
[Sponsors] 
December 14, 2012, 04:27 
Problem with groovyBC urgent

#1 
Senior Member
Mohammad Shakil Ahmmed
Join Date: Oct 2012
Location: AU
Posts: 123
Rep Power: 5 
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.................... 

December 14, 2012, 05:34 

#2  
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 3,915
Rep Power: 40 
Quote:
The gradient groovyBC calculates gets written (the refGradientfield). 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 

December 14, 2012, 10:59 

#3 
Senior Member
Anton Kidess
Join Date: May 2009
Location: Delft, Netherlands
Posts: 919
Rep Power: 17 
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...oamtechnology 

December 16, 2012, 04:29 

#4 
Senior Member
Mohammad Shakil Ahmmed
Join Date: Oct 2012
Location: AU
Posts: 123
Rep Power: 5 
@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? 

December 17, 2012, 11:57 

#5 
Senior Member
Anton Kidess
Join Date: May 2009
Location: Delft, Netherlands
Posts: 919
Rep Power: 17 
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...oamtechnology 

December 25, 2012, 19:10 

#6  
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 3,915
Rep Power: 40 
Quote:
__________________
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 

Thread Tools  
Display Modes  


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 multiphase 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 