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The relationship between forces and the pressure from sampledSurfaces in OF

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Old   April 23, 2018, 13:09
Default The relationship between forces and the pressure from sampledSurfaces in OF
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Hi Guys,

Currently I encounter a problem that the predicted noise based on the sampled pressure on the solid surfaces (patch: cube) is inconsistent with the root-mean-square values calculated based on the forces from the same surface (patch: cube) in OF. The related code in the system file is as following:

Code:
forcesCube
    {
        type            forces;
        functionObjectLibs ("libforces.so");
        outputControl timeStep;
        outputInterval 1;
    
        patches         ( cube );
        pName           p;
        UName           U;
        rhoName         rhoInf;
        log             true;
        rhoInf          1;
        CofR            (0 0 0);
    }
fieldAverage
    {
        type            fieldAverage;
        functionObjectLibs ( "libfieldFunctionObjects.so" );
        enabled         true;
        outputControl   outputTime;

        fields
        (
            U
            {
                mean        on;
                prime2Mean  on;
                base        time;
            }

            p
            {
                mean        on;
                prime2Mean  on;
                base        time;
            }
        );
    } 
             sampled_surface
    {
        type                   surfaces;
        functionObjectLibs    ("libsampling.so");
        enabled                true;
        outputControl          timeStep;
        outputInterval         5;
        surfaceFormat          raw;
        interpolationScheme    cell;
        fields
        ( 
              p
         );
        surfaces
        (
              wall
              {
                 type        patch;
                 patches     (cube);
              }
         ); 
     } 
}
I'm now thinking about the relationship between the forces calculated by OF acting on the object and the sampled pressure from the surfaces of the same object, which is suppose to be consistent since the only difference is the integrated area of the surface (Frankly, I'm not sure if my understanding is correct).

Base on my knowledge, the forces in OF is calculated relying on the x, y, z coordinates, while the sampledSurface requires information of surface areas. I suspect the sampled pressure from the cube with rounded corners may not be reliable due to the curved surfaces. But I have no idea about how to test it. Any suggestions? Thanks in advance.
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forces, openfoam, sampledsurface

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