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'[OT] Air flow smoothing for anemometer test rig su'
2011\12\06@110516 by Robin D. Bussell

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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.


2011\12\06@162128 by Yigit Turgut

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1- Buy a fan that is driven by a motor which has exact specifications
as mentioned in the datasheet
2 -Buy a PVC pipe that will fit to fan diameter, cut it in half and
attach to both ends of the fan (might not fit exactly, you can fill
the gaps with hot silicone gun etc)
3- Place anemometers to both ends (if only 1 available than do it by turn)
3- You can precisely control the fan speed and direction by adjusting
duty cycle/period of a PWM (refer to datasheet)
4- By logging anemometer output and correlating with supplied PWM
signal, you can derive the characteristic plot

Let me know if it works (:


On Tue, Dec 6, 2011 at 6:05 PM, Robin D. Bussell <spam_OUTRobinBTakeThisOuTspamexcelerate.info> wrote:
{Quote hidden}

>

2011\12\06@171952 by alan.b.pearce

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> > 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 :)

Tube full f straws is probably the way to go. It seems to be the common way that experimenters produce laminar water flow for those fancy fountains where squirt of water acts like rods and don't spray everywhere. Try some search terms looking for these things (I can't remember what terms I used when I looked some time back).



-- Scanned by iCritical.

2011\12\07@035218 by MarcoG

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Perhaps you may find useful suggestions also on an old EPE magazine article
(February 2003) written by the regretted John Becker: a Wind Tunnel.

regards,
Marco



{Original Message removed}

2011\12\07@110631 by Denny Esterline

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On Tue, Dec 6, 2011 at 9:05 AM, Robin D. Bussell <.....RobinBKILLspamspam@spam@excelerate.info>wrote:

{Quote hidden}

Put your test on the inlet side of the fan. Smoothing out the flow after
the fan is much more difficult.

-Denn

2011\12\07@114902 by Gordon Williams

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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 removed}

2011\12\08@052152 by cdb

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On Wed, 7 Dec 2011 09:52:15 +0100, MarcoG wrote:
:: written by the regretted John Becker: a Wind Tunnel.

Off topic I know, did he pass on? I remember he 'retired' due to heart problems. In fact as EPE were left without a main contributor they became Silicon Chip of the UK more or less, the reason it was no longer worth subscribing to them.

If I recall correctly he was self taught in the electronics field.

Colin
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2011\12\08@060348 by MarcoG

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I have read on this: www.electro-tech-online.com/members-lounge/94950-john-becker-r-i-p.html
and also on EPEmag: www.epemag3.com/index.php?option=com_content&task=view&id=344&Itemid=102
("a Tribute to John becker")

But if I'm not wrong, also on this List.

Marco



{Original Message removed}

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