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Coefficient of isotropic diffusion in icp_torch model

Posted May 3, 2015, 4:59 a.m. EDT Low-Frequency Electromagnetics, Plasma Physics, Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers Version 5.0, Version 5.1 6 Replies

Ivan Ivanov
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Hello,
I have one question to the developers of icp_torch model of PLasma module- Equlibrium discharges.
What does mean the isotropic diffusion coefficient in this model in main laminar flow settings and what values it may be? Isotropic diffusion coefficient may influenced on Peclet number ? Please, could you tell us about the interval of this coefficient vs power of plasma? Could you explain the isotropic diffusion coefficient : 10-10*tanh(1000*(t-0.08))?
6 Replies Last Post Jun 6, 2015, 9:58 a.m. EDT
Daniel Smith COMSOL Employee

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Posted: 9 years ago May 4, 2015, 9:17 a.m. EDT
Hi Ivan, the isotropic diffusion is added to help with convergence when the plasma starts to form. Without this the model becomes numerically unstable. The amount of isotropic diffusion is then ramped down from its initial value of 10 to 0. This begins to happen around 0.08[s], when the plasma is fully developed. The transient behavior of the system may not be entirely accurate because of the isotropic diffusion, but the steady state solution (corresponding to the solution at the last time step) should be OK because the isotropic diffusion coefficient is 0 at that time.
Hi Ivan, the isotropic diffusion is added to help with convergence when the plasma starts to form. Without this the model becomes numerically unstable. The amount of isotropic diffusion is then ramped down from its initial value of 10 to 0. This begins to happen around 0.08[s], when the plasma is fully developed. The transient behavior of the system may not be entirely accurate because of the isotropic diffusion, but the steady state solution (corresponding to the solution at the last time step) should be OK because the isotropic diffusion coefficient is 0 at that time.
Ivan Ivanov
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Posted: 9 years ago May 4, 2015, 10:36 a.m. EDT

Hi Ivan, the isotropic diffusion is added to help with convergence when the plasma starts to form. Without this the model becomes numerically unstable. The amount of isotropic diffusion is then ramped down from its initial value of 10 to 0. This begins to happen around 0.08[s], when the plasma is fully developed. The transient behavior of the system may not be entirely accurate because of the isotropic diffusion, but the steady state solution (corresponding to the solution at the last time step) should be OK because the isotropic diffusion coefficient is 0 at that time.


Daniel, thank you for reply. Does this coefficient depends from level of power of plasma? When i changed the plasma power in icp_torch model to 15 or 20 kW, model was error. I just want to know the trend of isotropic diffusion coefficient of high power plasma. What the picture will be with plasma power level about 200 kW? As i understand, t=[0.08] is a empirical value or not? And does it depends of power level?
Thank you for attention to my problem!
[QUOTE] Hi Ivan, the isotropic diffusion is added to help with convergence when the plasma starts to form. Without this the model becomes numerically unstable. The amount of isotropic diffusion is then ramped down from its initial value of 10 to 0. This begins to happen around 0.08[s], when the plasma is fully developed. The transient behavior of the system may not be entirely accurate because of the isotropic diffusion, but the steady state solution (corresponding to the solution at the last time step) should be OK because the isotropic diffusion coefficient is 0 at that time. [/QUOTE] Daniel, thank you for reply. Does this coefficient depends from level of power of plasma? When i changed the plasma power in icp_torch model to 15 or 20 kW, model was error. I just want to know the trend of isotropic diffusion coefficient of high power plasma. What the picture will be with plasma power level about 200 kW? As i understand, t=[0.08] is a empirical value or not? And does it depends of power level? Thank you for attention to my problem!
Ivan Ivanov
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Posted: 9 years ago May 7, 2015, 3:39 p.m. EDT
Anybody know the solution of problem?
Anybody know the solution of problem?
Ivan Ivanov
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Posted: 9 years ago May 16, 2015, 9:26 a.m. EDT
And when I enable Lorrents force in icp_model, model haven't got a result.What does it mean? Model correctly works only without Lorrents force? But it is wrong!
And when I enable Lorrents force in icp_model, model haven't got a result.What does it mean? Model correctly works only without Lorrents force? But it is wrong!
Ivan Ivanov
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Posted: 9 years ago May 18, 2015, 3:19 p.m. EDT
Could you describe the main settings in this model (attach file from highlights Comsol 5.0)?
This file is real and right picture of icp torhes.
Could you describe the main settings in this model (attach file from highlights Comsol 5.0)? This file is real and right picture of icp torhes.

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Ivan Ivanov
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Posted: 9 years ago Jun 6, 2015, 9:58 a.m. EDT
Does anybody know?
Does anybody know?

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