CFD Online Discussion Forums - Possible bug in OpenFoam Interpolation class

Hello everybody,

I'm currrently using the class interpolationCellPoint, but I experienced a strange behaviour in its usage.

I'm using this class in two different ways:
- the first, I declare an object Uinter of class interpolationCellPoint in the header file of my custom class:

Code:

#include "interpolationCellPoint.H" // need by Uinter

namespace Foam {

class myClass {

public:

...some objects...

interpolationCellPoint<vector> Uinter;

vector velInterp(point &iVelPoint,label &iVelCell);

private: 

...

   }

}

and I define it in constructor:

Code:

#include "myClass.h"

namespace Foam {

defineTypeNameAndDebug(myClass, 1);

// Default Constructor

myClass::myClass(const volVectorField& U):

    ...some definitions...

    // Set the pointer to the velocity field

    U_(U),

    // Uinter construction

    Uinter(U),

...other definitions...

{}

}

where const volVectorField& U comes from my custom solver based on simpleFoam. Then in velInterp I call the interpolate member function of Uinter:

Code:

#include "myClass.h"

namespace Foam {

vector myClass::velInterp(point &iVelPoint,label &iVelCell)

    {

V=Uinter.interpolate(iVelPoint, iVelCell);

return(V);

}

}

That works correctly and gives me a vector output as expected.

- the second, I declare and define the variable Uinter of class intersectioCellPoint directly inside the velInterp function, so it is no more a myClass public member, but it borns and dies directly inside the function:

Code:

#include "myClass.h"

namespace Foam {

vector myClass::velInterp(point &iVelPoint,label &iVelCell)

    {

interpolationCellPoint<vector> Uinter(U_);

V=Uinter.interpolate(iVelPoint, iVelCell);

return(V);

}

}

I obviously expect that these two methods are equivalent, but I noticed that the vectors V are different.

I can't figure out the reason for this discrepancy in the results.
Is it my fault or have I found a bug?