Abrasive flow finishing

bmccord at whittman-hart.com bmccord at whittman-hart.com
Fri Dec 19 17:59:13 GMT 1997


How do you calculate the point of dimensioning return for something like
that?

i.e. if you want to try to "dimple" an intake or something to improve
performance how do you determine how many dipoles and the placement.

Also, a golf ball spins in flight or at least has the opportunity to,
something fixed like the surface or a plane or an intake manifold can spin
so how would this effect the hole theory?

Just food for thought.





gcouger at ionet.net on 12/17/97 07:17:27 PM

Please respond to diy_efi at efi332.eng.ohio-state.edu

To:   diy_efi at efi332.eng.ohio-state.edu
cc:    (bcc: Billy McCord/Whittman-Hart LP)
Subject:  Re: Abrasive flow finishing




It's been a while but I set in on a PhD level course on turbulant
flow in open channels. By introducing small projections into the
surface you force the flow to become turbulant at a lower speed
and therefor forming a smaller bubble of turbulance. The small
turbulant bubbles act very much like ball bearings between the
in coming air and the skin.
Every thing I studied was for water. So it my be a little different
for air.
I would expect that the most benifit would be at the flow rates that
just started into turbulance.
Gordon
Gordon Couger
624 Cheyenne
Stillwater, OK 74075
405/624-2855   gcouger at ionet.net
Time Zone GMT-6

>I read an article recently in Design News concerning skin
>friction drag reductions.  They quote another article in
>Nature where skin friction drag was reduced by 13% on
>aerodynamic surfaces by adding random small bumps to
>the surface (vs a smooth surface).  Design News was considering
>the fuel reduction costs possible for typical commercial aircraft.
>A 13% skin friction drag equates to about a 6.5% overall
>drag reduction.  Big numbers when a 1% drag reduction saves
>a typical commercial aircraft about $100,000 annually in fuel
>costs.
>
>The idea is similar to the dimples used on golf balls which
>enable the golf balls to fly farther than undimpled
>balls.  I wonder what this might mean for engine intakes and
>exhausts?  Maybe an extrude honing type smooth surface is
>not the ideal surface even when injectors are near the valves.
>
>The dimples have to be in a random pattern, else you increase
>drag.  The theory is that random dimples (or chevrons) reduce
>bursting near an aerodynamic surface.  Busting is caused by
>low speed air streaks near the wall and is believed to be
>responsible for creating intense turbulence.
>
>Comments?
>
>Dan L
>










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