Golfball Dimples on spaceships (and planes)?Would a dimpled heat shield reduce heat transfer during reentry?How much bigger could Earth be, before rockets would't work?Why is (conventional) ramjet not used for 2nd stage of rocket propulsion?Pollution by rockets and missilesDrawbacks and advantages of two slidable & rotatable control surfaces for BFS sized spaceshipsWhat are the pros and cons of Aerospike nosecones?Which components do we calculate for center of pressure? Where is the distance of components while computing the cp and cg of a rocket?
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Golfball Dimples on spaceships (and planes)?
Would a dimpled heat shield reduce heat transfer during reentry?How much bigger could Earth be, before rockets would't work?Why is (conventional) ramjet not used for 2nd stage of rocket propulsion?Pollution by rockets and missilesDrawbacks and advantages of two slidable & rotatable control surfaces for BFS sized spaceshipsWhat are the pros and cons of Aerospike nosecones?Which components do we calculate for center of pressure? Where is the distance of components while computing the cp and cg of a rocket?
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The best of us get stupid ideas which run through our heads day in and day out without finding an answer. That's why I came here:
A golf ball has dimples to reduce drag and increase flight distance (As you can read here). This works by creating a small "windshield" which causes the air to travel around the ball more smoothly and by doing this reduces drag.
What would happen if we were to apply this to a rocket or a lander? Does air pressure at Max Q change the dynamics so much that something like this won't have an effect? If it wouldn't work on rockets, could it improve airplanes?
A possible problem is the structural integrity being lowered or it even being impossible for the relatively thin hulls of a rocket body.
The effect on a rocket might also be small since, as the article states
This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake.
which implies that the effect comes from the end of the ball creating less turbulence (not where such dimples could be created in a rocket so maybe that's better for a plane?).
A German video shows this used in an engine block's air intake system to increase static pressure and air flow. So the spin of a golf ball is not needed for the effect.
rockets aerodynamics
edited Sep 6 at 1:16
Camille Goudeseune
2,89410 silver badges32 bronze badges
asked Sep 5 at 7:21
FlewriderFlewrider
3331 silver badge6 bronze badges
$endgroup$
add a comment
|
$begingroup$
The best of us get stupid ideas which run through our heads day in and day out without finding an answer. That's why I came here:
A golf ball has dimples to reduce drag and increase flight distance (As you can read here). This works by creating a small "windshield" which causes the air to travel around the ball more smoothly and by doing this reduces drag.
What would happen if we were to apply this to a rocket or a lander? Does air pressure at Max Q change the dynamics so much that something like this won't have an effect? If it wouldn't work on rockets, could it improve airplanes?
A possible problem is the structural integrity being lowered or it even being impossible for the relatively thin hulls of a rocket body.
The effect on a rocket might also be small since, as the article states
This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake.
which implies that the effect comes from the end of the ball creating less turbulence (not where such dimples could be created in a rocket so maybe that's better for a plane?).
A German video shows this used in an engine block's air intake system to increase static pressure and air flow. So the spin of a golf ball is not needed for the effect.
rockets aerodynamics
edited Sep 6 at 1:16
Camille Goudeseune
2,89410 silver badges32 bronze badges
asked Sep 5 at 7:21
FlewriderFlewrider
3331 silver badge6 bronze badges
$endgroup$
3
$begingroup$
see also space.stackexchange.com/questions/23490/…
$endgroup$
– JCRM
Sep 5 at 9:56
$begingroup$
@JRCM oh that question didn't get shown when I searched for golf ball and dimple. Thanks!
$endgroup$
– Flewrider
Sep 5 at 10:06
$begingroup$
I remembered it, but it took me a few goes to actually find it.
$endgroup$
– JCRM
Sep 5 at 10:09
2
$begingroup$
A slightly more accurate handwaving explanation of both dimples on spheres and vortex generators on airplane wings: they convert a few large turbulent eddies into many small ones, thereby reducing drag (and smoothing over the knee in the lift-drag curve).
$endgroup$
– Camille Goudeseune
Sep 6 at 1:00
1
$begingroup$
Mythbusters actually did this experiment with a car, and it had positive results if I recall. It would be pretty useless for anything traveling in the vacuum of space, but might have some effect on planes within an atmosphere. Just not sure if it's worth the extra weight and structural instability that might result. (MB did it by covering the entire car in about 3 inches of clay, significantly increasing its weight.)
$endgroup$
– Darrel Hoffman
Sep 6 at 19:02
add a comment
|
$begingroup$
The best of us get stupid ideas which run through our heads day in and day out without finding an answer. That's why I came here:
A golf ball has dimples to reduce drag and increase flight distance (As you can read here). This works by creating a small "windshield" which causes the air to travel around the ball more smoothly and by doing this reduces drag.
What would happen if we were to apply this to a rocket or a lander? Does air pressure at Max Q change the dynamics so much that something like this won't have an effect? If it wouldn't work on rockets, could it improve airplanes?
A possible problem is the structural integrity being lowered or it even being impossible for the relatively thin hulls of a rocket body.
The effect on a rocket might also be small since, as the article states
This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake.
which implies that the effect comes from the end of the ball creating less turbulence (not where such dimples could be created in a rocket so maybe that's better for a plane?).
A German video shows this used in an engine block's air intake system to increase static pressure and air flow. So the spin of a golf ball is not needed for the effect.
rockets aerodynamics
edited Sep 6 at 1:16
Camille Goudeseune
2,89410 silver badges32 bronze badges
asked Sep 5 at 7:21
FlewriderFlewrider
3331 silver badge6 bronze badges
$endgroup$
The best of us get stupid ideas which run through our heads day in and day out without finding an answer. That's why I came here:
A golf ball has dimples to reduce drag and increase flight distance (As you can read here). This works by creating a small "windshield" which causes the air to travel around the ball more smoothly and by doing this reduces drag.
What would happen if we were to apply this to a rocket or a lander? Does air pressure at Max Q change the dynamics so much that something like this won't have an effect? If it wouldn't work on rockets, could it improve airplanes?
A possible problem is the structural integrity being lowered or it even being impossible for the relatively thin hulls of a rocket body.
The effect on a rocket might also be small since, as the article states
This allows the smoothly flowing air to follow the ball's surface a little farther around the back side of the ball, thereby decreasing the size of the wake.
which implies that the effect comes from the end of the ball creating less turbulence (not where such dimples could be created in a rocket so maybe that's better for a plane?).
A German video shows this used in an engine block's air intake system to increase static pressure and air flow. So the spin of a golf ball is not needed for the effect.
rockets aerodynamics
rockets aerodynamics
edited Sep 6 at 1:16
Camille Goudeseune
2,89410 silver badges32 bronze badges
asked Sep 5 at 7:21
FlewriderFlewrider
3331 silver badge6 bronze badges
edited Sep 6 at 1:16
Camille Goudeseune
2,89410 silver badges32 bronze badges
asked Sep 5 at 7:21
FlewriderFlewrider
3331 silver badge6 bronze badges
edited Sep 6 at 1:16
Camille Goudeseune
2,89410 silver badges32 bronze badges
edited Sep 6 at 1:16
Camille Goudeseune
2,89410 silver badges32 bronze badges
edited Sep 6 at 1:16
Camille Goudeseune
2,89410 silver badges32 bronze badges
2,89410 silver badges32 bronze badges
asked Sep 5 at 7:21
FlewriderFlewrider
3331 silver badge6 bronze badges
asked Sep 5 at 7:21
FlewriderFlewrider
3331 silver badge6 bronze badges
asked Sep 5 at 7:21
FlewriderFlewrider
3331 silver badge6 bronze badges
3331 silver badge6 bronze badges
3
$begingroup$
see also space.stackexchange.com/questions/23490/…
$endgroup$
– JCRM
Sep 5 at 9:56
$begingroup$
@JRCM oh that question didn't get shown when I searched for golf ball and dimple. Thanks!
$endgroup$
– Flewrider
Sep 5 at 10:06
$begingroup$
I remembered it, but it took me a few goes to actually find it.
$endgroup$
– JCRM
Sep 5 at 10:09
2
$begingroup$
A slightly more accurate handwaving explanation of both dimples on spheres and vortex generators on airplane wings: they convert a few large turbulent eddies into many small ones, thereby reducing drag (and smoothing over the knee in the lift-drag curve).
$endgroup$
– Camille Goudeseune
Sep 6 at 1:00
1
$begingroup$
Mythbusters actually did this experiment with a car, and it had positive results if I recall. It would be pretty useless for anything traveling in the vacuum of space, but might have some effect on planes within an atmosphere. Just not sure if it's worth the extra weight and structural instability that might result. (MB did it by covering the entire car in about 3 inches of clay, significantly increasing its weight.)
$endgroup$
– Darrel Hoffman
Sep 6 at 19:02
add a comment
|
3
$begingroup$
see also space.stackexchange.com/questions/23490/…
$endgroup$
– JCRM
Sep 5 at 9:56
$begingroup$
@JRCM oh that question didn't get shown when I searched for golf ball and dimple. Thanks!
$endgroup$
– Flewrider
Sep 5 at 10:06
$begingroup$
I remembered it, but it took me a few goes to actually find it.
$endgroup$
– JCRM
Sep 5 at 10:09
2
$begingroup$
A slightly more accurate handwaving explanation of both dimples on spheres and vortex generators on airplane wings: they convert a few large turbulent eddies into many small ones, thereby reducing drag (and smoothing over the knee in the lift-drag curve).
$endgroup$
– Camille Goudeseune
Sep 6 at 1:00
1
$begingroup$
Mythbusters actually did this experiment with a car, and it had positive results if I recall. It would be pretty useless for anything traveling in the vacuum of space, but might have some effect on planes within an atmosphere. Just not sure if it's worth the extra weight and structural instability that might result. (MB did it by covering the entire car in about 3 inches of clay, significantly increasing its weight.)
$endgroup$
– Darrel Hoffman
Sep 6 at 19:02
3
3
$begingroup$
see also space.stackexchange.com/questions/23490/…
$endgroup$
– JCRM
Sep 5 at 9:56
$begingroup$
see also space.stackexchange.com/questions/23490/…
$endgroup$
– JCRM
Sep 5 at 9:56
$begingroup$
@JRCM oh that question didn't get shown when I searched for golf ball and dimple. Thanks!
$endgroup$
– Flewrider
Sep 5 at 10:06
$begingroup$
@JRCM oh that question didn't get shown when I searched for golf ball and dimple. Thanks!
$endgroup$
– Flewrider
Sep 5 at 10:06
$begingroup$
I remembered it, but it took me a few goes to actually find it.
$endgroup$
– JCRM
Sep 5 at 10:09
$begingroup$
I remembered it, but it took me a few goes to actually find it.
$endgroup$
– JCRM
Sep 5 at 10:09
2
2
$begingroup$
A slightly more accurate handwaving explanation of both dimples on spheres and vortex generators on airplane wings: they convert a few large turbulent eddies into many small ones, thereby reducing drag (and smoothing over the knee in the lift-drag curve).
$endgroup$
– Camille Goudeseune
Sep 6 at 1:00
$begingroup$
A slightly more accurate handwaving explanation of both dimples on spheres and vortex generators on airplane wings: they convert a few large turbulent eddies into many small ones, thereby reducing drag (and smoothing over the knee in the lift-drag curve).
$endgroup$
– Camille Goudeseune
Sep 6 at 1:00
1
1
$begingroup$
Mythbusters actually did this experiment with a car, and it had positive results if I recall. It would be pretty useless for anything traveling in the vacuum of space, but might have some effect on planes within an atmosphere. Just not sure if it's worth the extra weight and structural instability that might result. (MB did it by covering the entire car in about 3 inches of clay, significantly increasing its weight.)
$endgroup$
– Darrel Hoffman
Sep 6 at 19:02
$begingroup$
Mythbusters actually did this experiment with a car, and it had positive results if I recall. It would be pretty useless for anything traveling in the vacuum of space, but might have some effect on planes within an atmosphere. Just not sure if it's worth the extra weight and structural instability that might result. (MB did it by covering the entire car in about 3 inches of clay, significantly increasing its weight.)
$endgroup$
– Darrel Hoffman
Sep 6 at 19:02
add a comment
|
2 Answers
2
active
oldest
votes
$begingroup$
The dimples on a golfball is structurally the simplest iteration of a vortex generator. Vortex generators are most definitely used in practice to improve aircraft performance. (for some usage examples, see the tag over at Aviation.SE)
Turbulence will happen, that's the fundamental nature of aerodynamics. Controlling the transition into turbulence is the fundamental consideration in aerodynamic design, hence the inclusion of controlled vortex generators is naturally also a part of rocket design. (but they may not end up looking like dimples)
For specifics on how high velocity and pressure (Max Q happens around Mach 1-2) affects this in the context of rockets, the paper you are looking for is An Investigation of Cavity Vortex Generators in Supersonic Flow
answered Sep 5 at 9:18
HohmannfanHohmannfan
15.6k1 gold badge52 silver badges111 bronze badges
$endgroup$
$begingroup$
I like that for their simplicity they can double the distance that is covered! And thanks for the paper!
$endgroup$
– Flewrider
Sep 5 at 9:25
22
$begingroup$
Maybe worth making explicit that golf balls spend very little of their time supersonic.
$endgroup$
– Russell Borogove
Sep 5 at 16:12
3
$begingroup$
@RussellBorogove - And apparently with current golf club (and ball) technology, video here it is not possible to hit a golf ball at supersonic speeds.
$endgroup$
– Glen Yates
Sep 5 at 20:44
2
$begingroup$
An important difference when comparing balls to planes is that planes are expected to fly in a known orientation while balls aren't. Therefore, designers can place vortex generators in the chosen part of a plane, but they need to be spread evenly on the surface of a ball.
$endgroup$
– Pere
Sep 6 at 10:37
1
$begingroup$
You could imagine a ball with a tail - like when playing bedminton - which in turn would orient the ball. Of course the drag lessens the flight time of the ball and you'd have to argue about the definition of a ball. But good point @Pere
$endgroup$
– Flewrider
Sep 6 at 12:48
|
show 2 more comments
$begingroup$
When talking about air flow there are some different types/definitions to know:
- Laminar (uniform, smooth) flow
- Turbulent flow
You're correct when you say
This allows the smoothly flowing air to follow the ball's surface a
little farther around the back side of the ball, thereby decreasing
the size of the wake.
The reason that works is because the dimples trip the air flow around the ball into turbulent flow. If the ball was perfectly smooth, it would be more laminar.
For a blunt object, turbulent flow causes the trailing wake to be smaller. This reduces drag. For a non-blunt object, typically you want laminar flow to reduce drag, not turbulent flow. What happens when an airplane stalls? The flow over the wing goes from laminar to turbulent, and when it does it separates more from the wing. This causes a sudden loss in lift (because obviously the wings generate the lift for the airplane to stay in the air). Airplane wings are designed mostly for laminar flow (and yeah there are some strategically placed vortex generators as the other poster mentioned).
You don't want a blunt object flying at high speed or above the speed of sound. When you fly above the speed of sound, you form shock waves in the surrounding air and have much higher drag forces than when flying slower. Look at high speed aircraft. They're all much "pointier".
Rockets fly at like mach 3-20 or somewhere between 3 times to 20 times the speed of sound (Mach 13 is 17000 km/hr). An airliner flies at about Mach 0.86 (or maybe 550 mph).
So you can't really take an aerodynamic technique that works on a low speed blunt object (golf ball dimples), and apply it to a high speed streamlined object. The physics are much different and there are many factors to consider to reduce overall drag.
answered Sep 6 at 19:21
echoecho
311 bronze badge
$endgroup$
$begingroup$
Hypersonic re-entry capsules are blunt.
$endgroup$
– Organic Marble
Sep 6 at 20:00
$begingroup$
@OrganicMarble Right, they are blunt and they're meant to slow the capsule down as much as possible while at the same time surviving extremely high temperatures. That's a special use case that doesn't really apply to the main point of the discussion. Most of the time you want your aircraft to be faster and more efficient, not purposefully slower with higher drag as is the case with a re-entry vehicle.
$endgroup$
– echo
Sep 25 at 19:42
add a comment
|
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
The dimples on a golfball is structurally the simplest iteration of a vortex generator. Vortex generators are most definitely used in practice to improve aircraft performance. (for some usage examples, see the tag over at Aviation.SE)
Turbulence will happen, that's the fundamental nature of aerodynamics. Controlling the transition into turbulence is the fundamental consideration in aerodynamic design, hence the inclusion of controlled vortex generators is naturally also a part of rocket design. (but they may not end up looking like dimples)
For specifics on how high velocity and pressure (Max Q happens around Mach 1-2) affects this in the context of rockets, the paper you are looking for is An Investigation of Cavity Vortex Generators in Supersonic Flow
answered Sep 5 at 9:18
HohmannfanHohmannfan
15.6k1 gold badge52 silver badges111 bronze badges
$endgroup$
$begingroup$
I like that for their simplicity they can double the distance that is covered! And thanks for the paper!
$endgroup$
– Flewrider
Sep 5 at 9:25
22
$begingroup$
Maybe worth making explicit that golf balls spend very little of their time supersonic.
$endgroup$
– Russell Borogove
Sep 5 at 16:12
3
$begingroup$
@RussellBorogove - And apparently with current golf club (and ball) technology, video here it is not possible to hit a golf ball at supersonic speeds.
$endgroup$
– Glen Yates
Sep 5 at 20:44
2
$begingroup$
An important difference when comparing balls to planes is that planes are expected to fly in a known orientation while balls aren't. Therefore, designers can place vortex generators in the chosen part of a plane, but they need to be spread evenly on the surface of a ball.
$endgroup$
– Pere
Sep 6 at 10:37
1
$begingroup$
You could imagine a ball with a tail - like when playing bedminton - which in turn would orient the ball. Of course the drag lessens the flight time of the ball and you'd have to argue about the definition of a ball. But good point @Pere
$endgroup$
– Flewrider
Sep 6 at 12:48
|
show 2 more comments
$begingroup$
The dimples on a golfball is structurally the simplest iteration of a vortex generator. Vortex generators are most definitely used in practice to improve aircraft performance. (for some usage examples, see the tag over at Aviation.SE)
Turbulence will happen, that's the fundamental nature of aerodynamics. Controlling the transition into turbulence is the fundamental consideration in aerodynamic design, hence the inclusion of controlled vortex generators is naturally also a part of rocket design. (but they may not end up looking like dimples)
For specifics on how high velocity and pressure (Max Q happens around Mach 1-2) affects this in the context of rockets, the paper you are looking for is An Investigation of Cavity Vortex Generators in Supersonic Flow
answered Sep 5 at 9:18
HohmannfanHohmannfan
15.6k1 gold badge52 silver badges111 bronze badges
$endgroup$
$begingroup$
I like that for their simplicity they can double the distance that is covered! And thanks for the paper!
$endgroup$
– Flewrider
Sep 5 at 9:25
22
$begingroup$
Maybe worth making explicit that golf balls spend very little of their time supersonic.
$endgroup$
– Russell Borogove
Sep 5 at 16:12
3
$begingroup$
@RussellBorogove - And apparently with current golf club (and ball) technology, video here it is not possible to hit a golf ball at supersonic speeds.
$endgroup$
– Glen Yates
Sep 5 at 20:44
2
$begingroup$
An important difference when comparing balls to planes is that planes are expected to fly in a known orientation while balls aren't. Therefore, designers can place vortex generators in the chosen part of a plane, but they need to be spread evenly on the surface of a ball.
$endgroup$
– Pere
Sep 6 at 10:37
1
$begingroup$
You could imagine a ball with a tail - like when playing bedminton - which in turn would orient the ball. Of course the drag lessens the flight time of the ball and you'd have to argue about the definition of a ball. But good point @Pere
$endgroup$
– Flewrider
Sep 6 at 12:48
|
show 2 more comments
$begingroup$
The dimples on a golfball is structurally the simplest iteration of a vortex generator. Vortex generators are most definitely used in practice to improve aircraft performance. (for some usage examples, see the tag over at Aviation.SE)
Turbulence will happen, that's the fundamental nature of aerodynamics. Controlling the transition into turbulence is the fundamental consideration in aerodynamic design, hence the inclusion of controlled vortex generators is naturally also a part of rocket design. (but they may not end up looking like dimples)
For specifics on how high velocity and pressure (Max Q happens around Mach 1-2) affects this in the context of rockets, the paper you are looking for is An Investigation of Cavity Vortex Generators in Supersonic Flow
answered Sep 5 at 9:18
HohmannfanHohmannfan
15.6k1 gold badge52 silver badges111 bronze badges
$endgroup$
The dimples on a golfball is structurally the simplest iteration of a vortex generator. Vortex generators are most definitely used in practice to improve aircraft performance. (for some usage examples, see the tag over at Aviation.SE)
Turbulence will happen, that's the fundamental nature of aerodynamics. Controlling the transition into turbulence is the fundamental consideration in aerodynamic design, hence the inclusion of controlled vortex generators is naturally also a part of rocket design. (but they may not end up looking like dimples)
For specifics on how high velocity and pressure (Max Q happens around Mach 1-2) affects this in the context of rockets, the paper you are looking for is An Investigation of Cavity Vortex Generators in Supersonic Flow
answered Sep 5 at 9:18
HohmannfanHohmannfan
15.6k1 gold badge52 silver badges111 bronze badges
answered Sep 5 at 9:18
HohmannfanHohmannfan
15.6k1 gold badge52 silver badges111 bronze badges
answered Sep 5 at 9:18
HohmannfanHohmannfan
15.6k1 gold badge52 silver badges111 bronze badges
answered Sep 5 at 9:18
HohmannfanHohmannfan
15.6k1 gold badge52 silver badges111 bronze badges
15.6k1 gold badge52 silver badges111 bronze badges
$begingroup$
I like that for their simplicity they can double the distance that is covered! And thanks for the paper!
$endgroup$
– Flewrider
Sep 5 at 9:25
22
$begingroup$
Maybe worth making explicit that golf balls spend very little of their time supersonic.
$endgroup$
– Russell Borogove
Sep 5 at 16:12
3
$begingroup$
@RussellBorogove - And apparently with current golf club (and ball) technology, video here it is not possible to hit a golf ball at supersonic speeds.
$endgroup$
– Glen Yates
Sep 5 at 20:44
2
$begingroup$
An important difference when comparing balls to planes is that planes are expected to fly in a known orientation while balls aren't. Therefore, designers can place vortex generators in the chosen part of a plane, but they need to be spread evenly on the surface of a ball.
$endgroup$
– Pere
Sep 6 at 10:37
1
$begingroup$
You could imagine a ball with a tail - like when playing bedminton - which in turn would orient the ball. Of course the drag lessens the flight time of the ball and you'd have to argue about the definition of a ball. But good point @Pere
$endgroup$
– Flewrider
Sep 6 at 12:48
|
show 2 more comments
$begingroup$
I like that for their simplicity they can double the distance that is covered! And thanks for the paper!
$endgroup$
– Flewrider
Sep 5 at 9:25
22
$begingroup$
Maybe worth making explicit that golf balls spend very little of their time supersonic.
$endgroup$
– Russell Borogove
Sep 5 at 16:12
3
$begingroup$
@RussellBorogove - And apparently with current golf club (and ball) technology, video here it is not possible to hit a golf ball at supersonic speeds.
$endgroup$
– Glen Yates
Sep 5 at 20:44
2
$begingroup$
An important difference when comparing balls to planes is that planes are expected to fly in a known orientation while balls aren't. Therefore, designers can place vortex generators in the chosen part of a plane, but they need to be spread evenly on the surface of a ball.
$endgroup$
– Pere
Sep 6 at 10:37
1
$begingroup$
You could imagine a ball with a tail - like when playing bedminton - which in turn would orient the ball. Of course the drag lessens the flight time of the ball and you'd have to argue about the definition of a ball. But good point @Pere
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– Flewrider
Sep 6 at 12:48
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I like that for their simplicity they can double the distance that is covered! And thanks for the paper!
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– Flewrider
Sep 5 at 9:25
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I like that for their simplicity they can double the distance that is covered! And thanks for the paper!
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– Flewrider
Sep 5 at 9:25
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22
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Maybe worth making explicit that golf balls spend very little of their time supersonic.
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– Russell Borogove
Sep 5 at 16:12
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Maybe worth making explicit that golf balls spend very little of their time supersonic.
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– Russell Borogove
Sep 5 at 16:12
3
3
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@RussellBorogove - And apparently with current golf club (and ball) technology, video here it is not possible to hit a golf ball at supersonic speeds.
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– Glen Yates
Sep 5 at 20:44
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@RussellBorogove - And apparently with current golf club (and ball) technology, video here it is not possible to hit a golf ball at supersonic speeds.
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– Glen Yates
Sep 5 at 20:44
2
2
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An important difference when comparing balls to planes is that planes are expected to fly in a known orientation while balls aren't. Therefore, designers can place vortex generators in the chosen part of a plane, but they need to be spread evenly on the surface of a ball.
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– Pere
Sep 6 at 10:37
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An important difference when comparing balls to planes is that planes are expected to fly in a known orientation while balls aren't. Therefore, designers can place vortex generators in the chosen part of a plane, but they need to be spread evenly on the surface of a ball.
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– Pere
Sep 6 at 10:37
1
1
$begingroup$
You could imagine a ball with a tail - like when playing bedminton - which in turn would orient the ball. Of course the drag lessens the flight time of the ball and you'd have to argue about the definition of a ball. But good point @Pere
$endgroup$
– Flewrider
Sep 6 at 12:48
$begingroup$
You could imagine a ball with a tail - like when playing bedminton - which in turn would orient the ball. Of course the drag lessens the flight time of the ball and you'd have to argue about the definition of a ball. But good point @Pere
$endgroup$
– Flewrider
Sep 6 at 12:48
|
show 2 more comments
$begingroup$
When talking about air flow there are some different types/definitions to know:
- Laminar (uniform, smooth) flow
- Turbulent flow
You're correct when you say
This allows the smoothly flowing air to follow the ball's surface a
little farther around the back side of the ball, thereby decreasing
the size of the wake.
The reason that works is because the dimples trip the air flow around the ball into turbulent flow. If the ball was perfectly smooth, it would be more laminar.
For a blunt object, turbulent flow causes the trailing wake to be smaller. This reduces drag. For a non-blunt object, typically you want laminar flow to reduce drag, not turbulent flow. What happens when an airplane stalls? The flow over the wing goes from laminar to turbulent, and when it does it separates more from the wing. This causes a sudden loss in lift (because obviously the wings generate the lift for the airplane to stay in the air). Airplane wings are designed mostly for laminar flow (and yeah there are some strategically placed vortex generators as the other poster mentioned).
You don't want a blunt object flying at high speed or above the speed of sound. When you fly above the speed of sound, you form shock waves in the surrounding air and have much higher drag forces than when flying slower. Look at high speed aircraft. They're all much "pointier".
Rockets fly at like mach 3-20 or somewhere between 3 times to 20 times the speed of sound (Mach 13 is 17000 km/hr). An airliner flies at about Mach 0.86 (or maybe 550 mph).
So you can't really take an aerodynamic technique that works on a low speed blunt object (golf ball dimples), and apply it to a high speed streamlined object. The physics are much different and there are many factors to consider to reduce overall drag.
answered Sep 6 at 19:21
echoecho
311 bronze badge
$endgroup$
$begingroup$
Hypersonic re-entry capsules are blunt.
$endgroup$
– Organic Marble
Sep 6 at 20:00
$begingroup$
@OrganicMarble Right, they are blunt and they're meant to slow the capsule down as much as possible while at the same time surviving extremely high temperatures. That's a special use case that doesn't really apply to the main point of the discussion. Most of the time you want your aircraft to be faster and more efficient, not purposefully slower with higher drag as is the case with a re-entry vehicle.
$endgroup$
– echo
Sep 25 at 19:42
add a comment
|
$begingroup$
When talking about air flow there are some different types/definitions to know:
- Laminar (uniform, smooth) flow
- Turbulent flow
You're correct when you say
This allows the smoothly flowing air to follow the ball's surface a
little farther around the back side of the ball, thereby decreasing
the size of the wake.
The reason that works is because the dimples trip the air flow around the ball into turbulent flow. If the ball was perfectly smooth, it would be more laminar.
For a blunt object, turbulent flow causes the trailing wake to be smaller. This reduces drag. For a non-blunt object, typically you want laminar flow to reduce drag, not turbulent flow. What happens when an airplane stalls? The flow over the wing goes from laminar to turbulent, and when it does it separates more from the wing. This causes a sudden loss in lift (because obviously the wings generate the lift for the airplane to stay in the air). Airplane wings are designed mostly for laminar flow (and yeah there are some strategically placed vortex generators as the other poster mentioned).
You don't want a blunt object flying at high speed or above the speed of sound. When you fly above the speed of sound, you form shock waves in the surrounding air and have much higher drag forces than when flying slower. Look at high speed aircraft. They're all much "pointier".
Rockets fly at like mach 3-20 or somewhere between 3 times to 20 times the speed of sound (Mach 13 is 17000 km/hr). An airliner flies at about Mach 0.86 (or maybe 550 mph).
So you can't really take an aerodynamic technique that works on a low speed blunt object (golf ball dimples), and apply it to a high speed streamlined object. The physics are much different and there are many factors to consider to reduce overall drag.
answered Sep 6 at 19:21
echoecho
311 bronze badge
$endgroup$
$begingroup$
Hypersonic re-entry capsules are blunt.
$endgroup$
– Organic Marble
Sep 6 at 20:00
$begingroup$
@OrganicMarble Right, they are blunt and they're meant to slow the capsule down as much as possible while at the same time surviving extremely high temperatures. That's a special use case that doesn't really apply to the main point of the discussion. Most of the time you want your aircraft to be faster and more efficient, not purposefully slower with higher drag as is the case with a re-entry vehicle.
$endgroup$
– echo
Sep 25 at 19:42
add a comment
|
$begingroup$
When talking about air flow there are some different types/definitions to know:
- Laminar (uniform, smooth) flow
- Turbulent flow
You're correct when you say
This allows the smoothly flowing air to follow the ball's surface a
little farther around the back side of the ball, thereby decreasing
the size of the wake.
The reason that works is because the dimples trip the air flow around the ball into turbulent flow. If the ball was perfectly smooth, it would be more laminar.
For a blunt object, turbulent flow causes the trailing wake to be smaller. This reduces drag. For a non-blunt object, typically you want laminar flow to reduce drag, not turbulent flow. What happens when an airplane stalls? The flow over the wing goes from laminar to turbulent, and when it does it separates more from the wing. This causes a sudden loss in lift (because obviously the wings generate the lift for the airplane to stay in the air). Airplane wings are designed mostly for laminar flow (and yeah there are some strategically placed vortex generators as the other poster mentioned).
You don't want a blunt object flying at high speed or above the speed of sound. When you fly above the speed of sound, you form shock waves in the surrounding air and have much higher drag forces than when flying slower. Look at high speed aircraft. They're all much "pointier".
Rockets fly at like mach 3-20 or somewhere between 3 times to 20 times the speed of sound (Mach 13 is 17000 km/hr). An airliner flies at about Mach 0.86 (or maybe 550 mph).
So you can't really take an aerodynamic technique that works on a low speed blunt object (golf ball dimples), and apply it to a high speed streamlined object. The physics are much different and there are many factors to consider to reduce overall drag.
answered Sep 6 at 19:21
echoecho
311 bronze badge
$endgroup$
When talking about air flow there are some different types/definitions to know:
- Laminar (uniform, smooth) flow
- Turbulent flow
You're correct when you say
This allows the smoothly flowing air to follow the ball's surface a
little farther around the back side of the ball, thereby decreasing
the size of the wake.
The reason that works is because the dimples trip the air flow around the ball into turbulent flow. If the ball was perfectly smooth, it would be more laminar.
For a blunt object, turbulent flow causes the trailing wake to be smaller. This reduces drag. For a non-blunt object, typically you want laminar flow to reduce drag, not turbulent flow. What happens when an airplane stalls? The flow over the wing goes from laminar to turbulent, and when it does it separates more from the wing. This causes a sudden loss in lift (because obviously the wings generate the lift for the airplane to stay in the air). Airplane wings are designed mostly for laminar flow (and yeah there are some strategically placed vortex generators as the other poster mentioned).
You don't want a blunt object flying at high speed or above the speed of sound. When you fly above the speed of sound, you form shock waves in the surrounding air and have much higher drag forces than when flying slower. Look at high speed aircraft. They're all much "pointier".
Rockets fly at like mach 3-20 or somewhere between 3 times to 20 times the speed of sound (Mach 13 is 17000 km/hr). An airliner flies at about Mach 0.86 (or maybe 550 mph).
So you can't really take an aerodynamic technique that works on a low speed blunt object (golf ball dimples), and apply it to a high speed streamlined object. The physics are much different and there are many factors to consider to reduce overall drag.
answered Sep 6 at 19:21
echoecho
311 bronze badge
answered Sep 6 at 19:21
echoecho
311 bronze badge
answered Sep 6 at 19:21
echoecho
311 bronze badge
answered Sep 6 at 19:21
echoecho
311 bronze badge
311 bronze badge
$begingroup$
Hypersonic re-entry capsules are blunt.
$endgroup$
– Organic Marble
Sep 6 at 20:00
$begingroup$
@OrganicMarble Right, they are blunt and they're meant to slow the capsule down as much as possible while at the same time surviving extremely high temperatures. That's a special use case that doesn't really apply to the main point of the discussion. Most of the time you want your aircraft to be faster and more efficient, not purposefully slower with higher drag as is the case with a re-entry vehicle.
$endgroup$
– echo
Sep 25 at 19:42
add a comment
|
$begingroup$
Hypersonic re-entry capsules are blunt.
$endgroup$
– Organic Marble
Sep 6 at 20:00
$begingroup$
@OrganicMarble Right, they are blunt and they're meant to slow the capsule down as much as possible while at the same time surviving extremely high temperatures. That's a special use case that doesn't really apply to the main point of the discussion. Most of the time you want your aircraft to be faster and more efficient, not purposefully slower with higher drag as is the case with a re-entry vehicle.
$endgroup$
– echo
Sep 25 at 19:42
$begingroup$
Hypersonic re-entry capsules are blunt.
$endgroup$
– Organic Marble
Sep 6 at 20:00
$begingroup$
Hypersonic re-entry capsules are blunt.
$endgroup$
– Organic Marble
Sep 6 at 20:00
$begingroup$
@OrganicMarble Right, they are blunt and they're meant to slow the capsule down as much as possible while at the same time surviving extremely high temperatures. That's a special use case that doesn't really apply to the main point of the discussion. Most of the time you want your aircraft to be faster and more efficient, not purposefully slower with higher drag as is the case with a re-entry vehicle.
$endgroup$
– echo
Sep 25 at 19:42
$begingroup$
@OrganicMarble Right, they are blunt and they're meant to slow the capsule down as much as possible while at the same time surviving extremely high temperatures. That's a special use case that doesn't really apply to the main point of the discussion. Most of the time you want your aircraft to be faster and more efficient, not purposefully slower with higher drag as is the case with a re-entry vehicle.
$endgroup$
– echo
Sep 25 at 19:42
add a comment
|
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see also space.stackexchange.com/questions/23490/…
$endgroup$
– JCRM
Sep 5 at 9:56
$begingroup$
@JRCM oh that question didn't get shown when I searched for golf ball and dimple. Thanks!
$endgroup$
– Flewrider
Sep 5 at 10:06
$begingroup$
I remembered it, but it took me a few goes to actually find it.
$endgroup$
– JCRM
Sep 5 at 10:09
2
$begingroup$
A slightly more accurate handwaving explanation of both dimples on spheres and vortex generators on airplane wings: they convert a few large turbulent eddies into many small ones, thereby reducing drag (and smoothing over the knee in the lift-drag curve).
$endgroup$
– Camille Goudeseune
Sep 6 at 1:00
1
$begingroup$
Mythbusters actually did this experiment with a car, and it had positive results if I recall. It would be pretty useless for anything traveling in the vacuum of space, but might have some effect on planes within an atmosphere. Just not sure if it's worth the extra weight and structural instability that might result. (MB did it by covering the entire car in about 3 inches of clay, significantly increasing its weight.)
$endgroup$
– Darrel Hoffman
Sep 6 at 19:02