
[Sponsors] 
how to find the maximum vorticity and streamfunction in driven caivty 

LinkBack  Thread Tools  Display Modes 
September 12, 2013, 09:36 
how to find the maximum vorticity and streamfunction in driven caivty

#1 
Senior Member

Dear friends:
i solved the 2D lid driven cavity problem using SIMPLE algorithm. could you please tell me how to obtain the maximum vorticity and stream function in the flow field. thanks 

September 12, 2013, 15:34 

#2 
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,210
Rep Power: 19 
did you find the answer?
__________________
Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked. 

September 12, 2013, 21:51 

#3 
Senior Member


September 13, 2013, 03:08 

#4 
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 3,347
Rep Power: 37 
At steady state, compute the vorticity from your velocity field and solve the elliptic equation Lap (Psi) = vorticity. This way you get both functions and all the values you need


September 14, 2013, 09:28 

#5 
Senior Member

thank you . i can obtain the whole field of them. but my problem is to find the maximum values so as to compare it with the benchmark solutions in the public paper. Since we only have the field on grid points. then how to find the maximum value?


September 15, 2013, 14:55 

#6  
Senior Member
Join Date: Aug 2011
Posts: 251
Rep Power: 8 
Quote:
Let's imagine your are in 2D and vorticity is stored in an array VOR(NI,NJ). VORMAX=VOR(1,1) DO J=1,NJ DO I=1,NI IF ( VOR(I,J).GT.VORMAX ) VORMAX = VOR(I,J) END DO END DO assume fortran coding 

September 15, 2013, 21:05 

#7 
Senior Member

thank you , but i can not fully agree with you. in this way, the maximum value will depend on the mesh density.


September 15, 2013, 21:40 

#8 
Senior Member
Join Date: Jul 2009
Posts: 244
Rep Power: 12 
Establish a gridindependent solution. Otherwise any approach you follow will depend on the grid, whether you use an interpolation method or simply find the max over the grid.


September 15, 2013, 22:18 

#9 
Senior Member
Join Date: Jul 2009
Posts: 244
Rep Power: 12 
But even that will be grid dependent if the underlying solution is grid dependent.


September 16, 2013, 02:54 

#10 
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 3,347
Rep Power: 37 
leflix is right, just add the i,j values where the maximum is obtained.
What you ask for is simply wrong. In a numerical solution nothing else exists but the grid value. This is established by the Nyquist theorem. When you want to compute some extragrid value, is common to use some interpolation to reconstruct a continous function. But the values you obtain are somehow arbitrarily, depending on the order of the polynomial reconstruction. Therefore, just use the grid value, they are meaningfull of your solution 

September 16, 2013, 06:12 

#11  
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,210
Rep Power: 19 
Hi Ztdep
Quote:
__________________
Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked. 

September 16, 2013, 15:17 
open foam

#12 
New Member
kaveh fathi
Join Date: Aug 2013
Posts: 2
Rep Power: 0 
hi everybody
can you help me about openFoam ?please I have run a program but the software shows some error .if you can help me I will send errors for you. 

September 16, 2013, 17:48 

#13 
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,210
Rep Power: 19 
hi
whats your problem?which university are you?
__________________
Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked. 

September 18, 2013, 04:15 
openFoam

#14 
New Member
kaveh fathi
Join Date: Aug 2013
Posts: 2
Rep Power: 0 
hi I am in razi university from kermanshah.
I am working with openfoam I am going to analyse ac cavity .my solver is boussinesqsimple .when I run the program there is some error in fvslution(include solver for pressuer & tempreture & velocity and SIMPLE solver) file .I have copied this file from another exaxmple without any changing. I should be say that the software reads constant & 0 files. 

Thread Tools  
Display Modes  

