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-   -   Convergence problems using extreme coefficient values like 1e-16 with porous jump (https://www.cfd-online.com/Forums/fluent/115582-convergence-problems-using-extreme-coefficient-values-like-1e-16-porous-jump.html)

 recepky April 2, 2013 16:16

Convergence problems using extreme coefficient values like 1e-16 with porous jump

Hi fellow CFD users,

I want to model a cylindirical membrane(plenty of membranes) in a cross flow condition, and when I use permemability and C2 coefficients like 2e-16 for face permeability and 3e+12 for C2, problem diverges. I have to use this coefficients because membranes that I want to model, has kind of 0.0001m/s velocity at 100000Pa values. :confused: I am sure these coefficients are the reason behind the divergence.

How can I solve this divergence problem ?

Thanks

 oj.bulmer April 3, 2013 11:07

As you guessed it, are you sure about these coefficients? How did you arrive at these values?

OJ

 recepky April 4, 2013 10:23

hi oj

I arrive this values by plotting xy curve from my experimental data velocity and pressure drop, from the xy polynomial trendline excel generated the y=Ax2+Bx equation that I used to find C2 and alfa permeability coeffitions. I double checked everything that I do in excel. I am sure these coefficients is right. Because these coefficients belongs to a membrane that 0.5micrometer or even lower pore sizes. It has very low permeability compairing to normal filters.

 shubhangini November 11, 2017 03:12

same problem

Quote:
 Originally Posted by recepky (Post 418354) hi oj I arrive this values by plotting xy curve from my experimental data velocity and pressure drop, from the xy polynomial trendline excel generated the y=Ax2+Bx equation that I used to find C2 and alfa permeability coeffitions. I double checked everything that I do in excel. I am sure these coefficients is right. Because these coefficients belongs to a membrane that 0.5micrometer or even lower pore sizes. It has very low permeability compairing to normal filters.
i too have the same problem.. it says workbench error.. but when i change face permeability to high value.. the simulation works smoothly.. i.e. my actual value is 1.52e-18 but i am using 1.52e+18 but this is of no use, not getting the correct radial velocity.:(:(:(:(
It's very disappointing.

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