Splitter design function and effects. Experience, Design knowledge?
08-21-2009, 02:20 PM
#91
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Thread Starter
Tony, then can you say with confidence that a layer of tape on our race car rear wings' leading edge can cause a 10% loss of lift? all the degrees in the world wont matter much unless you have studied some aero.
I fully understand the variables and that is why i mention them in qualifying such a statement. nothing posted here is specific as far as values, other than what was actually measured. (i.e. pressure readings at multiple points and through multiple positions of the sensor, and down force at the rear wing) nothing more , nothing less.
You mention effects of boundary layer dynamics , and yes, it is still debated today. wind tunnels and other imperical tests, generally prove concepts there.
mk
I fully understand the variables and that is why i mention them in qualifying such a statement. nothing posted here is specific as far as values, other than what was actually measured. (i.e. pressure readings at multiple points and through multiple positions of the sensor, and down force at the rear wing) nothing more , nothing less.
You mention effects of boundary layer dynamics , and yes, it is still debated today. wind tunnels and other imperical tests, generally prove concepts there.
mk
A technical thread based on assumptions that are speculative at best doesn't help anyone who comes to the board looking to understand more about a given topic. Sunday makes the point well, despite being shouted down by more speculative rambling.
As a caveat, I spent years racing sailplanes and have a couple of engineering degrees. I know a little fluid dynamics theory, and a fair bit about low speed aerodynamics. This is enough for me to stipulate that things are not always as they might appear. Sundays point about laminar flow is absolutely right, and this plus boundary layer effects make what might appear to be reasonable assumptions on first principles [eg differential pressure effects from simple flow over an airfoil] are often wrong.
As with most of these topics, saying it ten times won't make it any less wrong. What it will do is lead some readers to buy into the false logic. Say something wrong enough times and some segment of the audience will believe it. It must be hard for the mods to deal with, but I'd like to see threads like this one deleted. They do more harm than good.
As a caveat, I spent years racing sailplanes and have a couple of engineering degrees. I know a little fluid dynamics theory, and a fair bit about low speed aerodynamics. This is enough for me to stipulate that things are not always as they might appear. Sundays point about laminar flow is absolutely right, and this plus boundary layer effects make what might appear to be reasonable assumptions on first principles [eg differential pressure effects from simple flow over an airfoil] are often wrong.
As with most of these topics, saying it ten times won't make it any less wrong. What it will do is lead some readers to buy into the false logic. Say something wrong enough times and some segment of the audience will believe it. It must be hard for the mods to deal with, but I'd like to see threads like this one deleted. They do more harm than good.
08-21-2009, 02:23 PM
#92
Rennlist Member
Thread Starter
I saw that. It looked like a couple of them were routing air to the wheels, but generally, in looking at them again, the air flow is being routed up (air that probably is not captured by the splitter, and inlets there) or to the sides to increase downforce that grabs that air that is running under the car. Then there is the entire science of tunneling under the car as well and defusing to the rear. facinating!
mk
mk
The front diffusers are not there for cooling brakes. All these cars have very well ducted brakes with carbon fiber enclosures around the back of the disc and calipers.
The diffusers are there to make downforce...
Read this
http://www.mulsannescorner.com/ToyotaEagleMkIII-2.html
The diffusers are there to make downforce...
Read this
http://www.mulsannescorner.com/ToyotaEagleMkIII-2.html
08-21-2009, 02:32 PM
#93
Rennlist Member
Thread Starter
sorry, 8 years ago. 
That was my first race with POC, If I remember, I was leading the first few laps . by the way, the 220hp carreras , like vandecar were flying off the track and spinning when you came up to thunderhill later in the 2001 season. (ie vandecar and alarcon) so, dont give me that crap. there were two races. what place did you come in. what place did I come in?
EDIT: By the way, that was july 9th 2000 CCW POC race. I finished 4th with that spin. couldnt hang? I think I was on the front row in the race. July 10th next day. I know I finished in the same range, but I forgot where. How about you???
by the way, that was a car that was older than most of yours. it was a 260hp 1984 928 as well that weighed over 3000lbs and still had the stereo in it.
It did look good, didnt it! No aero at all. infact, the 928 was better aero going backward than forward!
mk
That was my first race with POC, If I remember, I was leading the first few laps . by the way, the 220hp carreras , like vandecar were flying off the track and spinning when you came up to thunderhill later in the 2001 season. (ie vandecar and alarcon) so, dont give me that crap. there were two races. what place did you come in. what place did I come in?
EDIT: By the way, that was july 9th 2000 CCW POC race. I finished 4th with that spin. couldnt hang? I think I was on the front row in the race. July 10th next day. I know I finished in the same range, but I forgot where. How about you???
by the way, that was a car that was older than most of yours. it was a 260hp 1984 928 as well that weighed over 3000lbs and still had the stereo in it.
It did look good, didnt it! No aero at all. infact, the 928 was better aero going backward than forward!
mk
Last edited by mark kibort; 08-21-2009 at 02:48 PM.
08-21-2009, 02:39 PM
#94
Mr. Excitement
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A technical thread based on assumptions that are speculative at best doesn't help anyone who comes to the board looking to understand more about a given topic. Sunday makes the point well, despite being shouted down by more speculative rambling.
As a caveat, I spent years racing sailplanes and have a couple of engineering degrees. I know a little fluid dynamics theory, and a fair bit about low speed aerodynamics. This is enough for me to stipulate that things are not always as they might appear. Sundays point about laminar flow is absolutely right, and this plus boundary layer effects make what might appear to be reasonable assumptions on first principles [eg differential pressure effects from simple flow over an airfoil] are often wrong.
As with most of these topics, saying it ten times won't make it any less wrong. What it will do is lead some readers to buy into the false logic. Say something wrong enough times and some segment of the audience will believe it. It must be hard for the mods to deal with, but I'd like to see threads like this one deleted. They do more harm than good.
As a caveat, I spent years racing sailplanes and have a couple of engineering degrees. I know a little fluid dynamics theory, and a fair bit about low speed aerodynamics. This is enough for me to stipulate that things are not always as they might appear. Sundays point about laminar flow is absolutely right, and this plus boundary layer effects make what might appear to be reasonable assumptions on first principles [eg differential pressure effects from simple flow over an airfoil] are often wrong.
As with most of these topics, saying it ten times won't make it any less wrong. What it will do is lead some readers to buy into the false logic. Say something wrong enough times and some segment of the audience will believe it. It must be hard for the mods to deal with, but I'd like to see threads like this one deleted. They do more harm than good.
It can get real thick when folks want to prove something rather than further the understanding on whole. I am right in the middle of building the air-dam, splitter and wing system for my car and was looking forward to what could have come from this thread. It has been taken over by the miss-spellers chapter of the Lets quibble about minutiae club.
08-21-2009, 02:40 PM
#95
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So SundayDriver, of all the folks that have posted here, these are my thoughts on their review of the forces and characteristics of a splitter. You say a few are right and a few are wrong. Of all below, do you agree with my assesement of their comments?
Again, Im still waiting for some factual data from you
Yes, good post
No, splitters are not wings (or air foils) and do not create a low pressure zone under the car.
No the splitter doesnt have most of its effect by pushing down on the surface, but by routing the high pressure air to the hood area through those vents or to the sides of the car
Again, Im still waiting for some factual data from you
Yes, good post
No, splitters are not wings (or air foils) and do not create a low pressure zone under the car.
No the splitter doesnt have most of its effect by pushing down on the surface, but by routing the high pressure air to the hood area through those vents or to the sides of the car
Since I am being quoted here...I want to make sure my post is clear...because you seem to be making an absolute of the dynamic I am stating in the post...but I certainly don't mean it that way.
Airfoil design, bernoulli, newton, ground affect, F=ma...etc.etc.etc. ALL have a roll to play here in describing what is happening. None are wrong, its just that lift is a very complicated physical process.
My point was that I believe (and some people much smarter than me relative to aerodynamics also believe) that a "flat" ie. zero angle of attack front spoiler generates most of its downforce by "accelerating" a greater "mass" of air up over the car which leads to a downward "force vector". HOWEVER, other aerodynamics are in play and if the spoiler does create a venturi affect underneath at the nose...it will also create a downforce with help from the "ground affect" which is a very complicated aerodynamic system. Edit - don't want or need to get into a detailed physics discussion on the ground effect.....
The reason I asked earlier about the amount of downforce on a front splitter is that many splitters are not mounted as securely as would be required if the entire additional downforce was borne solely by the splitter itself. It is not....this is what led me about a year ago to investigate this issue further and led to the "one molecule up/one down" example for that major component of the downforce.
I have no idea what portion of the downforce is due to increasing airmass flow up over the nose and what is due to low pressue under the spitter? It is likely entirely dependant on the design.
I would suggest you keep an open mind...as I did awhile back in better understanding the whole hp vs. torque debate.....awww crap!!! I had to say that didn't I
Last edited by DaveM993; 08-21-2009 at 03:01 PM.
08-21-2009, 02:55 PM
#96
sorry, 8 years ago.
That was my first race with POC, If I remember, I was leading the first few laps . by the way, the 220hp carreras , like vandecar were flying off the track and spinning when you came up to thunderhill later that season. (ie vandecar and alercon) so, dont give me that crap. there were two races. what place did you come in. what place did I come in?
by the way, that was a car that was older than most of yours. it was a 260hp 1984 928 as well that weighed over 3000lbs and still had the stereo in it.
It did look good, didnt it! No aero at all. infact, the 928 was better aero going backward than forward!
mk
That was my first race with POC, If I remember, I was leading the first few laps . by the way, the 220hp carreras , like vandecar were flying off the track and spinning when you came up to thunderhill later that season. (ie vandecar and alercon) so, dont give me that crap. there were two races. what place did you come in. what place did I come in?
by the way, that was a car that was older than most of yours. it was a 260hp 1984 928 as well that weighed over 3000lbs and still had the stereo in it.
It did look good, didnt it! No aero at all. infact, the 928 was better aero going backward than forward!
mk
"I was leading the first few laps"
I think you qualified second behind Vandecar and before Dino... I qualified fourth. Dino outbraked you into the first turn and I passed you on the outside of the turn prior to going up the hill on the first lap. You did not lead a single lap.
"by the way, the 220hp carreras , like vandecar were flying off the track and spinning when you came up to thunderhill later that season. (ie vandecar and alercon)
Vandecar won that race, never put a wheel wrong that day, let alone "flew off the track". Alarcon did not run that event. I am talking about that day, not "later that season".
"there were two races"
There was one Cup race that weekend, on Sunday
"what place did you come in"
2nd behind Vandecar
"what place did I come in"
don't know, don't care...behind me though
"that was a car that was older than most of yours it was a 260hp 1984 928 "
my car was a 220hp 1983 911SC, Vandecar's was a 1978 911 SC
"It did look good, didnt it!"
not really, too ricer for my taste
That it for me, gotta make some money...
AAAAH...I love the smell of ownage in the morning
08-21-2009, 02:59 PM
#97
Rennlist Member
Thread Starter
Hi Dave,
good post
yes, you are absolutely right. I too am still learning all the time of the concepts and theories and how they apply to our cars.
I do think that the 1/16th of an inch thickness splitter, if responsible for all the downforce, would vaporize and collapse. (oh wait, it did!
) But, it did with very little force. I used a thin material so I could truley asses what the forces were at racing speeds. turns out they were just as I expected and when i finally found the limit, it collapsed. (fixed with some cable support) when I added more splitter in 1" increments, I found the limit yet again. (It colapsed again) with more cables, it now looks like a 1920s biplane, but it works and works for the right reasons. Will it match the overpowering rear wing? thats left to be seen.
I think the pressure measurements were good at approximating the forces on the splitter in forms of differential pressure. I do however have to challenge you regarding the venturi effect under the car, with a large splitter. I think that with a splitter, there is no incentive (force, differential pressure) to allow the build up of pressuer to go under the car, as the air moves to differential pressure and the lower pressure is over the car. the air under the car is a straight shot from oncoming air and is at near ambient pressure, as I have measured. Im sure there is still some spill over from the splitter, but its not measureable so far. could be my car is too high in theair, or needs side skirts to keep the pressure down , or lower under the car. surely, that is the concept and im far from Panneling the underbody yet, but its a long term goal. probably more important at the faster tracks, but we are so slow out in nor cal.
mk
good post
yes, you are absolutely right. I too am still learning all the time of the concepts and theories and how they apply to our cars.
I do think that the 1/16th of an inch thickness splitter, if responsible for all the downforce, would vaporize and collapse. (oh wait, it did!
) But, it did with very little force. I used a thin material so I could truley asses what the forces were at racing speeds. turns out they were just as I expected and when i finally found the limit, it collapsed. (fixed with some cable support) when I added more splitter in 1" increments, I found the limit yet again. (It colapsed again) with more cables, it now looks like a 1920s biplane, but it works and works for the right reasons. Will it match the overpowering rear wing? thats left to be seen. I think the pressure measurements were good at approximating the forces on the splitter in forms of differential pressure. I do however have to challenge you regarding the venturi effect under the car, with a large splitter. I think that with a splitter, there is no incentive (force, differential pressure) to allow the build up of pressuer to go under the car, as the air moves to differential pressure and the lower pressure is over the car. the air under the car is a straight shot from oncoming air and is at near ambient pressure, as I have measured. Im sure there is still some spill over from the splitter, but its not measureable so far. could be my car is too high in theair, or needs side skirts to keep the pressure down , or lower under the car. surely, that is the concept and im far from Panneling the underbody yet, but its a long term goal. probably more important at the faster tracks, but we are so slow out in nor cal.
mk
Mark,
Since I am being quoted here...I want to make sure my post is clear...because you seem to be making an absolute of the dynamic I am stating in the post...but I certainly don't mean it that way.
Airfoil design, bernoulli, newton, ground affect, F=ma...etc.etc.etc. ALL have a roll to play here in describing what is happening. None are wrong, its just that lift is a very complicated physical process.
My point was that I believe (and some people much smarter than me relative to aerodynamics also believe) that a "flat" ie. zero angle of attack front spoiler generates most of its downforce by "accelerating" a greater "mass" of air up over the car which leads to a downward "force vector". HOWEVER, other aerodynamics are in play and if the spoiler does create a venturi affect underneath at the nose...it will also create a downforce with help from the "ground affect" which is a very complicated aerodynamic system. The reason an airfoil has lift close to the ground, that it would otherwise not have at a given speed to the relative air, is because the "pressure" difference now has an impact on the wing's lift due to the "immovable" ground beneath it. It is no longer accelerating a mass of air downward only, as is the true physical action an airfoil has that is not in ground affect. <<< unfortunately that was a huge simplification, but the point is valid...and I would rather not get into a physics debate.
The reason I asked earlier about the amount of downforce on a front splitter is that many splitters are not mounted as securely as would be required if the entire additional downforce was borne solely by the splitter itself. It is not....this is what led me about a year ago to investigate this issue further and led to the "one molecule up/one down" example.
I have no idea what portion of the downforce is due to increasing airmass flow up over the nose and what is due to low pressue under the spitter? It is likely entirely dependant on the design.
I would suggest you keep an open mind...as I did awhile back in better understanding the whole hp vs. torque debate.....awww crap!!! I had to say that didn't I
Since I am being quoted here...I want to make sure my post is clear...because you seem to be making an absolute of the dynamic I am stating in the post...but I certainly don't mean it that way.
Airfoil design, bernoulli, newton, ground affect, F=ma...etc.etc.etc. ALL have a roll to play here in describing what is happening. None are wrong, its just that lift is a very complicated physical process.
My point was that I believe (and some people much smarter than me relative to aerodynamics also believe) that a "flat" ie. zero angle of attack front spoiler generates most of its downforce by "accelerating" a greater "mass" of air up over the car which leads to a downward "force vector". HOWEVER, other aerodynamics are in play and if the spoiler does create a venturi affect underneath at the nose...it will also create a downforce with help from the "ground affect" which is a very complicated aerodynamic system. The reason an airfoil has lift close to the ground, that it would otherwise not have at a given speed to the relative air, is because the "pressure" difference now has an impact on the wing's lift due to the "immovable" ground beneath it. It is no longer accelerating a mass of air downward only, as is the true physical action an airfoil has that is not in ground affect. <<< unfortunately that was a huge simplification, but the point is valid...and I would rather not get into a physics debate.
The reason I asked earlier about the amount of downforce on a front splitter is that many splitters are not mounted as securely as would be required if the entire additional downforce was borne solely by the splitter itself. It is not....this is what led me about a year ago to investigate this issue further and led to the "one molecule up/one down" example.
I have no idea what portion of the downforce is due to increasing airmass flow up over the nose and what is due to low pressue under the spitter? It is likely entirely dependant on the design.
I would suggest you keep an open mind...as I did awhile back in better understanding the whole hp vs. torque debate.....awww crap!!! I had to say that didn't I
08-21-2009, 03:02 PM
#98
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They have NOTHING to do with cooling. Cooling of the brake rotors is done by routing an air hose to the center of the rotor (often using a sealed duct around the rotor center) so that the cooling air can expand out through the vent vanes. Cooling of the caliper is done by ducting air directly at it. No one uses a diffuser on the front splitter to cool the brakes of their car. You show a seriously lack of understanding of (or even familiarity with) anything approaching modern race car aero and cooling with this statement alone.
MK, have you read any Aero books? Also, you can rent a windtunnel pretty cheap in NC these days, just do that with a couple guys.
08-21-2009, 03:02 PM
#99
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Rob C, you win the prize!
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08-21-2009, 03:05 PM
#100
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I suspect that somewhere in your head, this post doesn't stand in stark contradiction to most every other post you've made on this thread, and for that, I applaud you.
08-21-2009, 03:09 PM
#101
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...and then turned into a 7 page lecture from the person originally asking for information, trying to prove to everyone just how much he knows about the subject.
08-21-2009, 03:19 PM
#102
Rennlist Member
Epic.
Professional Racing and Driving Coach
08-21-2009, 03:34 PM
#103
Rennlist Member
Thread Starter
This is the race we were you in. I suspect you were the black 911
http://www.youtube.com/watch?v=zCrMBe3j5ho
I thought we had 2 race that weekend. Im talking that weekend. Alarcon was not mentioned in that race. you have to read more carefully.
If the second race is where I spun,and you passed me, good for you .
Thunderhill there was one race and I have alarcon floundering. want to see that video? I had to start in the back after being 15lbs too light to the unfair 3100lbs spec for my old bugger. vandecar spun there too.
EDIT: what do you mean all the stickers?? I had only number panels made by a POC guy. too ricer? huh?? It was stock, like i said, even drove it to the track, and that was 9 years ago!! and drove it home!!
mk
http://www.youtube.com/watch?v=zCrMBe3j5ho
I thought we had 2 race that weekend. Im talking that weekend. Alarcon was not mentioned in that race. you have to read more carefully.
If the second race is where I spun,and you passed me, good for you .
Thunderhill there was one race and I have alarcon floundering. want to see that video? I had to start in the back after being 15lbs too light to the unfair 3100lbs spec for my old bugger. vandecar spun there too.
EDIT: what do you mean all the stickers?? I had only number panels made by a POC guy. too ricer? huh?? It was stock, like i said, even drove it to the track, and that was 9 years ago!! and drove it home!!
mk
Damn...not even close on anything...
"I was leading the first few laps"
I think you qualified second behind Vandecar and before Dino... I qualified fourth. Dino outbraked you into the first turn and I passed you on the outside of the turn prior to going up the hill on the first lap. You did not lead a single lap.
"by the way, the 220hp carreras , like vandecar were flying off the track and spinning when you came up to thunderhill later that season. (ie vandecar and alercon)
Vandecar won that race, never put a wheel wrong that day, let alone "flew off the track". Alarcon did not run that event. I am talking about that day, not "later that season".
"there were two races"
There was one Cup race that weekend, on Sunday
"what place did you come in"
2nd behind Vandecar
"what place did I come in"
don't know, don't care...behind me though
"that was a car that was older than most of yours it was a 260hp 1984 928 "
my car was a 220hp 1983 911SC, Vandecar's was a 1978 911 SC
"It did look good, didnt it!"
not really, too ricer for my taste
That it for me, gotta make some money...
AAAAH...I love the smell of ownage in the morning
"I was leading the first few laps"
I think you qualified second behind Vandecar and before Dino... I qualified fourth. Dino outbraked you into the first turn and I passed you on the outside of the turn prior to going up the hill on the first lap. You did not lead a single lap.
"by the way, the 220hp carreras , like vandecar were flying off the track and spinning when you came up to thunderhill later that season. (ie vandecar and alercon)
Vandecar won that race, never put a wheel wrong that day, let alone "flew off the track". Alarcon did not run that event. I am talking about that day, not "later that season".
"there were two races"
There was one Cup race that weekend, on Sunday
"what place did you come in"
2nd behind Vandecar
"what place did I come in"
don't know, don't care...behind me though
"that was a car that was older than most of yours it was a 260hp 1984 928 "
my car was a 220hp 1983 911SC, Vandecar's was a 1978 911 SC
"It did look good, didnt it!"
not really, too ricer for my taste
That it for me, gotta make some money...
AAAAH...I love the smell of ownage in the morning
08-21-2009, 03:38 PM
#104
Rennlist Member
Thread Starter
OMUSA I spent time in the design labs helping to develop specialized high flow cooling products and leadign edge digitaly controled motion systems.
You are just bitter because your hair is loose.
You are just bitter because your hair is loose.
Last edited by mark kibort; 08-21-2009 at 04:05 PM.
08-21-2009, 03:42 PM
#105
Rennlist Member
Thread Starter
which one do you want information out of?
Airplane performance stability and control
Jet propulsion
These are the only two books I can find in my bookcase right now from Aero classes.
The book im really looking for is the one I captured that wing profile from.
mk
Airplane performance stability and control
Jet propulsion
These are the only two books I can find in my bookcase right now from Aero classes.
The book im really looking for is the one I captured that wing profile from.
mk