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"Failed to find consistent initial values" -- Electric Field Distribution Model

Posted 02.05.2021, 23:44 GMT-4 Low-Frequency Electromagnetics Version 5.6 4 Replies

Anthony C
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Hi,

I'm currently trying to model the electric field distribution of liver tissue. I have two electrodes, one grounded and the other at 500V inside the liver domain. I am using Poisson's equation (which has a conductivity function of the electric field, ec.normE), and the electric currents physics. I also have an electric field dependent conductivity function in the model and it is applied under the liver material and is also part of the Poisson's equation.

When running the time dependent study, I get the following error: "Failed to find consistent initial values. Last time step is not converged."

I was wondering what this error means, and where in my model is causing this error. I am also relatively new to COMSOL, and any advice would be hugely appreciated!

Attached is the model.

Thank you for your time!

Attachments:

4 Replies Last Post 03.05.2021, 15:04 GMT-4
Edgar J. Kaiser Certified Consultant
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Posted: 4 years ago 03.05.2021, 03:34 GMT-4

Anthony,

I am wondering what you need the Poisson equation for. You can calculate the electric potential and field in the ec physics. Also I don't see the time anywhere in the model. So a stationary study using ec physics will probably do what you need.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Anthony, I am wondering what you need the Poisson equation for. You can calculate the electric potential and field in the ec physics. Also I don't see the time anywhere in the model. So a stationary study using ec physics will probably do what you need. Cheers Edgar
Anthony C
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Posted: 4 years ago 03.05.2021, 12:08 GMT-4

Hi Edgar,

Thank you for your response.

  1. In the research papers I've read, the electric field distribution in tissue is found solving following equation: . I could not find this kind of equation in the ec physics. The ec physics was only added so that I can add the electric field norm into the poisson equation, as seen in the function (electric field dependent conductivity).

  2. Currently, one of the electrodes is at a constant voltage. I plan on changing it and adding a square wave pulse to that electrode. Would that warrant a time dependent study? As the number of applied pulses will be important later on.

Thank you again for your help!

Hi Edgar, Thank you for your response. 1. In the research papers I've read, the electric field distribution in tissue is found solving following equation: \nabla*(\sigma(E) * \nabla V)=0. I could not find this kind of equation in the ec physics. The ec physics was only added so that I can add the electric field norm into the poisson equation, as seen in the \sigma(E) function (electric field dependent conductivity). 2. Currently, one of the electrodes is at a constant voltage. I plan on changing it and adding a square wave pulse to that electrode. Would that warrant a time dependent study? As the number of applied pulses will be important later on. Thank you again for your help!
Edgar J. Kaiser Certified Consultant
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Posted: 4 years ago 03.05.2021, 13:57 GMT-4

Check the equations in the ec physics. With your field dependent conductivity, zero source term Q and zero external current density Je it is exactly your equation.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Check the equations in the ec physics. With your field dependent conductivity, zero source term Q and zero external current density Je it is exactly your equation. Cheers Edgar
Anthony C
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Posted: 4 years ago 03.05.2021, 15:04 GMT-4

Ah, I somehow mislooked the similarities between the equations. Thank you for your time!

Ah, I somehow mislooked the similarities between the equations. Thank you for your time!

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