Heads... Intake and Exhaust Port Surface Texture
10-18-2005, 02:41 PM
#21
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Originally Posted by Nine Ball
...For example, take a golf ball. What are those dimples on the surface for? They are on the ball to help the flow "hug" the surface of the ball, which greatly reduces the boundary layer of flow across the surface. This creates less turbulence across the surface. Without the dimples, the golf ball would only fly about 2/3 of the distance it normally does. Thats why you never see smooth golf *****!...
Originally Posted by Nine Ball
...Airplanes use the shape of their wings to create lift, they aren't as concerned with surface texture. They are also streamlined by design, and do not create much drag. Same with cars, who would buy a dimpled body car? Some item designs are driven by aesthetics, some by function over form...
You'd be surprised how much drag an airplane can create.
10-18-2005, 05:58 PM
#22
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WOW! many Q&As, I seen an article in a magazine about ports for Formula 1 heads, they flowed a medium thru the port and micro cameras recorded how flow went , then use of CNC left the grooves, about .060 wide, so as to follow the flow lines thru the whole port, looked kind of weird, but then again they may not know much about engines.---- 900hp 180cu.in. N/A no power adders. just a thought and I prefer 9-***** theorys
10-18-2005, 06:08 PM
#23
Originally Posted by Fandango
I'm going to have to disagree with this. The dimples on a golf ball are there to make it fly further, due to lift. The spining of the golf ball, created by the impact with the club spins the top of the ball backwards, which accelerates the air over the top and lowers the air pressure above the ball. The ball spinning forward on the bottom will increase the pressure of the air and give the ball lift.
The purpose of the dimples is to do just that--to create a rough surface that promotes an early transition to a turbulent boundary layer. This turbulence helps the flow remain attached to the surface of the ball and reduces the size of the separated wake so as to reduce the drag it generates in flight. When the drag is reduced, the ball flies farther.
Taken from:
http://www.aerospaceweb.org/question...cs/q0215.shtml
10-18-2005, 06:35 PM
#24
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The golfball example is not applicable to this situation, it only applies to a sphere moving through a fluid. All the dimples do is allow the air to "stick" to the ball.
Main selling point of most light aircraft are their crusing speeds, if any of this were true, why is there not a single production aircraft that uses this dimple magic?
Main selling point of most light aircraft are their crusing speeds, if any of this were true, why is there not a single production aircraft that uses this dimple magic?
Last edited by Phoenix64; 10-18-2005 at 08:05 PM.
10-18-2005, 07:08 PM
#25
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Originally Posted by Phoenix64
The golfball example is not applicable to this situation, it only applies to a sphere moving through a fluid. And you guys have it wrong anyways. All the dimples do is prevent the air from "sticking" to the ball. Very simple concept, and only works with spheres.
Main selling point of most light aircraft are their crusing speeds, if any of this were true, why is there not a single production aircraft that uses this dimple magic?
Main selling point of most light aircraft are their crusing speeds, if any of this were true, why is there not a single production aircraft that uses this dimple magic?
What do you have to back up your theories?
10-18-2005, 07:51 PM
#26
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Good visual refernce.
http://wings.avkids.com/Book/Sports/...r/golf-01.html
I'm a dumbass, ports aren't straight.
Now that I think more about it, the dimples would provide an advantage at sharp turns, allowing the boudry layer to stick, but on straight portions it just adds drag maybe?
http://wings.avkids.com/Book/Sports/...r/golf-01.html
I'm a dumbass, ports aren't straight.
Now that I think more about it, the dimples would provide an advantage at sharp turns, allowing the boudry layer to stick, but on straight portions it just adds drag maybe? Last edited by Phoenix64; 10-18-2005 at 08:03 PM.
10-18-2005, 08:36 PM
#27
surface texture always affects the thickness of the boundary layer, no matter what shape the surface is. In school, we did our rough calculations using a simple 2D tile with varying surface textures. The idea is to apply the calculations derived from the 2D flow across that surface and apply it across an entire 3D body made up of small tiles. Look up the details on subsonic airflow inside of a pipe, its a more accurate representation of an intake port flow.
10-18-2005, 09:22 PM
#28
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Originally Posted by Phoenix64
The golfball example is not applicable to this situation, it only applies to a sphere moving through a fluid. And you guys have it wrong anyways. All the dimples do is prevent the air from "sticking" to the ball. Very simple concept, and only works with spheres.
Main selling point of most light aircraft are their crusing speeds, if any of this were true, why is there not a single production aircraft that uses this dimple magic?
Main selling point of most light aircraft are their crusing speeds, if any of this were true, why is there not a single production aircraft that uses this dimple magic?
Why dont you see it on a wing? i'll tell you why! The flow separation at the trailing edge of a wing is nearly non exsistant... unless it is induced and wanted by the pilot because of the streamlined design of the wing. On a poorly designed wing... yes.. the dimples would help
10-18-2005, 09:23 PM
#29
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Essentually what Nine Ball is trying to get you to understand is fluid friction. The dimples are a necessary evil of you will. If you look at the diagram of the golf ***** you'll notice that the wake behind the golf ball with the dimples is less than the ball without. In the wake the air is also stagnant and creates a high pressure volume. The pressure differential between the back of the ball and the front of the ball slows it down. The dimples actually create friction and that friction helps the air "wrap" around the ball and reduce the wake, as the diagram shows. As a result, the pressure differential is reduced.
Depending on the situation, the negative can be used as a positive. In head flow the friction helps the air "wrap" around the ports allowing a greater volume of air to be moved through the port that otherwise would not have been able to.
Depending on the situation, the negative can be used as a positive. In head flow the friction helps the air "wrap" around the ports allowing a greater volume of air to be moved through the port that otherwise would not have been able to.
10-18-2005, 09:42 PM
#30
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So...... you have a layer of air (liquid, in the past I did some study on the Tesla Turbine for my nitro RC cars) that sticks to the port walls if they are prepared with a controlled scratching, and that enables the whole environment to be more "slippery" for a volume of air to pass through with greater velocity. Is that right? Does it basically "wet" the walls?
10-18-2005, 10:36 PM
#31
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Originally Posted by Nine Ball
You can disagree with it, but you'd be partially wrong. The dimples are not there to create lift, its the spinning motion of the ball that creates lift. The dimples are there to reduce drag. A golf ball has no lift if it isn't spinning. Golfers learn to strike the ball and create spin, to control the hook, slice, and lift. The ball itself does not create lift, it is forced to create lift. Here is a summarizing statement from that link I posted above:
The purpose of the dimples is to do just that--to create a rough surface that promotes an early transition to a turbulent boundary layer. This turbulence helps the flow remain attached to the surface of the ball and reduces the size of the separated wake so as to reduce the drag it generates in flight. When the drag is reduced, the ball flies farther.
Taken from:
http://www.aerospaceweb.org/question...cs/q0215.shtml
The purpose of the dimples is to do just that--to create a rough surface that promotes an early transition to a turbulent boundary layer. This turbulence helps the flow remain attached to the surface of the ball and reduces the size of the separated wake so as to reduce the drag it generates in flight. When the drag is reduced, the ball flies farther.
Taken from:
http://www.aerospaceweb.org/question...cs/q0215.shtml
I think with your original post, my first and your reply we covered the idea correctly. I could have worded it better. spinning + dimples = fly further.
Have you seen the golf ball that was baned from the PGA? It had a set of larger dimples on one plane of the ball, to make it always fly straight.
Partially worong means partially right too.
The same idea can bee seen in Mitsu lancers which have vortex generators at the rear of the roof, which essentially grab the air flowing over the roof and pull it down over the rear window to better act on the rear wing.
10-18-2005, 10:56 PM
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The air always adheres to the walls, no matter how smooth it is. Thats a given, especially in low speed subsonic environments. There is nothing that is more "slippery", the increased friction is being used in a positive manner.
The higher the friction, read: rougher walls, the more the fluid adheres to the walls. This friction helps "pull" the air around the corners. Essentially what you're doing is shaping the flow so you can move it faster around corners. It has a lot to do with the shearing involved with the air.
There is a lot more to head flow. This is just one of MANY considerations and processes going on.
The higher the friction, read: rougher walls, the more the fluid adheres to the walls. This friction helps "pull" the air around the corners. Essentially what you're doing is shaping the flow so you can move it faster around corners. It has a lot to do with the shearing involved with the air.
There is a lot more to head flow. This is just one of MANY considerations and processes going on.
10-19-2005, 09:51 AM
#33
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Guys - Let's keep this on topic. I pasted some links for golf and airplane forums. Sorry, couldn't resist.
http://www.golflinks.com/Default.aspx?AffiliateId=3
http://www.simviation.com/cgi-bin/yabb/YaBB.cgi
http://www.golflinks.com/Default.aspx?AffiliateId=3
http://www.simviation.com/cgi-bin/yabb/YaBB.cgi
10-19-2005, 09:56 AM
#34
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Originally Posted by Fandango
The same idea can bee seen in Mitsu lancers which have vortex generators at the rear of the roof, which essentially grab the air flowing over the roof and pull it down over the rear window to better act on the rear wing.
The way a vortex generator works is to create turbulence along the trailing edge of an object in order to eliminate the laminar flow of air coming from the object. I'm trying to come up with a good example, but the only one I can come up with is inappropriate. Ever have a wet object you're trying to remove from another object and you have hydro suction? Air can do the same thing. If you have laminar flow over/around some objects, a suction is created at the trailing edge that adds a significant amount of drag. When you create a vortex, the turbulence "releases" the suction and eliminates the drag. That's the reason they're used on specific places on an aircraft. If it helps anyone, I'll go out and talk with one of our mechanics about the vortex generators on our aircraft and get a good technical description... well and to double check my information.
http://www.aerospaceweb.org/question...cs/q0009.shtml
On a car im thinking they make the air thats comming over the roof stick to th surface of the the body panels to 1)reduce drag, and 2)with the air sticking to the body of the car, I dont know how I really want to word this, but basicly puts the spoiler into better non turbulent air. With non turbulent air, im thinking the spoiler can make more down force with the same if not less drag.
If any of this is not correct, please excuse, im still a newb to this.
10-19-2005, 11:55 AM
#35
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Not sure how a vortex generator applies inside a port. Have a question. Assuming the data as far as smooth verses rough port walls is conclusive that rougher walls produce better flow numbers, which would be more ideal. A linear, crosshatch or a radial pattern?
Or would that make a difference at all? Also, what data is available as far as the finish grit? Even mirror polished (like mine) is full of craters on a magnified level.
Or would that make a difference at all? Also, what data is available as far as the finish grit? Even mirror polished (like mine) is full of craters on a magnified level.
10-20-2005, 01:46 AM
#36
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What about the swirl hump/bump thing that comes in stock LSx heads, as far as adding energy to the airstream and making the flow stick better?
Thats how it was explained to me. The "wing" sees smooth air, which allows it to create better downforce.
Originally Posted by stang killer
I was reading over a discussion of that a couple of days go.
Here is a good read that was posted in the thread
http://www.aerospaceweb.org/question...cs/q0009.shtml
On a car im thinking they make the air thats comming over the roof stick to th surface of the the body panels to 1)reduce drag, and 2)with the air sticking to the body of the car, I dont know how I really want to word this, but basicly puts the spoiler into better non turbulent air. With non turbulent air, im thinking the spoiler can make more down force with the same if not less drag.
If any of this is not correct, please excuse, im still a newb to this.
Here is a good read that was posted in the thread
http://www.aerospaceweb.org/question...cs/q0009.shtml
On a car im thinking they make the air thats comming over the roof stick to th surface of the the body panels to 1)reduce drag, and 2)with the air sticking to the body of the car, I dont know how I really want to word this, but basicly puts the spoiler into better non turbulent air. With non turbulent air, im thinking the spoiler can make more down force with the same if not less drag.
If any of this is not correct, please excuse, im still a newb to this.
10-20-2005, 01:39 PM
#37
On an LS1 we have the injector aimed at the intake valve. With the rough port wall, fuel mixture theory then wouldn't there only be benefit to rough port beyond the injector's line of site? What if you had smooth mirror finish from the entry of the intake port up to where the the injector sprays fuel, and then a rough wall from there to the intake valve? Would that create the best of both worlds? Or would it create all kinds of tumble/swirl problems with a portion (floor) of the port having faster smooth flow and then past the injector slower flow from the rough wall?
10-21-2005, 08:01 AM
#39
Originally Posted by bootleg
Question: What would be the better option for the throttle body surface? Mine is polished at the moment, would it be better if it were textured?
10-21-2005, 11:53 AM
#40
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Originally Posted by 1CAMWNDR
No. The throttle body should be as smooth as possible I'd think since it is only moving air. You do not need to keep fuel suspended in the air stream so there is no need for a textured surface.