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

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 April 2, 2013, 17:16 Convergence problems using extreme coefficient values like 1e-16 with porous jump #1 New Member   Recep Kaya Join Date: Feb 2013 Posts: 6 Rep Power: 7 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. I am sure these coefficients are the reason behind the divergence. How can I solve this divergence problem ? Thanks

 April 3, 2013, 12:07 #2 Senior Member   OJ Join Date: Apr 2012 Location: United Kindom Posts: 475 Rep Power: 14 As you guessed it, are you sure about these coefficients? How did you arrive at these values? OJ recepky likes this.

 April 4, 2013, 11:23 #3 New Member   Recep Kaya Join Date: Feb 2013 Posts: 6 Rep Power: 7 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 likes this.

November 11, 2017, 03:12
same problem
#4
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shubhangini
Join Date: Aug 2017
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Quote:
 Originally Posted by recepky 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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