Menu

Discussion Forum

New Discussion
Filtra

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Coefficient of isotropic diffusion in icp_torch model

Posted 3 mag 2015, 04:59 GMT-4 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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

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 6 giu 2015, 09:58 GMT-4
Daniel Smith COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 4 mag 2015, 09:17 GMT-4
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 4 mag 2015, 10:36 GMT-4

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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 7 mag 2015, 15:39 GMT-4
Anybody know the solution of problem?
Anybody know the solution of problem?
Ivan Ivanov
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 16 mag 2015, 09:26 GMT-4
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 18 mag 2015, 15:19 GMT-4
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.

Attachments:

Ivan Ivanov
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 10 years ago 6 giu 2015, 09:58 GMT-4
Does anybody know?
Does anybody know?

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content