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Help to make a function that will gradually decrease a value of a parameter

Posted Aug 17, 2015, 6:46 a.m. EDT Materials Version 5.1 3 Replies

Md Sayeedur Rahman
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Hi all,

I am very new user of COMSOL. I am trying to learn from this discussion forum. I got stuck in a problem.

I am trying to make a function that will gradually decrease a value of a given parameter for example: At the top of a rectangular box, the initial value of a parameter will be 0.25 but it will decrease with time when the solver advances with time and at the bottom of the rectangular box the value of that parameter will become 0.001. The final value is not fixed. It can be anything. So, the value of the parameter will decrease at a controlled rate.

If you do not understand my description, please see the graphical description in the attachment. It will give you a better idea of my problem.

Does anybody know how I can make such a function in COMSOL? Thanks in advance.

Attachments:

3 Replies Last Post Aug 18, 2015, 5:11 a.m. EDT
Lasse Murtomäki
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Posted: 9 years ago Aug 17, 2015, 7:13 a.m. EDT
You can define functions globally or within the Component --> Definitions. Let's say that you have an analytical function as a function of time and its name is "an1". You can use that function as a boundary condition, for example, calling it asn "an1(t)", like any mathematical function.

BR
Lasse
You can define functions globally or within the Component --> Definitions. Let's say that you have an analytical function as a function of time and its name is "an1". You can use that function as a boundary condition, for example, calling it asn "an1(t)", like any mathematical function. BR Lasse
Md Sayeedur Rahman
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Posted: 9 years ago Aug 17, 2015, 7:39 a.m. EDT
Thanks for the suggestion. I already know that. But my question is, is there any kind of built in function in COMSOL that will gradually decrease the value of the parameter?
Thanks for the suggestion. I already know that. But my question is, is there any kind of built in function in COMSOL that will gradually decrease the value of the parameter?
Edgar J. Kaiser Certified Consultant
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Posted: 9 years ago Aug 18, 2015, 5:11 a.m. EDT
A parameter can't do that. But you can define a variable on the domain that depends on y, e.g.:

var(y) = 0.25 - (220-y)/220*(y<220)

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
A parameter can't do that. But you can define a variable on the domain that depends on y, e.g.: var(y) = 0.25 - (220-y)/220*(y

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