LAB REPORT FREE AND FORCED VORTEX PDF

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Lab report free and forced vortex for bachelor of chemical engineering students (EH220) UiTM...

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UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA FLUIDS AND THERMODYNAMICS LABORATORY (CHE486) EXPERIMENT: FREE AND FORCED VORTEX GROUP: 4 NAME Nurfadzwin binti Rozlan Amyira Natasha binti Mahari Siti Nurnhadira binti Sharip Nur Afiza binti Mahmud Muhammad Azrai bin Mohd Dzahari

No. 1 2 3 4 5 6 7 8 9 10 11 12 13

Title Abstract/Summary Introduction Aims Theory Apparatus Methodology/Procedure Results Calculations Discussion Conclusion Recommendations Reference Appendix TOTAL MARKS

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Allocated Marks (%) 5 5 5 10 5 10 10 10 20 5 5 5 5 100

STUDENT ID 2019406296 2019291162 2019405752 2019488502 2019405314

Marks

1.0 ABSTRACT

The purpose of this experiment are to study the vortex motion. There are two types of vortex which are free and forced vortex. Thus , the objectives of this experiment is to study the free and forced vortex. Hence , after that to find the surface profile for the free and forced vortex and compare both of the surface profile. The reasons that motivates this experiment is to know the natural phenomena that are associated with vortex motion. For the free vortex experiment, it is divide into two parts which are the free vortex with a large opening on the bottles and the other part is for the free vortex with a smaller opening which 1.0 cm holes is made to each cap. Then the bottles filled with water was swirled lightly and the free vortex formed was observed. Moreover for the forced vortex, the thread or string was twisted 20, 40 and 60 times and the bottles was let to be spin. The formation of vortex was observed once the rotation becomes stable.

2.0 INTRODUCTION

Vortex motion is defined as a motion that results in the circular paths. In which the fluid flow that rotate around the axis line. There are two types of vortex motion which are free vortex and forced vortex.

The free vortex formed when the fluid rotates without the help of external force. The internal action that is either the cause of the action occur or because of some rotation that denoted to the fluid. For instance, the whirlpool in the river.

The forced vortex is caused by external forces on the fluid. The fluid mass in this type of flow rotate at constant angular velocity. The examples of forced vortex flow are flow of liquid inside impeller of a centrifugal pump or the flow of water through runner.

In this experiment, a free vortex is created by using swirling of two bottles where their opening is tape together. While the forced vortex is created using twisted string or thread that acted upon the fluid.

3.0 OBJECTIVES

1. To demonstrate the free and forced vortex experiments. 2. To compare the surface profile for free and forced vortex. 3. To investigate the natural phenomena associated with a free vortex.

4.0 THEORY A vortex is an area in a fluid, be it in air or water where the flow moves around an axis line and can take a straight or a curved shaped. It is formed when stirring is applied to the fluid or if the fluid is spun. Vortex is a natural phenomenon, it can happen anywhere, such as on land, on air and also water. When vortices are formed, they can interact with the surrounding fluid. A vortex can be categorized into two – free and forced vortex. (Villaluz, 2017).

In a free vortex, there are no external force required to rotate the fluid mass. This also meant that the total mechanical energy remains constant in the entire flow field. The energy in the flow field is not destroyed nor added. During the experiment, the water from the bottle is drained through the opening of the bottle without any outside force. Aside from water draining from the opening of the bottle, other examples of a free vortex are the flow of water through the kitchen sink, the draining of the bath tub and also the flow of liquid around a circular bend in pipe. The free vortex flow is irrotational, which leads to the free vortex being known as the irrotational vortex.

Figure 1: The surface profile of a free vortex.

If free vortex happens naturally – without any outside force, forced vortex is the opposite. In forced vortex flow, to maintain it, the mechanical energy has to be spent from outside and the external torque needs to be applied continuously. (Mecholic, 2021). Forced vortex can be created by spinning a vessel with fluid inside. This will lead to the angular velocity being similar at all points. Forced vortex is not an irrotational flow unlike free vortex flow, it is a rotational flow with a constant vorticity. In this

experiment, the forced vortex is demonstrated by tying and twisting a rope to a bottle filled with water, and the rope is then let go. The surface profile will then be formed as shown in Figure 2. Other examples of a forced vortex are water rotating in a washing machine, or a blender and also the flow of water through the runner of a turbine.

Figure 2: The surface profile of a forced vortex.

5.0 APPARATUS 5.1 Free Vortex     

Two 1500 mL mineral bottle Water Food colouring Duct tape Knife/Nail

5.2 Forced Vortex       

One 1500 mL mineral bottle Water Rope/String Food colouring Knife/Nail Drill Transparent container

6.0 PROCEDURE FREE VORTEX EXPERIMENT

1. Two bottles were prepared and the cap from each bottle was pull out. 2. 1cm holes were made to each cap. 3. ¾ of water is put in one of the bottle. 4. The opening of the bottles is connected using duct tape. 5. The bottles are then turned upside down so that the one filled with water is on top. 6. The bottle is swirled lightly so that the water goes down. 7. The vortex formed is observed. 8. Step 1 to 7 is repeated with 3 cm hole of bottle cap.

FORCED VORTEX EXPERIMENT 1st Method

1. The cap of a 1500 ml plastic bottle was cut into two hole using nail or knife . 2. The thread was made between two holes at the cap of bottle using string as in the Figure 3 below. 3. The bottle is filled with water. 4. Food coloring is added. 5. Then, the string was twist 20 times and the bottle was let to be spin. 6. The formation of vortex was observed once the rotation became stable. 7. The experiment is repeated with 40 and 60 times of twisted string. 2nd Method

1. 4/5 of water is put into a transparent jar container 2. Prepare a drill and tape a spoon together with the drill steel rode. 3. Put the drill steel rode with spoon inside the container. 4. Then, start the drill with low speed. 5. Observe and record the surface profile of the vortex. 6. Repeat the experiment with medium and high speed of the drill. 7. Observe the height of vortex produced & recorded.

Figure 3

7.0 RESULT Forced Vortex (2nd Method) Speed Observation

Low

Medium

High

Height of Vortex(cm)

4.0

9.6

15.8

Free Vortex Observation

Size of Vortex Size of Hole on Bottle Cap

Smaller Diameter 1cm

Larger Diameter 3cm

8.0 DISCUSSION For the free vortex to formed, water flows out of the vessels through the central hole in the bottle cap and the degree of rotation depends on the initial disturbance. the water flows spirally into the middle of the streamline in motion so that by neglecting the losses incurred by the viscosity, the energy per unit mass stays constant. The free vortex experiment required us to observe the vortex created by using different size of hole to give different size of shape to the vortex. The different hole used is 1cm and 3cm. From the experiment, the larger hole in diameter gives the larger and faster vortex created and followed by the smaller diameter hole. This is because the vortex created depends on the diameter of the hole. When the size of hole bigger, the more water will flow out of the bottle and caused it not accumulated. This vortex was created by the force of the water flow in the bottle and the pattern of flow formed is cir cumferential. For the forced vortex, we used two equipment , drill and water bottle depend on the equipment that we have at home. For the drill, we filled in a container with water and used drill with different speed to rotate the bottle cap. the surface profile of the forced vortex is parabolic shape and depends on the angular velocity of rotation. The rotational speed of the drill was measured by the time of 10 rotations of the bottle cap. The experiment was repeated three times by using different speed of drill. For this experiment , the speed of drill and the time taken to complete the 10 rotations of bottle cap is calculated.In other we also used a string and tied at the side of bottle cap. The bottle cap rotated for 20 times. Once the rotation become stable, the surface will form a paraboloid revolution. The experiment is successfully conducted when the force vortex can be seen in the container or water bottle. The surface profile is small when low speed is used. For medium speed, the surface profile is bigger while for the high speed is used, the surface profile become biggest. This experiment shown that the speed affected the surface profile.

9.0 CONCLUSION

In the free vortex experiment, we can conclude that the size of vortex affected by the diameter of hole on bottle cap. The bigger the diameter of hole can produce bigger diameter of vortex. Meanwhile for the forced vortex experiment, we can conclude that the speed of drill affect the length of vortex. When the rate of speed of the drill is higher, the vortex produced will be higher in length. Last but not least, the difference between these two experiment in forced vortex need force to produce vortex while free vortex experiment do not need any force, it will produce by gravitational force when we put the bottle upside down.

10.0 RECOMMENDATIONS 1. Make sure the tape is tightly wrapped around between the two bottle caps so that the water spill can be avoided or reduced when the bottle is turned upside down. 2. Make sure the holes poked on both bottle caps are equal in size so that the vortex formed can be observed clearly. 3. Make sure the bottle was filled with the same amount of water every time the experiment is repeated.

11.0 REFERENCE 1. JSME FED. (2016). Forced Vortex [YouTube Video]. Retrieved from https://www.youtube.com/watch?v=h3DvpNniJ_8&feature=youtu.be 2. Sick Science. (2009). Tornado Tube - Cool Science Experiment [YouTube Video]. Retrieved from https://www.youtube.com/watch?v=mzw3DcDblIg&feature=youtu.be 3. https://www.facebook.com/mecholic. (2016, February 17). Mecholic: Free And Forced Vortex Flow. Retrieved January 19, 2021, from Mecholic website: https://www.mecholic.com/2015/10/free-and-forced-vortex-flowcomparison.html 4. Free and Forced Vortex flow with Examples. (2014). Retrieved January 20, 2021, from Blogspot.com website: http://mechanicsoffluids.blogspot.com/2014/12/free-and-forced-vortex-flowwith.html 5. Mohsin Siddique. (2015, March 16). Fluid MechanicsVortex flow and impulse momentum. Retrieved January 21, 2021, from Slideshare.net website: https://www.slideshare.net/yourmohsin/fluid-mechanicsvortex-flow-andimpulse-momentum 6. Habib Ahmari, & Shah Md Imran Kabir. (2019, August 14). Experiment #8: Free and Forced Vortices. Retrieved January 21, 2021, from Pressbooks.pub website: https://uta.pressbooks.pub/appliedfluidmechanics/chapter/experiment8/#:~:text=There%20are%20two%20types%20of,central%20hole%20in%20th e%20base.&text=A%20forced%20vortex%2C%20on%20the,external%20forc es%20on%20the%20fluid.

12.0 APPENDIX

Figure 12.1 : Experiment done by Amyira Natasha

Figure 12.2 : Experiment done by Muhammad Azrai

Figure 12.3 : Experiment done by Siti Nurnhadira

Figure 12.4 : Experiment done by Nurfadzwin

Figure 12.4 : Experiment done by Nur Afiza

Figure 12.4 : Report similarity checked by Turnitin...