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failed to find consistent intial values
Posted Jul 14, 2015, 11:38 p.m. EDT Chemical Reaction Engineering, Studies & Solvers Version 5.0 1 Reply
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I am trying to model the biochemical interactions between an inflammatory cytokine and biomolecules present in cartilage tissue. The cartilage tissue in the model is represented by a rectangular domain of width 1.5 mm and height of 1 mm. I have been successful in developing this model for cartilage degradation using comsol. However, we now want to simulate the transport and interaction of candidate drugs with the cytokine and biomolecules present in the cartilage. To solve this problem we first divided the problem into 2 distinct models (see attached file, IL-1 diffusion test R4(test) R-1.mph). The geometry for the second model (comp 1) is a slight modification to the original geometry used for model 1. It basically represents a layer of fluid surrounding the cartilage tissue and contains sodium chloride and the candidate drug. The sodium ion, chloride ion and drug are transported by passive diffusion and due to differences in electrostatic potential between the tissue and the fluid surrounding it. The charge distribution in the tissue depends on the tissue aggrecan concentration, which is mapped from model 1 using the "idmap" operator. This model too worked successfully in comsol. For the next step, I introduced a chemical reaction term to represent the interaction between the drug and the cytokine IL-1 (see attached file, IL-1 diffusion test R4(test) R2.mph). However, I keep getting an error message "Failed to find appropriate initial conditions". Could you please let me know if there are any ways to solve this problem.
Regards,
Saptarshi
Regards,
Saptarshi
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1 Reply Last Post Jul 15, 2015, 6:38 p.m. EDT
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Posted:
9 years ago
Hi, I try to find a steady-state solution exactly the same as the t=0 value for the transient. Run the steady-state first and use the output of that as the initial value for the transient. I've had pretty good luck with that.
I think what is happening is that at, say, a boundary interface between two Dirichlet or a Dirichlet/Neumann then the solution wont be exactly the same as the input value, and it is that non-input value that needs to be used to kick-start the transient.
One minor annoyance is that the steady-state solution will refuse to recognize the term "t" if you have use it for the stationary hop, so what I do there is duplicate, say, the material property. The first has the value as though t was zero. The second has the value of t.
Then in solver mode you click on "modify the physics". When running the initial stationary you disable anything with the term "t" in it, and then when running in transient mode you disable all of the silly entries you created just to initialize the transient.
No harm in trying ....
Regards, John
I think what is happening is that at, say, a boundary interface between two Dirichlet or a Dirichlet/Neumann then the solution wont be exactly the same as the input value, and it is that non-input value that needs to be used to kick-start the transient.
One minor annoyance is that the steady-state solution will refuse to recognize the term "t" if you have use it for the stationary hop, so what I do there is duplicate, say, the material property. The first has the value as though t was zero. The second has the value of t.
Then in solver mode you click on "modify the physics". When running the initial stationary you disable anything with the term "t" in it, and then when running in transient mode you disable all of the silly entries you created just to initialize the transient.
No harm in trying ....
Regards, John