CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > CFX

MFX - Frequency resonance

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   October 25, 2007, 09:15
Default MFX - Frequency resonance
Posts: n/a
Hello everybody,

I did the tutorial of a piezoelectric micropump described in "Multi-field Analysis Using Code Coupling" and I have two questions:

1) When I change the fluid to water, the simulation returns an error of negative volume element. Could anybody explain it?

2) I tried to excitate the piezoelectric ceramic in its frequency resonance applying a sinusoidal voltage input, but the model doesn't change its behavior, no matter what frequency. Is it possible to do it?

  Reply With Quote

Old   October 25, 2007, 14:36
Default Re: MFX - Frequency resonance
Posts: n/a
1) The negative-volume indicates a folded-mesh (collapsed cell faces). This may happen if your mesh suddenly moves a particular location with unphysical values. There can be several reasons for this, e.g. unconverged solution-fields at the time of mesh motion, messed-up boundary conditions or physical properties, very large time-steps, bad-value for mesh-diffusion coeffcient (or mesh smoothing coeffcient). Check all of these one by one for your case.

Are you coupling CFX with ANSYS? If yes please let me know where one can find this tutorial. I want to see how one can apply votlage input in a structual analysis. Do you have some special elements for electrodynamics equations? I guess your second question is not for CFX users rather for ANSYS FEA users.
  Reply With Quote

Old   October 26, 2007, 17:30
Default Re: MFX - Frequency resonance
Posts: n/a
There is a tutorial in ANSYS' help, under the topic 'Coupled-Field Analysis Guide' (here: "Coupled-Field Guide -> Chapter 4. Multi-field Analysis Using Code Coupling -> 4.4. Example Simulation of a Piezoelectric Actuated Micro-Pump"), that explain how to model a piezoelectric pump using CFX and ANSYS.

About the first question, I agree with you about the reasons to cause negative volume elements, but I still don't understand what is wrong in this particular example. All I did was to change the fluid to water. All the rest (mesh, boundary conditions, time-steps, ...) is the same as the example.

What you're looking for is element SOLID5 (structural and voltage dofs).
  Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
sampling interval and sampling frequency beauty FLUENT 7 October 22, 2016 06:01
FSI - verification force mapping with mfx Vinzent CFX 15 September 18, 2011 18:00
Will a multi-grid method damp out the high frequency physical wave? hadesmajesty Main CFD Forum 8 October 13, 2009 00:26
Backward FAcing Step - Frequency CFDtoy Main CFD Forum 8 October 29, 2006 21:51
Reasons for failed validation at high frequency zonexo Main CFD Forum 5 October 23, 2006 09:32

All times are GMT -4. The time now is 22:22.