Sunday, April 10, 2011

HHM - Chezy's Equation

Chezy's Equation

The Chezy formula can be used to calculate mean flow velocity in conduits and is expressed as

v = c (R S)^1/2 (1)
where
v = mean velocity (m/s, ft/s)
c = the Chezy roughness and conduit coefficient
R = hydraulic radius of the conduit (m, ft)
S = slope of the conduit (m/m, ft/ft)

In general the Chezy coefficient - c - is a function of the flow Reynolds Number - Re - and the relative roughness - ε/R - of the channel.

ε is the characteristic height of the roughness elements on the channel boundary

More..

HHM - Hydraulic Jump

Hydraulic Jump

A hydraulic jump is a sudden rise in water level due to decreasing velocity.

In flowing water, the water before the jump is moving much faster than the water after the jump. When the velocity of the water decreases to critical flow speed a jump occurs. Above this velocity, the water is moving too quickly to allow gravity waves to move upstream. At the point where the water reaches critical flow speed, the gravity waves become unable to move upstream, and build up at the jump, forming the sudden increase in water level, called a hydraulic jump.

Froude’s Number:

In order for a hydraulic jump to occur, the flow must be supercritical. The jump becomes more turbulent and more energy is dissipated as Froude’s number increases. A jump can only occur when the Froude’s number is greater than 1.0. Froude’s number (Fr) is a ratio relating inertia and gravity forces.

V=velocity

g=gravitational constant

y=depth of flow in open channel

Types of Hydraulic Jumps:

Name	Froude’s Number	Energy dissipation	Characteristics
Undular Jump	1.0-1.7	<5%	Standing waves
Weak Jump	1.7-2.5	5-15%	Smooth rise
Oscillating Jump	2.5-4.5	15-45%	Unstable; avoid
Steady Jump	4.5-9.0	45-70%	Best design range
Strong Jump	>9.0	70-85%	Choppy, intermittent

In standing waves there is only a slight difference in depths y1 and y2. Near Fr₁ = 1.7 a series of small rollers develops.
When the Froude’s number is between 1.7 and 2.5, the flow is in the pre-jump condition. The water surface is quite smooth, the velocity is reasonably uniform, and the energy loss is low.
The transition region is when the Froude’s number is between 2.5 and 4.5. An oscillating action of the jump exists. Each oscillation of the jump produces a large wave of irregular period that can travel downstream for miles and damage earth banks. It is recommended to avoid this range of Froude numbers in the design of stilling basins.
The best range for dissipating energy effectively is with a Froude number from 4.5-9.0. The jump is well balanced and the action is at its best. Energy losses range from 45% to 70%.
Effective, but rough jumps occur at dissipating energy when Froude’s number is greater than 9.0. Energy losses range from 70% to 85%. Other types of stilling basins may be more economical.

HHM - Classification of Bed Slope Profiles

CLASSIFICATION OF CHANNELS FOR GRADUALLY-VARIED FLOW

Open channels are classified as being mild, steep, critical, horizontal, and adverse in gradually-varied flow studies. If for a given discharge the normal depth of a channel is greater than the critical depth, the channel is said to be mild. If the normal depth is less than the critical depth, the channel is calledsteep. For a critical channel, the normal depth and the critical depth are equal. If the bottom slope of a channel is zero, the channel is called horizontal. A channel is said to have an adverse slope if the channel bottom rises in the flow direction. In summary:

Mild channels	y _n> y _c
Steep channels	y _n< y _c
Critical channels	y _n = y _c
Horizontal channels	S ₀ = 0
Adverse channels	S ₀< 0

where y _n = normal depth and y _c = critical depth.

HHM - Classification of Centrifugal Pumps

Centrifugal Pump:

A centrifugal pump is one of the simplest pieces of equipment. Its purpose is to convert energy of an electric motor or engine into velocity or kinetic energy and then into pressure of a fluid that is being pumped.

The energy changes occur into two main parts of the pump, the impeller and the volute. The impeller is the rotating part that converts driver energy into the kinetic energy. The volute is the stationary part that converts the kinetic energy into pressure.

Centrifugal Force:

Liquid enters the pump suction and then the eye of the impeller. When the impeller rotates, it spins the liquid sitting in the cavities between the vanes outward and imparts centrifugal acceleration. As the liquid leaves the eye of the impeller a low pressure area is created at the eye allowing more liquid to enter the pump inlet.

Centrifugal pumps are used for large discharge through smaller heads

Classification:

1. Turbo-pumps or Rotodynamic pump

a. Radial flow or Centrifugal pump

i. Volute Pump

1. Single Stage Pump

2. Multi-stage Pump

ii. Turbine Pump

1. Single Stage Pump

2. Multi-stage Pump

b. Axial flow or Propeller pump

c. Semi axial flow or Mixed flow pump

2. Positive Displacement Pumps

a. Reciprocating Pumps

b. Rotary Pumps

3. Jet Pumps

Estimation and Costing - Important Questions

Unit 1:

Define Estimating? Method of Estimation? Explain with examples?

What are Detailed Estimate and Abstract Estimate? List out Types of Estimation?

Give the area co-efficient required for Painting of wood work in the preparation of detailed estimate?

Give the % of steel used for RCC Item of work for Column footings, Columns, Plinth Beam, and Roof Slab in the preparation of detailed estimate?

Write short notes on a) Plinth Area Estimate, b). Revised Estimate, c), Supplementary Estimate, and d) Actual or Complete Estimate

List out main items of work of a building with unit of measurement?

List out the common L.S. provisions required for a Building?

List and explain any eight general items of work involved in the estimation for a building along with the process of calculations.

“An estimate is never the actual cost of work" justify your answer with a suitable example

Enumerate different methods for estimating building works along with a suitable example

Explain the following general items of work involved in the estimation for a building and its process calculation.

(a) Earthwork excavation for foundation trenches

(b) Earthwork in filling

(d) Damp proof course

Write down unit of measurement, unit rate of payment and mode of measurement for the following general items of work.

(a) Rain-water, Vent, Waste pipes etc.

(b) Ventilating cowls.

(d) Sanitary fittings.

(e) Glass-panes.

(f) Broken glass coping.

List out limits of measurement and degrees of accuracy in estimating.

Unit 2:

Prepare a preliminary estimate for a framed four storied office building having a carpet area of 250 sq m for each floor. Assume areas occupied by corridor, verandah, lavatories, staircase etc as 25% of built up area and that occupied by walls and columns as 8.5% of the same. The following details may be used for estimation

(a) Built-up area rate for ground floor (excluding foundation) = Rs1,500/- per sqm

(b) Built-up area rate for 1st and 2^nd floor = Rs1,650/- per sq m

(d) Extra for foundation = 20% of superstructure cost

(e) Extra for special architectural treatment = 1% of building cost

(f) Extra for water supply and sanitary = 7

(g) Extra for electrical installation = 8% of building cost

(h) Extra for contingencies = 4% of overall cost

(i) Extra for work charge establishment = 10

(j) Extra for other source = 5% of building cost.

Unit 3:

The formation width of a road embankment is 9.0m. The side slopes are 2.5:1. The depths along the center line of road at 50.0m intervals are 1.2,1.1,1.4,1.2,0.9,1.5 and 1.0.m. It is required to calculate the quantity of earthwork by

(a) Prismoidal rule.

(b) Trapezoidal rule.

Estimate the cost of earthwork for laying of road for 400m length from the following data. Formation width of the road is 10meter. Side slopes are 2:1 in banking 1:1 in cutting.

Station Distance in meter RL of ground RL of formation

25 1000 51.00 55.00

26 1040 50.00

27 1080 50.50

28 1120 50.80

29 1160 50.60 Downward gradient of 1 in 250

30 1200 50.70

31 1240 51.20

32 1280 51.40

33 1320 51.30

34 1360 51.00

35 1400 50.60

Calculate the quantity of each work for 200m length for a portion of a road in an uniform ground the heights of bank at the two ends being 1.00m and 1.60m. The formation width is 1.0 m and side slopes 2:1 (H:V). Assume that there is no transverse slope. Use the following methods and justify which method is good.

(a) Prismoidal formula and

(b) Mean - sectional area method

Unit 4:

Explain Analysis of Rates? Factors affecting rate of an item of work? Give different heads used in Analysis of Rates.

Describe the procedure for the calculation of rate per unit cum of cement concrete 1:2:4 with stone ballast 40 mm

Describe the procedure for the calculation of rate per unit sq.m of the following items

(a) White washing three coats.

(b) White washing two coats.

Describe the procedure for the calculation of rate per unit cu.m of RCC work in beams, slabs etc., 1:2:4 work excluding steel but including centering, shuttering, bending and binding.

Describe the procedure for the calculation of rate per unit cu.m of Random Rubble stone masonary in foundation and plinth.

Unit 5:

Define reinforcement? List and explain various types of reinforcement?

What do you mean by development of length of reinforcement?

What do you mean by lap length, explain with suitable sketches

What are the cover rules to be followed in RCC.

Draw reinforcement details along with curtailment lengths in the following slabs.

(a) Simply supported.

(b) Continuous over several spans.

Differentiate between development length in tension and compression.

Unit 6:

Distinguish Contractor and Contract? Types of Contract? Explain?

What do you understand about Contract Document?

Write a short note on the following with respect to contract document.

(a) Security deposit.

(b) Retention money.

Write a short note on the following:

(a) Informal tender.

(b) Sale of tender papers.

Explain the following

(a) Market rate.

(b) Work-charged establishment.

Differentiate between Security deposit and Retention money.

Elaborate earnest money along with its necessary

Write a short note on the following:

(a) Time limits for tender notice

(b) Sale of tender papers.

Unit 7:

What do you understand about Valuation? Explain?

Explain the following method of valuation of a building along with an example.

Valuation based on profit
Depreciation method of valuation.

A colonizer intends to purchase a land of 100,000 sq m area located in the suburb of a big city to develop it into plots of 700 sq.m each after providing necessary roads and parks and other amenities. The current sale price of small plots in the Neighbourhood is Rs.25.00 per sq.m. The colonizer wants a net prot of 25%. Work out the maximum price of the land at which the colonizer may purchase the land

A building is situated by the side of a main road of Hyderabad city on a land of 600 sq.m. The built up portion in 22m x 17m. The building is first class type and provided with water supply, sanitary and electric fittings, and the age of the building is 30 years. Workout the valuation of the property. Assume plinth area rate is Rs.200.00 and cost of land as Rs.6000 per sq.m.

Explain the following method of valuation of a building along with an example.

(a) Rental method of valuation

(b) Direct comparison with the capital value.

Unit 8:

List and explain standard speciations of a first class building.

Give the detailed specifications of the following items of works.

(a) Colour washing

(b) Lime concrete in foundation.

Give the detailed specifications of the following items of works.

(a) Cast iron water pipes

(b) Mangalore tiled roof.

Give the detailed specifications of the following items of works.

(a) Earthwork in excavation in foundation

(b) Random rubble stone masonry.

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.