TABLE OF CONTENTSEXPERIMENT 1: VELOCITY MEASUREMENT USING PITOT TUBE No. Title 1.1 Summary/Abstract 1.2 Purpose and Objective 1.3 Theory 1.4 Equipment and Description of Experimental Apparatus 1.5 Procedure 1.6 Data, Observation and Result 1.7 Analysis and Discussions 1.8 Conclusions 1.9 References 1.10 Appendixes EXPERIMENT 2: DETERMINING OF DISCHARGE COEFFICIENT No. Title 2.1 Summary/Abstract 2.2 Purpose and Objective 2.3 Theory 2.4 Equipment and Description of Experimental Apparatus 2.5 Procedure 2.6 Data, Observation and Result 2.7 Sample Calculations 2.8 Analysis and Discussions 2.9 Conclusions 2.10 References Experiment 1: Velocity Measurement Using Pitot Tube. Page 3 3 3 6 7 8 10 11 11 11 Page 12 12 12 14 14 15 18 19 19 20 1.1 SUMMARY/ABSTRACT. In this experiment, there are one major thing should be done which are determining the air flow velocity along the Pitot tube. According from that, there is velocity profiles produced due to the different in pressure when doing this experiment (static pressure and stagnation pressure). Based on that, Bernoulli’s equations are needed to compute the velocity for each condition. 1.2 PURPOSE/OBJECTIVES. In this experiment student will learn the method of measuring air flow velocity using Pitot tube. Then, the student will understand the working principle of Pitot tube as well as the importance of Bernoulli’s equation in deriving and calculating the velocity. 1.3 THEORY. 1 the core region still outside the boundary layer showing up as an area of more or less uniform velocity. It's proportional to the fluid's density. With Pitot tube. Reynolds Number The Reynolds number is a measure of the way in which a moving fluid encounters an obstacle. Re vd 2 .A pitot tube is used to explore the developing boundary layer in the entry length of a pipe which has air drawn through it. the shear stress set up close to this boundary due to the relative motion between the fluid and the wall leads to the development of a flow boundary layer. With Pitot tube.81 m/s2). g is gravitational acceleration constant (9. the velocity distribution profiles can be determined at a number of cross-sections at different locations along a pipe. The boundary layer may be either laminar or turbulent in nature depending on the flow Reynolds number. where one of the points is at static velocity. v 2p or 2 gh' (1) p is the pressure difference between the pitot tube and the wall pressure tapping measured using manometer bank provided (gx where x is the level of fluid used in the manometer). h’ is the pressure difference expressed as a 'head' of the fluid being measured (air) The air density at the atmospheric pressure and temperature of that day (kg/m3) . air flow velocities in the pipe can be obtained by first measuring the pressure difference of the moving air in the pipe at two points. and the fluid's speed. and inversely proportional to the fluid's viscosity (viscosity is the measure of a fluid's "thickness"--for example. the size of the obstacle. If velocity profiles for cross-sections different distances from the pipe entrance are compared. Once the boundary layer has grown to the point where it fills the whole pipe crosssection this is termed "fully developed pipe flow". the rate of growth of the boundary layer along the pipe length can be determined. When fluid flows past a stationary solid wall. The growth of this boundary layer can be revealed by studying the velocity profiles at selected cross-sections. The Bernoulli equation is then applied to calculate the velocity from the pressure difference. honey has a much larger viscosity than water does). The transition from laminar to turbulent flow." You can describe such laminar flow as dominated by the fluid's viscosity--it's tendency to move smoothly together as a cohesive material. : Fluid density v : fluid velocity d : obstacle size : Coefficient of fluid dynamic viscosity A small Reynolds number refers to a flow in which the fluid has a low density so that it responds easily to forces. or has too small a viscosity to keep it organized. encounters a small obstacle. You can describe such turbulent flow as dominated by the fluid's inertia-the tendency of each portion of fluid to follow a path determined by its own momentum. the fluid can't get around the obstacle without breaking up into turbulent swirls and eddies. the fluid is able to get around the obstacle smoothly in what is known as "laminar flow. occurs at a particular range of Reynolds number (usually around 2500). In such a situation. the flow is normally laminar. In such a situation. Starting with the basic equation of hydrostatics: p = gh (2) We can follow this procedure through using the following definitions: Example: Manometer tubes 1(static ‘pressure’*) 2(stagnation ‘pressure’) 3 . Calculation of air flow velocity The manometer tube liquid levels must be used to calculate pressure differences. A large Reynolds number refers to a flow in which the fluid has a large density so that it doesn't respond easily to forces. critcal flow. moves slowly. moves rapidly. or has a large viscosity to keep it organized. h and pressure heads in all these experiments. Below this range. encounters a large obstacle. the flow is normally turbulent. above it. the equivalent pressure difference p is: p = k gh = k g(x1 . . If x1 and x2 are read in mm. Therefore the equivalent vertical separation of liquid levels in manometer tubes.2 kg/m 3 for this gives: h' k ( x1 x 2 ) . To use the first equation (1). cos air 1000 [N/m2] (6) 4 .72(x1 .Liquid surface readings X1 X2 (mm) Angle of inclination. h = (x1 .x2)cos [N/m2] (5) The p obtained is then used in second equation (1) to obtain the velocity.x2)cos (3) If k is the density of the kerosene in the manometer. convert this into a 'head' of air.81 m/s2. = 0 ‘Pressure’ term is used since this reading is in mm of manometer fluid and not the pressure of unit Pa. then: p = 7. Assuming a value of 1.x2) cos (4) The value for kerosene is k = 787 kg/m3 and g = 9. h’. 4 EQUIPMENT AND DESCRIPTION OF EXPERIMENTAL APPARATUS.1. 5 . read and record both manometer tube levels of the wall static and the pitot tube until the transverse position viii. mm. 6 . 1574 mm and 2534 mm from the pipe inlet. Note that the connecting tube. 294 mm.1. Set the manometer such that the inclined position is at 00. is placed. Start the fan with the outlet throttle opened. touching the top of the pipe. 774 ii. Position the pitot tube with the traverse position of 0mm. Repeat the velocity traverse for the same air flow value at the next position with the pitot tube assembly. where the tip is touching the bottom of the pipe. These are: 54 mm. the pressure tapping at the outer end of the assembly.5 PROCEDURE. Make sure that the blanking plug is placed at the holes that are not in use. i. Five mounting positions are provided for the pitot tube assembly. is connected to a convenient manometer tube. nearest to the pipe inlet). the L-shape metal tube of the pitot tube is facing the v. Note that there is a pipe wall static pressure tapping near to the position where the pitot tube assembly vi. iv. Mount the pitot tube assembly at position 1 (at 54mm. The static pressure tapping is connected to a manometer tube. Starting with the traverse position at 0mm. Ensure that the standard inlet nozzle is fitted for this experiment and that the orifice plate is removed iii. incoming flow. vii. from the pipe break line. Make sure that the tip. 48 61.8872 33. x1 7 .0211 9.4780 20.0000 Pitot Tube at 2534 mm Static ‘Pressure’ Reading 178 (mm).6591 30.6785 Pitot Tube at 1574 mm Static ‘Pressure’ Reading 194 (mm).64 92.76 77.6785 10.2039 11.6290 10.0000 8.2039 11.48 61.6290 11.7508 11.76 46.48 586.6785 20.2039 15.0860 0.2 77. OBSERVATIONS AND RESULTS.3739 Traverse Position (mm) Pitot Tube at 294 mm Static ‘Pressure’ Reading 110 (mm).2 84.2 61.04 10.2733 12. x1 Stagnation ‘Pressure’ Reading (mm).0211 8.0211 10.0211 8.76 46.2 77.6785 8.2039 11.6591 7.2 154. x2 104 102 100 100 99 100 101 102 104 ∆x (mm) ∆p (N/m²) Velocity (m/s) 6 8 10 10 11 10 9 8 6 46.1.88 0 0. x1 Stagnation ‘Pressure’ Reading (mm).7 DATA.36 571. x2 102 101 100 100 90 101 102 104 104 ∆x (mm) ∆p (N/m²) Velocity (m/s) 8 9 10 10 20 9 8 6 6 61.2039 10.32 46.48 77. x1 Stagnation ‘Pressure’ Reading (mm).2039 10.76 54.48 30.72 679.2 69.32 8.0211 11.28 262. x2 104 102 101 100 100 100 102 104 105 ∆x (mm) ∆p (N/m²) Velocity (m/s) 8 10 11 12 12 12 10 8 7 61.76 69.2363 30.2039 11.32 61. Data sheet for Velocity Measurement Using Pitot Tube Traverse Position (mm) 0 10 20 30 40 50 60 70 80 Traverse Position (mm) 0 10 20 30 40 50 60 70 80 Pitot Tube at 54 mm Static ‘Pressure’ Reading 110 (mm).92 77.64 92.92 92.6290 10.2733 12. x2 194 188 160 118 106 120 160 190 194 ∆x (mm) ∆p (N/m²) Velocity (m/s) 0 6 34 76 88 74 34 4 0 0 46.2 84.7508 12.2733 11.4 69. x1 Stagnation ‘Pressure’ Reading (mm).32 262.76 77.8448 10.64 77.0211 11.6 1.6785 Pitot Tube at 774 mm Static ‘Pressure’ Reading 112 (mm).32 10. 36 92.7745 12.v = (2 Δp)1/2 = 8.7745 12.64 92.32 (N/m²) Velocity.64 77.2039 10.48 12.6290 10.6785 m/s (ρair)1/2 8 .72 (x1 – x2) cos θ Velocity.7745 12.2733 12.64 100.36 100.2733 12.2 69.Stagnation ‘Pressure’ Reading (mm). Δp = 7.48 69.8 SAMPLE CALCULATION Equations: ∆p = 7.72 (110-104) cos 0 = 46. x2 166 166 165 165 165 166 168 169 169 0 10 20 30 40 50 60 70 80 ∆x (mm) ∆p (N/m²) Velocity (m/s) 12 12 13 13 13 12 10 9 9 92. x2 = 104 mm Pressure difference.6290 1.2733 11. v = (2 Δp) 1/2 = (2 gh’) ½ (ρair) 1/2 Pitot Tube at 54 mm: Static Pressure Reading. x1 = 110 mm Stagnation Pressure reading.36 100. Air Velocity Vs. This pressure is the stagnation pressure of the fluid. the moving fluid is brought to rest (stagnates) as there is no outlet to allow flow to continue. Bernoulli's equation is used to calculate the dynamic pressure and hence fluid velocity. The basic pitot tube consists of a tube pointing directly into the fluid flow. also known as the total pressure or (particularly in aviation) the pitot pressure. 35 30 25 20 Air Velocity (m/s) 15 10 5 0 0 10 20 30 40 50 60 70 80 90 Traverse Position (mm) 54mm 294mm 774mm 1574mm 2534mm 1. As this tube contains fluid. The measured stagnation pressure cannot of itself be used to determine the fluid velocity (airspeed in aviation). However.8 ANALYSIS AND DISCUSSIONS. Bernoulli's equation states: Stagnation pressure = static pressure + dynamic pressure 9 . Traverse Position. a pressure can be measured. A pitot tube is a pressure measuring instrument used to measure fluid flow velocity by determining the stagnation pressure. the student will understand the working principle of pitot tube as well as the importance of Bernoulli’s equation in deriving and calculating the velocity. There are some experimental error of the instruments itself that are too long to be used this can contribute on how to get a better result. In this experiment we use orifice plate as a main component. There are three major error when doing experiments which are random error. student should reading carefully to avoid parallax error that can affect the calculation on determining the velocity of air. http://www. fixed error and experimental error. Based on this experiment.uniten. The velocity profile should be a parabolic shape. 1. the shear stress set up close to boundary due the relative motion between the air and the wall of the pipe. Besides that.1 SUMMARY/ABSTRACT. When the air flows past the pipe. 2. we can conclude the velocity profile is a parabolic shape. When taking the reading of manometer tube. Therefore. Also using the static pressure tapings provided.html http://moodle. Appendix A (Sample Calculation): Experiment 2: Determination of Discharge Coefficient.Based on the figure above and graph plotted.my/moodle/course/view. we also can determine and know the velocity profile at the different location along a pipe using pitot tube. 1. In this experiment. Therefore the objectives are achieved. conclude that the velocity of air is not same at any points. we are determining the pressure distribution along the 10 .10 REFERENCES. An orifice plate meter is a device for measuring the discharge for the flow of liquids or gases through a pipe. we are going to determine the discharge coefficient experimentally for an orifice plate in an airflow pipe.edu.11 APPENDIXES. Hence. In contrast. there is maximum value at the middle points of pitot tube due to the no friction forces act on it or shear stress act in it.9 CONCLUSIONS.php?id=111 1. This happen due to the reaction forces occur. the air is moving freely. Therefore the value of velocity increases until one points and then decreases again as initial points.com/flow-meters-d_493. The Bernoulli equation is then applied to calculate the velocity from the pressure difference. it shows same velocity profile as a result. we can say that the air velocity or the graph figure should be differ on each situation.engineeringtoolbox. Then. From that. There is no value in velocity at the initial points due to the friction force on the wall surfaces. This velocity can be calculated by using Bernoulli’s equation from given the different pressure (static and stagnation pressures). I) These two coefficients are normally combined to give a single coefficient of discharge: C D = Cc. then the discharge coefficient can be determined as follows:- CD Q A o 2gh (3) Q i A i C ' D 2gh i Values of Qi can be determined if the standard nozzle is fitted at the pipe inlet. Calculating the CD of orifice plate: 11 . by the energy equation: Q A j v j A o Cc v j A oCc C v 2gh (1) where Q = Aj = Ao = vj = Cc = Cv = g = h = discharge (volume/time) jet cross-section area at minimum contraction (vena contracta) orifice cross-section area (d2/4: d = orifice size) jet velocity at minimum contraction (vena contracta) coefficient of contraction of jet coefficient of velocity of jet gravitational acceleration (9.81 ms -2) pressure difference 'head' of air across orifice (refer to equation (6) of Exp. The pressure difference between the two sides of the plate is related to the jet velocity.Cv Q CEquation D Ao 2 gh(1) now becomes (2) If Q can be determined independently. the discharge = (k/air )* (xbefore nozzle –xafter nozzle): in which Ai = standard nozzle cross-section area (= d2 /4) and C’D assumed to be 0.2 PURPOSE/OBJECTIVES. From the obtained C D of the orifice plate.3 THEORY. The orifice plate meter forms a jet.97. In this experiment student need to determine the discharge coefficients. we will determine the CD of a small nozzle. (4) If hi = the drop in pressure head across the inlet. 2. 2.pipe downstream of the orifice plate. which expands to fill the whole pipe. some diameter distance downstream. Values of h I are obtained from the manometer tube levels connected to the pipe inlet pressure tapping and open to the atmosphere. and therefore the discharge. C D for orifice plate and the small nozzle. with the Q i obtained from standard nozzle where C D of standard nozzle is assumed Q to be 0. apply equation (3) Ao 2 gho ……………………………(5) Where ho = (k/air)*(x across orifice) Ao = cross section area of orifice plate hole 2. we can calculate the C D of orifice plate.From equation (4).4 EQUIPMENT AND DESCRIPTION OF EXPERIMENTAL APPARATUS. Assuming that Qi across standard nozzle o C D Qo across and orifice plate is the same. Figure 2 : Experiment Diagram 12 .97. surface should face the approaching airflow. OBSERVATIONS AND RESULTS.654 0.671 0. Gradually increase air flow by increasing the damper opening to 100%. including iv. Insert the orifice plate in position (taking care to observe the instructions as to) in which the ii.153 0. 2. Table 2.6.6 DATA. and take read at all opening. any open to the air (reading should be taken after the fan is on). the first tapping point adjacent to the standard inlet nozzle which should be fitted.5 PROCEDURE i.632 13 .1: Static ‘Pressure’ Readings when using Standard Nozzle (80mm) Damper Openings (% Openings) 0% 25 % Points 50 % 75 % 100 % mm of kerosene Room ‘Pressure’ 102 102 102 102 102 After Nozzle 105 108 109 109 109 54 mm 105 108 109 110 110 294 mm 105 109 110 111 111 774 mm 105 111 112 114 113 Before Orifice 105 112 114 119 114 After Orifice 119 190 210 220 222 1574 mm 116 170 188 194 198 2534 mm 114 158 170 177 178 Cd 1. Connect all the static pressure tapping points to the manometer tubes ensuring that one manometer tube remains unconnected to record room air pressure and that one is attached to iii.2. Turn on fan with low airflow (damper plate closed) and read all manometer tubes.689 0. 2: Static ‘Pressure’ Readings when using Small Nozzle (50 mm) Damper Openings (% Openings) 0% 25 % Points 50 % 75 % 100 % mm of kerosene Room ‘Pressure’ 104 102 102 102 102 After Nozzle 112 139 146 148 150 54 mm 112 141 148 150 152 294 mm 109 126 130 132 132 774 mm 109 125 130 132 132 Before Orifice 110 127 131 133 133 After Orifice 122 190 206 212 214 1574 mm 119 174 190 194 198 2534 mm 117 164 176 180 181 Cd 1.413 3.240 3.242 3.Table 2.260 *(Sample Calculation on Appendix B) 14 .6.254 3. Cd VS Re 1.2 1.6.9 0.8 0.6.1: Kerosene Vs Tapping Position.7 0.6 13000 14000 15000 16000 17000 18000 19000 20000 21000 22000 Re Graph 2.1 1 Cd 0.Kerosene VS Tapping Position Kerosene 8 7 6 5 4 3 2 1 0 240 220 200 180 160 140 120 100 Tapping Position Standard Nozzle Small Nozzle Graph 2.2: Cd Vs Re for Standard Nozzle. 15 . 5 3 2. the velocity is higher. According to the Bernoulli’s equation. In addition. This is due to the contraction in diameter at the centre of the orifice plate. When the velocity increases. Based on the experiment and figure above.5 2 Cd 1.5 1 0. 2. the pressure decreases and vice versa.3: Cd Vs Re for Small Nozzle.Cd VS Re 3. namely Bernoulli's principle which states that there is a relationship between the pressure of the fluid and the velocity of the fluid. the velocity of air became higher than normal. with an orifice plate.7 ANALYSIS AND DISCUSSIONS.5 0 0 10000 20000 30000 40000 50000 60000 70000 80000 Re Graph 2.6. It uses the same principle as a Venturi nozzle. An orifice plate is a device used for measuring the volumetric flow rate. This was approved by the manometer reading in this experiment. when the air flow part through the orifice plate. when the pressure is lower. the air flow is measured through the difference in pressure from the upstream side to the 16 . C D for orifice plate and the CD for small nozzle. the size of orifice plate and the small nozzle. Show that the orifice plate made the air velocity increased. 2.9 REFERENCES. usage of orifice plate in the experiment will cause a drop in pressure. The plate obstructing the flow offers a precisely measured obstruction that narrows the pipe and forces the flowing air to constrict. student can determine the discharge coefficient. When calculation had been done. Area for orifice plate is the main parameter that can affect these values. There are different values in discharge coefficient for orifice plate and small nozzle. This is due to the equation difference on calculating these C d values. http://www. In this experiment. In this experiment. after the orifice plate. As mentioned before. the pressure is increase. We know that the air velocity is depending on the orifice plate and the size of the nozzle too. In contrast with the graph plotted. These reading are calculated based on the reading of manometer.engineeringtoolbox. Hence. noted that the C d value obtained for orifice and small nozzle is not same. we know that when the damper opening increases. the air velocity decreased a little but still in a high magnitude. Based on this experiment. the value of C D increases for orifice plate. Knowing that there are hole at the center of orifice plate hence it will resist the airflow as in figure below: Therefore.8 CONCLUSIONS.html 17 . Therefore the objectives are achieved.com/flow-meters-d_493. 2. we obtained the different value for C D based on the value of diameter for orifice. the manometer reading changes when the damper opening changes. By doing this experiment. then the atmospheric pressure is low. Basically. when the air velocity is high.downstream side of a partially obstructed pipe. This is proved by the calculation based on Bernoulli’s equation. the C d value for orifice plate is decreases while the C d value for small nozzle in increases. This is because the air flows past faster when the percentage of damper opening became higher. therefore the manometer reading will increase. 0278/[(п/4)(0.81)(787/1. Qsmall nozzle = Ai CD√2ghi = п/4(0.67 18 . CD small nozzle = Q/Asmall nozzle(√2gh) = 0.10 http://moodle.0278 4.03/0. Reynolds Number.153 3.05)2√(2)(9.edu.05)2√ (2) (9.81) (787/1.uniten.81) (787/1.81) (787/1.029 2. 2.029/ [(п/4) (0.08)2(1.php?id=111 http://en.my/moodle/course/view.08)2(0. (0% damper openings) 1. Appendix B (Sample Calculation): Determination of Discharge Coefficient.53) √ [2(9. QI = Ai CD√2ghi = п/4(0.23) ((119-105)/1000)] = 1. Re = ρvd/ μ = (1.82) 1.23) ((122-110)/1000)] = 0.413 5.2)(0.20)((112-104)/1000)] = 1. CD orifice plate = Q/AO√2gh = 0.97) √ [2(9.wikipedia.08x10-3 = 13666.org/wiki/Orifice_plate APPENDIXES.002)(0.23) ((105-102)/1000)] = 0.