Reynold Number experiment report

1

R EPOR T

Title: REYNOLD NUMBER SUBJECT

: Experiment 3

PROF.

: Yoon Kyunghwan

MAJOR

: Mech. Engineering

STUDENT NO.

: 321291910

NAME

: Yolanda Putri Y

DATE

: March 27  2014

th

1

REYNOLD NUMBER 1

Yolanda Putri Yuda Department of Mechanical Engineering, Dankook University, South Korea

Key Words: Abstract: Reynold number (Re) is a ratio of inertial (destabilizing) force to the viscous damping (stabilizing) force. It is observed to indicate the types of the flow whether laminar, transition, or turbulent. The aim of this experiment is to distinguish between laminar flow and turbulent flow by observing changing ink line through internal flow in tube  based on the critical Reynold Number. Based on the data gained (Height) in both High Reynold Number and Low Reynold Number experiment, calculation data are investigated to determine the type of the flow. The result obtained is when the ink opens (High Reynold Number experiment), the volumentric flow rate increases. This condition is equal to the equation Q = V / t. At that time, the Reynold Number of the fluid approaches 3912.9 ~ 4891.1 which indicates that the flow is turbulent. The opposite way, when the ink valve is closed slowly (Low Reynold Number experiment), the volumentric flow rate decreases and being constant. In this case, the Reynold  Number of the flow are less than 3500 (2934.7 ~ 3423.8) which indicates that the type of the flow is transition flow leads to laminar flow.

1. Introduction 1.1 Purpose The aim of this experiment is to distinguish  between laminar flow and turbulent flow by observing changing ink line through internal flow in tube based on the critical Reynold Number. 1.1 Theory Osborn Reynold (1883) conducted a number of experiments to determine the types of the flow through the Laws of Resistance in pipe. By the Reynold Number, the flow allows to be classified as Laminar Flow, Transition Zone, and Turbulent Flow. Reynold Number (R) is dimensionless parameter. It is a ratio of inertial (destabilizing) force to the viscous damping (stabilizing) force. When the R increases, the inertial force will be higher and the flow destabilizes into turbulence. Critical Reynold number is the Reynold Number that exists anywhere in transition region where the critical velocity V averaged through the cross section at which laminar pipe flow changes to transitional.

Picture 1. Types of flow The change from laminar flow to turbulent flow occurs at: Re  2000 2000 ≤ Re ≤ 3500

Laminar flow Transition flow

Re  3500 Turbulent flow To quantify turbulence the Reynolds number which represents relation between inertial and viscous forces can be calculated as: Re

=









 =

2 Where: V = flow velocity (m/s)

5. Water Supply tank 6. Drain Cock For adjusting the flow rate in the experiment tube. 7. Measured Box with ruler (to measure the weight).

= density (kg/m3) = inside diameter of pipe section (m)



D Q A

= dynamic viscosity of the fluid (kg/ms) = volumetric flow rate (m 3/s) = cross sectional area of the pipe (m 2)



= kinematics viscosity (m /s)



2

The average speed of the fluid is related with Volumetric Flow Rate (Q in m 3/s), so the Re can be expressed as follows:   V= =  





So that, Re

=

 

=

  

2.2 Procedures 1. Prepare a constant temperature water bath which has transparent wall to make easy to observe the flow. 2. Fill the bath with water and let the water overflow form a certain height. 3. Open the exit-valve and control the valve of ink tube to make a thin ink line. For High Reynold Number 4. Increase the inner flow rate by opening the valve slowly. 5. If the turbulent flow is detected, measure the height of the flowed water for 10 second. 6. Repeat the steps above 3 times.

   

2. Experiment Method 2.1 Apparatus

For Low Reynold Number 4. Open the exit-valve to maximum and decrease the inner flow rate by closing the valve slowly. 5. If the laminar flow is detected, measure the height of the flowed water for 10 second. 6. Repeat the steps above 3 times.

7. Data Analysis Table 1. Data record 4

7 5

6

2

1

3

Picture 2: Reynold Number Experiment Apparatus Caption: 1. Base Plate 2. Experiment Tube 3. Inlet Section for controlling the ink flow 4. Ink tube The unit used black ink to observe and investigate the laminar and turbulent flow which assume that the temperature is constant.

Table 2. Main data given Water Temperature Coefficient of Viscosity Density of the Water Inner diameter of Tube Time

18.6 0C 1.04 x 10 -3 N.S/m2 998.28 kg/m3 25 mm 10 second

3 Based on the record and main data above, the other  parameters such as Volume of flowed water, Weight of flowed water, Q, and Re can be calculated manually with the sample calculation equation below (first data record for High Reynold  Number): Known: H (Height)

= 40 = 0.04 = 25 = 0.025 = 10

D T

mm m mm m second -3

3

V (m )

= 1.04 x 10  N.S/m



= 998.28 kg/m3

High

1

0.0008

0.7986

0.00008

Reynold

2

0.001

0.9982

0.0001

 Number

3

0.001

0.9982

0.0001

Low

1

0.0006

0.5989

0.00006

Reynold

2

0.0007

0.6987

0.00007

 Number

3

0.0007

0.6987

0.00007

Re

Ask: V, W, Q, Re

High

1

Answer:

Reynold

2

 Number

3

Low

1

2. W

3. Q

= 0.2 x 0.1 x H = 0.2 x 0.1 x 0.04 = 8 x 10-4 m3

=

Turbulent

4891.132

Turbulent

4891.132

Transition to Laminar

 Number

2

Transition to Laminar

3423.792 3

Transition to



Laminar

3423.792

  

From the data calculation above, graphs are established to distinguish between laminar and turbulent flow.

 3

= 8 x 10  m /s

=

Turbulent

2934.679



-5

=

Type of Flow

3912.905

Reynold

=Vx -4 3 3 = 8 x 10  m x 998.28 kg/m = 798.624 kg

=

4. Re

Q (m /s)

2



1. V

3

W (kg)

         

Relation between Q and Re

       

= 3912.905439 (Transition to Turbulent) Tabel 3. Calculation Data Re

Number of

H (m)

T (s)

D (m)

Experiment

High

1

0.04

10

0.025

Reynold

2

0.05

10

0.025

 Number

3

0.05

10

0.025

Low

1

0.03

10

0.025

Reynold

2

0.035

10

0.025

 Number

3

0.035

10

0.025

1 Re Q

2

3

1

2

3

3912.9 4891.1 4891.1 2934.7 3423.8 3423.8 0.00008 0.0001

0.0001 0.00006 0.00007 0.00007

Picture 3. Relation between Volumentric Flow Rate with Reynold Number

4 Based on picture 3 above, the relation of Volumentric flow rate (Q) with Reynold Number (Re) is directly proportional. It means that if volumentric flow rate of the fluid is higher, the Reynold Number of the flow will increase according to the Volumentric Flow Rate. The Volumentric Flow Rate increases when the ink valve opens. So that if the Reynold Number is higher, the flow of the fluid might be turbulent (in a steady state / ideal condition).

High Reynold Number VS Low Reynold Number

calculation data, the Reynold Number of the flow are less than 3500 (2934.7 ~ 3423.8) which indicates that the type of the flow is transition flow leads to laminar flow. So, to distinguish whether the flow of the fluid is laminar or turbulent, can be seen by observing the critical Reynold Number of the flow. Recommendation: In this experiment, it is better if use potassium  permanganate to the water to give a brighter visible ink line so that it will be easier to indicate whether the ink line is laminar or turbulent.

5. Reference

1

2

3

HRN

3912.9

4891.1

4891.1

LRN

2934.7

3423.8

3423.8

Picture 4. Distinguish Between High Reynold  Number and Low Reynold Number According to the relation between Volumentric Flow Rate and Reynold number, the graph in  picture 4. states the high reynold number shows Re 3912.9 ~ 4891.1. It means that the Flow indicates that it is turbulent flow which basically has Re 3500.

In the other hand, the Low Reynold Number shows that Re are less than 3500 (2934.7 ~ 3423.8) which indicate that the flow belongs to transition flow leads to laminar flow.

4. Conclusion From the result obtained and the plotted graphs, it can be concluded that when the ink opens, it will add the volume of the water flow and make the volumentric flow rate increases. This condition is equal to the equation Q = V / t. At that time, the Reynold Number of the fluid approaches 3912.9 ~ 4891.1 which indicates that the flow is turbulent. The opposite way, when the ink valve is closed slowly, the volumentric flow rate decreases and  being constant. In this case, based on the

1. J.P. Holman. 2010.  Heat Transfer 10h Edition. Southern Methodist University : McGraw-Hill. 2. O. Reynolds, “On the dynamical theory of incompressible viscous fluids and the determination of the criterion,” Phil. Trans. Roy. Soc., A 186, 123 – 164 (1895). 3. Experiments’  modul of Marine Machinery and System Laboratory. 2012. Department of Marine Engineering, Institut Teknoogi Sepuluh  Nopember Surabaya, Indonesia. 4. Guidelines of Reynold Number experiment. 2014. Department of Mechanical Engineering, Dankook University, South Korea.