Reynold Number experiment report

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Title: REYNOLD NUMBER

Title: REYNOLD NUMBER

SUBJECT

SUBJECT

:

: Experiment

Experiment 3

3

PROF.

PROF.

:

: Yoon

Yoon Kyunghwan

Kyunghwan

MAJOR

MAJOR

:

: Mech.

Mech. Engineering

Engineering

STUDENT

STUDENT NO.

NO. :

: 321291910

321291910

NAME

NAME

:

: Yolanda

Yolanda Putri

Putri Y

Y

DATE

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 Laminar flow

2000 ≤ Re ≤ 3500 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

=



 =

  

REYNOLD NUMBER

Yolanda Putri Yuda1

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

V = flow velocity (m/s)

 = density (kg/m3)

D = inside diameter of pipe section (m)

 = dynamic viscosity of the fluid (kg/ms)

Q = volumetric flow rate (m3/s)

A = cross sectional area of the pipe (m2)

 = kinematics viscosity (m2/s)

The average speed of the fluid is related with Volumetric Flow Rate (Q in m3/s), so theRe can be expressed as follows: V = 

=

2. Experiment Method

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.

6. Drain Cock

For adjusting the flow rate in the experiment tube.

7. Measured Box with ruler (to measure the weight).

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 over-flow 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.

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

Table 2. Main data given

Water Temperature 18.60C Coefficient of

Viscosity

1.04 x 10-3 N.S/m2 Density of the Water 998.28 kg/m3 Inner diameter of Tube 25 mm Time 10 second 1 2 3 4 5 6 7

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 mm = 0.04 m D = 25 mm = 0.025 m T = 10 second  = 1.04 x 10-3 N.S/m2  = 998.28 kg/m3 Ask: V, W, Q, Re Answer: 1. V = 0.2 x 0.1 x H = 0.2 x 0.1 x 0.04 = 8 x 10-4 m3 2. W = V x = 8 x 10-4 m3x 998.28 kg/m3 = 798.624 kg

3.

4.

Tabel 3. Calculation Data

Re Number of Experiment H (m) T (s) D (m) High Reynold  Number 1 0.04 10 0.025 2 0.05 10 0.025 3 0.05 10 0.025 Low Reynold  Number 1 0.03 10 0.025 2 0.035 10 0.025 3 0.035 10 0.025 V (m3) W (kg) Q (m3/s) High Reynold  Number 1 0.0008 0.7986 0.00008 2 0.001 0.9982 0.0001 3 0.001 0.9982 0.0001 Low Reynold  Number 1 0.0006 0.5989 0.00006 2 0.0007 0.6987 0.00007 3 0.0007 0.6987 0.00007 Re Type of Flow High Reynold  Number 1 3912.905 Turbulent 2 4891.132 Turbulent 3 4891.132 Turbulent Low Reynold  Number 1 2934.679 Transition to Laminar 2 3423.792 Transition to Laminar 3 3423.792 Transition to Laminar

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

Picture 3. Relation between Volumentric Flow Rate with Reynold Number

1 2 3 1 2 3 Re 3912.9 4891.1 4891.1 2934.7 3423.8 3423.8 Q 0.00008 0.0001 0.0001 0.00006 0.00007 0.00007

Relation between Q and

Re

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).

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

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. 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.

1 2 3 HRN 3912.9 4891.1 4891.1 LRN 2934.7 3423.8 3423.8

High Reynold Number VS Low

Reynold Number