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Old   March 30, 2009, 11:22
Default Fluent parameter sensitivity study
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Ridlo
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Hi all,

I'm a mechanical engineering student, and working on my final project now.

Appreciate if you can give comment and advise to my subject.

--->

My final project tentative tittle is "Sensitivity study of fluent parameter on 2 dimensional airfoil aerodynamics analysis".



The idea is to identify fluent characteristic in dealing with aerodynamic design. Well one of fluent function is as a tool to analyze aerodynamics properties of a design, therefore it is mandatory to well recognize the characteristic of the tool (fluent) so we can insert the required properties properly and resulting close to actual data that will validate the design optimally.

Temporarily I'm limiting the object on 2 dimensional model, infinite airfoil, and on subsonic wind.

But this is still a rough figure, really need to be define properly.

Frankly speaking though I like aerodynamics, I'm still new with CFD and I'm still confuse about "what are the (main) parameters that need to be defined" and later on studied it's sensitivity.
My adviser said it includes meshing properties, turbulence model (I think this one related with the reynold properties), etc.

Really appreciate if you can give me your comment/feedback so I can have a better figure on this subject.

Thanks alot
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Old   April 2, 2009, 10:13
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Janarthanan Alagesan
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Hi Ridlo,

From your post I couldn't figure out what is your project requirement. So I'm giving some general details.

For the case of meshing properties you can do a study on mesh density, domain effect and Yplus.

In turbulence modeling you can change the boundary condition variables such as turbulence intensity, turbulence length scale, wall roughness etc and check how it affects the result. Also you can compare the results of the available turbulence models and its variants.

You can compare the available pressure - velocity coupling and the discretaization schemes.

You must do the above mentioned studies before conducting the real simulations.

If you are new to fluent then you can get some tutorials related to airfoil.
http://courses.cit.cornell.edu/fluent/airfoil/index.htm

If you can clearly state your project requirement then I can give some information related to it.

Cheers, Alagesan.
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Old   April 3, 2009, 10:44
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Hi Alagesan,

Thanks for the reply.

I was also blank at the first time, right now blur (at least not blank anymore ).

After discussed in detail, the objective is to have optimum parameter to get sensitive/detail enough data but also fast enough to simulate/analyze with common computer spec (I'm working on core2duo T6400 2.0 Ghz). This optimum parameter will be use later on as reference to conduct all testing which has the same limitation (2d and on sub-sonic speed)

The testing is on Coefficient of Lift (CL) & Coefficient of Drag (CD) versus Angle of Attack compare to wind tunnel result on infinite wing (2D).

The parametera that will be analyzed are :

1. Mesh density, domain effect, and Yplus (exactly as what you've mentioned ). After having the optimum mesh density on structured mesh, then the data will be study to nonstructural mesh, then study the domain effect. Right now I'm searching for mesh manual/theory. and also refreshing my mind bout boundary layer to understand the Yplus and later on domain effect. (please correct me if I'm wrong).

2. turbulence modeling with two models (thanks again ), Sparat-Allmaras and K-Omega. I'm still have no idea bout this turbulence modeling, what is the Sparat-Allmaras and K-Omega, what is their parameter, and what makes them different.

The study will be conducted with several Mach number and Reynold number based on the data which already obtained from wind tunnel testing.

Thanks for the link it's very usefull. Do you have any link regarding the explenation/elaboration of meshing, boundary layer, and turbulence modeling? Including the theory of it. Since this is the main parameter that I will study and I guess it basic knowledge that I have to well-understand.

Thanks a lot,
Ridlo
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Old   April 4, 2009, 08:06
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Janarthanan Alagesan
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Hi Ridlo,

You can get all meshing details from Gambit user guide. From fluent user guide you can get all the details about the turbulence model, boundary condition and the solver setting etc.

For calculation of the first cell height for the given Y plus use the following link.
http://geolab.larc.nasa.gov/APPS/YPlus/

Some more airfoil tutorials available at
http://www.aero.ses.soton.ac.uk/courses/SESS6011/

Cheers, Alagesan.
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