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the problem of reactions and domains

Posted 13 nov 2014, 22:57 GMT-5 Low-Frequency Electromagnetics, Plasma Physics Version 4.4 3 Replies

Crane Cheng
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I am learning to use COMSOL and I have a problem. For the 1-d discharge model, we use polygon to divide one domain into multiple domains, but how can I add different reactions to the different domains?
3 Replies Last Post 17 nov 2014, 10:11 GMT-5
Luke Gritter Certified Consultant
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Posted: 1 decade ago 14 nov 2014, 13:27 GMT-5
Crane,

Despite having editable "Domain Selection" boxes on the settings tab for each reaction, the software seems to require that all reactions are enabled on all plasma domains. You can get around this by setting the reaction rate to zero on any domains where you don't want the reaction to be active. To do this, use Variables nodes (under Definitions) to create a variable that is equal to one in the domains where the reaction is active and zero elsewhere. Then multiply the reaction rate by this variable.

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Luke Gritter
AltaSim Technologies
Crane, Despite having editable "Domain Selection" boxes on the settings tab for each reaction, the software seems to require that all reactions are enabled on all plasma domains. You can get around this by setting the reaction rate to zero on any domains where you don't want the reaction to be active. To do this, use Variables nodes (under Definitions) to create a variable that is equal to one in the domains where the reaction is active and zero elsewhere. Then multiply the reaction rate by this variable. -- Luke Gritter AltaSim Technologies
Crane Cheng
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Posted: 1 decade ago 16 nov 2014, 21:02 GMT-5
Dear Luke,
Thank you for your reply. But how to deal with the reactions that is from Cross Section Import? it seems that reactions that from Cross Section Import don't have the reaction rate option? is it possible that using a variable multiplied by the collision cross section data or Townsend coefficient data? it looks very inconvenient if a reaction has huge data.
Dear Luke, Thank you for your reply. But how to deal with the reactions that is from Cross Section Import? it seems that reactions that from Cross Section Import don't have the reaction rate option? is it possible that using a variable multiplied by the collision cross section data or Townsend coefficient data? it looks very inconvenient if a reaction has huge data.
Luke Gritter Certified Consultant
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Posted: 1 decade ago 17 nov 2014, 10:11 GMT-5
Crane,

When the reaction rate is defined using cross sections or a lookup table, you can still use the same technique. Activate "Equation View" using the "Show" icon, and click on the Equation View sub-node that appears directly under the reaction you want to modify. Both the rate coefficient and the reaction rate are defined here, and you can modify either of these variables to achieve the desired effect.

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Luke Gritter
AltaSim Technologies
Crane, When the reaction rate is defined using cross sections or a lookup table, you can still use the same technique. Activate "Equation View" using the "Show" icon, and click on the Equation View sub-node that appears directly under the reaction you want to modify. Both the rate coefficient and the reaction rate are defined here, and you can modify either of these variables to achieve the desired effect. -- Luke Gritter AltaSim Technologies

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