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linear momentum calculation in KinematicCloudI.H

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Old   April 6, 2012, 12:22
Default linear momentum calculation in KinematicCloudI.H
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Chi-Wei Tsang
Join Date: Mar 2012
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Dear all,

I am confused with the way OpenFOAM calculates linear momentum of system:

template<class CloudType>
inline Foam::vector
Foam::KinematicCloud<CloudType>::linearMomentumOfS ystem() const
vector linearMomentum(vector::zero);
forAllConstIter(typename KinematicCloud<CloudType>, *this, iter)
const parcelType& p = iter();
linearMomentum += p.mass()*p.U();
return linearMomentum;

I think that p.mass() returns the mass of a "particle" in a parcel. So the mass of a parcel should be p.mass() * p.nParticle(). Then the linearMomentum should be p.mass() * p.nParticle() * p.U() instead of p.mass() * p.U().

For your reference, below is the way how OpenFOAM calculates total mass of a system:

template<class CloudType>
inline Foam::scalar Foam::KinematicCloud<CloudType>::massInSystem() const
scalar sysMass = 0.0;
forAllConstIter(typename KinematicCloud<CloudType>, *this, iter)
const parcelType& p = iter();
sysMass += p.mass()*p.nParticle();
return sysMass;

What do you think? Thank you!

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