Mythbusters tests "golf ball" dimples

[ChazInMT]

Originally Posted by ACEV

Attached air flow is exactly what one needs to remove.

I'm out.

[gone7]

We have the MythBusters actual test, so show me Mr. Eaker's test and results. I don't mind being "edjumacated" with actual tests and results.

[aerohead]

Originally Posted by ACEV

See response at the dimples thread. But basically, what works is the proof, and theories are not proof of anything and never have been.

There is nothing theoretical about boundary layers.This is a fully mature element of the science of fluid mechanics,demonstrated time and time again with peer-reviewed analysis.
If MythBusters demonstrated a drag reduction it cannot be attributed to the drag reduction effect associated with the dimples on a golf ball.
Smooth automobiles already operate at super-critical Reynolds number with turbulent boundary layer without any aid from tripping devices.

[ChazInMT]

OK ACEV, you asked for it. Apparently I wasn't direct enough for you, so I'll say it all here in plain English.

You have no clue what you're talking about, stating that "Attached air flow is exactly what one needs to remove" is so far beyond stupid that it stymies the imagination. It is like saying we don't need air to breath in order to live. (Of course knowing you, you'll come up with some BS factoid regarding liquid breathing because that's the kind of person you are)

The picture was meant to suggest that even a bunch of morons understand that, without attached flow, an aerodynamically low drag Cd cannot be achieved.

It has been explained here in this thread that there are serious doubts as to the Mythbuster test, nobody else has tried to test it. Science (look it up) mandates that the person making the claim that "X" has an impact, back it up with facts. Science does not mandate that a person may make a claim that, "I think "X" has an impact now you prove why it isn't true."

Mr. Eakers is what we call an expert on the subject of Aerodynamics, his credentials speak for themselves, when he says dimples are crap, that's all I need to hear. I know better than to try and dispute what someone says when they have spent a career learning about it, and are in fact, highly paid professionals in their field of expertise.

The guy Aerohead you choose to go head to head with here is well-regarded in this Forum as an established authority on automobile aerodynamics, he has patiently tried to explain to you why dimples don't work. But you don't seem to be willing to acknowledge his effort as anything other than a bunch of, "Blah blah blah whatever, you still aren't proving why Mythbusters was wrong." You don't mention even 1 of the many talking points he establishes in your response.

You are proving to be a troll who tries to pass him/her self off as an expert somehow, and what you say has no credibility.

My "I'm out" comment really meant: This is my last communication with you, post whatever you want. I feel it is important to be sure that someone stumbling into this thread recognize that what you say is suspect and not worthy of consideration.

You're of course entitled to your opinion and you may believe whatever you wish, and feel free to post here all you want. I just want others to know your beliefs are not based on anything resembling proven facts.

And don't think I'm slamming you because you disagree with the established view here, I'm slamming you because you are disagreeing without backing up what you say or are willing to discuss anything other than, "Mythbusters is proof enough."

Keep in mind a golfball is a small spinning sphere in open air, a car is a lumpy shaped object moving along with solid ground 3 to 12 inches away. These facts make a huge difference in what the air does in relationship to their passage.

Again, I've had my final say, I'm out, for good, no more troll food from me.

[gone7]

@aerohead,
Thank you, but you failed to prove that "boundary layers" have any bearing on the topic. Perhaps you'd like to explain for the benefit of all.

@ChazInMT,
Now you're just being mean. You make all sorts of statements based upon assumption, but you fail to show proof for your position. It is too bad you cannot be courteous with your opinion.

Here are a few of your assumptions:
1 You stated, "Apparently I wasn't direct enough for you, so I'll say it all here in plain English.". Evidently, you thought you were needing to be direct. Instead, you should have been plain and clear and non-confrontational.

2. "stymies the imagination" Really? Could it be that your imagination is weak?

3. "even a bunch of morons understand that, without attached flow, an aerodynamically low drag Cd cannot be achieved.". Wow! You just alienated all astronautical engineers everywhere.

4. Your fourth paragraph is a straw-man argument. It is meaningless, in this context, that many have doubts. It is also weird that you would point out that no one else has tried to test it. How ironic. The fact is that if something has been tested and shown, then others must prove it wrong, not the other way around. Since you state that no one else has tested it, then what is your point? You take a very unscientific position.

5. I appreciate your statement of "that's all I need to hear". That may indeed be good enough for you. It isn't for me. I want to see practical proof of someone's position, not theoretical assumptions. Theories are not, and never will be, facts.

6. You need to let Eakers and aerohead speak for themselves. I don't believe they need you to be their apologist.

Need I go on?

It is amazing how people make the worst assumptions about others. Can't you just assume the best? After all, that is what common courtesy is all about. Why do you think you need to "slam" someone?

For everyone's benefit let me state that the cornerstone of scientific research has always been, and will always be, observation. One of the correct assumptions about that fact is that it should be easy to make clear to even a grade-school-educated person what one is trying to get across. When a person who claims to know scientific fact cannot do that, they are a failure and are ignorant of the facts; as Albert Einstein said.

It was never my intention to offend anyone, but rather try to nudge people into being able to prove what they say with observable and easily duplicated facts. That some feel they are being attacked only shows their inability to prove their points to the benefits of all those reading these posts.

This is a place to share one's knowledge and questions and experiences. Those who do not want to take part in a polite manner should not be involved. Please go troll somewhere else.

Thank you.

[aerohead]

Originally Posted by ACEV

@aerohead,
Thank you, but you failed to prove that "boundary layers" have any bearing on the topic. Perhaps you'd like to explain for the benefit of all.

@ChazInMT,
Now you're just being mean. You make all sorts of statements based upon assumption, but you fail to show proof for your position. It is too bad you cannot be courteous with your opinion.

Here are a few of your assumptions:
1 You stated, "Apparently I wasn't direct enough for you, so I'll say it all here in plain English.". Evidently, you thought you were needing to be direct. Instead, you should have been plain and clear and non-confrontational.

2. "stymies the imagination" Really? Could it be that your imagination is weak?

3. "even a bunch of morons understand that, without attached flow, an aerodynamically low drag Cd cannot be achieved.". Wow! You just alienated all astronautical engineers everywhere.

4. Your fourth paragraph is a straw-man argument. It is meaningless, in this context, that many have doubts. It is also weird that you would point out that no one else has tried to test it. How ironic. The fact is that if something has been tested and shown, then others must prove it wrong, not the other way around. Since you state that no one else has tested it, then what is your point? You take a very unscientific position.

5. I appreciate your statement of "that's all I need to hear". That may indeed be good enough for you. It isn't for me. I want to see practical proof of someone's position, not theoretical assumptions. Theories are not, and never will be, facts.

6. You need to let Eakers and aerohead speak for themselves. I don't believe they need you to be their apologist.

Need I go on?

It is amazing how people make the worst assumptions about others. Can't you just assume the best? After all, that is what common courtesy is all about. Why do you think you need to "slam" someone?

For everyone's benefit let me state that the cornerstone of scientific research has always been, and will always be, observation. One of the correct assumptions about that fact is that it should be easy to make clear to even a grade-school-educated person what one is trying to get across. When a person who claims to know scientific fact cannot do that, they are a failure and are ignorant of the facts; as Albert Einstein said.

It was never my intention to offend anyone, but rather try to nudge people into being able to prove what they say with observable and easily duplicated facts. That some feel they are being attacked only shows their inability to prove their points to the benefits of all those reading these posts.

This is a place to share one's knowledge and questions and experiences. Those who do not want to take part in a polite manner should not be involved. Please go troll somewhere else.

Thank you.

1. a smooth golf ball is subjected to a laminar boundary layer and suffers flow separation ahead of it's maximum cross-section,ending up with a large wake of low base pressure, high profile drag,and low range on the fairway.
2. dimples incorporated into the golf balls surface provide an artificial roughness which forces the laminar boundary layer to transition immediately over to a turbulent boundary layer which can remain attached to 115-degrees aft of the balls forward stagnation point.The added flow attachment allows for some static pressure regain before the flow does separate into a smaller wake of higher base pressure,allowing reduced profile drag and greater range on a fairway drive.(if the ball didn't spin,a small patch of sand glued to the front of the ball would provide the same necessary roughness as the dimples do).
3. in this context,the dimples are soley responsible for altering the boundary layer.That's all they do.
4. from the research of Osborne Reynolds it was discovered that at some 'critical' velocity,for a given object,the boundary layer will naturally transition from a laminar,to a turbulent type.
5. since Reynolds number is a function of a bodies length,as compared to it's velocity in a specific fluid,when calculated for automobiles it is found that all production motor vehicles will achieve critical Reynolds number near 20 mph,and from there on,their drag coefficient will be constant up to transonic flow velocities,where compression effects begin to enter the picture.
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6. the un-modified Ford Taurus in the MythBusters episode would have a fully turbulent boundary.
7. dimples,as a turblulent boundary layer-forcing technology would be superflous.Once the candle is lit you can put away the matches!
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8.if MythBusters measured a drag reduction it cannot be attributed to the effect dimples render to golf balls.
9. the axisymmetric jet pumping action of free flight which aids the golf ball is not present in ground-effect.
9.a reasonable explanation would be that the dimples acted as turbulators (as Mitsubishi's vortex-generators on their Lancer notch-back) which fed vortical kinetic energy into an aft-body flow field,allowing sustained attachment where the flow would have otherwise been lost.The drag of the dimples was overshadowed enough by the overall profile drag reduction to show a net benefit (as the VGs do with the Lancer).

[Grant-53]

We do well to remember what exactly is the scientific method. Briefly one makes an hypothesis. One devises an experiment that will either prove or disprove the hypothesis. One records the data that determines whether the hypothesis is proved or disproved. The experiment can be repeated and the results observed by others. At this point we may have some verifiable proof. Everything else is conjecture, argument, or assumption.

[Otto]

OK, so instead of dimples on a smooth belly pan, anybody tried taping or gluing on some vortex generators (like used on light aircraft wings, etc.) for A-B-A testing?

[Cd]

This is the bottom of the VW 'CC' midsection. I have also seen these on Audis which have excellent body panels complete with NACA ducting .
I believe some Jetta models have them as well.

Others here have speculated that these dimples are for rigidity.

Lexus had a pretty good PR move by claiming that the bottom of their LS430 had dimpled panels for reduced drag ( they even made a commercial of it )

The car had a .25 Cd

[gone7]

@aerohead #46,
Could you please put that into simple language so we all can understand? Your good points are very difficult to visualize.

Basically, what I have learned about a round shape going thru the air is that the fairly aerodynamic front is offset by they very unaerodynamic back side, therefore negating any beneficial affect. A Borg sphere in space has no such effect upon it since it is in a vacuum. One must assume that the ideas you put forward are having to do within atmospheric situations.

Also, once we have the test done, ie; by MythBusters, then the observable facts have been presented for all to see. The idea presented by Grant-53 must have his definition basis in observation. At this point we do know that dimples in a car body surface do increase fuel economy since we have all observed it.

If we feel that there is something missing in the given test, then it should be pointed out. If we feel that there are other things in the test making the fuel economy better, then they should be pointed out.

Short of that, the average person should be able to rely upon the fact of the fuel mileage improvement as demonstrated. If we overthink everything, we will never move forward.