CFD on LSR website

[Pinacate]

www.racecaraerodynamics.com has some CFD analysis of a very simple Modified Sports class car exploring ride height, pitch, and roll sensitivity and yaw stability.

[A2WindTunnel]

Good info and aero data post!

[wolcottjl]

THANKS!

[manta22]

Pinacate-- Is that your website? If so I just sent you an e- mail

Regards, Neil  Tucson, AZ (the corner of Pinacate & Larkdale)

[Pinacate]

Neil,

Sorry, my email is messed up so I couldn't reply your email. The site is in the Tucson area, and we watched fellow Tucsonan Bonner make his 300 MPH run.

[manta22]

Pinacate;

I was there too! I guess I should buy you lunch some day for posting such useful info. I'm building a B/GMS mid- engine car to take to the salt next year and your data verifies some of what I thought was the right approach to aero.

Regards, Neil  Tucson, AZ (Diamond Bell Ranch)

[saltfever]

Wow!! Lots of good information that will take time to work through. Thanks for all the effort in putting it all together and sharing the link.   

[Blue]

Anyone who has added nose or stretched their front wheelbase needs to read this page:

http://www.racecaraerodynamics.com/pages/Yaw%20Sensitivity.html

I couldn't have said it better.  Long noses are unstable, endplates or tails at the rear can fix this.  The only thing I'd add to this site is a drag and downforce comparison of the blunt-tail car body to a properly tapered tail with duffuser.

[Pinacate]

Blue,

Sorry everything takes longer than I want. Soon (a few months), we'll get to a more realistic body and start looking at diffusers, drag, but shape and front end shape.

Recently, we've been looking at devices to keep the cars from flying when they are sideways. On the very simple body, roof rails mounted the length of the body cut the lift by about 25%. Some other types of rails were more effective but would also have an effect when the car is running straight. It looks like the idea of running splitters down the side of the car (running boards) doesn't work. They seem to mess up the air flow under the car when it is sideways. In 2009 the LeMans prototype cars when to a profiled skid plate under the cars in attempt to lessen the problem of them flying when they are sideways. It looks like they cut the lift on the simple body by over a factor of 4 when it is sliding sideways. It will be a couple of weeks at least before all this analysis gets double checked, written up and published  to the web site.

[Jonny Hotnuts]

Anyone who has added nose or stretched their front wheelbase needs to read this page:

http://www.racecaraerodynamics.com/pages/Yaw%20Sensitivity.html

I couldn't have said it better.  Long noses are unstable, endplates or tails at the rear can fix this.  The only thing I'd add to this site is a drag and downforce comparison of the blunt-tail car body to a properly tapered tail with duffuser.

A longer wheel base will improve forward stability.
I agree if a longer nose is added past an un-moved wheel base will have a negative affect on the vehicles yaw properties.

The vehicle in question with a huge angle of attack, generating massive progressively higher uncontested frontal down force a mile in front of the front wheels is a recipe for drama. I have seen pics of this car with huge amounts of spoiler angle. I can only guess that this was an attempt to gain some traction due to the back getting light.

I don’t mean to speak ill of BSR, only making an observation.

My first years car had a similar front wedge design. Thankfully the handling was so bad I we were able to acknowledge there was a problem before we got very fast and didn’t have any serious issues. I credit stretching the wheel base and redesigning the nose the primary factors in curing the handling problem.

Truly hope all the BSR people are all doing well.

[Blue]

Blue,

Sorry everything takes longer than I want. Soon (a few months), we'll get to a more realistic body and start looking at diffusers, drag, but shape and front end shape.

Recently, we've been looking at devices to keep the cars from flying when they are sideways. On the very simple body, roof rails mounted the length of the body cut the lift by about 25%. Some other types of rails were more effective but would also have an effect when the car is running straight. It looks like the idea of running splitters down the side of the car (running boards) doesn't work. They seem to mess up the air flow under the car when it is sideways. In 2009 the LeMans prototype cars when to a profiled skid plate under the cars in attempt to lessen the problem of them flying when they are sideways. It looks like they cut the lift on the simple body by over a factor of 4 when it is sliding sideways. It will be a couple of weeks at least before all this analysis gets double checked, written up and published  to the web site.

Fascinating work, and very important to the safety of this sport.  Please keep everyone posted.

[Blue]

Anyone who has added nose or stretched their front wheelbase needs to read this page:

http://www.racecaraerodynamics.com/pages/Yaw%20Sensitivity.html

I couldn't have said it better.  Long noses are unstable, endplates or tails at the rear can fix this.  The only thing I'd add to this site is a drag and downforce comparison of the blunt-tail car body to a properly tapered tail with duffuser.

A longer wheel base will improve forward stability.
I agree if a longer nose is added past an un-moved wheel base will have a negative affect on the vehicles yaw properties.

The vehicle in question with a huge angle of attack, generating massive progressively higher uncontested frontal down force a mile in front of the front wheels is a recipe for drama. I have seen pics of this car with huge amounts of spoiler angle. I can only guess that this was an attempt to gain some traction due to the back getting light.

I don’t mean to speak ill of BSR, only making an observation.

My first years car had a similar front wedge design. Thankfully the handling was so bad I we were able to acknowledge there was a problem before we got very fast and didn’t have any serious issues. I credit stretching the wheel base and redesigning the nose the primary factors in curing the handling problem.

Truly hope all the BSR people are all doing well.

In this situation we need to take a harder look at the air going under the car.  Contrary to popular belief, air going under us is our friend, using it properly is the challenge.  A correctly designed diffuser on the aft half of the belly (given a smooth belly in the first place) will yield far more downforce with less drag than all of these "skirted" bellies we've seen with 100% separated flow under the car. 

It is a BIG leap of understanding, yet there is less drag and more downforce to be had under the car than over the top by ridding ourselves of these traditional "skirts", and paying correct attention to how the air works between the belly and the salt.

[Dreamweaver]

Am I correct that the software used on the inked site is wayyyyy to expensive and or computer intensive for the average hotrodder?

Any cost effective software solutions out there?

[Jerry O]

Blue.... When you say diffuser's, are you talking about the same style diffusers used on Indy cars. I worked on a couple Indy car teams back in the mid 80's and 90's. The diffusers that were used on those cars made a tremendous amount of down force. So much that when we ran street courses those big steel man hole covers that are in the street had to be welded down because the cars would suck them off the ground when going over them. I have been to the wind tunnel with several of these cars and to watch the car suck it self down to the ground just from the air going under the car is totally amazing. I am currently building a flat bottom streamliner and have designed a diffuser into the belly. I don't have a lot of areo knowledge but am simply trying to apply this technology to my car.  The one thing I am concerned with is allthough the diffuser will add down force, what effect will the exit air have on the car. I know from wind tunnel testing the exit air can be very turbulent.

[maguromic]

Jerry, Cant you use a low drag, low down force speedway set up?  Its been a while since I worked on Indy cars also, but the mid 90's Reynards had either a 4" or 5" tall diffusers on the speedway trays.  I would think you would also need to run some sort of low drag wing with a 6" to 8" cord to help energize the air coming out. Just my two cents. 

These pictures are from the very successful Audi and Porsche Spyder LMP cars from  LeMans last year with low down force diffusers.  Tony

Audi A10 LMP



Porsche Spyder LMP



Penske Porsche Spyder LMP, Its a little different from the factory Porsche, you can notice the difference in the center.