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Doubt about transitorial analysis

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Greetings!

I have a doubt about transitorial analysis. Let me explain: I´ve been looking for tutorials about the subject and I found one of CFD concerning a cylinder, I leave the link so you can check it:

www.comsol.com/showroom/downloadfile/model/97/version/comsol42a/file/models.mph.cylinder_flow.pdf

In this toturial a Step function is declared and is used to vary the average speed from 0 (zero) to U_mean.

My question is: Why is the funtion Step_1 used in the argument t[1/s]? According to me, we could use t[s] to obtain a "linear variation", even t would be valid as an argument to the function Step_1.

The point is, I have done this changes and the program is marking me errors.

Thanks

3 Replies Last Post 2012年11月7日 GMT-5 13:07
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2012年11月6日 GMT-5 00:37
Hello,

the reason for the t[1/s] is to make "t" witout units as most functions expect unitless values,
"t" has by default a unit of "s" so t[s] means s^2 type units
if you wtite t[1/min] t would count in minutes, that is 1,2,3 would correspond to minutes, while t[1/h] in hours etc

--
Good luck
Ivar
Hello, the reason for the t[1/s] is to make "t" witout units as most functions expect unitless values, "t" has by default a unit of "s" so t[s] means s^2 type units if you wtite t[1/min] t would count in minutes, that is 1,2,3 would correspond to minutes, while t[1/h] in hours etc -- Good luck Ivar

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Posted: 1 decade ago 2012年11月7日 GMT-5 12:50
Thank you very much.

Greetings from México
Thank you very much. Greetings from México

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2012年11月7日 GMT-5 13:07
Hola

Youre welcome
From Switzerland, here ;)

--
Good luck
Ivar
Hola Youre welcome From Switzerland, here ;) -- Good luck Ivar

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