Racers/Aero guys please step in here and school me a little.
05-09-2010, 04:18 PM
#1
Le Mans Master
Thread Starter
Racers/Aero guys please step in here and school me a little.
Hello. Back to my projects and stuff, and I have a question. Is there more air pressure on the vertical rear of a c5 corvette (taillights/license plate area), or under the rear (right behind the rear suspension cradle)?
I've noticed through many phases of experimentation that above 80 mph the pressure seems to be tremendous, much much more than just a few mph less. Can I significantly change the pressure under the rear by installing a big cut plate of fiberglass or something to make it completely flat from the rear sus. cradle and inbetween the mufflers all the way back to the mufflers/exhaust tips? Basically I'm thinking of a sheet about 24" wide and 20" long, a 'diffuser' of sorts, home made, painted black. Something that won't catch on fire from the heat of the exhaust components.
Can anyone point me to some good aero reading?
Tia.
I've noticed through many phases of experimentation that above 80 mph the pressure seems to be tremendous, much much more than just a few mph less. Can I significantly change the pressure under the rear by installing a big cut plate of fiberglass or something to make it completely flat from the rear sus. cradle and inbetween the mufflers all the way back to the mufflers/exhaust tips? Basically I'm thinking of a sheet about 24" wide and 20" long, a 'diffuser' of sorts, home made, painted black. Something that won't catch on fire from the heat of the exhaust components.
Can anyone point me to some good aero reading?
Tia.
05-09-2010, 04:45 PM
#2
McBeath's book is the best practical book I've read yet
Both areas you've referenced are low pressure, although the velocity magnitudes are polar opposites. Behind the car the pressure is low, although the air is stalled and extremely turbulent (on a stock bodied car). Below the car is low pressure extremely high velocity air, (and with a diffuser) close to laminar flow.
Rear diffuser will increase efficiency (lower drag) while also increasing rear downforce, so if your fabrication capabilities allow, a rear diffuser (even a simple one) is a great addition to a track car.
EDIT- If you want some additional reading/aero study, click through every page of Mulsanne's corner and study LMP/GTP design concepts. They do a great job of annotating photos and after you have a basic understanding of aero Mulsanne's is a fantastic resource
Both areas you've referenced are low pressure, although the velocity magnitudes are polar opposites. Behind the car the pressure is low, although the air is stalled and extremely turbulent (on a stock bodied car). Below the car is low pressure extremely high velocity air, (and with a diffuser) close to laminar flow.
Rear diffuser will increase efficiency (lower drag) while also increasing rear downforce, so if your fabrication capabilities allow, a rear diffuser (even a simple one) is a great addition to a track car.
EDIT- If you want some additional reading/aero study, click through every page of Mulsanne's corner and study LMP/GTP design concepts. They do a great job of annotating photos and after you have a basic understanding of aero Mulsanne's is a fantastic resource
Last edited by jhester; 05-09-2010 at 04:47 PM.
05-09-2010, 04:56 PM
#3
Burning Brakes
I am only begining with aero, but started with these two books:
Competition Car Aerodynamics by Simon McBeath, ISBN 9781844252305
Race Car Aerodynamics by Joseph Katz, ISBN 978 083760142 7
They were recommended in similar CF threads and other places I researched. It is a very technical subject, and getting accuracy and effectiveness in your specific application will be difficult. Know in advance that without testing in a wind tunnel, you most likely will not really know what your results are. Seat of the pants judgements will only carry you to very limited improvements in the tradeoff between downforce and drag.
Others with more knowledge can provide guidance in addition to you searching for CF threads on the subject.
Competition Car Aerodynamics by Simon McBeath, ISBN 9781844252305
Race Car Aerodynamics by Joseph Katz, ISBN 978 083760142 7
They were recommended in similar CF threads and other places I researched. It is a very technical subject, and getting accuracy and effectiveness in your specific application will be difficult. Know in advance that without testing in a wind tunnel, you most likely will not really know what your results are. Seat of the pants judgements will only carry you to very limited improvements in the tradeoff between downforce and drag.
Others with more knowledge can provide guidance in addition to you searching for CF threads on the subject.
05-09-2010, 05:07 PM
#4
Le Mans Master
Thread Starter
McBeath's book is the best practical book I've read yet
Both areas you've referenced are low pressure, although the velocity magnitudes are polar opposites. Behind the car the pressure is low, although the air is stalled and extremely turbulent (on a stock bodied car). Below the car is low pressure extremely high velocity air, (and with a diffuser) close to laminar flow.
Rear diffuser will increase efficiency (lower drag) while also increasing rear downforce, so if your fabrication capabilities allow, a rear diffuser (even a simple one) is a great addition to a track car.
EDIT- If you want some additional reading/aero study, click through every page of Mulsanne's corner and study LMP/GTP design concepts. They do a great job of annotating photos and after you have a basic understanding of aero Mulsanne's is a fantastic resource
Both areas you've referenced are low pressure, although the velocity magnitudes are polar opposites. Behind the car the pressure is low, although the air is stalled and extremely turbulent (on a stock bodied car). Below the car is low pressure extremely high velocity air, (and with a diffuser) close to laminar flow.
Rear diffuser will increase efficiency (lower drag) while also increasing rear downforce, so if your fabrication capabilities allow, a rear diffuser (even a simple one) is a great addition to a track car.
EDIT- If you want some additional reading/aero study, click through every page of Mulsanne's corner and study LMP/GTP design concepts. They do a great job of annotating photos and after you have a basic understanding of aero Mulsanne's is a fantastic resource
As far as the 'pressure' is concerned, let me be a little more clear on what I'm looking for/experiencing. I have a massive trans oil cooler installed in my trunk, in the deep well all the way down as deep as I could place it. I'm trying to feed and exhaust the cooler with air, and I'm probably going to take air in from the bottom of the well (cut holes in the trunk tub) and exhaust air out the license plate area. I'm wondering what direction the trans fan will need to turn in order to 'go with the flow'.
Now to the reason why I referred to the areas as "high" pressure. Right now at speeds above 80, the turbulence/high pressure (relatively speaking) pushes the heat from the trunk into the passenger bay (when the top is down on my convertible). This doesn't happen at lower speeds, but get above 80, and the heat is on!
Right now I'm thinking about placing a naca duct into a sheet of something about 24" wide and 20" long upside down, pulling air from under the car and up through the cooler, and then blowing it out a hole in the license plate area. Is my thinking correct on how air will flow in this scenario?
Last edited by 2000BSME; 05-09-2010 at 05:19 PM.
05-09-2010, 08:01 PM
#5
Team Owner
I am only begining with aero, but started with these two books:
Competition Car Aerodynamics by Simon McBeath, ISBN 9781844252305
Race Car Aerodynamics by Joseph Katz, ISBN 978 083760142 7
They were recommended in similar CF threads and other places I researched. It is a very technical subject, and getting accuracy and effectiveness in your specific application will be difficult. Know in advance that without testing in a wind tunnel, you most likely will not really know what your results are. Seat of the pants judgements will only carry you to very limited improvements in the tradeoff between downforce and drag.
Others with more knowledge can provide guidance in addition to you searching for CF threads on the subject.
Competition Car Aerodynamics by Simon McBeath, ISBN 9781844252305
Race Car Aerodynamics by Joseph Katz, ISBN 978 083760142 7
They were recommended in similar CF threads and other places I researched. It is a very technical subject, and getting accuracy and effectiveness in your specific application will be difficult. Know in advance that without testing in a wind tunnel, you most likely will not really know what your results are. Seat of the pants judgements will only carry you to very limited improvements in the tradeoff between downforce and drag.
Others with more knowledge can provide guidance in addition to you searching for CF threads on the subject.
good books easy to understand most of them.Plate area would be low pressure. Your exhaust will clear a plate in the rear or a diffuser?
Last edited by John Shiels; 05-09-2010 at 08:06 PM.