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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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Function to return larger of two arguments

Posted 2016年11月15日 GMT-5 15:55 Heat Transfer & Phase Change, Parameters, Variables, & Functions Version 4.4 4 Replies

Bryan Burk
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Hey Comsolers,
I have an equation that depends on one of two variables (x and y), whichever one is larger at the spatial location in the geometry where the equation is being evaluated. The values of these variables at any given spatial location depend on input parameters and other things so that I cannot simply use variable x up to a certain point and then use y after that. Is there a built in MAX(x,y) function or is there another way to do this?

Thanks,
Bryan
4 Replies Last Post 2016年11月17日 GMT-5 07:21
Steve Conrad
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Posted: 8 years ago 2016年11月15日 GMT-5 19:26
Yes, there is a max(a,b) function. COMSOL is case-sensitive, so MAX(a,b) may not work.

--
Steven Conrad, MD PhD
LSU Health
Yes, there is a max(a,b) function. COMSOL is case-sensitive, so MAX(a,b) may not work. -- Steven Conrad, MD PhD LSU Health
Bryan Burk
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Posted: 8 years ago 2016年11月16日 GMT-5 12:31
I was under the impression that max(a,b) would give me the value of b at the location of the maximum of a, which isn't quite what I want to do.
I was under the impression that max(a,b) would give me the value of b at the location of the maximum of a, which isn't quite what I want to do.
Steve Conrad
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Posted: 8 years ago 2016年11月16日 GMT-5 13:40
According to the reference manual, it will give the maximum of the two arguments. I've attached a snip of the reference manual. I also tested the function in a COMSOL model, and it behaves as I described. It can be used with global or solution (spacially aware) arguments, so you can use it to find the max of two variables in your geometry. I'm using 5.2a, but I doubt the function would have changed from 4.4

--
Steven Conrad, MD PhD
LSU Health
According to the reference manual, it will give the maximum of the two arguments. I've attached a snip of the reference manual. I also tested the function in a COMSOL model, and it behaves as I described. It can be used with global or solution (spacially aware) arguments, so you can use it to find the max of two variables in your geometry. I'm using 5.2a, but I doubt the function would have changed from 4.4 -- Steven Conrad, MD PhD LSU Health

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Gunnar Andersson COMSOL Employee

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Posted: 8 years ago 2016年11月17日 GMT-5 07:21

I was under the impression that max(a,b) would give me the value of b at the location of the maximum of a, which isn't quite what I want to do.


If you create a Component Coupling of type Maximum, then you get this behavior. The function max() behaves the way Steve describes.
[QUOTE] I was under the impression that max(a,b) would give me the value of b at the location of the maximum of a, which isn't quite what I want to do. [/QUOTE] If you create a Component Coupling of type Maximum, then you get this behavior. The function max() behaves the way Steve describes.

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