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@NineLivesJohnny

Anyone have Aero questions?

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On 5/18/2019 at 12:03 AM, turbogrill said:

What about hard tops on miata? Seems like the first aero improvement? Then airdam/wing etc

 

So when we run the CFD on topless Miata's the air behind the windshield is an absolute wash of turbulent air.   so hardtops are worth their weight when it comes to reducing drag and making a wing work. 

 

 

On 5/17/2019 at 8:48 PM, wvumtnbkr said:

I think a big piece of lexan bent to fit the back would make more of a difference.

 

Depends on what you're looking to do. i saw the additions of the "long tail" old mclaren f1 talk. as a way of reducing drag. curved surfaces where the air is separating from the body = higher drag. you really want a sharp edge and nothing for the air to attach to.  

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9LR's newest service, CFD "virtual" wind tunnel.
 

In short, we take your 3D vehicle model and perform CFD (computational fluid dynamics) analysis using OpenFOAM.  The output package consists of numerical lift/drag/balance values, pressure and velocity images, and a report outlining areas of opportunity with recommendations for improvement.  If you do not have a 3d model we are proud to offer a reverse engineering service which completes the package for most racers.

kl7Tzff.jpg

 

The main appeal of this service is gaining crucial insight into the flow structure around your car.  Parts can be created and tested for less money than a wind tunnel, but the additional understanding of how components interact can shortcut development substantially. In some cases replacing a physical wind tunnel, but often making tunnel time more efficient.


Models will include underbody and wheel-well details. It will be detailed to represent the disturbances, such as a ~3" deep recess, to properly characterize the flow. 






Additional details here:

https://9livesracing.com/shop?olsPage=products%2Fcfd-wind-tunnel&page=1&sortOption=descend_by_created_at
 

 

We're excited about this service and what it can bring to the community!

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5 hours ago, TiredBirds said:

"Aerodynamics are for people who can't build engines". Enzo Ferrari 

 

Also, I believe, posted over the door in their F1 development center.

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On 5/22/2019 at 8:31 AM, TiredBirds said:

"Aerodynamics are for people who can't build engines". Enzo Ferrari 

Gotta love Enzo. He made this famous quote while at the same time removing the roof off the 330 p3-> P4 to reduce lift. 

The Italians are so tricky, but you haven't seen real cheating until you got close to the German teams. 

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4 hours ago, @NineLivesJohnny said:

Gotta love Enzo. He made this famous quote while at the same time removing the roof off the 330 p3-> P4 to reduce lift. 

The Italians are so tricky, but you haven't seen real cheating until you got close to the German teams. 

I think Chad Knaus might know a thing or 2 about it.

 

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Has anyone done any experiments with wind deflectors on the A pillars to reduce drag from having open windows?

We're a low-power light weight car that simply hits a drag induced wall going down longer straights.

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1 hour ago, erich said:

Has anyone done any experiments with wind deflectors on the A pillars to reduce drag from having open windows?

We're a low-power light weight car that simply hits a drag induced wall going down longer straights.

 

I have no idea how effective they are, but I see a notation about A pillar Gurney Flaps in the SuperMiata race series rule set.  It states the flap may extend no more than 1".

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On 5/14/2019 at 3:14 PM, Alchemy Autosport said:

Here is a question, how are people managing spring rates with big aero?  Adding damper pots is off the table for cost reasons.  I have considered some homemade measuring devices but if anyone has a good rule of thumb for Splitter/Air Dam and Big (9libes) rear wing setups on a miata, I am all ears.

you need to have a LOT of aero for that to matter. generally with gt cars you shouldn't worry. 

On 5/30/2019 at 3:20 PM, Originalsterm said:

Are vortex generators on the trailing edge of the roof worth anything?

yes. we actually just competed a CFD run on the evo 8-9 VG's. they kicked the air up and off the car, this allows air from the sides of the car to hit the wing. Cliff notes, wing works better while sliding. AKA rally car. 

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1 hour ago, @NineLivesJohnny said:

Cliff notes, wing works better while sliding. AKA rally car. 

I assume this means that "if the car is sliding, the wing works better with the VG than without" not "the wing works better when the car is sliding than when the car is not sliding", correct? 

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11 minutes ago, ABR-Glen said:

I assume this means that "if the car is sliding, the wing works better with the VG than without" not "the wing works better when the car is sliding than when the car is not sliding", correct? 

correct. 

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that's  the weird thing about aero knowledge...some say that the vortex generators add energy to the air and cause it to resist separation and mimic a less curved roof line..

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2 hours ago, ablesnead said:

that's  the weird thing about aero knowledge...some say that the vortex generators add energy to the air and cause it to resist separation and mimic a less curved roof line..

 

That's exactly what they're supposed to do. Sometimes you end up with happy accidents from unintended consequences, but VGs are definitely not designed to "kick the air up and off the car".

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17 hours ago, LAMR2 said:

 

That's exactly what they're supposed to do. Sometimes you end up with happy accidents from unintended consequences, but VGs are definitely not designed to "kick the air up and off the car".

Agreed. was a interesting thing to discover. 

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28 minutes ago, @NineLivesJohnny said:

Agreed. was a interesting thing to discover. 

What CFD software do you use and what is the size of the smallest cells in the mesh?

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0.1% right here.

Built myself a ride height sensor and logged the data coming off of it. I then used it in conjunction with some other variables like speed and spring rate and whatnot to see how much of a difference my splitter/air dam was making. 

Turns out, kind of a lot. Onlookers told me that the splitter was bending so much(up to 4 inches)  that it would drag on the ground almost everywhere around the track. I took a few things out of the tests including that it needs to be stronger, but also that I'd like to measure drag too. 1205728900_RideHeightSpreadsheet.PNG.e1e829c8a1b3bac56a24d9cad5c0c925.PNG754944629_Rideheightdata.thumb.PNG.1a529e7ff158888e3bd70715a2793abf.PNG

As you can see, there is a very noticeable difference in ride height from one test to another. The red graph is the one with the splitter and the blue is without. The speeds are not the same (obviously) so some matching was required to find data points with the same speed. This data is smoothed out a little so it is not so messy but you can still tell where there are bumpy parts and brake zones and things like that. 

 

 

I also had a few different configurations with a few different 'elements' or components so to speak that would go on the splitters I had/have. Unfortunately none of them had a significant difference but it was nice to know what was happening. 

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3 hours ago, The Aero Man said:

0.1% right here.

Built myself a ride height sensor and logged the data coming off of it. I then used it in conjunction with some other variables like speed and spring rate and whatnot to see how much of a difference my splitter/air dam was making. 

Turns out, kind of a lot. Onlookers told me that the splitter was bending so much(up to 4 inches)  that it would drag on the ground almost everywhere around the track. I took a few things out of the tests including that it needs to be stronger, but also that I'd like to measure drag too. 1205728900_RideHeightSpreadsheet.PNG.e1e829c8a1b3bac56a24d9cad5c0c925.PNG754944629_Rideheightdata.thumb.PNG.1a529e7ff158888e3bd70715a2793abf.PNG

As you can see, there is a very noticeable difference in ride height from one test to another. The red graph is the one with the splitter and the blue is without. The speeds are not the same (obviously) so some matching was required to find data points with the same speed. This data is smoothed out a little so it is not so messy but you can still tell where there are bumpy parts and brake zones and things like that. 

 

 

I also had a few different configurations with a few different 'elements' or components so to speak that would go on the splitters I had/have. Unfortunately none of them had a significant difference but it was nice to know what was happening. 

Didn't somebody say my idea to use zip ties on the shock shafts was dumb...

 

Haha.  Camera with a scale could work too if you don't have the hardware.

 

Good work!

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If you can show different sectors, you could show just the area where the car is going down the front straight, ignore all the other variables that come into play.

 

 

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On 8/5/2019 at 3:56 PM, wvumtnbkr said:

Didn't somebody say my idea to use zip ties on the shock shafts was dumb...

 

Haha.  Camera with a scale could work too if you don't have the hardware.

 

Good work!

Camera would be much harder to correlate the suspension travel with speed.  Looks like this has both ride height and speed getting logged at once so you can do a direct comparison.

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49 minutes ago, MMiskoe said:

Camera would be much harder to correlate the suspension travel with speed.  Looks like this has both ride height and speed getting logged at once so you can do a direct comparison.

Oh, for sure this is better.   I was meaning the cheap way to do it...

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11 hours ago, wvumtnbkr said:

Oh, for sure this is better.   I was meaning the cheap way to do it...

Put a hole in the top of the fender above your control arm/spindle/whatever. Attach a rod to the top of your control arm that is long enough to protrude above the fender at full droop. Mark the rod at static ride height and a few inches of ride height above and below.

 

If your driver doesn't like taking notes while driving, mount a GoPro facing forward so you can see what the height of the rod is at specific places on the track. Do some testing.

 

Cheap enough? :) 

Edited by mender
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