Fluid Lab 1 Report

FACULTY OF MECHANICAL ENGINEERINGIn the name of Allah, The Most Beneficent, The Most Merciful

Lab CO1: Fundamentals of pressure, viscosity and surface tension of fluids

BMM 3521 Engineering Fluid Mechanics

Lab Instructor

Lab LocationFluid Mechanics Laboratory

Lab Objectives

By the end of the laboratory session, students should be able to: Discuss errors in actual and gauge pressure. Determine effect of viscosity for different type of fluids Analyze the surface tension behavior in capillary of various gaps20

Group MembersStudent IDSection

Jagatis a/l BalaiyahMA 0910804

Thiwaan Rao a/l Narasimma NaiduMA 0913604

Nur Fazira binti TalibMA1010304

Mohammad Khairulnizam bin IbrahimMA 0911204

Due Date: 6th March 2012 Delivered Date: 6th March 2012

1.0 INTRODUCTION

Liquid that we used for the experiment are the water, detergent, and oil. The important terms to be discussed in this report are the gauge pressure, the viscosity of the 3 different fluids and the surface tension behavior of the fluids.

Pressure is equals to force per unit area applied in a direction perpendicular to the surface of an object. Pressure of fluids will be measured through a Bourdon Gauge in this experiment. The Bourdon Gauge is also tested for calibration to get the accurate reading.

Viscosity is a measure of the resistance of a fluid, which is being deformed by either shear or tensile stress. In fluids terms, viscosity is an internal friction. Thus, water is having a lower viscosity, while honey is having a higher viscosity. In a simple words, the less viscous the fluid is, the greater its ease of movement in fluidity.

Surface tension is a property of the surface of a liquid that allows it to resist an external force. Surface tension has the dimensionof force per unitlength or ofenergyper unitarea. The cohesive forces among the liquid molecules are responsible for this phenomenon of surface tension.

1.1 Objective

1. To discuss about the errors in actual and gauge pressure.2. To determine the effect of viscosity for different type of fluids.3. To analyze the surface tension behavior in capillary of gaps.

1.2 Scope

In order to finish this experiment completely and able to achieve the objective of study, it requires precise scope of work and proper plan. Manipulate and interpret the data. Tabulate data collected and graph for better analysis and understanding Create a work procedure for this lab experiment.

1.3 Hypothesis

a. For the Bourdon gauge, the gauge pressure is directly proportional to the actual pressure. As the reading of the gauge pressure increases, the actual pressure will also increase. b. The largest the diameter, the fastest it fall through the liquid. As the liquids that have higher viscosity, the velocity of the falling ball bearing will decrease. c. Water has a greatest surface tension compare to the others liquids oil and detergent

2.0 METHODOLOGY2.1Pressure MeasurementEquipment

i. Bourdon gaugeii. Loadiii. Hydrostatic benchProcedure

a. The initial pressure is recorded.b. Then the next load of 15 N is placed on the piston and the reading of increment in pressure is gained and is recorded. c. The steps in (c) are repeated with addition of weight 15 N until 90 N.d. The steps in (c) and (d) are repeated in a reverse way by removing the load and the decrement of pressure for each weight reduced is the recorded. e. Each steps from (b) to (d) are repeated three times to obtain different readingsf. All the data obtained is then recorded in the table and the average is calculated.

Principle of Bourdon tube pressure gauge2.2Viscosity

Equipmenti. Measuring cylindersii. Oiliii. Detergentiv. Waterv. Ball bearings (with diameters of 1.6mm, 2.4mm, 3.2.. and 4mm)vi. Stopwatchvii. MagnetProcedure

a. Fill the three-graduated measuring cylinders with water, oil, and detergent respectively.b. The 4mm diameter ball bearing is released from the top of the jar containing the water.c. The time is recorded with a stopwatch when the bearing ball released until it reach the selected distance in the measuring cylinder, which is 20cm.d. A magnet is used to get the ball bearing out of the water.e. Step (c) and (d) is repeated using other three different size of ball bearing of 3.2mm, 2.4mm and 1.6mm respectively. f. The experiment is repeated using different mediums, which are oil and detergent.g. Each reading is recorded three times.h. All the data is recorded in a table and the average is calculated.2.3Capillary Action

Equipmenti. Tankii. Capillary tubes (with diameters of 0.8mm, 1.0mm, 1.5mm, and 2.0mm)iii. Plastic shimiv. RulerProcedurea. The tank container is filled with water.b. The capillary tube with bore diameter of 0.8mm, 1.0mm, 1.5mm, and 2.0mm are inserted onto its holder and were placed into the tank container filled with water.c. The difference of height between the cylinder container water level and the water level inside the capillary tube for each diameter is measured with a ruler and recorded. Then the capillary tube with its holder are taken out and cleaned.d. Steps (b) and (c) are repeated using oil and detergente. The data are recorded in a table.

3.0 RESULTS

3.1Pressure Measurement (Bourdon Gauge)Mass added to piston(N)Increasing pressure(Pa)Decreasing pressure(Pa)

123Average123Average

1529.0031.0029.0030.0033.0035.0033.0034.00

3062.0063.0061.0062.0063.0064.0064.0064.00

4591.0089.0090.0090.0092.0091.0093.0092.00

60117.00120.00116.00118.00121.00120.00122.00121.00

75132.00133.00138.00134.00136.00137.00135.00136.00

90151.00151.00150.00151.00153.00155.00155.00154.00

Diameter of the piston, dp= 0.035 m

Area of the piston, Ap= 9.6211 x 10-4 m2

Load added to the Piston, L(N)Actual pressure, P (N/m2) Gauge Pressure Reading (N/m2)

Increasing PressureDecreasing Pressure

Gauge ReadingErrorGauge readingError

1515.5930.0014.4134.0018.41

3031.1862.0030.8264.0032.82

4546.7790.0042.2392.0044.23

6062.36118.0055.64121.0058.64

7577.95134.0056.05136.0058.05

9093.54151.0057.46154.0060.46

6.2Viscosity

Diameter Of The Ball, mmTime Fall, s

WaterDetergent

1st2nd3rdAve1st2nd3rdAve

1.60.530.550.560.551.221.251.231.23

2.40.410.440.410.420.950.920.930.93

3.20.340.370.350.350.750.760.770.75

4.00.280.260.280.270.610.610.630.62

Diameter Of The Ball, mmTime Fall, s

Oil

1st2nd3rdAve

1.60.650.630.650.64

2.40.420.440.430.43

3.20.390.410.390.40

4.00.330.350.320.33

*Specific Gravity at 20C:

Water: 1.0

Oil: 0.89

Detergent: 1.04

Distance, L = 20 cm = 0.20mDiameter of the Ball Bearing, mmTime Fall, sVelocity, m/sV=L/t

OilWaterDetergentOilWaterDetergent

1.60.640.551.230.31250.36360.1626

2.40.430.420.930.46510.47620.2151

3.20.400.350.750.50000.57140.2667

4.00.330.270.620.60610.74080.3226

From Stokes Law,

Terminal velocity,

Where;d is the diameter of sphere is the density of the sphere is the density of the fluid is the kinematics viscosity of the fluid

Therefore,

Density of steel ball = Density of steel 7.85 g/cm3 7850 kg/m3

Diameter sphere = 1.6 mmFluidDensity of Fluid,kg/m3Velocity, Vm/sKinematics viscosity, m2/sViscosity, Ns/m2Reynolds Number, Re

Oil8900.31250.021819.4020.0229

Water10000.36360.016416.4000.0355

Detergent10400.16260.035136.5040.0074

Diameter sphere = 2.4 mmFluidDensity of Fluid,kg/m3Velocity, Vm/sKinematics viscosity, m2/sViscosity, Ns/m2Reynolds Number, Re

Oil8900.46510.022019.580.0507

Water10000.47620.018818.800.0608

Detergent10400.21510.039841.390.0130

Diameter sphere = 3.2 mmFluidDensity of Fluid,kg/m3Velocity, Vm/sKinematics viscosity, m2/sViscosity, Ns/m2Reynolds Number, Re

Oil8900.50000.027324.300.0586

Water10000.57140.020920.900.0875

Detergent10400.26670.042844.510.0192

Diameter sphere = 4.0 mmFluidDensity of Fluid,kg/m3Velocity, Vm/sKinematics viscosity, m2/sViscosity, Ns/m2Reynolds Number, Re

Oil8900.60610.028125.010.0863

Water10000.74080.020220.200.1467

Detergent10400.32260.044245.970.0199

6.3 Surface tension (Capillarity)

Bore Size Diameter, mmCapillary

WaterOilDetergent

ht, cmhtd/4, mmht, cmhtd/4, mmht, cmhtd/4, mm

0.8123.9811.44.479.13.82

1.0143.1810.73.578.63.06

1.542.1210.22.388.42.04

2.021.599.81.798.21.53

Sample calculation (water, ht):

4.0 DISCUSSION

1) Students must present result of experiment in table and the data is enough to plot required graph for discussion.

1. Pressure Measurement (Bourdon Gauge)

Relationship between Force with Actual, Increasing Gauge and Decreasing Gauge Pressures2. Viscosity

Relationship between force, F and weight,WAccording to graph above, it is clearly shown that velocity increases when diameter of ball bearing is increased. This is because as the diameter of the ball bearing increases, the weight of ball also increases and hence the velocity of ball bearing falling through the fluids is increased due to the gravitational force. Only the viscosity of detergent can be determined in the experiment due to the limitation of Stokes Law and hence in this experiment. According to the Stokes Law, the balls Reynolds Number must not exceed 0.02 otherwise the flow will be turbulent and the value will not be valid. In the experiment, oil and water both give the value of Reynolds Number that exceeds 0.02, which are the turbulent flow. The only fluid, which Reynolds Number is less than 0.02 is the detergent and the coefficient of viscosity of detergent, is ranged between 4.8159 - 5.2312 kg/m.s.

Viscosity of liquids affect the velocity of the ball bearing as it falls. This is because the shearing stress exerted to the ball bearing is higher as the viscosity of the liquids is high. Therefore, velocity of the ball will be slower in the fluid of high viscosity. According to the graph above, oil is more viscous than water and detergent is more viscous than the oil. Therefore, it can be concluded that the viscosity of the liquid: Detergent> Oil> Water

3. Surface tension (Capillarity)

Based on the graph above, the level rise in the capillary is inversely proportional to the bore diameter of the capillary tube. As the bore diameter of the capillary tube increase, the capillary rise level decreases. According to the formula, the capillary rise level varies with the type of the fluid. The detergent that has the highest density has causes the capillary rise the lowest compared to other fluids. According to the Fluid Mechanics Fundamental and Application 2nd edition in SI units, Table 2-4 (surface tension of fluids in air at 1atm and 20C)

20C water = 0.073 N/mSAE 30 oil = 0.035 N/mSoap solution 0.025N/m

Based on the graph above, the detergent has the highest surface tension compared to other fluids that are water and oil. However, the fact stated that the water should be the highest surface tension. This is due to the instrument that used was not accurate. Besides, the capillary rise level obtained in the experiment will depend very much on the cleanliness of the capillary tubes and on whether any impurities are present in the water. As a result, the measured capillary rise level was not accurate.

2) Bourdon Gauge must show how increasing pressure and decreasing pressure is related for actual and gauge pressure. Discuss the results gained in term of pressure errors of gauge and actual.

Based on the experiment results, the error occurs between the actual pressure and the gauge pressure is small. However, from the data obtained, the increasing and decreasing pressures in the gauge are slightly inconsistent. This is because to some factors such as parallax error during the data is taken and friction force in the piston during the experiment.

3) Compare viscosity of different liquids by means of falling ball bearing with different diameters. Discuss the results gained.

Based on the experiment results the ball bearing falls slowly through a measuring cylinder that contain of detergent compare to the oil and water. Suppose it would fall at the same distance in water much faster than detergent and oil. From the result it can concluded that the viscosity of liquids will effect as the velocity of the ball bearing as it fall. As the viscosity of the liquids increase, the velocity of the ball decrease. Hence, detergent is more viscous than water and the frictional forces of the ball bearing "rubbing" against the detergent are greater, that why causing it to fall slowly. Therefore, it can be concluded that the viscosity of the liquid:

Detergent> Oil> Water

Besides that, sizes or diameters of the ball bearing also will affect the time falling through the liquid. The largest the diameter of the ball bearing, the faster it fall through the liquid. The ball bearing is released from rest and falling under the influence of gravitational force. With the two forces acting on it, that is the gravitational force and the viscosity drag force.

4) Analyze the water movement in small capillaries due to surface tension for all the distances available. Discuss the results gained.

From the experiment results, capillarity indicates the height, ht, and the water movement, while the various bore sizes represent the diameter of the capillary tube. From the data recorded, water possessed the highest value for ht, follow by oil and detergent. This shows that the water has a greatest surface tension force compared to oil and detergent. Moreover, the smallest the diameter of bore, the larger the height ht. The height, ht, is depends on the density of the liquid. This is due to the surface tension force is proportional to radius of the capillary tube. Hence, decreasing the bore sizes will increase the ht.5.0 QUESTION AND ANSWER

a) From the obtained data and the plotted graphs, what is the relationship of the gauge pressure versus the actual pressure?

From the graph above and data recorded, the gauge pressure is directly proportional to the actual pressure. As the reading of the gauge pressure increase, the actual pressure will also increase. However, there are also some error occur between the gauge pressure and the actual pressure where it is too small.

b) What are the differences in term of result for different sized balls and different liquid?

Viscosity of the liquids will effect of the velocity of falling of the ball bearing; also the sizes of the ball bearing. As the ball bearing fall from rest under influence of gravitational force, mainly two forces will act on it that is gravitational force and the viscous drag force. The largest the diameter, the fastest it fall through the liquid. Besides that, as the liquids that has higher viscosity, the velocity of the falling ball bearing will decrease. This is due to the frictional force in the liquid.

c) Explain about surface tension and why it is so important?

Surface tensionis a property of the surface of aliquidcaused bycohesionof like molecules, which is responsible for many of the behaviours of liquids. Themolecules at the surfacedo not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. This forms a surface "film" which makes it more difficult to move an object through the surface than to move it when it is completely submersed.Surface tension is important because it forms a film like effect on the surface of water, making it more difficult for an object or organism to move through the water when it is completely underneath it. For example, small insects such as thestrider can walk on water because their weight is not enough to penetrate the surface, if carefully placed on the surface, a small needle can be made to float on the surface of water even though it is several times as dense as water. If the surface is agitated to break up the surface tension, and then needle will quickly sink.

6.0 CONCLUSION

In conclusions, we achieved our objectives at the end of the lab sections. We succeed to determine the difference between the actual pressure and gauge pressure by using simple equipment like Bourdon gauge. The gauge pressure is directly proportional to the actual pressure. As the reading of the gauge pressure increases, the actual pressure will also increase. However, there are also some error occur between the gauge pressure and the actual pressure where it is too small.

In additions, we found out that viscosity of the liquids will effect of the velocity of falling of the ball bearing; also the sizes of the ball bearing. The largest the diameter, the fastest it fall through the liquid. As the liquids that have higher viscosity, the velocity of the falling ball bearing will decrease. This is due to the frictional force in the liquid.

For surface tension, the capillarity is depends on few factors, like the various diameter of the bores and the viscosity, density of the liquids too. Water has a greatest surface tension compare to the others liquids oil and detergent.

7.0 REFFERENCES

[1] http://en.wikipedia.org/wiki/Viscosity[2] http://en.wikipedia.org/wiki/Surface_tension[3] http://physics.about.com/od/physicsexperiments/a/surfacetension.html[4] Yunus A. Cengel and John M. Cimbala (2006). Fluid Mechanis Fundamentals and Applications. McGraw-Hill.[5] http://www.differencebetween.net/science/difference-between-gauge-pressure-and- absolute-pressure/[6] http://hyperphysics.phy-astr.gsu.edu/HBASE/surten.html[7] http://www.science.uwaterloo.ca/~cchieh/cact/c123/liquid.html[8] http://hyperphysics.phy-astr.gsu.edu/hbase/surten2.html[9] http://www.engineeringtoolbox.com/pressure-d_587.html