Menu

Discussion Forum

New Discussion
Filter

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.

set rotating boundary condition in 3D annulus flow

Posted May 9, 2019, 5:02 p.m. EDT Computational Fluid Dynamics (CFD) Version 5.4 2 Replies

Chunlou Li
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Dear all, I'm kind of new user of Comsol. Any suggestion will be appreciated regarding to my question. I want to model fluid flow in annulus (between two cylinders) with the inter cyliner rotating with a given speed. The 2 ends of the annulus are the inlet and outlet. With either 5.4 or 5.3, I cannot find where to set that wall condition. The options under "moving wall" include "sliding wall" and "moving wall", but no "rotating wall". Somebody can point me to the right direction? thank you very much.

Chunlou

2 Replies Last Post May 10, 2019, 8:29 a.m. EDT
Alexis Prel
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 6 years ago May 10, 2019, 8:27 a.m. EDT
Updated: 6 years ago May 10, 2019, 8:28 a.m. EDT

I am not familiar with the fluid flow modules, but in the moving wall condition, is it not possible to specify a vector expression for the wall's velocity?

If the above is possible, then you could input the local instaneous velocity as a function of spatial coordinates. So for a point such that is equal to the inner cylinder's radius, I would expect this velocity assuming a constant pulsation

where the sign of determines whether the rotation is clockwise or counter-clockwise.

Note that I assumed that the axis is both the axis of symmetry and the axis of rotation of the inner cylinder. You have to tinker a little bit if your origin is different.

I am not familiar with the fluid flow modules, but in the `moving wall` condition, is it not possible to specify a vector expression for the wall's velocity? If the above is possible, then you could input the local instaneous velocity as a function of spatial coordinates. So for a point P=(x_P, y_P, z_P) = (r_P, \theta_P, z_P) such that r_P is equal to the inner cylinder's radius, I would expect this velocity assuming a constant pulsation \omega ||\vec v|| = r_P |\omega| v_x = \sin(\theta_P) \cdot r_P \cdot \omega v_y = - \cos(\theta_P) \cdot r_P \cdot \omega v_z = 0 where the sign of \omega determines whether the rotation is clockwise or counter-clockwise. Note that I assumed that the axis (x, y, z) = (0, 0, z) is both the axis of symmetry and the axis of rotation of the inner cylinder. You have to tinker a little bit if your origin is different.
Alexis Prel
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 6 years ago May 10, 2019, 8:29 a.m. EDT

Actually, I just realized that the pulsation ω needs not to be constant for this to work.

Actually, I just realized that the pulsation ω needs not to be constant for this to work.

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