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Home , Measuring instrument, Pressure head

Experiment No: 1 of and pressure head by Piezometer, U-tube manometer

Experiment No:2 Study of a Bourdon Pressure Gage

Objective:

To calibrate a Bourdon type pressure gage and to establish the curve of Bourdon Gage. Also determine the gage errors.

1. Apparatus:

i. Dead Weight Calibrator. ii. Set of Test weights iii. Weight balance. iv. Bourdon pressure gage.

1.1 Introduction

Instrument calibration is one of the primary processes used to maintain instrument accuracy. It is the process of configuring an instrument to provide results within an acceptable range. Known weights have been applied on a Dead Weight Calibrator to apply pressure to a fluid for checking the accuracy of readings from a pressure gage.

Various types of pressure have been used to measure the pressure intensity at any point in static or moving fluid. One of these devices is the Bourdon tube pressure gage. Bourdon-tube pressure gages are most widely used now-a-days because of their reliability, compactness, low cost and ease of use. It consists of a curved tube (Figure 1) of elliptical cross-section bent into a circular arc.

Figure 1: Dead Weight Calibrator

When pressure is applied to the tube, it tends to straighten out, and the deflection of the end of the tube is communicated through a system of levers to a recording pointer.

This is widely used for steam and compressed . The pressure indicated is the difference between the system pressure and to the external (ambient) pressure, and is usually referred to as the gauge pressure

1.2 Related Theory:

The bourdon gage is the most popular pressure measuring device for both liquids and gasses. It can be connected to any source of pressure such as a pipe or vessel containing a pressurized fluid.

I. Bourdon Gage:

The Bourdon Gauge (Figure 2) is fitted with a transparent dial, which lets you see the internal workings of the gauge. The gauge consists of a thin walled closed ended tube which is oval in cross section. This tube is bent through an of about 270o along its long axis. The open end of the tube is welded to a hollow mounting block which allows the pressurized fluid to reach the tube. This causes the pressure from the source to be transmitted directly to the inside of the bourdon tube. The applied pressure causes the oval tube to become rounder (since a round cross section has the maximum area for a given circumference). As it becomes rounder, the bourdon tube tends to uncurl which causes its free end to move. A system of linkages and levers transmits this motion to the gauge needle which moves over the scale.

Figure 2: Bourdon Gage

II. Dead Weight Calibrator:

In order to obtain very accurate pressure measurements, it is essential to regularly re- calibrate the gauge. This is because the tube tends to become weaker with extended use. The usual procedure is to apply a known pressure to the gauge using a device called a Dead Weight Calibrator. The normal calibration procedure is to load the gauge for known , using a dead weight calibrator including a liquid of known specific gravity (use water as the liquid). This dead weight tester uses a simple piston and cylinder arrangement to provide a source of pressurized liquid (in the experiment water will produced a better result than oil) which is transmitted to the gauge. Since the true pressure of the liquid can be easily calculated, the value can be compared directly to the reading on the gauge over the complete scale range. (The scale range is the range of pressures from zero to the full-scale deflection value). The dead weight tester consists of a cylindrical piston which is free to move vertically in a close fitting cylinder.

A Platen is attached to the piston which can be loaded with a series of accurate weights. The pressure developed in the cylinder is transmitted via a transparent tube to the gauge under test. The cylinder is mounted on a base board which is supported on leveling screws and fitted with a .

1.3 Governing Equations:

The use of the piston and weights with the cylinder generates a measurable reference pressure:

Where,

F = applied to the liquid in the calibrator cylinder in Newton (N).

M = Total including the mass of the piston in kilogram (kg).

A = Cross-sectional area of the piston in meter (m2).

g = Acceleration due to gravity in meter per square second (m/s2).

1.4 Equipment Set Up:

Position the calibrator without the piston on the hydraulic bench top and ensure that the base is horizontal by adjusting the feet and using the spirit level. This is necessary to ensure vertical transfer of the applied load and free rotation of the piston.

Open all cocks on the pressure gage base.

Connect the inflow cock to the bench flow connector and the outflow cock to the lower tube from the calibrator cylinder.

Open slowly the bench valve to produce a flow, tilt the pressure gage to ensure that air is driven out from the manifold and then close the middle cock on the manifold. When there is no further air emerging and the calibrator cylinder is full, close the bench valve and the inflow cock on the manifold.

1.4.1 Data for the Piston:

a. Mass of the piston (Mp) = 498g b. Diameter of the piston (d) = 0.01767m

1.5 Procedure:

1. Measure the weight of the calibration .

2. Note down the weight of the piston and it’s cross sectional area.

3. Remove the piston and pour the water into the cylinder until it is full to overflow level. Any air trapped in the tube may be cleared by tilting and gently tapping the apparatus.

4. Insert the piston carefully and spin it to minimize any friction effects.

5. Note the pressure reading from the gage.

6. Add the weights in convenient increments, and at each increment, observe the pressure gage reading.

7. Take the similar sets of readings with decreasing weights.

Note: If due to the slight leakage, piston reaches the cylinder bottom, more water must be added to the cylinder.

1.6 Table of Observations and Calculations:

All readings and calculations are to be tabulated as follows:

Mass Actual Pressure Gage Reading (kPa) Percent Error (%) (kg) (kPa) Loading Unloading Loading Unloading

Relative Error = (Measured Value – Actual Value) /Actual Value

Percent Error = │Relative Error│ × 100

Note: Also, show the sample calculation to calculate the Relative Error and Percent Error.

1.7 Graphical Relationship:

Plot the following graphs:

1) Actual Pressure against Measured Pressure (Gage Reading).

2) Percent Error against Measured Pressure (Gage Reading).

1.8 Conclusion and Recommendations:

Comment on the accuracy of the gage. Is the relative height between the calibrator and the gage important in calibration? General comments about the experiment

Your recommendations.

Experiment No: 3 Verification of Bernoulli’s theorem

OBJECTIVE OF THE EXPERIMENT:

1. To demonstrate the variation of the pressure along a converging-diverging pipe section.

2. The objective is to validate Bernoulli’s assumptions and theorem by experimentally proving that the sum of the terms in the Bernoulli equation along a streamline always remains a constant.

Apparatus Required: Apparatus for the verification of Bernoulli’s theorem and measuring tank with stop setup for measuring the actual flow rate.

THEORY:

The Bernoulli theorem is an approximate relation between pressure, velocity, and elevation, and is valid in regions of steady, incompressible flow where net frictional are negligible. The equation is obtained when the Euler’s equation is integrated along the streamline for a constant (incompressible) fluid. The constant of integration (called the Bernoulli’s constant) varies from one streamline to another but remains constant along a streamline in steady, frictionless, incompressible flow. Despite its simplicity, it has been proven to be a very powerful for .

Bernoulli’s equation states that the “sum of the kinetic (velocity head), the pressure energy (static head) and Potential energy (elevation head) per unit weight of the fluid at any point remains constant” provided the flow is steady, irrotational, and frictionless and the fluid used is incompressible. This is however, on the assumption that energy is neither added to nor taken away by some external agency. The key approximation in the derivation of Bernoulli’s equation is that viscous effects are negligibly small compared to inertial, gravitational, and pressure effects. We can write the theorem as

P V 2 Pressure head ( )+ Velocity head ( )+ Elevation (Z) = a constant g 2g

Where, P = the pressure.(N/m2) r = density of the fluid, kg/m3

V = velocity of flow, (m/s) g = acceleration due to gravity, m/s2

Z = elevation from datum line, (m)

Figure 1.1: Pressure head increases with decrease in velocity head.

P1/w+V12/2g+Z1= P2/w+V22/2g+Z2= constant

Where P/w is the pressure head

V/2g is the velocity head

Z is the potential head.

The Bernoulli’s equation forms the basis for solving a wide variety of fluid flow problems such as jets issuing from an orifice, jet trajectory, flow under a gate and over a weir, flow metering by obstruction meters, flow around submerged objects, flows associated with pumps and turbines etc.

The equipment is designed as a self-sufficient unit it has a sump tank, measuring tank and a pump for water circulation as shown in figure1. The apparatus consists of a supply tank, which is connected to flow channel. The channel gradually contracts for a length and then gradually enlarges for the remaining length. In this equipment the Z is constant and is not taken for calculation.

Fig: Bernoulli’s Apparatus

Procedure:

1. Keep the bypass valve open and start the pump and slowly start closing valve.

2. The water shall start flowing through the flow channel. The level in the Piezometer tubes shall start rising. 3. Open the valve on the delivery tank side and adjust the head in the Piezometer tubes to steady position. 4. Measure the heads at all the points and also discharge with help of diversion pan in the measuring tank. 5. Varying the discharge and repeat the procedure.

Observations:

Distance between each piezometer = 7.5 cm

Density of water = 0.001 kg/cm3

1) Note down the Sl. No’s of Pitot tubes and their cross sectional areas.

2) of water collected q = ……………. cm3 3) taken for collection of water t = …………….sec

OBSERVATION & RESULT TABLE:

Area of the Discharge Total

Tube flow ‘A’ in ‘Q’ in Velocity Velocity Pressure (cm2) (cm3/sec) ‘V’ in head in head in head No (cm/sec) (cm) (cm) ‘H’ (cm)

1

2

3

4

5

6

7

8

9

10

11

Sample Calculations:

1. Discharge Q = q / t =………….. cm3/sec 2. Velocity V= Q/ A= ...... = ………. cm/sec

Where A is the cross sectional area of the fluid flow

3. Velocity head V2/2g = ………….. cm 4. Pressure head (actual or piezometer tube reading)

P/w= ……………… cm

5. Total Head H= Pressure head + Velocity Head = ………...... …….. cm

Result & Discussion:

Plot the graph between P/w and x.

Plot the graph between V2/2g and x.

QUIZ:

A. Bernoulli’s equation holds good for non ideal fluids True False B. The pressure head is given by P/γ V2/2g C. Bernoulli’s theorem deals with law conservation of momentum True false D. What is piezometer tube?

REFERENCES:

1) Fluid mechanics - Dr.R.K.Bansal 2) Experiments in fluid mechanics - Sarabjit Singh 3) Wikipedia

EXPERIMENT: 4 Reynolds experiment to study types of flow

OBJECTIVE:

To perform the Reynolds experiment for determination of different regimes of flow.

APPARATUS REQUIRED:

Reynolds Apparatus test rig and stop watch

INTRODUCTON:

The purpose of this experiment is to illustrate the influence of Reynolds number on pipe flows. Reynolds number is a very useful dimensionless (the ratio of dynamic forces to viscous forces) that aids in classifying certain flows. For incompressible flow in a pipe

Reynolds number based on the pipe diameter, ReD = VaveDρ/μ, serves well. Generally, laminar flows correspond to ReD < 2100, transitional flows occur in the range 2100 < ReD < 4000, and turbulent flows exist for ReD > 4000. However, disturbances in the flow from various sources may cause the flow to deviate from this pattern. This experiment will illustrate laminar, transitional, and turbulent flows in a pipe.

THEORY:

The flow of real fluids can basically occur under two very different regimes namely laminar and turbulent flow. The laminar flow is characterized by fluid particles moving in the form of lamina sliding over each other, such that at any instant the velocity at all the points in particular lamina is the same. The lamina near the flow boundary move at a slower rate as compared to those near the center of the flow passage. This type of flow occurs in viscous fluids, fluids moving at slow velocity and fluids flowing through narrow passages.

The turbulent flow is characterized by constant agitation and intermixing of fluid particles such that their velocity changes from point to point and even at the same point from time to time. This type of flow occurs in low density Fluids flow through wide passage and in high velocity flows.

Reynolds conducted an experiment for observation and determination of these regimes of flow. By introducing a fine filament of dye in to the flow of water through the glass tube, at its entrance he studied the different types of flow. At low velocities the dye filament appeared as straight line through the length of the tube and parallel to its axis, characterizing laminar flow. As the velocity is increased the dye filament becomes wavy throughout indicating transition flow. On further increasing the velocity the filament breaks up and diffuses completely in the water in the glass tube indicating the turbulent flow. After conducting his experiment with pipes different diameters and with water at different Reynolds concluded that the various parameters on which the regimes of flow depend can be grouped together in a single non dimensional parameter called Reynolds number. Reynolds number is defined as, the ratio of inertia force to the viscous force .Where viscous force is shear stress multiplied area and inertia force is mass multiplied acceleration.

Re = VDρ/ µ =VD/v (v = )

Where

Re-Reynolds number

V - Velocity of flow

D - Characteristic length=diameter in case of pipe flow

Ρ - Mass density of fluid =1000

3. - dynamic of fluid = 0.55x v

- Kinematic viscosity of fluid

Reynolds observed that in case of flow through pipe for values of Re<2000 the flow is laminar while offer Re>40000 it is turbulent and for 2000

Type of flow Reynolds number Pipe flow Canal flow

Laminar flow < 2000 < 500

Transition flow 2000 to 4000 500 to 2000

Turbulent flow > 4000 >2000

EQUIPMENTS:

A stop watch, a , and Reynolds apparatus which consists of water tank having a glass tube leading out of it. The glass tube has a bell mouth at entrance and a regulating valve at outlet, a dye container with an arrangement for injecting a fine filament of dye at the entrance of the glass tube. Potassium permanganate ( to give brightly reddish color streak), measuring tank.

OBSERVATIONS:

Inner diameter of glass tube, D = Cross - sectional area of glass tube, A = (π / 4) x D² Mean of water – t - =

Kinematic viscosity of water-ν- =

Discharge Time taken Discharge Velocity Reynold’s for discharge ‘V’ Type of Number ‘q’ in ‘Q’ in flow 3 ‘Re’ (liters) ‘t’ in (sec) (cm /sec) (cm/sec)

1

2

3

4

Perform the following calculations for each set of readings

Discharge –Q =

Velocity of flow – V =

MANUAL:

Start the experiment by pressing start button with default values of temperature of water and time taken and diameter of pipe. Then pass the experiment with few cycles and note the observation. Observation1:

6. Start the experiment and allow the water to flow in to the tank of the apparatus. Water level in the is slightly rising along with rise in tank. Control valve of the glass tube should be slightly opened for removing air bubbles. 7. After the tank is filled outlet valve of the glass tube and inlet valve of the tank should be closed, so that water should be at rest. Observation2:

A. Keeping the velocity of flow is very small and inlet of the die injector is slightly opened, so that the die stream moves at a straight line throughout the tube showing the flow is laminar. B. Again measure the discharge and increase the velocity of flow.

Observation3:

A. Note the observations till the die stream in the glass tube breaks up and gets diffused in water.

B. Repeat the experiment by decreasing the rate of flow and by changing the temperature and diameter of pipe.

RESULT:

4) Reynolds number –Re = VD/ ν

5) Regime of flow =

QUIZ: c. Flow to be laminar the Reynolds number should be greater than 2000.

True

False d. For flow to be turbulent the flow should be more than 400.

True

False e. Concept of Reynolds number is used in open channels.

True

False

8. The behavior of path lines is laminar flow.

True

False

9. If the Reynolds number is in between 2000 and 4000 then the flow is.

Turbulent

Transition

Laminar

REFERENCES:

3) FLUID MECHANICS - RK BANSAL

4) EXPERIMENTS ON FLUID MECHANICS - SARABJIT SINGH

5) WIKIPEDIA

6) The constructor- http://theconstructor.org/

Experiment No. 05

Determination of Darcy’s friction factor for a given pipe & FRICTION (MAJOR) LOSSES IN PIPES

OBJECTIVE:

To measure the friction factor for flow through different diameter of pipes over a wide range of Reynolds number and compare with corresponding theoretical value.

APPARATUS REQUIRED:

Flow losses in pipe apparatus with flow control device and manometer

Collecting tank = 30 cm (L)*30 cm (W)* h cm

Stop watch

THEORY:

Various fluids are transported through pipes. When the fluid flows through pipes, energy losses occur due to various reasons, among which friction loss is the predominant one. Darcy-Weisbach equation relates the head loss due to frictional or turbulent through a pipe to the velocity of the fluid and diameter of the pipe as

4 flv2 hf 2gD Where hf = Loss of head due to friction

L=length of pipe between the sections used for measuring loss of head D= Diameter of the pipe, 1”,3/4”,1/2”

f= Darcy coefficient of friction

Figure: Losses in pipes during flow

DESCRIPTION:

The experiment is performed by using a number of long horizontal pipes of different diameters connected to water supply using a regulator valve for achieving different constant flow rates. Pressure tapings are provided on each pipe at suitable distances apart and connected to U-tube differential manometer. Manometer is filled with enough

to read the differential head „hm‟. Water is collected in the collecting tank for arriving actual discharge using and the piezometric level attached to the collecting tank.

FORMULAE USED:

1). Darcy coefficient of friction (Friction factor) 2gDh f f 4Lv2

Where h f hm * m 1 hm is differential level of manometer fluid measured in meters)

Q =Actual discharge measured from volumetric technique. act vD 2).Reynolds number ReD1 where is the coefficient of dynamic viscosity of flowing fluid. The viscosity of water is 8.90*10-4 Pa-s at 250 C. Viscosity of water at different temp is listed below:

Temperature(0C) 10 20 30 40 50 60 70 80 90 100

Viscosity () 13.08 10.03 7.978 6.531 5.471 4.668 4.044 3.550 3.150 2.822

Pa-s *10-4

PROCEDURE:

1. Note the pipe diameter „D‟, the density of the manometer fluid(mercury) „ m‟ =13600 kg/m3 and the flowing fluid(water) „ ‟=1000 kg/m3.

2. Make sure only required water regulator valve and required valves at tapings connected to manometer are opened.

3. Start the pump and adjust the control valve to make pipe full laminar flow. Wait for some time so that flow is stabilized.

4. Measure the pressure difference „hm‟ across the orifice meter. 5. Note the piezometric reading „Z0‟ in the collecting tank while switch on the stopwatch.

6. Record the time taken „T‟ and the piezometric reading „Z1‟ in the collecting tank after allowing sufficient quantity of water in the collecting tank. 7. Increase the flow rate by regulating the control valve and wait till flow is steady.

8. Repeat the steps 4 to 6 for different flows.

RESULTS AND DSICUSSION

OBSERVATION AND COMPUTATION-IIDATE: ______A) FOR PIPE NO. 1:

Diameter of pipe „D‟= 0.0254 m Area of pipe „A‟= m2 Length of Pipe „L‟= 1 m 2 0 Area of collecting tank Act= 0.09 m Coefficient of dynamic viscosity at C= Pa.s. 3 3 Density of the manometer liquid m= 13.6 x 1000 kg/m Density of the flowing liquid = 1000 kg/m

Tabulation 5.1- For pipe No. 1. Actual No. Measurement Calculated values f Re No. Log (Re)

3 Time Z1(m) Z0(m) hm(m) Collecting Volume(m ) Discharge Velocity hf(m) 2gDhf vD 2 T tank Act*hct Qact (8)/A m f 4Lv

(sec) hct(m) (7)/(2) (5)* 1

(3)-(4)

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)

1

2

3

4

5

B)FOR PIPE NO. 2:

Diameter of pipe „D‟= 0.019 m Area of pipe „A‟= m2 Length of Pipe „L‟= 1 m 2 0 Area of collecting tank Act=0.09 m Coefficient of dynamic viscosity at C= Pa.s. 3 3 Density of the manometer liquid m= 13.6 x 1000 kg/m Density of the flowing liquid =1000 kg/m Tabulation 5.2- For pipe No. 2 .

No Actual Measurement Calculated values f Re Log(R . No. e)

3 Time Z1(m) Z0(m) hm(m) Collecting Volume(m Discharge Velocity hf(m) 2gDh vD f tank ) f 4Lv2 T(sec) Qact (8)/A m hct(m) Act*hct (5)* 1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)

1

2

3

4

5

Precautions:-

 When fluid is flowing, there is a fluctuation in the height of piezometer tubes, note the mean position carefully.  There in some water in collecting tank.  Carefully keep some level of fluid in inlet and outlet supply tank.

Viva Questions:-

 Define major loss in pipe?  Define equilent pipe?  Define friction factor in the pipe?

EXPERIMENT NO. 6 Determination of Minor losses in pipes (any two)

Aim:- To determine the minor losses due to sudden enlargement, sudden contraction and bend.

Apparatus Used:-

A flow circuit of G. I. pipes of different pipe fittings viz. Large bend, Small bend, Elbow, Sudden enlargement from 25 mm dia to 50 mm dia, Sudden contraction from 50 mm dia to 25 mm dia, U- tube differential manometer, collecting tank.

Theory:- Minor Losses:-

Figure: Loss due to sudden enlargement Figure: Loss due to bend

Figure: Loss due to sudden contraction

The local or minor head losses are caused by certain local features or disturbances. The disturbances may be caused in the or shape of the pipe. This deformation affects the velocity distribution and may result in eddy formation. Sudden Enlargement:- Two pipe of cross-sectional area A1 and A2 flanged together with a constant velocity fluid flowing from smaller diameter pipe. This flow breaks away from edges of narrow edges section, eddies from and resulting turbulence cause dissipation of energy. The initiations and onset of disturbances in turbulence is due to fluid momentum and its area. It is given by:- h exit =V2/2g

Eddy loss:- Because the expansion loss is expended exclusively on eddy formation and continues substance of rotational motion of fluid masses. Sudden Contraction:- It represents a pipe line in which abrupt contraction occurs. Inspection of the flow pattern reveals that it exists in two phases. 2 hcon = (Vc – V2) /2g

Vc = velocity at vena contracta

Losses at bends, elbows and other fittings:-

The flow pattern regarding separation and eddying in region of separations in bends, valves. The resulting head loss due to energy dissipation can be prescribed by the relation h = KV2/2g. Where V is the average flow velocity and the resistance coefficient K dependson parameter defining the geometry of the section and flow. Resistances of large elbows can be reduced appreciably by splitting the flow into a number of streams by a jet of guide vanes called cascades.

Procedure:-

1. Note down the relevant as diameter and length of pipe between the pressure tapping, area of collecting tank etc. 2. Pressure tapping of a pipe a is kept open while for other pipe is closed. 3. The flow rate was adjusted to its maximum value. By maintaining suitable amount of steady flow in the pipe. 4. The discharge flowing in the circuit is recorded together with the water level in the left and right limbs of manometer tube. 5. The flow rate is reduced in stages by means of flow control valve and the discharge & reading of manometer are recorded. 6. This procedure is repeated by closing the pressure tapping of this pipe, together with other pipes and for opening of another pipe.

Observation:- Diameter of pipe D = Length of pipe between pressure tapping L = Area of collecting tank = Types of the fitting =

Sr. Manometer reading Discharge measurement Coefficient No. of loss K= 2 2g/V .hL Left limb Right Difference of Initial final time Discharge head in h1 limb h2 terms of water hf = 13.6 (h2-h1) 1 2 3

Precautions:-

1. When fluid is flowing, there is a fluctuation in the height of piezometer tubes, note the mean position carefully. 2. There in some water in collecting tank. 3. Carefully keep some level of fluid in inlet and outlet supply tank.

Result:-

Viva Questions:-

1. Define hydraulic gradient and total energy lines? 2. Define eddy loss?

Experiment 7: Study and use of Moody’s diagram or Nomogram of Manning’s equation

Moody’ Diagram: In , the Moody chart or Moody diagram is a graph in non-dimensional form that relates the Darcy-Weisbach friction factor fD, Reynolds number Re, and surface roughness for fully developed flow in a circular pipe. It can be used to predict pressure drop or flow rate down such a pipe. In 1944, Lewis Ferry Moody plotted the Darcy–Weisbach friction factor against Reynolds number Re for various values of relative roughness. This chart became commonly known as the Moody Chart or Moody Diagram. It adapts the of Hunter Rouse but uses the more practical choice of coordinates employed by R. J. S. Pigott, whose work was based upon an analysis of some 10,000 experiments from various sources.[4] Measurements of fluid flow in artificially roughened pipes by J. Nikuradse were at the time too recent to include in Pigott's chart. The chart's purpose was to provide a graphical representation of the function of C. F. Colebrook in collaboration with C. M. White, which provided a practical form of transition curve to bridge the transition zone between smooth and rough pipes, the region of incomplete turbulence.

Moody's team used the available data (including that of Nikuradse) to show that fluid flow in rough pipes could be described by four dimensionless (Reynolds number, pressure loss coefficient, diameter ratio of the pipe and the relative roughness of the pipe). They then produced a single plot which showed that all of these collapsed onto a series of lines, now known as the Moody chart. This dimensionless chart is used to work out pressure drop, (or head loss) and flow rate through pipes. Head loss can be calculated using the Darcy–Weisbach equation in which the Darcy friction factor appears :

Experiment 8 Determination of Manning’s constant or Chezy’s constant for given rectangular channel section

OBJECTIVE: To determine the Manning’s coefficient of the flume or bed of the channel with the flow of water. It investigates the roughness of the bed as required design.

SCOPE: Using the Manning’s formula, it can investigate the roughness Co the different types of beds of the flume and the roughness of the river bed. It helps to know the roughness of the bed when it constructers the open channel in the field as designed.

APPARATUS:

 Long length flume  Needle gauge  Orifice meter  Types of beds

THEORY:

Manning’s Coefficient v = (1/n)(R^2/3)(S^1/2) R = A = b x d P = b + d+ d = b +2d v= Velocity of flow R = Hydraulics radius S= Bed slope n = Manning’s value or coefficient A = Wetted area of flume b= Width of flume d= Wetted depth of flume P = Wetted perimeter

Here, Q = A x v v = (1/n)(R^2/3)(S^1/2) Q = A x (1/n)(R^2/3)(S^1/2)

So, that n = [A x (R^2/3)(S^1/2)]/Q

Note: Here, A = wetted area of the channel that is, b x d

OBSERVATION:

Observation Table: Area of Tank = B x D

S.N Level Diff. Volume, V Time, T Discharge, Q Velocity, v (H2-H1)

Calculation Table :

Number of v b D A R S Q n Remarks observations 1 2 3 4 5

RESULTS & DICUSSSIONS:

PRECAUTIONS:

Experiment 9. HYDRAULIC JUMP ANALYSIS

OBJECTIVE: To compare the experimental value of depth before a hydraulic jump to that calculated from theory and calculate energy loss in a hydraulic jump.

SCOPE: The formation of hydraulic jump is associated with a sudden rise in the water depth, large scale turbulence and dissipation of energy. It is employed at the foot of spillways and other hydraulic structures of dissipate energy for the protection of bed against scour. This experiment helps to understand the features of hydraulic jump.

APPARATUS:

(a) Open channel flume (b) Stop watch

THEORY: We have, 2(q^2)/g=y1.y2 (y1+y2) Where, y1 = Depth before jump. y2 = Depth after jump. q= Discharge per unit width of the flume, Specific discharge g = acceleration due to gravity

Energy loss, EL = [(y2-y1)^3]/4y1.y2

Fig: Hydraulic Jump

EXPERIMENTAL PROCEDURE:

(a) Start the pump and set the sluice gate to about 25mm (b) Adjust the flow rate to give about 300 mm head above the sluice (c) Raise the adjustable weir to form a hydraulic jump within the central portion of the flume. (d) Note the depth before and after the jump (e) Measure the flow rate and hand (f) Repeat for a head 500 mm above the sluice and steps c, d & e.

Figure: Hydraulic Jump Set up

OBSERVATIONS:

Gate opening = Channel width = Area of Tank = Number of Head in cm Depth y1 Cm Depth y2 cm Level Time Sec. observations Difference (H2 - H1)cm 1 2 3 4

CALCULATIONS:

(a) Discharge per unit width q. (b) Use q and y2 to compute y1. (c) Compute E using theoretically derived y1 and experimental value. (d) Show the figure of the apparatus and simple description

PRESENTATION:

(a) Present a sample calculation (b) Present the results in a tabular form

COMMENTS:

Comment on the variation of y1 and on the accuracy of depth measurement. Discuss application of hydraulic jump in irrigation structures.

EXPERIMENT No 10 Determination of coefficient of discharge for given rectangular or triangular notch.

Aim:- To determine the coefficient of discharge of Notch ( V , Rectangular and Trapezoidal types).

Apparatus Used:-

Arrangement for finding the coefficient of discharge inclusive of supply tank, collecting tank, pointer, scale & different type of notches

Theory:-

Notches are overflow structure where length of crest along the flow of water is accurately shaped to calculate discharge.

Formula Used:-

For V notch the discharge coefficient Cd = Q

8/15 √ 2g H 5/2 tan θ / 2 For Rectangular notch Cd = Q

2/3 √ 2g BH3/2

For Trapezoidal notch Cd = Q_ 3/2 (2/3) √2g (B + tan θ / 2) H Where:- Q = Discharge H =Height above crest level A. = Angle of notch B = Width of notch

Procedure:-

 The notch under test is positioned at the end of tank with vertical sharp edge on the upstream side.  Open the inlet valve and fill water until the crest of notch.  Note down the height of crest level by pointer gauge.  Change the inlet supply and note the height of this level in the tank.  Note the volume of water collected in collecting tank for a particular time and find out the discharge.  Height and discharge readings for different flow rate are noted.

Observations:- BreaDth of tank = Length of tank = Height of water to crest level for rectangular notch is = Height of water to crest level for V notch = Height of water to crest level for Trapezoidal notch = Angle of V notch = Width of Rectangular notch =

Discharge Final Head Type height above reading crest Of Initial Final Differen above level Cd height height ce Volume notch width Of tank Of tank In height Q

Result:-

Precaution:-  Make the water level surface still, before takings the reading.  Reading noted should be free from parallax error.  The time of discharge is noted carefully.  Only the internal dimensions of collecting tank should be taken for consideration and calculations.

Viva Questions:- 1. Differentiate between :- Uniform and non uniform flow Steady and unsteady flow 2. Define notch? 3. What is coefficient of discharge?

EXPERIMENT NO 11 Determination of coefficient of discharge for a given Venturimeter.

Aim:- To determine the coefficient of discharge of Venturimeter.

Apparatus Used:- Venturimeter, installed on different diameter pipes, arrangement of varying flow rate, U- tube manometer, collecting tube tank, vernier calliper tube etc.

Formula Used:- 2 2 Cd = Q √ A - a

A a √ 2 g h Where A = Cross section area of inlet a = Cross section area of outlet Δh = Head difference in manometer Q = Discharge Cd = Coefficient of discharge g = Acceleration due to gravity

Theory:-

Venturimeter are depending on Bernoulli’s equation. Venturimeter is a device used for measuring the rate of fluid flowing through a pipe. The consist of three part in short a Converging area part b Throat c Diverging part

Procedure:-

1. Set the manometer pressure to the by opening the upper valve.

2. Now start the supply at water controlled by the stop valve.

3. One of the valves of any one of the pipe open and close all other of three.

4. Take the discharge reading for the particular flow.

5. Take the reading for the pressure head on from the u-tube manometer for corresponding reading of discharge.

6. Now take three readings for this pipe and calculate the Cd for that instrument using formula.

7. Now close the valve and open valve of other diameter pipe and take the three reading for this.

8. Similarly take the reading for all other diameter pipe and calculate Cd for each. Observations:-

Diameter of Venturimeter= Area of cross section = Venturimeter= Area of collecting tank=

Discharge Manometer Reading

Cd= Fin Differe 2 2 Initial al nce Time Q√A - a reading reading (sec) Q h1 h2 h2-h1 h2-h1 h= Aa√2g∆h 13.6(h2-h1)

Result:-

Precautions:-

1.Keep the other valve closed while taking reading through one pipe. 2.The initial error in the manometer should be subtracted final reading. 3.The parallax error should be avoided. 4.Maintain a constant discharge for each reading. 5.The parallax error should be avoided while taking reading the manometer.

Viva Questions:-

1. Venturimeter are used for flow measuring. How?

2. Define co efficient of discharge?

3. Define parallax error?

4. Define converging area part?

5. Define throat?

6. Define diverging part?

Experiment No. 12 Demonstration and use of and current meter

CURRENT METER

The operation of the current meter is used in conjunction with a wading rod and a current meter counter. This method requires observe the velocities of the flow at different depths across the streams.

Current Meter Working Principle: Water Flow is measured through pulse signal produced per revolution. This signal is generated by an encapsulated reed switch which resides inside the current meter body.

Accessories:

The wading rod can be used with current meter as well as ADCP as positioning system. The water depth is displayed along with the % depth as the rod is moved up and down as well as the ‘Point’ velocity through use current meter / ADCP.

Figure: Field use of Current

Features of Current Meter  The design for reliable and accurate field data under the prevailing Indian environmental conditions and under cyclonic weather condition.  The system shall be easy to operate and maintain.  The current meter can be fitted with a stabilizer tail fin which is attached to a hanger bar and Colombus gauging weight in sizes of 7, 15, 23, 34, 45, 68, 90 or 135 Kg. This assembly is suspended from a gauging winch with armoured signal cable. A rating table is used to convert number of pulses to velocity.  The current meter is of Type “AA” current meter. It allows the measurement of water flow in streams, open canals, pressure pipes & lakes to a fine degree of accuracy and repeatability with its advanced contact switching system and interchangeable impact resistant bucket system that provides trouble free operation.  The current meter is made to be used in the most extreme environments and ensures reliable field service for many years.  The current meter is supplied in a kit which is affordable and user friendly, allowing the operator to measure water flow using a simple traditional method. Experiment No. 13 Determination of hydraulic coefficients for sharp edge orifice.

Aim:

To determine the coefficient of discharge of orifice meter.

Apparatus: Orifice meter, Stop watch, Collecting tank and Differential U-tube manometer.

Description:

Orifice meter is a device used for measuring the rate of flow of a fluid through a pipe. Orificemeter works on the same principle as that of Venturimeter i.e. by reducing the area of flow passage a pressure difference is developed between the two sections and the measurement of pressure difference is used to find the discharge.

It consists of a flat circular plate which has a circular sharp edge hole called orifice, which is concentric with the pipe. The orifice diameter is kept generally 0.5 the diameter of the pipe, though it may vary from 0.4 to 0.8 times the pipe diameter.

A mercury U-tube manometer is connected at section (1), which is at a distance of about 1.5 to 2.0 times the pipe diameter upstream from the orifice plate, and at section (2) which is at a distance of about half the diameter of the orifice on the downstream side from the orifice plate to know the pressure head between the two tappings.

Procedure:

The pipe is selected for conducting experiment.

The motor is switched on; as a result water flows through pipes. The readings of H1and H2 are noted.

The time taken for 10cm rise of water in collecting tank is noted.

The experiment is repeated for different discharges in the same pipe.

Coefficient of Discharge is calculated

Formulae 3 Actual Discharge: Q actual = Ah/t (m /sec)

2gH

3 Theoretical Discharge Q theo. = a a (m /sec) 2 1 2a 2 a

1 2 Where A= Area of collecting tank in m2

h= Height of water collected in tank = 10cm 2 a1= Area of inlet pipe in m 2 a2= Area of throat in m

t=time taken for h cm rise of water H= (H1-H2)(Sm/S1-1) Where H1 and H2 are Manomertic heads in first and second limbs Sm and S1 are Specific gravity of manometric fluid (mercury) and water flowing through the pipeline system.

Density of the manometer liquid = 13.6 x 1000 kg/m3 m 3 Density of the flowing liquid = 1000 kg/m Coefficient of Discharge Cd = Q actual/ Q theo

Volume of Collecting tank (Ah) =30cm (L) * 30cm (W) * 10cm (h) = Diameter of the inlet pipe = 25 mm

Diameter of the throat = 12.5 mm

2 a1= Area of inlet pipe in m = 2 a2= Area of throat in m = OBSERVATION TABLE

Sl. H1 H2 H=(H1H2)*12.6 Time taken for Qactual Qtheo. Cd= No. (m) (m) (m) 10cm rise of water (1) (2) (1)/(2) (sec)

1

2

3

4

5

6

Mean Coefficient of Discharge = Sample Calculation Result and Discussion