Computational Fluid Dynamics (CFD)

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Computational Fluid Dynamics (CFD)

Postby Corey » Sat Apr 21, 2012 10:35 pm

Hey everyone,

Browsing the MR2oc's Aerodynamics Section I found some sticked threads for both the Mk1 and Mk2 MR2's regarding CFDs. (I also found a thread on the GT4DC with respect to the 205)

They are really fascinating threads and a few members have gone to the effort of modeling (in 3d) both body styles and seeing how they react to subtle changes. (like undertrays, wings, windows up/down etc)

I've spent a few weeks trying to learn the programs required to do this kind of work, but it's a pretty steep curve when it comes to making the actual models. So far I can barely make COMSOL compute the flow around a circle in 2D.

I was wondering if there are any owners on the board who have experience with CFD (Ansys, solidworks, Comsol) who could take a stab at doing some experiments?

Here is the MR2OC thread on the Mk2.

http://www.mr2oc.com/showthread.php?t=410768&page=1

As a head start, there are free models on Google Sketch up available of the ST185 with RC hood and bumper.

http://sketchup.google.com/3dwarehouse/ ... 55fb4adf80

I would love to see just how much lift the Celica body produces, and what we could do to minimize that. I've also wondered just how much downforce or affect the rear wing has.

Cheers
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Re: Computational Fluid Dynamics (CFD)

Postby ZeroDrift » Mon Apr 23, 2012 2:27 pm

I have no experience with this, but would love to learn! If you can get a list of software together I can try my hand at it. While I have a very limited amount of experience with auto cad I think this would be great practice!
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Re: Computational Fluid Dynamics (CFD)

Postby CMS-GT4 » Mon Apr 23, 2012 4:13 pm

I think Conrad might be one of the few that actually has the software and training for this. He was able to simulate stress tests when he designed his under brace. Some of this software is modular so they have to have the package for that particular testing type. I had always planned on taking one of my 1/24 scale models and going back to my old highschool where they had a mini wind tunnel for testing drag and lift. We used to compete in building C02 drag cars, and we used the wind tunnel for part of our testing. We did a lot of research in aero dynamics there and aerospace due to the Airforce ROTC program. I hear some of the programs there have been shut down and I since moved away. I doubt I will ever be able to go by and find out. I actually designed a record breaking car that's design was based on the shape of a duck's bill but was not allowed to use it. The teacher forced use to use open wheel designs and no balsa wood, which I still do not understand to this day. Our designs were permitted by the rules.

As for the rear wing, I have read a bit on the subject, and to my understanding if the rear wing is not going above the roof line it is not really effective. I imagine our stock wing is about useless other than to produce drag on high speed runs. There is some data floating around about the st205 wing and how it actually produces a fair amount of downforce. There is also some info on the STi wing explaining how one of its functions is to allow enough downforce for jumps to help keep the rear from toppling over the front. I have jumped a few cars at some decent speeds with no wings, so I am not sure what factors come into play with downforce, speed and jumping. Also consider most rally 185s only ran the oem wing, and those seemed to handle jumps fairly well enough.

It would be cool to see some data on our car. I think the CS version has its drag coefficient listed online, but there is not a lot of data on it that I have seen. Pat mentioned the stability his car had at those high speeds, remember he hit 210+ mph. He says the car was very stable.
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Re: Computational Fluid Dynamics (CFD)

Postby Corey » Mon Apr 23, 2012 8:24 pm

ZeroDrift wrote:I have no experience with this, but would love to learn! If you can get a list of software together I can try my hand at it. While I have a very limited amount of experience with auto cad I think this would be great practice!


I've been playing around with Catia to try and make the initial 3D/2D model. And then that model is imported into Ansys or Comsol to do the physics on it.

I cant even begin to figure out Ansys, but I used Comsol in university so at least I have a place to start.

Finally figured out how to import my first 2D model from Catia into Comsol, and I finally got some interesting flow plots.

Now the challenge is figuring out the correct boundary and initial conditions so the physics make sense. That and making the model more detailed.
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