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prescribed displacement/frequency domain study

Posted Jan 20, 2024, 3:54 p.m. EST Studies & Solvers, Structural Mechanics, Physics Interfaces Version 6.1 6 Replies

Nelson Leon
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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 Jan 23, 2024, 2:15 a.m. EST
Acculution ApS Certified Consultant
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Posted: 10 months ago Jan 21, 2024, 8:23 a.m. EST

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
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.
Nelson Leon
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Posted: 10 months ago Jan 21, 2024, 4:04 p.m. EST
Updated: 10 months ago Jan 21, 2024, 4:04 p.m. EST

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?
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?
Dave Greve
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Posted: 10 months ago Jan 21, 2024, 7:20 p.m. EST
Updated: 10 months ago Jan 21, 2024, 7:12 p.m. EST

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??

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??
Nelson Leon
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Posted: 10 months ago Jan 22, 2024, 4:33 p.m. EST
Updated: 10 months ago Jan 22, 2024, 4:25 p.m. EST

when t = 0

when t = 0
Dave Greve
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Posted: 10 months ago Jan 22, 2024, 6:13 p.m. EST
Updated: 10 months ago Jan 22, 2024, 6:06 p.m. EST

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).

OK if you are doing a time-dependent study then t is automatically time and the driving function should be written 200[um]*sin(2*pi*60[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).
Henrik Sönnerlind COMSOL Employee

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Posted: 10 months ago Jan 23, 2024, 2:15 a.m. EST
Updated: 10 months ago Jan 23, 2024, 8:41 a.m. EST

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)
-------------------
Henrik Sönnerlind
COMSOL
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 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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