Aerodynamic Discussion Thread
04-25-2014, 11:20 AM
#522
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The thing that I found deceiving about that vid is that with CFD, we're used to seeing reds signify high pressure areas and blues are low pressure. At first I was like, WTF why is the base of the windshield the lowest pressure spot on that model??
But, in that video they are showing friction, not pressure - where red is high friction (due to fast-moving air) and blue is low friction (slow air). The gist of Bernoulli's principle is that an increase in the speed of a fluid = a deacrease in pressure. So, if you want to translate what you see in that vid to pressure, the colors flip-flop.
This might have been obvious to others, but it threw me off for a moment.
Looking at the friction/speed of air on the car body is quite useful for considering NACA duct locations though..
-Ryan
But, in that video they are showing friction, not pressure - where red is high friction (due to fast-moving air) and blue is low friction (slow air). The gist of Bernoulli's principle is that an increase in the speed of a fluid = a deacrease in pressure. So, if you want to translate what you see in that vid to pressure, the colors flip-flop.
This might have been obvious to others, but it threw me off for a moment.
Looking at the friction/speed of air on the car body is quite useful for considering NACA duct locations though..
-Ryan
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04-26-2014, 08:05 AM
#526
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Will work in a miata? I'd be concerned about heat soak. I was just a little surprised looking at it... air goes through, hits duct wall then straight up with a slight forward tilt.
That's using the low pressure zone of the hood... I liked.
That's using the low pressure zone of the hood... I liked.
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04-26-2014, 01:40 PM
#527
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The air exiting the heat exchanger is moving so much slower than the air entering that it doesn't have any problems making a surprising amount of bends and turns to find its way out.
I've seen discussions about this referencing race cars which have up to 180* bends in the post-heat exchanger ducting that took the air back forwards to an exit even. As long as the exit point is a low pressure area, the inlet is much higher in pressure, and the whole path in/out is well built (doesn't flex with pressure and open up gaps) and sealed, the air will find its way.
The ducting on the inlet side is much more sensitive to sharpness of bends - you want smooth, gradual, few curves to preserve all the flow and pressure possible into the cooler.
-Ryan
I've seen discussions about this referencing race cars which have up to 180* bends in the post-heat exchanger ducting that took the air back forwards to an exit even. As long as the exit point is a low pressure area, the inlet is much higher in pressure, and the whole path in/out is well built (doesn't flex with pressure and open up gaps) and sealed, the air will find its way.
The ducting on the inlet side is much more sensitive to sharpness of bends - you want smooth, gradual, few curves to preserve all the flow and pressure possible into the cooler.
-Ryan
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04-28-2014, 01:40 AM
#528
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This ^. The high pressure air, take care with it, treat it well, make sure it gets to where it needs to go without expending much energy to do it. The low pressure air, just don't **** it up, feed it to a low pressure zone, maybe give it a reverse naca duct/diffuser if it needs to speed back up much.
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04-29-2014, 10:30 AM
#529
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The new DTM cars have a lot of pretty cool aero design. I like the ductwork moving air out from under the car (with NACA ducts venting something!)
All of the pictures can be found HERE at the original article. I like the side mirror design (getting it away from the boundary layer air along the body) and the side exit exhaust they have had for a while.
I've also noticed that a lot of cars that vent their wheel wells put a fence behind the front tire to protect the negative pressure. Might be a good alternative to just having the fender cut on the bottom half
All of the pictures can be found HERE at the original article. I like the side mirror design (getting it away from the boundary layer air along the body) and the side exit exhaust they have had for a while.
I've also noticed that a lot of cars that vent their wheel wells put a fence behind the front tire to protect the negative pressure. Might be a good alternative to just having the fender cut on the bottom half
Last edited by ecc3189; 04-29-2014 at 02:05 PM. Reason: actually doing research...
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05-03-2014, 12:15 AM
#533
In the larger scheme of things, we're chasing aerodynamic efficiency and downforce because pure mechanical grip has a limit, and it's surprising how close the mechanical limits can tie dissimilar cars together.
For example, I remember seeing a 60 to 0 brake test where a Mercedes S500 matched an Acura NSX. Surely we're just talking one stop, but the extra weight of the S500 increased the grip of the tires to the point that it matched the NSX. With no aero help, many cars seem to go around the same corner at relatively similar speeds.
For example, I remember seeing a 60 to 0 brake test where a Mercedes S500 matched an Acura NSX. Surely we're just talking one stop, but the extra weight of the S500 increased the grip of the tires to the point that it matched the NSX. With no aero help, many cars seem to go around the same corner at relatively similar speeds.
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05-10-2014, 11:53 AM
#538
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So with the P1 and the LaFerrari how are the active aero computers programmed? It seems that both can sense when you are on a straight and they will assume the lowest drag configuration. But I noticed in that video that the LaFerrari didn't have its rear spoiler out coming around that really tight last corner, but it looked like it was sensing some high speed corners and deploying the rear spoiler and feathering the diffuser.
Also, Koenigsegg is entering the active aero game with the One:1, so it should get interesting. Here's a video about it that I watched the other day.
Also, Koenigsegg is entering the active aero game with the One:1, so it should get interesting. Here's a video about it that I watched the other day.
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05-10-2014, 02:53 PM
#540
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If you could drive one what would it be? 918, P1 or LaFerrari. Since now the LaFerrari XX has been released from the Crazy floor of the Ferrari Plant. They now said the LaFerrari XX will be dropping the V12 for a F1 inspired turbo 1.6L V6. McLaren is now going to take the fight back to Ferrari with a full track version of the P1 with more Aerodynamic package. We will see who will be the king of the Nurburgring.
a little of topic but, I asked this question to a group of Miata buddies at World Of Beer,"If money was no object and you could buy any track day car in the world what would it be, but it HAS to be your daily driver?"
a little of topic but, I asked this question to a group of Miata buddies at World Of Beer,"If money was no object and you could buy any track day car in the world what would it be, but it HAS to be your daily driver?"
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