
[Sponsors] 
May 8, 2012, 05:34 
question about Nested Grid for two fluids

#1 
New Member
Join Date: May 2012
Posts: 3
Rep Power: 5 
I started a simple flow example:
rectangular block and make it partly nested half water (depth=0.3m) and half air a water flow with constant velocity comes from right boundary, u= 0.1 m/s the simulation will be easily done if 'one fluid' is chosen, whether 2d or 3d. However, if I choose two fluids(water and air), while all the other condition and parameters exactly the same with one fluid situation, the errors will occur. 'convective flux exceeded stability limit' will soon come along. After 2 or 3 of them, excessive convection failures make calculation terminated. And only 4e09 second is calculated. I'm stuck....I need advice. Thank you! 

May 10, 2012, 21:10 

#2  
Senior Member
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9 
Quote:


May 10, 2012, 21:55 

#3 
New Member
Join Date: May 2012
Posts: 3
Rep Power: 5 
yes, there is an outlet boundary~
the mesh is as followed: block1 x:0~1.0, nxcelt=50, y:0~0.1, nycelt=5, z:0~0.5,nzcelt=25 ; block2 x:0.5~0.8,nxcelt=30, y:0.02~0.08, nycelt=6, z:0.1~0.4, nzcelt=30 ; Boundaries of block1 are: right: V , left: O , front and back: S , bottom:W , top:P ; for block2 they are all Symmetry 

May 10, 2012, 23:24 

#4 
Senior Member
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9 
hmm. is air modeled as compressible fluid?


May 11, 2012, 00:00 

#5 
New Member
Join Date: May 2012
Posts: 3
Rep Power: 5 
The flow mode is chosen as incompressible, so both two fluids are calculated as incompressible, right?
I thought that interblock boundary type coefficient(alphamb) might affect, so I changed it from default to 0.5 or 1.0, but still didn't work.... 

May 19, 2012, 02:08 

#6 
Senior Member
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9 
It is hard to figure out without seeing the problem. Have any ideas yourself?


May 27, 2012, 09:50 

#7 
New Member
Mahdiar Farhoudi
Join Date: Feb 2012
Location: Tehran, Iran
Posts: 17
Rep Power: 5 
That is exactly my problem too!
did you get what to do? you can also check out: Help > CUSTOM TUTORIALS > Hydraulics Tutorial > Variation: Run as a TwoFluid Problem 

Tags 
nested block, two fluids 
Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
"grid points" or "grid interface"  ztdep  Main CFD Forum  1  June 6, 2007 15:00 
Grid Quality and the Solution  Faraz  Main CFD Forum  4  January 10, 2000 19:18 
grid spacing question  clifford bradford  Main CFD Forum  5  November 10, 1999 19:40 
A question about elliptic grid generation  A.Rajani Kumar  Main CFD Forum  3  March 12, 1999 10:33 
Numerical methods for discontinuous grid interfaces?  Hansong Hang  Main CFD Forum  12  September 16, 1998 22:26 