal pump.
Answer
Sign in to view the complete answer paper.
Obtain an expression for the work done by impeller of a centrifugal pump on water per second per unit weight of water.
Answer
Sign in to view the complete answer paper.
PART-B
A trapezoidal channel to carry 142 m3/minute of water is designed to have a minimum cross – section. Find the bottom width and depth if the bed slope is 1 in 1200, the side slopes at 450 and chezy’s co-efficient =55.
Answer
Sign in to view the complete answer paper.
By applying the momentum equation to open channel flow, show that the consequent depths and flow rate are related by
Answer
Sign in to view the complete answer paper.
State Buckingham’s π theorem. What do you mean by repeating variables? How are the repeated variables selected in dimensional analysis?
Answer
Sign in to view the complete answer paper.
The variables controlling the motion of a floating vessel through water are the drag force F, the speed and the Length L, the density ρ and dynamic viscosity μ of water and acceleration due to gravity g. Derive expression for F by dimensional analysis.
Answer
Sign in to view the complete answer paper.
A 1: 20 model of a flying boat is towed through water. The prototype is moving in sea- water of density 1024 kg/m3 at a velocity of 15 m/s. Find the corresponding speed of the model. Also determine the resistance due to waves on model, if the resistance due to waves of prototype is 500 N.
Answer
Sign in to view the complete answer paper.
A jet of water having a velocity of 35 m/s impinges on a series of vanes moving with a velocity of 20m/s. The jet makes an angle of 300 to the direction of motion of vanes when entering and leaves at an angle of 1200. Draw the triangles of velocities at inlet and outlet and find:
The angles of vanes tips so that water enters and leaves without shock,
Answer
Sign in to view the complete answer paper.
The work done per unit weight of water entering the vanes, and
Answer
Sign in to view the complete answer paper.
The efficiency.
Answer
Sign in to view the complete answer paper.
Show that the hydraulic efficiency for a Francis turbine having velocity of flow through runner as constant, is given by the relation
Answer
Sign in to view the complete answer paper.
If vanes are radial at inlet, then show
Answer
Sign in to view the complete answer paper.
An outward flow reaction turbine has internal and external diameters of the runner as 0.6 m and 1.2 m respectively. The guide blade angle is 15o and velocity of flow through the runner is constant and equal to 4 m/s. If the speed of the turbine is 200 r.p.m., head on the turbine is 10 m and discharge at outlet is radial, determine:
The runner vane angles at inlet and outlet,
Answer
Sign in to view the complete answer paper.
Work done by the water on the runner per second per unit weight of water striking per second,
Answer
Sign in to view the complete answer paper.
Hydraulic efficiency, and
Answer
Sign in to view the complete answer paper.
The degree of reaction.
Answer
Sign in to view the complete answer paper.
A pelton wheel is supplied with water under a head of 35 m at the rate of 40.5 kilo litre/min. The bucket deflects the jet through an angle of 160o and the mean bucket speed is 13 m/s. Calculate the power and hydraulic efficiency of the turbine.
Answer
Sign in to view the complete answer paper.
Define the terms: specific speed of a turbine, unit speed, unit power and unit rate of flow of a turbine. Derive the expressions for specific speed and unit speed.
Answer
Sign in to view the complete answer paper.
Define cavitation. What are the effects of cavitation? Give the necessary precautions against cavitation?
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 30m. 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. Calculate:
- Minimum NPSH, and
- Maximum allowable height of the pump from free surface of water in the sump.
Answer
Sign in to view the complete answer paper.
How will you obtain an expression for the minimum speed for starting a centrifugal pump?
Answer
Sign in to view the complete answer paper.
A Francis turbine has been manufactured to develop 15000 horse power at the head of 81 m and speed 375 r.p.m. The mean atmospheric pressure at the site is 1.03 kgf/cm2 and vapour pressure 0.03 kgf/m2. Calculate the maximum permissible height of the runner above the tail water level to ensure cavitation free operation. The critical cavitation factor for Francis turbine is given by
Answer
Sign in to view the complete answer paper.