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golf ball toughts and reducing drag


By iFred, Section Wind
Posted on Mon Nov 14th, 2005 at 09:14:12 PM MST
reducing drag

Golf balls have dimples to reduce drag during air time. how would a blade profile say on either a vwat of hwat behave if it had less drag? would it start in slower winds?

Golf balls have a textured surface which reduces the weight signature and creates a frontal suction effect from what I understand. Basically the dimples create frontal vortices and this is what creates helps pull the ball and reduce drag.

What I guess I am saying is that by using mother nature in a particular way, could not the drag be reduced on blade profiles producing greater lift and less drag? Thus starting in less wind speeds?

Awaiting comments

golf ball toughts and reducing drag | 6 comments (6 topical, 0 editorial)

Re: golf ball toughts and reducing drag (3.00 / 0) (#1)
by kitno455 on Mon Nov 14th, 2005 at 02:18:35 PM MST
(User Info)

it is my understanding that the dimples prevent large eddies from forming behind the ball, by causing a thin layer of turbulence to prevent boundary layer from becoming thick and separating. interesting that this has nothing to do with the front of the ball :) the truth is probably far more complex...

allan



Re: golf ball toughts and reducing drag (3.00 / 0) (#2)
by cr8zy1van (salsa117@hotmail.com) on Mon Nov 14th, 2005 at 03:01:11 PM MST
(User Info)

You would do well by looking into vortex generators. Basically it reduces the seperation of air from the surface of your blade. This in turn lowers the drag. A quick Google search turned up this link:
http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml

You can also look at this interesting post earlier on the board. It deals with irregular shaped blades, based on nature (whale fins in this case)
http://www.fieldlines.com/story/2004/8/2/75837/29146

Searching the board will also bring tips for reducing tip losses for HAWT's, a lot of efficiency can be gained by paying extra attention to one's tips. eg:http://www.fieldlines.com/story/2005/7/27/174854/382


In aviation, vortex generators are sometimes seen as a band aid to fix bad design, but since not all of us has perfect construction/testing facilities, these may be of a little help.



Re: golf ball toughts and reducing drag (3.00 / 0) (#3)
by Ungrounded Lightning Rod on Mon Nov 14th, 2005 at 09:12:07 PM MST
(User Info)

And if you follow those links you'll see that the air detaches from a sphere when it's about halfway around it, leaving a low-pressure region behind the spehere and a high-pressure region ahead of it.  (The illustration shows a sphere with wind from nine oclock detaching about 11:30).  Dimples work by trading a little extra drag for keeping the air attached to maybe 1:30 to 2:00, which improves things by creating a high-pressure ring on the backside that more than compensates for the extra drag.

But in the same articles you se that on a well-designed airfoil the air remains attached to the trailing edge or very near it, where the airfoil is narrowing down to a sharp point.  So detached airflow creates only a very narrow region of vacuum.  Reducing that provides little reduction in drag - probably nowhere near enough to pay for the extra drag of the dimples.

(I wonder if there's something you can do with dimples to improve attachment on part of the cycle of a drag-type VAWT that would give you a net gain.)

[ Parent ]



Re: golf ball toughts and reducing drag (3.00 / 0) (#4)
by elvin1949 (elvin1949@yahoo.com) on Mon Nov 14th, 2005 at 10:50:28 PM MST
(User Info)

ULR
 I think Rotornuts is working on that.
later
elvin

[ Parent ]


Re: golf ball toughts and reducing drag (3.00 / 0) (#5)
by finnsawyer on Tue Nov 15th, 2005 at 09:44:40 AM MST
(User Info)

O.K.  So what happens to the air flow when you attach a cone shape to the down wind side of the sphere.  I believe it cuts the force on the sphere in half and is the reason for streamlining.  And what if we place our windmill blades concentrically at the junction point of the sphere and cone?
GeoM
[ Parent ]


Re: golf ball toughts and reducing drag (3.00 / 0) (#6)
by iFred (ifred2006@yahoo.com) on Tue Nov 15th, 2005 at 10:25:29 AM MST
(User Info)

I did find the links very interesting and informative. It explained allot including other forces, drags and buffer zones. Seems there is a velocity threshold however with a textured surface, behond which you loose control. Not sure what this means right now, going to sit and think for a bit till I get it. There is something nagging me about it, not sure what.
>> all energy used to produce this comment or post came from solar and wind energy! It works!


golf ball toughts and reducing drag | 6 comments (6 topical, 0 editorial)
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