CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Solver and geometry choose for drag coefficient calculation around circular cylinder at large Re

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 26, 2009, 05:42
Default Hi,all I have a question with
  #1
lin
Senior Member
 
Hua Zen
Join Date: Mar 2009
Posts: 138
Rep Power: 17
lin is on a distinguished road
Hi,all
I have a question with which solver and geometry to choose for drag coefficient calculation around circular cylinder at large Re(around 10^6).

The question about the solver is whether to choose simpleFoam or turbFoam.

The plus for simpleFoam is that I only want to drag coefficient,one averaged quantity.
The plus for turbFoam is that,this kind of flow seems not to be stationary,so called vortex shedding.

Also I have the problem to choose the geometry.The problem is whether I could only calculate half cylinder and use symmetryplane at the center line, or I have to use the whole cylinder geometry all.

The plus for half cylinder and symmetryplane is that,on average,the drag coefficient should be equal on both side.
The plus for whole cylinder is ,for transient flow,the flow field seems not to be symmetry.

So,all in all,there seems to be four choices for me .

(A) simpleFoam with symmetryplane
(B) simpleFoam with whole cylinder
(C) turbFoam with symmetryplane
(D) turbFoam with whole cylinder

Can any experts shed some light on this naive question? Just choose one and some explanation is welcome.
lin is offline   Reply With Quote

Old   February 26, 2009, 07:28
Default Hello, Your questio
  #2
Member
 
Maruthamuthu Venkatraman
Join Date: Mar 2009
Location: Norway
Posts: 80
Rep Power: 17
maruthamuthu_venkatraman is on a distinguished road
Hello,
Your question is not at all Naive!

1. AT Re 10^6 you have both tubulent boundary layer and turbulent wakes.
Your seperation will be delayed.

2. Since the flow is unsteady and to monitor the drag convergence with steady oscillation i would recommed u to model the full cylinder with symmtery on the top and bottom domain . This is only if you want to catch the frequency.

3. If you are just interested only in Average drag and not interested in unsteadiness then you shall run a steady state solution using SIMPLEFOAM with any of the low re ke model. It will give u good results.

Hope it helps you ...





Remember to keep Y plus less than 1 if u r using any of the low re ke models .

Good luck
maruthamuthu_venkatraman is offline   Reply With Quote

Old   February 26, 2009, 11:59
Default Hi, Maruthamuthu Thanks for y
  #3
lin
Senior Member
 
Hua Zen
Join Date: Mar 2009
Posts: 138
Rep Power: 17
lin is on a distinguished road
Hi, Maruthamuthu
Thanks for your information.

I will try the transient solver with full cylinder later,though I am only interest in the averaged Cd.

Last day I have tried simpleFoam with half cylinder and symmetryplane at the centerline using 3 k-epsilon models,getting Cd about,0.69,0.46,2.62,respectively.Very strange. The experimental data should be around 0.25 and there has been some report that could reproduce it with fluent.Though I do not know the details.All the simulation I did,y+ is in the range 30-300.

One question about your post is ,Re around 10^6 is large ,why recommend me to use low Re turbulent model?
lin is offline   Reply With Quote

Old   April 16, 2009, 10:50
Default
  #4
Member
 
Maruthamuthu Venkatraman
Join Date: Mar 2009
Location: Norway
Posts: 80
Rep Power: 17
maruthamuthu_venkatraman is on a distinguished road
Low Re Ke model has an ability to correct the near wall fluid flow behaviour using Viscous damping functions. But you must keep your y+ 1.

If u browse the book of Turbulence modeling by Wilcox under low reynolds number effects, you will get it. Basically High Re ke models doesnt account for viscous corrections. So Low Re ke model is devised to solve such application.

I havent looked at your post. Hence there is a delay. May be you might have found it already
maruthamuthu_venkatraman is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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 Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
drag coefficient of cylinder Libellen FLUENT 10 August 29, 2008 21:56
About drag coefficient of 2D circular cylinder! Haoyin Shan FLUENT 0 May 6, 2007 23:50
Drag Coefficient of Flow across a Circular Cylinde Zhihua Li FLUENT 3 April 20, 2004 01:01
Circular cylinder drag at high Re Anton Lyaskin Main CFD Forum 0 January 14, 2003 04:48
Drag Coefficient(Cd) of circular cylinder Ram FLUENT 2 June 4, 2000 14:32


All times are GMT -4. The time now is 00:23.