What Denny said; use the inlet.  Also you need to have your inlet bell
shaped to reduce turbulence.  There is probably an optimal shape and size
for the inlet (elliptical segment?) but you would have to look it up.

Also laminar air flow does not mean uniform velocity across the flow
direction.  Turbulent airflow creates a more uniform flow field except near
the wall.  Have a look in a fluid mechanics book.

Gordon Williams



----- Original Message -----=20
From: "Denny Esterline" <desterline@gmail.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Wednesday, December 07, 2011 11:06 AM
Subject: Re: [OT] Air flow smoothing for anemometer test rig suggestions
sought


> On Tue, Dec 6, 2011 at 9:05 AM, Robin D. Bussell
<RobinB@excelerate.info>wrote:
>
> > Hi Folks,
> >           What are your thoughts on simple (ish ) ways of conditioning
> > the output of a fan to give a nice smooth air flow for testing an
> > ultrasonic anemometer? I'm not too fussed about absolute speed accuracy=
,
> > it's more having a nice smooth source to test the stability of the
> > direction sensing that I'm interested in.
> >
> > Something like the Dyson Air Multiplier:
> >  http://www.dyson.co.uk/store/fans.asp
> >  looks like it might make an off the shelf solution but might be
> > difficult to get bought (or to keep hold of once the office sees it!  )=
..
> >
> > Tube full of straws to induce laminar flow?  Just a long tube to let
> > things "settle down"  after the blades?
> >
> > Any input welcome :)
> >
> > Cheers,
> >
> > Robin Bussell.
> >
> >
> >
> >
> Put your test on the inlet side of the fan. Smoothing out the flow after
> the fan is much more difficult.
>
> -Denny
> --=20
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