[Kosuke Seto]

Hi, FOAMers.

I'm modifying the "advective" boundary condition to make sound generated from flow fields go through the boundaries without reflecting.
I do know that the boundary condition "waveTransmissive" will do, but this is for the compressible analysis, and I'm doing incompressible ones so I'm modifying "advective".

My question is as follows.

In this boundary condition, the member function "advectionSpeed()" determine the speed of the sound at the boundaries.

// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

template<class Type>
Foam::tmp<Foam::scalarField>
Foam::soundAdvectiveFvPatchField<Type>::advectionSpeed() const
{
    const surfaceScalarField& phi =
        this->db().objectRegistry::template lookupObject<surfaceScalarField>
        (phiName_);

    fvsPatchField<scalar> phip =
        this->patch().template lookupPatchField<surfaceScalarField, scalar>
        (
            phiName_
        );

    if (phi.dimensions() == dimDensity*dimVelocity*dimArea)
    {
        const fvPatchScalarField& rhop =
            this->patch().template lookupPatchField<volScalarField, scalar>
            (
                rhoName_
            );

        return phip/(rhop*this->patch().magSf());
    }
    else
    {
    
        return phip/this->patch().magSf();
    }
}

I wanna change the expression in "return" statement like "return 340" because the sound speed is 340m/s.
Off cause, the situation is not this easy.

Then, how can I configure the sound speed here?
From above, the variable phip is declared as fvsPatchField<scalar>, but writing
fvsPatchField<scalar> soundSpeed_;
in the header file doesn't work.

Thanks for any help!
Kosuke