# Recirculation region in streamline plot?

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 12, 2012, 04:21 Recirculation region in streamline plot? #1 Member     kiwi Join Date: Mar 2012 Location: South East Asia Posts: 54 Rep Power: 6 Hi,dear all, Recently stuck in "recirculation region" and "circulation region" ,is there any difference in terms of streamline plot? I read some text say that recirculation region is defined by closer streamline compared to normal streamline,is it true? If the flow field is steady, a streamline is a good indicator of flow characteristics such as recirculation zones. from http://www.flow3d.com/resources/news...ion-zones.html

 April 12, 2012, 08:22 #2 Senior Member   Andrew Join Date: Mar 2009 Location: Washington, DC Posts: 195 Rep Power: 9 your recirculation zone is going to be concentric circles. this is flow over a backwards facing step:

April 12, 2012, 20:49
#3
Member

kiwi
Join Date: Mar 2012
Location: South East Asia
Posts: 54
Rep Power: 6
Hi, Mettler,

Do you call that concentric circle as recirculation area or circulation area?
As circulation area is always formed as long as you have imbalance of velocity or pressure, but how about recirculation area?

The re-term means it flow back, am i right?
do you consider the circle as i attached is recirculation area?
Attached Images
 recirculation area.jpg (10.1 KB, 25 views)

 April 13, 2012, 10:11 #4 Senior Member   Andrew Join Date: Mar 2009 Location: Washington, DC Posts: 195 Rep Power: 9 a recirculation zone will be due to the physics of the flow. If you look at the step flow (flwo is from left to right), when the fluid goes over the step it will begin to curve up towards the top wall, as a result there will be flow along the backside of the step due to the low pressure of the moving fluid. This will cause the flow to move along the backside, which will drag some of the fluid along the top wall. This flow then gets entrained in the moving flow, thus causing a circulation zone..also, a stagnant zone. I think your zones of imbalance are not the same because they dissipate and are not located in the same spot, right? I am think of eddies - is that what you have?

 April 14, 2012, 16:30 #5 Member     kiwi Join Date: Mar 2012 Location: South East Asia Posts: 54 Rep Power: 6 Dear Mettler, sorry for late reply, as i am try to understand it. Yes, there is what i have.A strong fluid jet come from top and when the fluid travel down for a short distance, it hit the tube, some fluid go into the tube, others go outside and form the circle. But it is running in the laminar flow model, will it experience the viscous dissipation? VISCOUS DISSIPATION as the i set the viscoity to 0.00005, a vely low viscosity. I read through the eddy flow , it is due to the In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid flows past an obstacle. from wiki so i make the following statement about my result "a strong fluid jet come from top, when it hit the tube, the tube cause the eddy flow, the eddy flow form a vortex beside a tube and leads to formation of recirculation region" can i link the eddy flow, vortex and recirculation region together?

 April 14, 2012, 16:56 #6 Senior Member   Andrew Join Date: Mar 2009 Location: Washington, DC Posts: 195 Rep Power: 9 a recirculation zone will not move..it will always be there. I think you just have an eddy. The eddy should travel with the flow and dissipate. But, if the zone doesn't move and continuously re-circulates, then that is a 'recirculation zone'. If that is the case, I would say that the tube causes a recirculation zone to form beside the tube. (or where it is)

 April 15, 2012, 20:54 #7 Member     kiwi Join Date: Mar 2012 Location: South East Asia Posts: 54 Rep Power: 6 Hi, Mettler, Thank you very much, it really exactly what you describe when i am able to play the animation.and after few google search, i fully agree with your explanation. Now leave one last question, I found "eddies are shed continuously from each side of the body, forming rows of vortices in its wake. http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street" can i conclude that the circle is a vortex which caused by eddies? i only see a circle form throughout my simulation.

 April 15, 2012, 22:02 #8 Senior Member   Andrew Join Date: Mar 2009 Location: Washington, DC Posts: 195 Rep Power: 9 an eddy is a vortex. It just dissipates. Think of a tiny whirlpool. The next time you are by a small creek you can see them caused by the rocks or sticks..

 April 16, 2012, 01:41 #9 Member     kiwi Join Date: Mar 2012 Location: South East Asia Posts: 54 Rep Power: 6 Hi, Mettler, Thanks for solving my question. All problem solved. start to fall in love with beauty of CFD.thanks

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post clo OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 33 September 26, 2012 04:04 fruitkiwi Main CFD Forum 0 March 15, 2012 21:51 lionlove0903 OpenFOAM Post-Processing 2 March 14, 2011 16:25 Kart OpenFOAM Meshing & Mesh Conversion 1 February 4, 2010 05:38 adorean Open Source Meshers: Gmsh, Netgen, CGNS, ... 24 April 27, 2005 08:19

All times are GMT -4. The time now is 03:32.