CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM Verification & Validation

Problem with groovyBC ---urgent

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 14, 2012, 04:27
Default Problem with groovyBC ---urgent
  #1
Senior Member
 
Mohammad Shakil Ahmmed
Join Date: Oct 2012
Location: AU
Posts: 123
Rep Power: 5
ahmmedshakil is on a distinguished road
Hi Foamers,
I am solving transient heat conduction problem. For the boundary condition I have used the heat flux boundary condition as follows---

dT/dx = 2.92e5*exp(-10e4*pos().x*pos().x) (just the gaussian beam at the upper surface )
But what the problem is for me now, I am getting the temperature greater than the published paper that I have decided for validation. I have checked the grid , and all sorts of stuffs. I have also done other simulations but for all the problem I am getting greater value than the other software(COMSOL), for example the peak temperature for the COMSOL I am getting 950K and for OpenFOAM I am getting 1260K.
I struggling with the problem..............
any idea????
or any one who has worked with the gaussian beam in OpenFOAM pls help me out of this problem....................
ahmmedshakil is offline   Reply With Quote

Old   December 14, 2012, 05:34
Default
  #2
Assistant Moderator
 
Bernhard Gschaider
Join Date: Mar 2009
Posts: 3,915
Rep Power: 40
gschaider will become famous soon enoughgschaider will become famous soon enough
Quote:
Originally Posted by ahmmedshakil View Post
Hi Foamers,
I am solving transient heat conduction problem. For the boundary condition I have used the heat flux boundary condition as follows---

dT/dx = 2.92e5*exp(-10e4*pos().x*pos().x) (just the gaussian beam at the upper surface )
But what the problem is for me now, I am getting the temperature greater than the published paper that I have decided for validation. I have checked the grid , and all sorts of stuffs. I have also done other simulations but for all the problem I am getting greater value than the other software(COMSOL), for example the peak temperature for the COMSOL I am getting 950K and for OpenFOAM I am getting 1260K.
I struggling with the problem..............
any idea????
or any one who has worked with the gaussian beam in OpenFOAM pls help me out of this problem....................
No idea.

The gradient groovyBC calculates gets written (the refGradient-field). The first step would be to check if this is the gradient you expect from your reference simulation.

BTW: what I noticed in your expression is 10e4 ... which is an OK, but rather unorthodox way of writing 10^5. Sure this is not a typo?
__________________
Note: I don't use "Friend"-feature on this forum out of principle. Ah. And by the way: I'm not on Facebook either. So don't be offended if I don't accept your invitation/friend request
gschaider is offline   Reply With Quote

Old   December 14, 2012, 10:59
Default
  #3
Senior Member
 
akidess's Avatar
 
Anton Kidess
Join Date: May 2009
Location: Delft, Netherlands
Posts: 919
Rep Power: 17
akidess will become famous soon enough
Is your expression really the thermal gradient, or is it the heat input? Latter has to be divided by the thermal conductivity before you plug it into groovyBC.
__________________
*On twitter @akidTwit
*Spend as much time formulating your questions as you expect people to spend on their answer.
*Help define the OpenFOAM stackexchange Q&A site: http://area51.stackexchange.com/prop...oam-technology
akidess is offline   Reply With Quote

Old   December 16, 2012, 04:29
Default
  #4
Senior Member
 
Mohammad Shakil Ahmmed
Join Date: Oct 2012
Location: AU
Posts: 123
Rep Power: 5
ahmmedshakil is on a distinguished road
@gschaider: I have checked the gradient with replayTransientBC... at each position '(pos().x)' it's giving the value correct. But I am little bit confused about the gradient calculation: as I am giving the value at every face centers(boundary) and its calculate the gradient, and between two face centers there is vertex for which the value is not imposed, and this question arises to my mind as I am using 'exp' function. Please let me know whether I am wrong/right?? And if I am correct how can I imposed it??
@akidess: it's a heat input and I had divided it with thermal conductivity. To my best knowledge, you may have worked with the Gaussian Heat Source, could you please tell me how you did this in openFoam?
ahmmedshakil is offline   Reply With Quote

Old   December 17, 2012, 11:57
Default
  #5
Senior Member
 
akidess's Avatar
 
Anton Kidess
Join Date: May 2009
Location: Delft, Netherlands
Posts: 919
Rep Power: 17
akidess will become famous soon enough
Indeed I have used Gaussian distributions in groovyBC as well. I have a gradientExpression which is the heat input divided by the thermal conductivity, a fractionExpression of 0. The heat input is a function of the form q(x) = a*exp(-b*x^2). There is nothing obviously wrong in what you have posted.
__________________
*On twitter @akidTwit
*Spend as much time formulating your questions as you expect people to spend on their answer.
*Help define the OpenFOAM stackexchange Q&A site: http://area51.stackexchange.com/prop...oam-technology
akidess is offline   Reply With Quote

Old   December 25, 2012, 19:10
Default
  #6
Assistant Moderator
 
Bernhard Gschaider
Join Date: Mar 2009
Posts: 3,915
Rep Power: 40
gschaider will become famous soon enoughgschaider will become famous soon enough
Quote:
Originally Posted by ahmmedshakil View Post
@gschaider: I have checked the gradient with replayTransientBC... at each position '(pos().x)' it's giving the value correct. But I am little bit confused about the gradient calculation: as I am giving the value at every face centers(boundary) and its calculate the gradient, and between two face centers there is vertex for which the value is not imposed, and this question arises to my mind as I am using 'exp' function. Please let me know whether I am wrong/right?? And if I am correct how can I imposed it??
For a volume field the gradient is only imposed on the faces (and for point-fields there is no gradient BTW)
__________________
Note: I don't use "Friend"-feature on this forum out of principle. Ah. And by the way: I'm not on Facebook either. So don't be offended if I don't accept your invitation/friend request
gschaider is offline   Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
GroovyBC problem in the defining inlet velocity iampolaris OpenFOAM Running, Solving & CFD 7 October 18, 2014 09:25
Problem about multi-phase analysis (Urgent) Prof. Lau (PolyU) CFX 2 February 9, 2007 18:59
Urgent problem - orthotropic material in ICEM Luk CFX 6 August 30, 2006 08:06
URGENT UDF's erosion_macro problem alex FLUENT 7 October 18, 2005 18:18
Multiphase Problem (Urgent) Dadang CFX 4 June 21, 2004 07:46


All times are GMT -4. The time now is 20:17.