CFD Online URL
[Sponsors]
Home > Forums > Main CFD Forum

Backward FAcing Step - Frequency

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 20, 2006, 17:20
Default Backward FAcing Step - Frequency
  #1
CFDtoy
Guest
 
Posts: n/a
I am looking at a BFS problem and would like to know if any measurement of the frequency of the backward facing step chamber has been carried out. (Backward facing step system has its own resonant frequency ..the frequency of the chamber itself..)

Could anyone direct me to papers or comment about it?

CFDtoy
  Reply With Quote

Old   October 21, 2006, 01:23
Default Re: Backward FAcing Step - Frequency
  #2
diaw
Guest
 
Posts: n/a
CFDtoy wrote:

Backward facing step system has its own resonant frequency ..the frequency of the chamber itself..

---------

diaw writes:

Could you please clarify this statement a little more? I simulate & research related phenomena & would be interested in the basis for your statement.

desA
  Reply With Quote

Old   October 22, 2006, 13:19
Default Re: Backward FAcing Step - Frequency
  #3
CFDtoy
Guest
 
Posts: n/a
Based on the step height to the length of the chamber it can act on its own as a resonant chamber sort of. I was wondering if anyone has tried to measure the frequency of such backward facing step chambers??

CFDtoy

  Reply With Quote

Old   October 23, 2006, 08:55
Default Re: Backward FAcing Step - Frequency
  #4
Jonas Holdeman
Guest
 
Posts: n/a
Please explain what you mean by "chamber" in the BFS problem. In the standard problem, the downstream duct is uniform and its length is infinite, but truncated for numerical computations with downstream/exit boundary conditions that simulate the infinite length.

In a device like a whistle or organ pipe there is a definable chamber and an inlet/outlet, but a strong interaction between inlet and outlet flow. But that is not the case with the BFS problem.
  Reply With Quote

Old   October 23, 2006, 13:08
Default Re: Backward FAcing Step - Frequency
  #5
CFDtoy
Guest
 
Posts: n/a
Hi Jonas: I guess I ll rephrase the problem. You are right, the backward facing step problem has inf length downstream.

= <--BFS problem----> ================= = =

= Step length defined=

= ..................................... =

= Step height defined=

=====================

If in the case that the downstream exit is confined and the BFS is made to look like a cavity ...what about the frequency of such chambers?

I am sure there is a finite frequency exist for the chamber...based on the step height and length of the duct there...

Can you suggest or comment about finding the resonant frequency of such chamberS?

CFDtoy
  Reply With Quote

Old   October 23, 2006, 16:46
Default Re: Backward FAcing Step - Frequency
  #6
ag
Guest
 
Posts: n/a
There is quite a bit of work that has been done on cavity acoustics - the classic paper describing a reasonably good empirically based frequency estimate is the one by Rossiter. Do a google search on "Rossiter equation" and you should find quite a bit. A backward facing step on the other hand has no resonant frequency (that I'm aware of) because only one frequency source is present (the shear layer) and there is no real feedback path.
  Reply With Quote

Old   October 27, 2006, 11:21
Default Re: Backward Facing Step - Frequency
  #7
Andrew
Guest
 
Posts: n/a
There are in fact two very distinct feedback mechanisms in the mixing layer flow. The first is from acoustic disturbances, with the second produced by fluctuations that are induced by concentrations of vorticity present within the layer itself.
  Reply With Quote

Old   October 28, 2006, 22:31
Default Re: Backward FAcing Step - Frequency
  #8
CFDtoy
Guest
 
Posts: n/a
ag ! That was a great reply ..i found the rossiter eqn and several interesting dynamics and models> Curretly goin thru them..

In the same spirit, can u comment on oscillatory flow into small fluidic channels with these cavity in them ..have u come across any papers onthat ?

Thanks a bunch !

CFDtoy
  Reply With Quote

Old   October 29, 2006, 21:51
Default Re: Backward FAcing Step - Frequency
  #9
ag
Guest
 
Posts: n/a
I haven't done any work in the area of smal fluidic channels. My work has been focused in the area of aircraft bays.
  Reply With Quote

Reply

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
How to write k and epsilon before the abnormal end xiuying OpenFOAM Running, Solving & CFD 8 August 27, 2013 16:33
Backward facing step. Fluids Main CFD Forum 7 December 4, 2012 12:28
Upgraded from Karmic Koala 9.10 to Lucid Lynx10.04.3 bookie56 OpenFOAM Installation 8 August 13, 2011 05:03
IcoFoam parallel woes msrinath80 OpenFOAM Running, Solving & CFD 9 July 22, 2007 03:58
Could anybody help me see this error and give help liugx212 OpenFOAM Running, Solving & CFD 3 January 4, 2006 19:07


All times are GMT -4. The time now is 09:03.