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Old   December 8, 2009, 15:01
Default total newbie - Basic Questions
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Hi to all... Glad to find this Forum and hope to get an answer...

I am total new to cfd with no related education to that...


I like to make models in 3d studio max... and recently i make a model of a car...

i would like to see the flow of the model - aerodynamic .

Questions

1) Is there any application that can import in 3ds format ? .obj ? vrml ?

2) is there any simply program that import the 3d model... and just run it to see the flow ??
As i have notice most of the programs are not so simple.. because are for engineering and have so many parameters ....

i am windows platform child but i know tha basic of unix-linux systems also as i like them.. and have some experience on them


thanks in advance
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Old   December 8, 2009, 16:57
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Hi, this is my first post, so bear with me, but ill try to explain what you have to do to get your simulation correct.

firstly (and i could be wrong, feel free to correct me anyone if i am) you will need to draw your model in an engineering program, for example, using NX, ANSYS, or similar software. the reasons are that you will need to give certain information like conditions and parameters, for example, the flow velocity, or if your car is made from steel or aluminium, or whatever material you desire, you will need to specify so otherwise it will not be a realistic simulation. importing the 3D model from another program will more than likely cause problems, and again, will more than likely not be compatible in the first place, and if it is compatible, some vital functions may not be. so youre better off starting afresh, drawing it in another program that you know for sure is compatible.

however, the problems dont really end there, because youre going to need to specify the volume of flow, and mark out how fine/coarse you want the represented flow. again, this important for accuracy reasons. therte are a huge amount of variables to consider, so i would suggest deciding on a number of things before you attempt to model your car.

this will be difficult without prior knowledge of engineering theory or CFD experience. your best bet is to approach someone who can help you, sit down at a computer with them, and they will be able to tell you exactly how to achieve your goal. i hope i was of some help if any! Good luck!
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Old   December 9, 2009, 04:25
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Quote:
Originally Posted by onetrickhorse View Post
your best bet is to approach someone who can help you, sit down at a computer with them, and they will be able to tell you exactly how to achieve your goal. i hope i was of some help if any! Good luck!
That would be the best... but i dont have anyone to show me...


about modeling the car inside programs like ansy etc.. i find it seem to me little difficult compared with the programs i am using all ready .


Hope in the future would be some nice tutorials about the beginners

Thanks for the informations
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Old   December 9, 2009, 10:40
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I don't know 3d studio max, but if you can create a Iges or Step file, than you could import that into a CFD software.
But then the real problems are to know where and which way to refine the mesh; and, for example, do you have any idea of what turbulence model to choose, and why?
I guess if you wanna do Colourful Fluid Dynamics you can. If you wanna do Computational Fluid Dynamics and have some credible results ... that's another story, you need to know what you're doing.
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Old   December 9, 2009, 17:47
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let me try to explain it to you by means of an example:
Can 3d studio max be used to construct a big sphere or a big melon around your car model, then subtract the car volume from the melon volume, and you end up exporting that remaining volume?
that is why you need to use an engineering cad modeler.
Good luck
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Old   December 10, 2009, 01:26
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I doubt that there is a gentle way into this, but it is possible. First of all, provided that your 3D Studio model is good (in other words, it is most important that it should form a closed body, or several closed bodies), you have something to work with. I'm pretty sure 3D Studio will be able to export that geoemetry as an STL (stereo-lithography) file. Most CFD mesh generation programs can work with STL geometry. If you don't want to spend money, the next step is to obtain and install OpenFOAM on a computer running Linux. Now use the openFoam utilitities blockMesh and snappyHexmesh to create a grid for it, and run it in simpleFoam, generating pretty pictures with Paraview. This is a perfectly feasible toolchain, and all of it is for free. If you have a friend who can help you with this, it is pretty easy. If you don't, set several months aside to learn the necessary skills! Even then, there is no guarantee that your answer will be any more meaningful than a pretty picture.

So, it is not essential to work with a full-blown CAD program for this, or a $3000/month CFD program, but don't be under any illusions about this being easy.

You can also take a look at http://www.symscape.com/ , there are some tools there that could come in handy.
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Old   December 10, 2009, 02:09
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Well Caslor

Reality of life is that you need to pick basics first and move from there. Without basics YOU WILL BE "LOST" in a thick jungle of ANSYS.

Best way for you is Solidwork offer easy simulations own its won Try that.

That is the easiest way YOU MUST LEARN "FLUID DYNAMICS" else you will get lost pretty badly.
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Old   December 10, 2009, 03:52
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Thanks for the interesting .....

Yes i agree that must learn tha basic first....
i will try to find a book to read...

i find a demo version of a program called enShight .
In this one you can import a Wavefront .obj file format... and that is very good as i could import very nice and problem free all my models...

but still couldnt do a lot as i am missing the basic training ....


about ''what turbulence model to choose, and why? '' the answer is = no :P

i just wanted to import the model and see how the air flows around the model ... where has more resistance.. and will be nice to see in visual where i have positive/negative air pressure - upward/downward forces from the wind travel
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Old   December 10, 2009, 04:08
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Sorry mate, there is no "just" in "i just wanted to import the model and see how the air flows around the model ... where has more resistance.. and will be nice to see in visual where i have positive/negative air pressure - upward/downward forces from the wind travel" You might find some programs that promise to make this process easy, but the fact is that even with these codes you still need to understand your fluid dynamics. It is probable that most of the people in this forum have post-graduate qualifications in fluid dynamics, and there is good reason for it. There are other ways of acquiring the specialised knowledge (the formally untrained Wright brothers come to mind) but you still need to have that expertise.
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Old   December 10, 2009, 11:49
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Well Caslor
I started same way as you are trying, i,e, some samples. Slowly slowly I started getting lost in thick jungle of ANSYS. Only way around is

1) PIN POINT YOUR PROBLEM
2) READ SOME VERY VERY BASIC EQUTIONS FIRST
3) READ IN DEPTH HOW "PROBLEMS ARE SOLVED"

Then try.

I am now on Third phase. Tough Road but THERE IS NO QUICK FIX.

------------------------------------------------------
Joke
Sorry mate no book called "ANSYS FOR DUMMIES YET".
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