What causes a Vortex to form

learner · August 19, 2009, 08:04

Hey friends,
I am a new member of this forum. I'm a Mechanical Engineer and hence I have to deal with many Fluid Mechanics phenomena often.
Though I am not dealing with CFD directly or full fletchedly I was always intrigued by the concepts of fluid flow and would like to have a clear and correct understanding of these concepts. And there would be no better place and people than this forum to get the answers. So friends, I am starting with a phenomena which I never qiute clearly understood.

The question :

I always wondered that what makes a flowing liquid to form a Vortex ?

We shall take the example of the water flowing in the bathtub which when enters the plug forms a Vortex instead of flowing straight into the plug and just falling into it.

My doubts are rearding the following points :

1. What is the role of pressure difference in the Vortex formation? And how is this pressure difference created?

2. If the pressure difference does cause the water to be sucked in the plug then why doesnt the water which is flowing in straight line before nearing the plug continue to do so and just empty into the plug in a straight path?

What causes the water to turn and rotate along the plug hole? What and how is this rotation created? What is the reason that the straight flowing molecules suddenly get the rotational motion, what initiates this rotation?

3. How is the bottom center of the Vortex formed and why does the velocity of the water increase as the approaches the axis of rotation?

4. In general I want to learn the basic concept of why the vortex is formed and all the physics related to it.

I am genuinely interested to have my basic fundamentals clear and strong in fluid mechanics.

I did not find a satisfying answer to my questions anywhere, so I really request all you memebers to take some of your valuable time off and please elaborate on these theories and please guide me so that my concepts can be strong.

Looking forward for your assistance.

learner · August 20, 2009, 08:54

Guys 39 views and not a single reply???

I am on a forum of specialised people in the field of Fluid Mechanics and Dynamics, and strangely receiving no help on a very common phenomena in fluid mechanics.

Dear members ( especially the senior professionals or PG members) please show some interest in this though it may seem trivial issue for you. I ve been unable to clearly grasp this concept and get a visual picture of this process of vortex formation.

You can explain this to me and put an end to my much anxious search for a easy to understand and clear answer to this question. So PLEASE HELP.

Ahmed · August 20, 2009, 15:08

Try the Deformation of Continuous Media Movie
http://web.mit.edu/hml/ncfmf.html

Good Luck

zobekenobe · August 21, 2009, 01:19

ok...assume a cylindrical vortex having its axis aligned along the x direction....eventually the vortex is moving in the x direction perpendicular to the y axis....now the gradient du/dx pulls to this cylindrical vortex in the x direction .....therefore elongating it in that direction and produces vortex stretching....thats one aspect that i can visualise about vortex

August 19, 2009, 08:04	What causes a Vortex to form	#1
learner New Member Join Date: Aug 2009 Posts: 2 Rep Power: 0	Hey friends, I am a new member of this forum. I'm a Mechanical Engineer and hence I have to deal with many Fluid Mechanics phenomena often. Though I am not dealing with CFD directly or full fletchedly I was always intrigued by the concepts of fluid flow and would like to have a clear and correct understanding of these concepts. And there would be no better place and people than this forum to get the answers. So friends, I am starting with a phenomena which I never qiute clearly understood. The question : I always wondered that what makes a flowing liquid to form a Vortex ? We shall take the example of the water flowing in the bathtub which when enters the plug forms a Vortex instead of flowing straight into the plug and just falling into it. My doubts are rearding the following points : 1. What is the role of pressure difference in the Vortex formation? And how is this pressure difference created? 2. If the pressure difference does cause the water to be sucked in the plug then why doesnt the water which is flowing in straight line before nearing the plug continue to do so and just empty into the plug in a straight path? What causes the water to turn and rotate along the plug hole? What and how is this rotation created? What is the reason that the straight flowing molecules suddenly get the rotational motion, what initiates this rotation? 3. How is the bottom center of the Vortex formed and why does the velocity of the water increase as the approaches the axis of rotation? 4. In general I want to learn the basic concept of why the vortex is formed and all the physics related to it. I am genuinely interested to have my basic fundamentals clear and strong in fluid mechanics. I did not find a satisfying answer to my questions anywhere, so I really request all you memebers to take some of your valuable time off and please elaborate on these theories and please guide me so that my concepts can be strong. Looking forward for your assistance.

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August 20, 2009, 08:54		#2
learner New Member Join Date: Aug 2009 Posts: 2 Rep Power: 0	Guys 39 views and not a single reply??? I am on a forum of specialised people in the field of Fluid Mechanics and Dynamics, and strangely receiving no help on a very common phenomena in fluid mechanics. Dear members ( especially the senior professionals or PG members) please show some interest in this though it may seem trivial issue for you. I ve been unable to clearly grasp this concept and get a visual picture of this process of vortex formation. You can explain this to me and put an end to my much anxious search for a easy to understand and clear answer to this question. So PLEASE HELP.

August 20, 2009, 15:08		#3
Ahmed Senior Member Ahmed Join Date: Mar 2009 Location: NY Posts: 251 Rep Power: 18	Try the Deformation of Continuous Media Movie http://web.mit.edu/hml/ncfmf.html Good Luck

August 21, 2009, 01:19		#4
zobekenobe Member zobekenobe Join Date: Mar 2009 Location: Dublin, Ireland Posts: 72 Rep Power: 17	ok...assume a cylindrical vortex having its axis aligned along the x direction....eventually the vortex is moving in the x direction perpendicular to the y axis....now the gradient du/dx pulls to this cylindrical vortex in the x direction .....therefore elongating it in that direction and produces vortex stretching....thats one aspect that i can visualise about vortex