HHM - FAQ

Unit 1:

• Classification of Channels?

• Classification of Flows? (Answer)

• Write Chezy’s Equation? Write factors affecting Chezy’s C. (Answer)

• Determine the dimensions of the most economical trapezoidal earth-lined channel (Manning-s n = 0.02) to carry 14 m3/s at a slope of 4 in 10,000.

• Calculate the flow rate for a rectangular channel 5m wide for uniform flow at a depth of 1.5m. The bed slope is 1 in 1000. Use Chezy’s C is 50.

• Determine the dimensions of the most economical trapezoidal earth-lined channel (Chezy’s C is 55) to carry 6 m3/s at a velocity of 1.5m/s. Channel side slopes are at 1 vertical and 2 horizontal.

• Determine the dimensions of an economical Trapezoidal section of an open channel with sides slope 2H:1V laid at a slope of 1 in 1600 to carry a discharge of 36 cumecs assuming chezy’s coefficient C = 50

Unit 2:

• Explain GVF and RVF?

• Explain Hydraulic Jump? Types? (Answer)

• Classification of Bed Slope Profiles? (Answer)

• What is critical flow? Derive the condition for max. discharge for a given value of specific energy.

• The discharge of water through a rectangular channel of width 6 m is 18 m3/s when depth of flow of water is 2 m. Calculate: i). Critical depth and critical velocity and ii). Minimum specific energy

• A rectangular channel 6 m wide discharges 11200 liters/sec of water into a 6 m wide apron with no slope with a mean depth velocity of 6 m/s. What is the height of the jump? How much energy is absorbed in the jump?

• A hydraulic jump occurs in a 0.5 m wide rectangle channel at a depth of flow is 0.15m. Take Froude number is 2.5. Calculate loss of energy?

Unit 3:

• Write Dimensions for a) Discharge, b) Power, c) Velocity, d) Density

• What is dimensionally homogeneous equation? Give examples?

• Explain Laws of Similitude and its significance?

• In a 1:20 model of stilling basin, the height of the hydraulic jump in the model observed to be 20cm. What is the height of the hydraulic jump in the prototype? If the energy dissipated in the model is 1 HP. What is the corresponding value in prototype?

• Write Dimensions for a) Pressure, b) Viscosity c) Velocity d) Surface Tension

• In a 1:25 model of stilling basin, the velocity in the model observed to be 5 liters/sec. What is the velocity in the prototype? If the energy dissipated in the model is 1.5 HP. What is the corresponding value in prototype?

• In a 1:25 model of stilling basin, the height of the hydraulic jump in the prototype observed to be 4m. What is the height of the hydraulic jump in the model? If the energy dissipated in the prototype is 4000 HP. What is the corresponding value in model?

Unit 4:

• Explain Principle of Impulse Momentum?

• Derive Hydrostatic force of fluid for Stationary Normal Vane?

• Derive Hydrostatic force of fluid on a Moving Curved Vane?

• Derive Hydrostatic force of fluid for Stationary Inclined Vane?

• Find the force exerted by a jet of water of diameter 100mm on a stationary flat vane, when the jet strikes the vane normally with a velocity of 30m/sec.

• A jet of water of diameter 50mm having a velocity of 20m/sec strikes a inclined vane which is moving with a velocity of 10m/sec in the direction of the jet. Find the force exerted by a jet of water

• A jet of water of diameter 50mm moving with a velocity of 20m/sec strikes a fixed plate in such a way that the angle between the jet and the plate is 600. Find the force exerted by the jet on the plate a) in the direction normal to the plate b) in the direction of the jet.

Unit 5:

• A Kaplan turbine works under a head of 25m and runs at 150rpm. The diameters of the runner and boss are 4.50m and 2.5m respectively. The flow ratio is 0.43. The inlet vane angle at the extreme edge of the runner is 150⁰. If the turbine discharges radially at outlet, determine the discharge, the hydraulic efficiency, the guide blade angle at the extreme edge of the runner and outlet vane angle at the extreme edge of the runner. And also draw the inlet and outlet velocity triangles.

• Differentiate between Reaction turbines and hydraulic turbines.

• What is a draft tube? Why is it used in a reaction turbine? Explain with the help of sketches three different types of draft tubes.

• A Pelton wheel has a tangential velocity of buckets of 15 m/sec. The water is being supplied under a head of 38m at the rate of 25lps. The bucket deflects the jet through an angle of 160⁰. If the coefficient of velocity of the nozzle is 0.98, find the power product by the turbine.

• Design a Francis turbine for the following data:

Gross head available = 70m

Losses in the penstocks =15% of gross head

Speed = 850 rpm

Out put power =360 kw

Hydraulic efficiency =94%

Overall efficiency = 85%

Assume 5% of the circumferential area of the runner is occupied by the thickness of vanes. The velocity of flow remains constant throughout. Assume any missing data suitably.

Unit 6:

• Where is the location of surge tank in hydro power installation? Explain with a neat sketch. (Answer)

• What are the conditions for the kinematic similarity to exist between model and prototype?

• A Kaplan turbine is to develop 2800 KW when running at 250 rpm under a net head of 50m. In order to predict its performance a model of scale 1:5 is tested under a net head of 25m. At what speed should the model run and what power would it develop. Determine the discharge in the model and in full scale turbine if the overall efficiency of the model is 85%.

• What is Thoma‘s cavitation factor? What is its significance?

· A Francis turbine working under a head of 5 m at a speed of 200 rpm develops 100 KW when the rate of flow of water is 1.8 m3/ sec. If the head is increased to 16m, determine the speed, discharge and power.

• Tests were conducted on a Francis turbine of 0.8m diameter under a head of 10m. The turbine developed 125 KW running at 240 rpm and consuming 1.2 m3/sec. If the same turbine is operated under a head of 16m predict its new speed, discharge and power.

• What are the requirements of a governor in hydropower Installation?

Unit 7:

• Define static and manometric head of a centrifugal pump. State the different types of head losses which may occur in a pump installation.

• A centrifugal pump lifts water under a static head of 40m of water of which 5m is suction lift. Suction and delivery pipes are both 15 cm in diameter. The head loss in suction pipe is 1.8 m and in delivery pipe 7m. The impeller is 38cm in diameter and 2.5 cm wide at mouth and revolves at 1200 rpm. Its exit blade angle is 35⁰. If the manometric efficiency of the pump is 85% determine the discharge and pressure at the suction and delivery branches of the pump.

• Explain the classification of centrifugal pumps. (Answer)

• A centrifugal pump 20 cm diameter running at 1500 rpm delivers 1m³/s against a head of 50m with an efficiency of 90%. Determine its specific speed. Derive the formula you use.

• Define a centrifugal pump. Explain the working of a single stage centrifugal pump.

• The water is to be pumped out of a deep well under a total head of 100m. A number of identical pumps of design speed 1000 rpm and specific speed 800 rpm with a rated capacity of 150 lps are available. How many pumps will be required and how should they be connected?

• A centrifugal pump delivers 0.05 cumec of water to a height of 20 m through a 10 cm diameter pipe 150 m long. If the overall efficiency of the pump is 75%. Find the h.p. required to drive the pump. Take f = 0.01

Unit 8: (Answers)

• Draw the typical layout of hydroelectric power plant and explain its components.

• Write down the advantages and disadvantages of hydroelectric power plants

• Explain different measures to be taken for safe operation of hydroelectric power plants.

• Classification of Hydroelectric Power Plants?