Menu

Discussion Forum

New Discussion
Filtrer

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Time dependent simulation of single degree of freedom system

Posted 13 janv. 2020, 01:20 UTC−5 Structural & Acoustics, Acoustics & Vibrations, Structural Mechanics 1 Reply

陈勇勇 陈
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

I use the lumped mechanical system interface to solve a single-degree-of-freedom system transient simulation. The harmonic frequency is the system natural frequency. Why does the steady-state acceleration in the calculation result change? As shown below.

Attachments:

1 Reply Last Post 13 janv. 2020, 14:12 UTC−5
Henrik Sönnerlind COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 5 years ago 13 janv. 2020, 14:12 UTC−5

Hi,

The plot looks like if the excitation is reduced to 75% of it previous value at time 0.25 s. Or, similarly, that the damping is increased by 25%.

Can you see anything jumping in the solver log or the convergence graph at that time? Do the time steps increase? Which time dependent solver is used? Do the displacements behave the same way as the accelerations?

If the time steps are very large, what you see is possibly an effect of numerical damping, rather than a physical result. Try limiting time steps and tightening tolerances.

Regards,
Henrik

-------------------
Henrik Sönnerlind
COMSOL
Hi, The plot looks like if the excitation is reduced to 75% of it previous value at time 0.25 s. Or, similarly, that the damping is increased by 25%. Can you see anything jumping in the solver log or the convergence graph at that time? Do the time steps increase? Which time dependent solver is used? Do the displacements behave the same way as the accelerations? If the time steps are very large, what you see is possibly an effect of numerical damping, rather than a physical result. Try limiting time steps and tightening tolerances. Regards, Henrik

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content