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 williaq April 3, 2011 09:18

guidance, flapper motion problem

(see repost)

 williaq April 3, 2011 09:34

Re-post: guidance, flapper motion problem

Repost: for some reason, my ascii-art picture was getting corrupted. Re-posting now with placeholders "." inserted.\
------------------------

Greetings all --

I'm a professional mechanical engineer, but mostly a mechanisms guy until now. I recently joined a small firm, and it's fallen to me to pursue some questions on a new project involving airflow. So I'm an experienced engineer, but a CFD newbie, and I know better than to reinvent the wheel -- I'd like to gain from the wisdom here. I would appreciate guidance, both the big-picture, *and* nitty gritty details. (I've done some searches on the forums, but feel free to redirect me if my questions are too far back).

Here's the deal: Below is an ascii-art side-view of the physical setup. In the picture, let x be the horizontal, and y be the vertical direction, and z be out of the page

Our system is quite simple -- think of it as a pipe with a pivoting damper. We have a rectangular tube, with one end sealed (except an inlet slit). and a damper/flapper in the middle, which pivots about a horizontal (z-direction) axis. A relative vacuum is applied at the outlet thus drawing air through the inlet, which is a horizontal slit, located at an arbitrary height. (Symbology below: x = tube wall; \ = flapper; o = flapper pivot; .=placeholder, so that the picture doesn't get corrupted when I post this message)

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
x.........\................................
.<inlet....\...............................
x...........o...............--------> flow
x............\....................(outlet)..
x.............\............................
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

^ y
|
|
o--> x
z

I would like to characterize the movement at the damper, for various flow rates, assuming a low-friction axis. Both with steady-state, and (secondarily) in transient flows. We've noticed instabilities and even oscillations in some mockups, and want to understand the factors governing this motion.

So there it is -- Guidance as I get started? (no guidance too basic). What is a suitable software for me to use, best way to approach a problem of this sort...

Thanks,
--Will

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