CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM

airfoil analysis need help!!!

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   April 8, 2010, 06:30
Exclamation airfoil analysis need help!!!
  #1
DLC
Member
 
Davide Lupo Conti
Join Date: Nov 2009
Posts: 34
Rep Power: 7
DLC is on a distinguished road
Hi Foamers!
I'm trying to do some simple 2D airfoil analysis.
in doing some tests on the classic NACA 0012 airfoil. has anyone done more or less the same thing? can anyone give me some hints?

I'm using simpleFoam as a solver (k-e turbulence model with the constants values of the simpleFoam tutorial), because icoFoam and turbFoam start with fireworks after few iterations...

my simulations need more or less 1700 iterations to converge to a steady state (looking to U and p distributions), is it reasonable?

I haven't figured out how to obtain forces on the airfoil... does anyone know how to do it?

I'm afraid I'm not using the correct turbulence model or the the wrong values of the k-e constants...

every hint is very useful!


thanks a lot

DLC
DLC is offline   Reply With Quote

Old   April 8, 2010, 07:39
Default
  #2
Senior Member
 
Join Date: Dec 2009
Posts: 112
Rep Power: 7
heavy_user is on a distinguished road
Quote:
Originally Posted by DLC View Post
Hi Foamers!
I'm trying to do some simple 2D airfoil analysis.
in doing some tests on the classic NACA 0012 airfoil. has anyone done more or less the same thing? can anyone give me some hints?

I'm using simpleFoam as a solver (k-e turbulence model with the constants values of the simpleFoam tutorial), because icoFoam and turbFoam start with fireworks after few iterations...

my simulations need more or less 1700 iterations to converge to a steady state (looking to U and p distributions), is it reasonable?

I haven't figured out how to obtain forces on the airfoil... does anyone know how to do it?

I'm afraid I'm not using the correct turbulence model or the the wrong values of the k-e constants...

every hint is very useful!


thanks a lot

DLC
Hi DLC,

getting force values is a matter of postprocessing.
You might want to checkout paraFoam for this or if you have a license you might want to use ensight (or similar).
Getting forces is then straight forward and well documented in the video-posts from ensight-page.
If you use paraFoam you might want to buy the manual, otherwise you will have fun guessing...

regards
heavy_user is offline   Reply With Quote

Old   April 8, 2010, 16:19
Default Fluent
  #3
Member
 
sahm's Avatar
 
S. Ali H.M.
Join Date: Nov 2009
Location: Chicago
Posts: 69
Rep Power: 7
sahm is on a distinguished road
Send a message via Yahoo to sahm
HI DLC
I have previously done a case on Naca 0012 airfoil with Fluent, but my results was looking wrong. how was your results? did you get correct results?
sahm is offline   Reply With Quote

Old   April 9, 2010, 06:55
Default
  #4
DLC
Member
 
Davide Lupo Conti
Join Date: Nov 2009
Posts: 34
Rep Power: 7
DLC is on a distinguished road
well, actually I cant tell yet if my results are correct... I tested a lot of different configurations, (BC and turbulence models) and managed to find a settings that actually converge to a stationary situation (looking to the p andU distribution), bun I haven't discovered yet how to calculate forces, thereore Cl, Cd, Cm... how did you manage to obtain these? a help on how to calculate forces would permit me to give results even tonight...
If you want to send me your test case, I can have a look to differences..

let me know

DLC
DLC is offline   Reply With Quote

Old   April 9, 2010, 09:24
Default
  #5
Senior Member
 
Join Date: Feb 2010
Posts: 213
Rep Power: 8
vaina74 is on a distinguished road
I'm not an expert, I'm a beginner, so use the search tool in the forum to check my suggestions. There is also a 2D airfoil case in tutorials/incompressible/simpleFoam. The turbulence model depends on your Reynolds number. If you have a high Re, I think you can use \kappa-\epsilon, \kappa-\omega SST or Spalart-Allmaras model. Otherwise you must use a low Re model.
I think 1000 iterations is enough, you can check your residuals.
In order to calculate lift and drag coefficients, you can include in controlDict code lines as:
Code:
functions
{
    forces
    {
        type        forces;
        functionObjectLibs ( "libforces.so" );  // lib to load
        outputControl timeStep;
        outputInterval 1;
        patches
        (
            wall  // change to your patch name
        );
        // name of fields
        pName       p;
        UName       U;
        log         true; // dump to file
        rhoInf      1025;
        CofR        ( 0 0 0 );
    }
    forcesCoeffs
    {
        type        forceCoeffs;
        functionObjectLibs ( "libforces.so" );  // lib to load
        outputControl timeStep;
        outputInterval 1;
        patches
        (
            wall  // change to your patch name
        );
        // name of fields
        pName       p;
        UName       U;
        log         true; // dump to file
        rhoInf      1025;
        CofR        ( 0 0 0 );
        liftDir     ( 0 1 0 );
        dragDir     ( 1 0 0 );
        pitchAxis   ( 0 0 0 );
        magUInf     7.30;
        lRef        0.305;
        Aref        0.001525;
    }
}

// Definition of terms:
// rhoInf - reference density
// CofR - Centre of rotation
// dragDir - Direction of drag coefficient
// liftDir - Direction of lift coefficient
// pitchAxis - Pitching moment axis
// magUinf - free stream velocity magnitude
// lRef - reference length
// Aref - reference area
vaina74 is offline   Reply With Quote

Reply

Tags
2 d, forces, k-epsilon, naca 0012, simplefoam

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Multi-element airfoil analysis CFD Rookie Main CFD Forum 11 October 31, 2013 17:02
Steady level flight airfoil analysis using ANSYS CFX v12 flutter CFX 18 December 14, 2011 00:18
Airfoil Mesh for DES Analysis - y+ Value asd Main CFD Forum 1 May 3, 2007 10:13
y+ for Airfoil Analysis asd Main CFD Forum 3 April 18, 2007 10:54
quasi steady analysis of 2d airfoil (pitching) Alex FLUENT 1 February 10, 2006 03:54


All times are GMT -4. The time now is 11:39.