# Calculating lift forces on various bodies

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 August 29, 2016, 17:08 Calculating lift forces on various bodies #1 New Member   Isaac Join Date: Feb 2013 Posts: 19 Rep Power: 6 Sponsored Links I have taken a simple model of an aircraft and successfully ran the simulation. I have split the model into fuselage, left wing and right wing. When I checked the forcecoeff file, it showed me one single number for lift, one single number for drag and one single number for moment. Since I was unable to create the patch commands, my snappyhexmesh commands looks something like this... geometry { CF.obj { type triSurfaceMesh; name CF; } RW.obj { type triSurfaceMesh; name RW; } LW.obj { type triSurfaceMesh; name LW; } where CF stands for fuselage and RW stands for right wing and LW stands for left wing

August 31, 2016, 08:30
#2
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Quote:
 Originally Posted by isaac1326 I have taken a simple model of an aircraft and successfully ran the simulation. I have split the model into fuselage, left wing and right wing. When I checked the forcecoeff file, it showed me one single number for lift, one single number for drag and one single number for moment. Since I was unable to create the patch commands, my snappyhexmesh commands looks something like this... geometry { CF.obj { type triSurfaceMesh; name CF; } RW.obj { type triSurfaceMesh; name RW; } LW.obj { type triSurfaceMesh; name LW; } where CF stands for fuselage and RW stands for right wing and LW stands for left wing

In controlDict file you need to define for each part properties of your forces coefficient, like this:

Quote:
 { type forceCoeffs; functionObjectLibs ( "libforces.so" ); outputControl timeStep; outputInterval 1; patches ( "airfoil.*" ); pName p; UName U; rhoName rhoInf; log true; liftDir (-6.98e-2 0 9.98e-1); dragDir ( 9.98e-1 0 6.98e-2); CofR (0.25 0 0); pitchAxis (0 1 0); magUInf 87.5; rhoInf 1000; lRef 1; Aref 0.1; }
Instead of patches you have to write CF, RW, ecc.ecc. and after that you will look lift and drag coefficients for each patch

August 31, 2016, 10:17
#3
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Isaac
Join Date: Feb 2013
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Yes, I have done that, when I open the postprocessing file
It just shows me
one CL value and one CD value
..
This was my control Dict File
Attached Files
 forceCoeffs Copy.txt (2.1 KB, 0 views) controlDictcopy.txt (4.8 KB, 0 views)

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