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prescribed displacement/frequency domain study

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im doing a 3d beam that have a prescribed displacement in the z direction but I needed to be with respect to time using this function below 200sin(120pi*t)[um] how do it add it on comsol

also how do i do a frequency domain study because it giving me a error that t is not defined.

6 Replies Last Post 23 gen 2024, 02:15 GMT-5

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Posted: 7 months ago

Start out with a frequency domain study (steady-state). Your frequency is seemingly 60 Hz, so that is what you input. Then go to a time-domain study.

-------------------
René Christensen, PhD
Acculution ApS
www.acculution.com
info@acculution.com

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Posted: 7 months ago
Updated: 7 months ago

that correct my frequency is 60 Hz so i need to do a

1. frequency domain, then using the result use
2. frequency to time domain as the next step?

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Posted: 7 months ago
Updated: 7 months ago

Frequency dependent gets you the sinusoidal steady state solution.

Time dependent with sin(wt) gets you the initial transient when the sinusoidal excitation is turned on at t = 0.

Which one do you want??

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Posted: 7 months ago
Updated: 7 months ago

when t = 0

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Posted: 7 months ago
Updated: 7 months ago

OK if you are doing a time-dependent study then t is automatically time and the driving function should be written 200[um]sin(2pi60[1/s]t).

(If you do a frequency dependent study all quantities are phasors and time does not explicitly appear.)

(The website seems to remove asterisks from equations so you need to put them where they belong).

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Posted: 7 months ago
Updated: 7 months ago

A comment on the formatting: The forum uses the 'Markdown' syntax. Asterisk then means italic. If you want the asterisk to be shown as is, put a backslash ( \ ) in front of it. For more details, see https://www.comsol.com/forum/formatting-guide

The expression should then look like 200[um]*sin(2*pi*60[1/s]*t).

Entered as

``````200[um]\*sin(2\*pi\*60[1/s]\*t)
``````
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Henrik Sönnerlind
COMSOL

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