lab 4(final)

Diameter = 0.0156 m

TITLE

PAGE

1.0 Abstract

2

2.0 Introduction

3

3.0 Objectives

4

4 .0 Theory

4

5.0 Materials/Apparatus

5

6.0 Procedure

6

7.0 Results

7

8.0 Calculations

8.1 Laminar flow

8.2 Transitional flow

8.3 Turbulent flow89

10

11

9.0 Discussion12

10.0 Conclusion14

11.0 Recommendations14

12.0 Reference15

13.0 Appendices

16

TABLE OF CONTENT

1.0 ABSTRACTOSBORNE REYNOLDS APPARATUSIn fluid mechanics, the Reynolds number (Re) is a dimensionless quantity that is used to help predict similar flow patterns in different fluid flow situations. The objective of this experiment is to compute Reynoldss number (Re). In addition, it is to observe the laminar, transitional and turbulent flow of dye streak in water. Hence, during experiment we need to produce the laminar, transitional and turbulent flow of water by using the Osborne Reynoldss Demonstration. We need to adjust the dye control needle until the identifiable dye line is achieved. At the same time, allowed the small overflow to maintain a constant level and regulated the water inlet valve to form different type of water flow. Then, in 10 seconds a volume of water is collected. Hence, the Reynolds number (Re) of water can be calculated by using volumetric method. The average result for laminar flow is101 (Re< 2100) , transitional 2172 ( 2100< Re 4000). Therefore, we achieved the supposedly Reynolds number (Re) for every each of the different type of water flow.2.0INTRODUCTIONExperiment on the laminar, transitional and turbulent flow of water can be examine by Osborne Reynolds Demonstration (Model: FM 11) that has been designed for students. It consists of a transparent header tank and flow visualization pipe. There fore, the header tank is provided with a diffuser and stilling materials at the bottom to provide a constant head of water to be discharged through a bell mouth entry to the flow visualization pipe. Then, by using a control valve at the discharge end the flow through this pipe can be regulate. The water flow rate through the pipe can be measured using the volumetric cylinder and the velocity of the water can be determined to allow the calculation of the Reynolds Number. On top of the header tank, a dye injection system is installed. Thus, flow pattern in the pipe can be visualized.The Osborne Reynolds Demonstration apparatus is equipped with a visualization tube for students to observe the flow condition. The rocks inside the stilling tank are to calm the inflow water so that there will not be any turbulence to interfere with the experiment. The water inlet / outlet valve and dye injector are utilized to generate the required flow. When performing scaling of fluid dynamics problems, Reynolds numbers frequently arise, and as such can be used to determine dynamic similitude between two different cases of fluid flow. Different flow regimes of the similar fluid can be categorized such as laminar flow occurs at low Reynolds numbers. Moreover, where viscous forces are dominant, and is characterized by smooth, constant fluid motion; turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities.Pipe Flow Conditions, for water flowing in pipe or circular conduits, L is the diameter of the pipe. Then, for Reynolds number less than 2100, the pipe flow will be laminar. For Reynolds number from 2100 to 4000 the pipe flow will be considered a transitional flow. Turbulent occur when Reynolds number is above 4000. The viscosity of the fluid also determines the characteristic of the flow becoming laminar or turbulent. Fluid with higher viscosity is easier to achieve a turbulent flow condition. The viscosity of fluid is also dependent on the temperature. There being no interaction (mixing) between shear planes as laminar flow denoted a steady flow condition where all streamlines follow parallel paths. Under this condition the dye observed will remain as a solid, straight and easily identifiable component of flow. Transitional flow is a mixture of laminar and turbulent flow with turbulence in the center of the pipe, and laminar flow near the edges. Each of these flows behaves in different manners in terms of their frictional energy loss while flowing, and have different equations that predict their behavior. Turbulent flow denotes an unsteady flow condition where streamlines interact causing shear plane collapse and mixing of the fluid. In this condition the dye observed will become disperse in the water and mix with the water. The observed dye will not be identifiable at this point.

3.0OBJECTIVES

The objective of this experiment is to compute Reynoldss number (Re). In addition, it is to observe the laminar, transitional and turbulent flow of dye.4.0THEORY

Fluid flow can be characterized as laminar, transitional and turbulent flow. Reynold number, Re is used to determine the fluid flow condition. Re can be defined as:

Where,U : velocity (m/s)

L : length or diameter (m)

V : kinematic viscosity (m2/s)For the Re less than 2000, the pipe flow will be laminar. Transitional flow, the Re is in between 2000 to 4000 and when the Re is above 4000, the turbulent flow will be occur. The viscocity is also important to determine the characteristics of fluid flow condition. Fluid with higher velocity is easier to achieve a turbulent flow condition. The characteristics of the laminar flow is all streamlines must follow the parallel paths, there being no interaction between the shear planes. The dye that must be observe will remain as solid, straight and easily identifiable components of flow.Transitional flow is the mixture of laminar and turbulent flow where the turbulent must be in center of the pipe and laminar should be near the edges of the pipe. Turbulent flow is an unsteady flow condition where all streamlines interact to aech other. These interaction may cause the shear plane collapse and mixing. The dye that be observed will not be identifiable at this point.5.0MATERIALS/APPARATUS

1. Dye reservoir6. Water inlet, V1

2. Dye injector7. Bell mouth

3. Head tank8. Water outlet, V2

4. Observation tube9. Overflow valve, V3

5. Distilled water10. Graduated cylinder

6. stopwatch11. goggle

6.0 PROCEDURE1. The dye injector was lowered until it is seen in the glass tube. 2. The inlet valve, V1 was opened and allowed water to enter stilling tank.3. A small overflow spillage through the over flow was ensured to maintain a constant level.4. Water was allowed to settle for a few minutes.5. The flow control valve was opened fractionally to let water flow through the visualizing tube.6. The dye control needle was slowly adjusted until a slow flow with dye injection was achieved.7. The water inlet valve, V1 and outlet valve, V2 was regulated until a straight identifiable dye line was achieved. The flow will be laminar.8. The flow rate was measured using a volumetric method.9. The experiment was repeated by regulating water inlet valve, V1 and outlet valve, V2 to produce transitional and turbulent flow.7.0RESULTS

Table 7.0: Average Re for laminar, transitional and turbulent flows.Volume

(ml)Time

(s)Flow rate, Q (L/s)Flow rate,

Q (m3/s)Reynolds Number, ReAverage Reynolds calculation, Re

Laminar flow

12.00101.2x10-11.2x10-6110= 101

11.00101.1x10-31.1x10-6101

10.00101.0x10-31.0x10-692

Transitional flow

230.00100.0232.3x10-52111= 2172

240.00100.0242.4x10-52202

240.00100.2042.4x10-52202

Turbulent flow

630.00100.0636.3x10-55782= 5812

630.00100.0636.3x10-55782

640.00100.0646.4x10-55873

8.0CALCULATIONS

Laminar flow: Re < 2100Transitional flow: 2100 < Re < 4000Turbulent flow: Re > 4000Kinematics viscosity for 25C water = 0.89 x 10-6 m/s

Thus,

Since,

Glass tube diameter (D) = 0.0156 m

Area (A) = 1.91x10-4 m2Thus,

8.1Laminar flow:

8.1.1First reading: 12.00 mL

Q= 1.2x10-6 m3/s

From the flow rate, the value of velocity is:

U=

= = 6.2827x10-3 m/s

Therefore,

= 110

8.1.2Second reading: 11.00 mL

Q = 1.1x10-6 m3/s


u=

= = 5.7592x10-3 m/s

Therefore,

= 101

8.1.3Third reading: 10.00 mL

Q = 1.0x10-6 m3/s


u=

= = 5.2356x10-3 m/s

Therefore,

= 92

8.1.4Average Re

Average Re= = 1018.2Transitional flow:8.2.1First reading: 230.00 mL

Q = 2.3x10-5 m3/sFrom the flow rate, the value of velocity is

u=

= = 0.1204 m/s

Therefore,

= 2111



u=

= = 0.1257 m/s

Therefore,

= 2202



u=

= = 0.1257 m/s

Therefore,

= 2202

8.2.4Average Re

Average Re= = 2172

8.3Turbulent flow:

8.3.1First reading: 630.00 mL

Q = 6.3x10-5 m3/s

From the flow rate, the value of velocity is

u=

= = 0.3298 m/s

Therefore,

= 5782


Q = 6.3x10-5 m3/s


u=

= = 0.3298 m/s

Therefore,

= 5782


Q = 6.4x10-5 m3/s


u=

= = 0.3351 m/s

Therefore,

= 5783

8.3.4Average Re

Average Re= = 58129.0DISCUSSIONSThis experiment was conducted to compute Reynoldss number, Re and observe the laminar, transitional and turbulent flows of dye in water. The valves were controlled until the flow of dye becomes laminar, then transitional and turbulent flows. The volume of water out within 10 seconds was collected three times by using measuring cylinder to get an average reading of volume. Then Reynolds number for each flow can be calculated.

(a) Laminar flow

(b) Transitional flow

(c) Turbulent flow

Figure 9.0: Flow types of dyeIt was observed to be laminar flow, as shown in Figure 9.0 (a) when straight identifiable dye line was achieved. In laminar flow, sometimes called streamline flow, the velocity, pressure and other flow properties at each point in the dye remain constant, which the dye travels smoothly or in regular path (Figure 9.1). The velocity of dye flow out is slow and the volume collected is not too much, then the average Reynolds number from the result obtained was 101. Since it is less than 2100, it is absolutely right to be laminar flow.However, as in Figure 9.0 (b), the condition of transitional flow was the dye observed become dispersed, and then mix in the water. The observed dye will not be identifiable at this point. The properties of this flow are not remains constant anymore. The volume collected also in a large amount than the laminar flow since the velocity of water becomes greater. Average Reynolds number from the result that has been calculated was 2172. The flow is transitional since its value was between 2100 and 4000.Figure 9.0 (c) shows that the observed dye was in turbulent flow. The dye undergoes irregular fluctuations or mixing. The velocity of dye at a given point continuously varies in magnitude and direction, which result in swirling and eddying as the bulk of the dye moves in specific direction. Based on the result obtained, the volume of water collected for three times are much greater than laminar and transitional flow. the velocity also become higher. The average Reynolds number is more than 4000, which is 5812. Therefore, it is turbulent.Below (Figure 9.1) is an illustration of laminar, transitional and turbulent flow of dye streak.

Figure 9.1: laminar, transitional, and turbulent flow of dye streak.In conducting this experiment, the error in Reynolds number depends on the velocity of the water, which affect volumetric flow rate to calculated Re. When wrong in visualized the flow of dye to be laminar, transitional, or turbulent, it probably effect the amount of water collected. Besides, sometimes the volume collected might be too much or too little. Then, it can be parallax error while using graduated cylinder.10.0CONCLUSION

The objective of this experiment is to compute Reynoldss number, Re and to observe the laminar, transitional and turbulent flow of dye streak in water. If Re is less than 2100, it is laminar flow. Re that is between 2100 and 4000, the flow is transitional. The turbulent flow will have Re more than 4000.

In conclusion, average Re for laminar, transitional and turbulent flows are 101, 2172 and 5812 respectively. In this experiment, all the observed dye is equivalent to the results obtained and the calculated Re. Three times of volume was taken to reduce the error of Re by taking an average.11.0

RECOMMENDATIONS

There are several recommendations that will significantly give better observations which would not deviate too much from the theoretical observations. The experiment should be repeated for a few times to get an average reading. Hence, more accurate reading can be recorded to increase accuracy and to ensure consistency in readings of volume, which carried out to reduce experimental error by calculating the average value.To collect the water, make sure that there will not be too much or too little whithin that fixed time. While observe the level of water in graduated measuring cylinder, white blank paper can be put at the back of it to avoid the parallax error. All steps in the procedure should be followed to get an accurate result. Besides, take alert for any changes of result in the physical condition, such as the flow of the dye and others.Before conducting the experiment, all the apparatus must be make sure in a good condition especially the Osborne Reynolds apparatus. The instructions of laboratory technician must be followed. Besides, the experiment should be handle carefully to prevent any unwanted things to happen. After the experiment is done, switch off the apparatus.12.0REFERENCES

Laboratory #7 Laminar and Turbulent Flow. Retrieved April 10, 2014, fromhttp://www.ce.utexas

.edu/prof/kinnas/319LAB/Lab/Lab%207-Laminar%20and%20Turbulent%20Flow/7-LamTu

b.htm

Laminar flow.Encyclopaedia Britannica. Encyclopaedia Britannica Online Academic Edition.

Encyclopdia Britannica Inc., 2014. Web. 11 Apr. 2014.