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Search: Posts Made By: banktoturn
Showing results 1 to 20 of 20
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Forum: Aerodynamics
02-02-2010, 10:02 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

The 'theory' has been tested & confirmed plenty of times. That won't be changed by the debate here.

banktoturn
Forum: Aerodynamics
12-16-2009, 02:58 PM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

Bundubasher,

It's more a question of the shape. Airplanes can be shaped in such a way that they don't suffer from flow separation under most conditions. This essentially means that they aren't...
Forum: Aerodynamics
12-14-2009, 11:48 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

Actually, dimples will tend to have more effect at lower speeds than higher speeds.
Forum: Aerodynamics
12-14-2009, 11:45 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

missil3,

How are you generating this data, and where did you get your "literature" values for CD? What you say is found in the literature is not correct. Try this site:

...
Forum: Aerodynamics
12-13-2009, 10:51 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

missil3,

I recommend that you take a minute to do a Google search for CD values of a sphere. You will see that the CD clearly decreases with increasing Reynolds numbers, unless some mechanism...
Forum: Aerodynamics
12-10-2009, 04:28 PM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

The results of your tests are the opposite of what one would expect. The CD of a sphere tends to go down as the Reynold's number increases, because the boundary layer becomes turbulent earlier at...
Forum: Aerodynamics
12-03-2009, 10:23 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

Hi Louis9624,

Actually, the situation is the opposite of your description. Without dimples, the flow at the surface of the ball tends to be laminar, which allows it to separate, or break free,...
Forum: Aerodynamics
11-07-2009, 10:08 PM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

iflircaircraft,

Lift and drag are independent of gravity. In the absence of gravity, an airplane could still fly tight turns (loops). The force responsible would be lift. For a given thrust,...
Forum: Aerodynamics
11-06-2009, 06:04 PM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

Is there a question in there somewhere? Perhaps you could find some subjects and predicates, and arrange them into some coherent sentences. For goodness sake, if you're here to communicate with...
Forum: Aerodynamics
11-06-2009, 02:51 PM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

You may have a group of sticklers in mind who don't agree on the definitions of different components of drag, but they are unambiguously defined. That some people get it wrong doesn't change that.
...
Forum: Aerodynamics
11-02-2009, 10:17 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

topspeed,

It's possible that dimples would help reduce drag for that shape, but it depends on several things. If the flow tends to separate early, say around the top edge of the backlight, then...
Forum: Aerodynamics
10-28-2009, 11:18 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

That's really interesting. Does that mean that some air is vented from a high-pressure area to the base?
Forum: Aerodynamics
10-28-2009, 09:38 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

lnewqban,

Dimples aren't helpful in every situation. The drag of a sphere is strongly affected by the location of the flow separation. Dimples force the boundary layer to be turbulent, which...
Forum: Aerodynamics
10-27-2009, 01:16 PM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

[quote]ORIGINAL: dick Hanson




That's a viable guess, but legal golf balls are restricted in terms of their initial velocity when leaving the club head. With that limitation, the spin...
Forum: Aerodynamics
10-27-2009, 12:37 PM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

It's a reasonable guess that the older balls may not get as much energy from the club. I suppose we could rely on the initial observations of smooth gutta-percha balls versus scuffed ones, to...
Forum: Aerodynamics
10-27-2009, 11:24 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

hugger-4641,

I don't know for sure, but my guess is that the dimples are more important. I base this guess on 3 things: 1) my observation that very worn range balls don't fly as far as new ones...
Forum: Aerodynamics
10-27-2009, 10:42 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

Those darn professors! The CD numbers in my post are measured values, and I've found several web pages with similar values. I haven't found clear references to measured lift values, and the one in...
Forum: Aerodynamics
10-27-2009, 09:05 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

hugger-4641,

The dimpled ball would go further, which is why they put dimples on them.

banktoturn
Forum: Aerodynamics
10-27-2009, 09:02 AM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

Sport_Pilot,

No web pages needed until you asked for numbers. I just found some nominal values for the coefficient of drag: the laminar CD for a sphere is 0.4 - 0.47, and the turbulent CD for a...
Forum: Aerodynamics
10-26-2009, 03:33 PM
Replies: 229
Views: 28,125
Posted By banktoturn

RE: Golf ball dimples

Dbacque's first post is right on, apart from the general assertion that "turbulent airflow over a surface creates less drag". For a sphere, or other 'blunt' shapes, the drag is strongly affected by...
Showing results 1 to 20 of 20


 
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