Discussion Forum

Hi

one danger with your bolean equations there are that they are discontinous, so the solver will have problems along the transition points. In v4 your have the smmotes pulse(), step() and ramp() functins that have smoother transitions. I can only sugest to try with those instead of your "hard" bolean steps

If the spatial limits do not change with time, you could perhaps cut up your domain along the lines, and remove the spatial dependence, and only keep the temporal one

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Good luck
Ivar

Thanks for your reply.

For the initial conditions of Vm where I needed to assign different initial conditions for different parts of the geometry I split the geometry into subdomains as in attached file but am getting initialization problems now.

Now I want to set the iextra and iintra to 0 in domain 1 and 1 in domain 2 respectively for 0<t<0.1 s and 0 everywhere for the rest of the time. How do I do that?

I sincerely appreciate your help.

Thanks
Deepika

Dear Ivar,

I have been working on this model for a while now and still having problems with initialization and varying input variables.

I need to:
1. vary the input current with time and space.
2. initialize the input variable Vm to Vfire in some areas in the geometry and Vrest in others.

I tried:
1. multi domains..had success with initialization but results limited at inner boundary. Pls see attached 2D_Bidomain_v1_subdomain
2. piecewise function for Vm and boolean expressions for input current but initialization was not successful. Pls see attached 2D_Bidomain_v1

I sincerely appreciate your help in resolving my problem.

Thanks
Deepika

Hi

I'm not sure qhat is wrong, but when I ask to load the inital values (right click on "Study Solver Config Solver 2 - Dependent variables - Compute to selected") I get mostly "0" and that is unexpected.

If I delete your study and recreate it from scratch I can solve and get values different from "0". But I have v4.2a not sure that is the reason.

Sometimes it is worth to remake a model from scratch, if one has changed it a lot, particularly for the early V4.0 and v4.1 versions

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Good luck
Ivar

Dear Ivar,

Thanks for your reply.

I followed your suggestion and recreated the study but I still get an initial value for Vm as 1V throughout the geometry when I'm actually expecting to see 1V (Vrest) in some areas and -1.2V(Vfire) as defined in piecewise function pw1(x).

Also I have defined I as Io*(x<1)*(y<1) but on initialization I is set to Io throughout the geometry.

Looking forward to your insight....

Thanks
Deepika

PS: the attached model has been solved only till initialization and Vm and I plotted in the results.

Hi

sorry but your file appear with "0 bytes" I believe the site had a problem the other day, that happened to me too ;) Try to upload it again

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Good luck
Ivar

Dear Ivar,

File attached again.

Thanks
Deepika

Dear Ivar,

Did you get a chance to look at my file....I sincerely appreciate your help.

Thanks
Deepika

Hi

sorry for the late reply, but I'm very busy these days for my job, and the FORUM is just for fun ;)

I have noticed that you do not respect the "units" this is very important in physics, while often in "math mode" one ignores them. But in your case you have a geometry defined in cm and default units SI. this explains why we cannot get any initial values in line with your model, the piecewise function is defined in meters, and you have cm hence no variation.

To observe this load your "initial values": right click the "Study 1 - Sover Configuration Study 1 Dependent variables" and select "Compute to selected". This will load all your matrices with the initial values and then you can compare them with wht you expect. You will see that Vm is all =1

Try to plot only pw1(x) (instead of Vm), then replace the formula by pw1(x[1/cm]) wich applies the correct unit transformation first and you will get a different result.

It's worth to check all orange "unit error" flagged values to clear them as this means your model is consistent, even if "orange" is only a warning, and COMSOL will attempt to sole as is, expecting you to have done your homework

By the way your last model is not solving, once reset it reclaims "data", not sure what this is, but I know that often, when having tweaked a lot on a model it might become corrupt, then its worth to restart from fresh with a new model
What I finally managed, with your model, was to clear solution, mesh reset all, remove the 3 functions in the data set, remove the solver and then regenerate a new run


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Good luck
Ivar