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.

How to apply a space and time dependent boundary condition?

Please login with a confirmed email address before reporting spam

Hi everyone,

I am trying to apply a sinusoidal prescribed displacement to the edge of a plate for 5 periods of the signal.

The applied signal has the form of F1(y,t)=u1(y)cos(2.pi.f0.t)+u2(y)sin(2.pi.f0.t) for prescribed component in x direction and F2(y,t)=v1(y)cos(2.pi.f0.t)+v2(y)sin(2.pi.f0.t) for prescribed component in y direction.

The variable y is associated with the mesh grid, i.e. the values of y are the values of the node positions along the extremity of the plate.

The four functions u1, u2, v1, v2 are interpolation functions which the discrete data sets I already have.

Is there any possible way to set up this kind of boundary conditions in COMSOL? I really appreciate if anyone can help me with this troublesome issue.

Bests,

Ngoc


4 Replies Last Post 2017年10月24日 GMT-4 05:24
Henrik Sönnerlind COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 7 years ago 2017年10月19日 GMT-4 10:01

Hi Ngoc,

Basically, you just type in the expressions in the text fields for the prescribed displacements.

u1(y)*cos(2*pi*f0*t)+u2(y)*sin(2*pi*f0*t)

f0 can be defined as a parameter.

For a more general discussion of how boundary conditions can be modified, see also

https://www.comsol.se/blogs/how-to-make-boundary-conditions-conditional-in-your-simulation/

Regards,

Henrik

-------------------
Henrik Sönnerlind
COMSOL
Hi Ngoc, Basically, you just type in the expressions in the text fields for the prescribed displacements. u1(y)\*cos(2\*pi\*f0\*t)+u2(y)\*sin(2\*pi\*f0\*t) f0 can be defined as a parameter. For a more general discussion of how boundary conditions can be modified, see also https://www.comsol.se/blogs/how-to-make-boundary-conditions-conditional-in-your-simulation/ Regards, Henrik

Please login with a confirmed email address before reporting spam

Posted: 7 years ago 2017年10月23日 GMT-4 08:17

Hi Henrik,

Thank you for answering my question. I have applied the prescribed BCs for my model and it worked when I used only Solids Mechanics physic. However, when I added Electrostatic and Piezoelectric effect for time analysis, COMSOL could not find converged solutions. Can you help me figure out where I did it wrong? I attached both models (before and after the electrostatic physic is added) here.

Bests,

Ngoc Nguyen

Hi Henrik, Thank you for answering my question. I have applied the prescribed BCs for my model and it worked when I used only Solids Mechanics physic. However, when I added Electrostatic and Piezoelectric effect for time analysis, COMSOL could not find converged solutions. Can you help me figure out where I did it wrong? I attached both models (before and after the electrostatic physic is added) here. Bests, Ngoc Nguyen


Henrik Sönnerlind COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 7 years ago 2017年10月23日 GMT-4 11:09

Hi Ngoc,

The first sanity check would be that the electric problem is grounded somewhere.

Regards, Henrik

-------------------
Henrik Sönnerlind
COMSOL
Hi Ngoc, The first sanity check would be that the electric problem is grounded somewhere. Regards, Henrik

Please login with a confirmed email address before reporting spam

Posted: 7 years ago 2017年10月24日 GMT-4 05:24

Hi Henrik,

Yes, it is indeed due to the lack of electrical boundary conditions. The simple plate model works now. I am moving on to a more complicated structure. Thank you and have a good day.

Bests,

Ngoc

Hi Henrik, Yes, it is indeed due to the lack of electrical boundary conditions. The simple plate model works now. I am moving on to a more complicated structure. Thank you and have a good day. Bests, Ngoc

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.