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May 18, 2012, 01:49 
InterFoam negative alpha

#1 
New Member
Kia
Join Date: Jun 2011
Posts: 6
Rep Power: 7 
Hello everyone I am new to OpenFOAM and hopefully i can explain my problem and have it fixed quickly.
I am using interFOAM to simulate blood flow and saline interaction. I have a catheter in a blood vessel and saline solution is injected into inlet of the catheter and comes out at the tip. I am modeling the blood as a Newtonian fluid and everything is laminar at this point. When I run the simulation, I get negative min(alpha1) numbers and my Liquid phase volume fraction number is supper small. And when I look at it using paraview, it show the saline alpha turn into blood alpha. The velocity and pressure look right so I do not know why my alpha is not being calculated correctly. HTML Code:
file:///home/kiwi/Dropbox/Photos/blood_saline_alpha1.png [IMG]file:///home/kiwi/Dropbox/Photos/blood_saline_alpha1.png[/IMG] Starting time loop Courant Number mean: 0 max: 0 Interface Courant Number mean: 0 max: 0 deltaT = 1.2e09 Time = 1.2e09 MULES: Solving for alpha1 Liquid phase volume fraction = 0 Min(alpha1) = 0 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 0 Min(alpha1) = 0 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 0 Min(alpha1) = 0 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 0 Min(alpha1) = 0 Max(alpha1) = 1 PIMPLE: iteration 1 GAMG: Solving for p_rgh, Initial residual = 1, Final residual = 0.00733461, No Iterations 11 time step continuity errors : sum local = 7.11934e12, global = 1.62818e13, cumulative = 1.62818e13 GAMG: Solving for p_rgh, Initial residual = 0.0789804, Final residual = 0.000539265, No Iterations 2 time step continuity errors : sum local = 8.32344e10, global = 7.85013e12, cumulative = 7.68731e12 GAMG: Solving for p_rgh, Initial residual = 0.00796039, Final residual = 7.21831e05, No Iterations 3 time step continuity errors : sum local = 1.20275e10, global = 1.6724e12, cumulative = 6.01491e12 PIMPLE: iteration 2 GAMG: Solving for p_rgh, Initial residual = 0.00233487, Final residual = 1.24411e05, No Iterations 3 time step continuity errors : sum local = 2.10593e11, global = 4.16641e13, cumulative = 5.59827e12 GAMG: Solving for p_rgh, Initial residual = 0.000394277, Final residual = 3.01518e06, No Iterations 3 time step continuity errors : sum local = 5.12505e12, global = 7.12971e14, cumulative = 5.52697e12 GAMG: Solving for p_rgh, Initial residual = 9.51221e05, Final residual = 5.60966e07, No Iterations 3 time step continuity errors : sum local = 9.54372e13, global = 1.71028e14, cumulative = 5.50987e12 PIMPLE: iteration 3 GAMG: Solving for p_rgh, Initial residual = 2.02063e05, Final residual = 1.54376e07, No Iterations 3 time step continuity errors : sum local = 2.62689e13, global = 3.58164e15, cumulative = 5.50628e12 GAMG: Solving for p_rgh, Initial residual = 5.171e06, Final residual = 7.63952e08, No Iterations 2 time step continuity errors : sum local = 1.30001e13, global = 2.05852e15, cumulative = 5.50423e12 GAMG: Solving for p_rgh, Initial residual = 1.22273e06, Final residual = 8.68386e08, No Iterations 1 time step continuity errors : sum local = 1.47774e13, global = 2.38579e15, cumulative = 5.50184e12 ExecutionTime = 16.13 s ClockTime = 17 s Courant Number mean: 4.08779e07 max: 0.000289305 Interface Courant Number mean: 0 max: 0 deltaT = 1.44e09 Time = 2.64e09 MULES: Solving for alpha1 Liquid phase volume fraction = 1.7146e11 Min(alpha1) = 0 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 3.4292e11 Min(alpha1) = 0 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 5.1438e11 Min(alpha1) = 0 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 6.85839e11 Min(alpha1) = 0 Max(alpha1) = 1 PIMPLE: iteration 1 GAMG: Solving for p_rgh, Initial residual = 0.000570361, Final residual = 4.18279e06, No Iterations 11 time step continuity errors : sum local = 1.02444e11, global = 2.32694e13, cumulative = 5.73453e12 GAMG: Solving for p_rgh, Initial residual = 0.72832, Final residual = 0.00497247, No Iterations 2 time step continuity errors : sum local = 1.19882e09, global = 1.12942e11, cumulative = 5.55967e12 GAMG: Solving for p_rgh, Initial residual = 0.294599, Final residual = 0.00267426, No Iterations 3 time step continuity errors : sum local = 1.73428e10, global = 2.39662e12, cumulative = 3.16304e12 PIMPLE: iteration 2 GAMG: Solving for p_rgh, Initial residual = 0.437679, Final residual = 0.00233468, No Iterations 3 time step continuity errors : sum local = 3.03803e11, global = 5.9927e13, cumulative = 2.56377e12 GAMG: Solving for p_rgh, Initial residual = 0.412863, Final residual = 0.00316053, No Iterations 3 time step continuity errors : sum local = 7.39308e12, global = 1.02173e13, cumulative = 2.4616e12 GAMG: Solving for p_rgh, Initial residual = 0.164912, Final residual = 0.000973731, No Iterations 3 time step continuity errors : sum local = 1.37731e12, global = 2.4518e14, cumulative = 2.43708e12 PIMPLE: iteration 3 GAMG: Solving for p_rgh, Initial residual = 0.0328144, Final residual = 0.000250931, No Iterations 3 time step continuity errors : sum local = 3.78993e13, global = 5.10882e15, cumulative = 2.43197e12 GAMG: Solving for p_rgh, Initial residual = 0.00806736, Final residual = 5.27134e05, No Iterations 3 time step continuity errors : sum local = 8.28767e14, global = 1.08536e15, cumulative = 2.43089e12 GAMG: Solving for p_rgh, Initial residual = 0.00199432, Final residual = 6.46556e08, No Iterations 11 time step continuity errors : sum local = 1.0254e16, global = 4.80509e19, cumulative = 2.43089e12 ExecutionTime = 27.71 s ClockTime = 29 s Courant Number mean: 4.90274e07 max: 0.0003464 Interface Courant Number mean: 0 max: 0 deltaT = 1.728e09 Time = 4.368e09 MULES: Solving for alpha1 Liquid phase volume fraction = 8.91177e11 Min(alpha1) = 0 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 1.09651e10 Min(alpha1) = 0 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 1.30185e10 Min(alpha1) = 1.24534e51 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 1.50719e10 Min(alpha1) = 6.11486e57 Max(alpha1) = 1 PIMPLE: iteration 1 GAMG: Solving for p_rgh, Initial residual = 0.0533576, Final residual = 0.000324406, No Iterations 4 time step continuity errors : sum local = 7.26737e13, global = 2.18295e13, cumulative = 2.21259e12 GAMG: Solving for p_rgh, Initial residual = 0.0135501, Final residual = 0.000108332, No Iterations 4 time step continuity errors : sum local = 2.39232e13, global = 1.49219e14, cumulative = 2.19767e12 GAMG: Solving for p_rgh, Initial residual = 0.00333453, Final residual = 1.67357e05, No Iterations 4 time step continuity errors : sum local = 3.66317e14, global = 1.43155e15, cumulative = 2.19624e12 PIMPLE: iteration 2 GAMG: Solving for p_rgh, Initial residual = 0.000663491, Final residual = 3.34355e06, No Iterations 4 time step continuity errors : sum local = 7.30476e15, global = 2.96115e16, cumulative = 2.19594e12 GAMG: Solving for p_rgh, Initial residual = 0.000135325, Final residual = 6.83283e07, No Iterations 4 time step continuity errors : sum local = 1.49233e15, global = 4.4585e17, cumulative = 2.1959e12 GAMG: Solving for p_rgh, Initial residual = 3.02876e05, Final residual = 2.95952e07, No Iterations 3 time step continuity errors : sum local = 6.46326e16, global = 2.59109e17, cumulative = 2.19587e12 PIMPLE: iteration 3 GAMG: Solving for p_rgh, Initial residual = 6.59564e06, Final residual = 6.65695e08, No Iterations 4 time step continuity errors : sum local = 1.45379e16, global = 2.34212e18, cumulative = 2.19587e12 GAMG: Solving for p_rgh, Initial residual = 2.63412e06, Final residual = 4.01697e08, No Iterations 2 time step continuity errors : sum local = 8.77245e17, global = 2.86944e18, cumulative = 2.19587e12 GAMG: Solving for p_rgh, Initial residual = 5.98916e07, Final residual = 4.62872e08, No Iterations 1 time step continuity errors : sum local = 1.01084e16, global = 5.20981e18, cumulative = 2.19586e12 ExecutionTime = 37.33 s ClockTime = 39 s 

May 18, 2012, 01:54 

#2 
New Member
Kia
Join Date: Jun 2011
Posts: 6
Rep Power: 7 
I do not know if the link works, i am new to dropbox also, here is another link to the paraview image of the alpha 1 and velocity
http://dl.dropbox.com/u/72086722/blo...ine_alpha1.png http://dl.dropbox.com/u/72086722/blo...20velocity.png 

May 18, 2012, 03:12 

#3 
Senior Member
Olivier
Join Date: Jun 2009
Location: France, grenoble
Posts: 262
Rep Power: 10 
hello,
You get negative alpha, but it's 6e57 and i don't think your tolerance error is that small ! Anyway, you have a liquid phase fraction of 1e10, which is pretty small. Have you run setFields in order to inititialyze ? or run for a longer time ... regards, olivier 

May 19, 2012, 05:04 

#4 
Senior Member
Anton Kidess
Join Date: May 2009
Location: Delft, Netherlands
Posts: 1,141
Rep Power: 20 
Also, doesn't the saline eventually mix with the blood? Because if it's not immiscible, interFoam is not the right solver to start with.
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May 19, 2012, 21:48 

#5 
New Member
Kia
Join Date: Jun 2011
Posts: 6
Rep Power: 7 
Thanks guys, I have run setFeilds to initialize the saline, but it still does not work. I have a feeling that this has to do with my mesh, because i ran the same setup on the pitzDaily by modifying the mesh and adding a second inlet.
And i also interFOAM with the same fluid property (water) and it gives me the same error. I am using interFOAM because although blood and saline are not immiscible fluids, i do not want them to mix. I want more of a flushing of the blood near the walls and i think interFOAM is the right one. However i will try to use TwoLiquidMixingFoam if there is a tutorial for that. 

May 22, 2012, 14:51 

#6 
New Member
Kia
Join Date: Jun 2011
Posts: 6
Rep Power: 7 
Thank you Anton and Oliver, TwoLiquidMixingFoam was the correct solver to use, I still get very low liquid phase fraction ( order of 0.002) but after running it for long time i get mixing and it finally comes out of the tip.
However i have a few question, If Dab diffusivity what is alphatab and where do i find these two values for blood and saline. Thank you 

May 23, 2012, 03:00 

#7 
Senior Member
Anton Kidess
Join Date: May 2009
Location: Delft, Netherlands
Posts: 1,141
Rep Power: 20 
See posts #33 and #34.
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December 12, 2013, 04:41 

#8 
New Member
Faraj
Join Date: Feb 2010
Posts: 22
Rep Power: 8 
I had the same problem, solved it by setting alpha = 0.5 to the all field.


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