Aerodynamic Discussion Thread
12-21-2014, 01:38 PM
#644
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I've often wondered if you could do both... Using the picture of the c6r vette as a reference. One could use the a diffusor like this, albeit a large one with more clear space behind it... and drop an aerofoil in behind/beneath it. Although I'm not sure one could achieve this with the proper angle of egress for the speeds for our typical none of the horsepower speeds.
the C7 used a similar setup but it was adjustable instead of fixed angle.
Just to show the evolution - The c5r had a more standard diffusor/strake setup that us meer mortals are more familiar with.
the C7 used a similar setup but it was adjustable instead of fixed angle.
Just to show the evolution - The c5r had a more standard diffusor/strake setup that us meer mortals are more familiar with.
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12-21-2014, 02:07 PM
#645
I've often wondered if you could do both... Using the picture of the c6r vette as a reference. One could use the a diffusor like this, albeit a large one with more clear space behind it... and drop an aerofoil in behind/beneath it. Although I'm not sure one could achieve this with the proper angle of egress for the speeds for our typical none of the horsepower speeds.
the C7 used a similar setup but it was adjustable instead of fixed angle.
Just to show the evolution - The c5r had a more standard diffusor/strake setup that us meer mortals are more familiar with.
the C7 used a similar setup but it was adjustable instead of fixed angle.
Just to show the evolution - The c5r had a more standard diffusor/strake setup that us meer mortals are more familiar with.
edit--check out that massive transaxle cooler with fan on the back of the Corvette.
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12-21-2014, 04:16 PM
#647
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Wasn't the change to the new-style short/wide flat rear planes due to a change in the rules by IMSA that no longer allowed diffusers with vertical fins?
So an airfoil builds pressure on the top surface, and for a diffuser you want less pressure/faster moving air on the underside. These two interests clash a bit. A pressure map of a typical diffuser shows the majority of the vertical force happening at the beginning of the angle change, so that is where you would least want to have an airfoil undernath - that's ok because that wouldn't work anyways as there is no ground clearance there.
So then looking further back... even though the forces are towards the front of the diffuser, the air's behavior all along the length of the diffuser dictate how effective it is. Placing the airfoil underneath the diffuser surface near the back (like the BMW on the last page) is going to create an obstruction to the diffuser's airflow as the topside of the airfoil slows air and builds pressure in the region between it and the diffuser.
I think the best application of the idea would be for the airfoil to be placed behind the diffuser exit. Use a wing with swan-neck style mounts or mount via endplates, suspended from the rear of the car, and the wing aoa adjusted for the airflow angle coming out of the diffuser. This way, the pressure build up above the wing can occupy the space behind the center of the rear of the car, and the diffuser's function isn't jeapordized.
That's how I'd do it at least.. but if the concept can work or not? Only one way for someone to find out.
-Ryan
So an airfoil builds pressure on the top surface, and for a diffuser you want less pressure/faster moving air on the underside. These two interests clash a bit. A pressure map of a typical diffuser shows the majority of the vertical force happening at the beginning of the angle change, so that is where you would least want to have an airfoil undernath - that's ok because that wouldn't work anyways as there is no ground clearance there.
So then looking further back... even though the forces are towards the front of the diffuser, the air's behavior all along the length of the diffuser dictate how effective it is. Placing the airfoil underneath the diffuser surface near the back (like the BMW on the last page) is going to create an obstruction to the diffuser's airflow as the topside of the airfoil slows air and builds pressure in the region between it and the diffuser.
I think the best application of the idea would be for the airfoil to be placed behind the diffuser exit. Use a wing with swan-neck style mounts or mount via endplates, suspended from the rear of the car, and the wing aoa adjusted for the airflow angle coming out of the diffuser. This way, the pressure build up above the wing can occupy the space behind the center of the rear of the car, and the diffuser's function isn't jeapordized.
That's how I'd do it at least.. but if the concept can work or not? Only one way for someone to find out.
-Ryan
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12-22-2014, 06:27 PM
#648
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So this might not be aero related but, it is my thread. I think it's cool how the process of a test vehicle. So when I was at the Porsche Museum in Stuttgart Germany they had there Porsche 918 test car on display. So here are my pics
Production 918
918 Test Car
Production 918
918 Test Car
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01-17-2015, 11:00 AM
#651
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On an F1 car, upwards of 50% of the downforce can come from the underbody/diffuser, and that is with significant limitations on what they can do. An unrestricted car built around the most effective floor/tunnels their engineers dream up could produce incredible downforce without the use of relatively high-drag elements like conventional wings.
-Ryan
-Ryan
It's one of the most appealing and creative uses of unrestricted aero that I've ever seen.
For My Ally Is The Force, And A Powerful Ally It Is - Speedhunters
Not much obvious on the outside:
But inside:
Using the low pressure behind the car to suck air out from under the car. Lots of downforce with extremely minimal addition in drag, if any at all. It might even be a drag reduction since the low pressure zone behind the car is partially pulling on air under the car, and less on the car itself
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01-17-2015, 12:57 PM
#652
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This is something I am working on this weekend. I will be placing a quite a few NACA ducts in my underbody to help move air for cooling.
Before resin
and finished for now
Before resin
and finished for now
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01-20-2015, 04:16 PM
#654
The one idea that pops into my head is to use the suction form the rear as exit for the transmission tunnel heat when closing off the floor. Just a couple of big air ducts from the diff across the trunk to the plate area. Could that be efficient enough to seal the floor completly (just have exhaust cooling exiting above the diffusor)?
But that's might be what RJ's showing?
But that's might be what RJ's showing?
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01-30-2015, 09:59 PM
#657
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In the article I found these pictures, they were talking about outer most part of the diffuser isn't getting proper flow.
Rear Diffuser Issues - Forum - F1technical.net
Rear Diffuser Issues - Forum - F1technical.net
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01-31-2015, 04:36 PM
#659
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So I was looking around again at diffuser designs and I seen what slimjim8201 wrote on f1technical.net.
Interesting data on Straight, convex and concave diffusers. Each are tested at 5, 10 and 15 degs.
Interesting data on Straight, convex and concave diffusers. Each are tested at 5, 10 and 15 degs.
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