This fvModel applies an explicit damping force to components of the vector field in the direction of gravity. Its intended purpose is to damp the vertical motions of an interface in the region approaching an outlet so that no reflections are generated. More...

Inheritance diagram for verticalDamping:

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Collaboration diagram for verticalDamping:

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Public Member Functions
	TypeName ("verticalDamping")
	Runtime type information. More...

	verticalDamping (const word &name, const word &modelType, const dictionary &dict, const fvMesh &mesh)
	Construct from components. More...

virtual	~verticalDamping ()
	Destructor. More...

virtual void	addSup (fvMatrix< vector > &eqn, const word &fieldName) const
	Source term to momentum equation. More...

virtual void	addSup (const volScalarField &rho, fvMatrix< vector > &eqn, const word &fieldName) const
	Source term to compressible momentum equation. More...

virtual void	addSup (const volScalarField &alpha, const volScalarField &rho, fvMatrix< vector > &eqn, const word &fieldName) const
	Source term to phase momentum equation. More...

virtual bool	movePoints ()
	Update for mesh motion. More...

virtual void	topoChange (const polyTopoChangeMap &)
	Update topology using the given map. More...

virtual void	mapMesh (const polyMeshMap &)
	Update from another mesh using the given map. More...

virtual void	distribute (const polyDistributionMap &)
	Redistribute or update using the given distribution map. More...

Public Member Functions inherited from damping
	TypeName ("damping")
	Runtime type information. More...

	damping (const word &name, const word &modelType, const dictionary &dict, const fvMesh &mesh)
	Construct from components. More...

virtual	~damping ()
	Destructor. More...

virtual wordList	addSupFields () const
	Return the list of fields for which the fvModel adds source term. More...

virtual bool	read (const dictionary &dict)
	Read dictionary. More...

Public Member Functions inherited from fvModel
	TypeName ("fvModel")
	Runtime type information. More...

	declareRunTimeSelectionTable (autoPtr, fvModel, dictionary,(const word &name, const word &modelType, const dictionary &dict, const fvMesh &mesh),(name, modelType, dict, mesh))

	fvModel (const word &name, const word &modelType, const dictionary &dict, const fvMesh &mesh)
	Construct from components. More...

autoPtr< fvModel >	clone () const
	Return clone. More...

virtual	~fvModel ()
	Destructor. More...

const word &	name () const
	Return const access to the source name. More...

const fvMesh &	mesh () const
	Return const access to the mesh database. More...

const dictionary &	coeffs () const
	Return dictionary. More...

virtual bool	addsSupToField (const word &fieldName) const
	Return true if the fvModel adds a source term to the given. More...

virtual scalar	maxDeltaT () const
	Return the maximum time-step for stable operation. More...

	FOR_ALL_FIELD_TYPES (DEFINE_FV_MODEL_ADD_SUP)
	Add a source term to an equation. More...

	FOR_ALL_FIELD_TYPES (DEFINE_FV_MODEL_ADD_RHO_SUP)
	Add a source term to a compressible equation. More...

	FOR_ALL_FIELD_TYPES (DEFINE_FV_MODEL_ADD_ALPHA_RHO_SUP)
	Add a source term to a phase equation. More...

template<class Type >
tmp< fvMatrix< Type > >	source (const GeometricField< Type, fvPatchField, volMesh > &field) const
	Return source for an equation. More...

template<class Type >
tmp< fvMatrix< Type > >	source (const GeometricField< Type, fvPatchField, volMesh > &field, const word &fieldName) const
	Return source for an equation with a specified name. More...

template<class Type >
tmp< fvMatrix< Type > >	source (const volScalarField &rho, const GeometricField< Type, fvPatchField, volMesh > &field) const
	Return source for a compressible equation. More...

template<class Type >
tmp< fvMatrix< Type > >	source (const volScalarField &rho, const GeometricField< Type, fvPatchField, volMesh > &field, const word &fieldName) const
	Return source for a compressible equation with a specified name. More...

template<class Type >
tmp< fvMatrix< Type > >	source (const volScalarField &alpha, const volScalarField &rho, const GeometricField< Type, fvPatchField, volMesh > &field) const
	Return source for a phase equation. More...

template<class Type >
tmp< fvMatrix< Type > >	source (const volScalarField &alpha, const volScalarField &rho, const GeometricField< Type, fvPatchField, volMesh > &field, const word &fieldName) const
	Return source for a phase equation with a specified name. More...

virtual void	preUpdateMesh ()
	Prepare for mesh update. More...

virtual void	correct ()
	Correct the fvModel. More...

template<class Type , class AlphaRhoFieldType , class ... AlphaRhoFieldTypes>
Foam::dimensionSet	sourceDims (const GeometricField< Type, fvPatchField, volMesh > &field, const dimensionSet &ds, const AlphaRhoFieldType &alphaRho, const AlphaRhoFieldTypes &... alphaRhos)

template<class Type >
Foam::dimensionSet	sourceDims (const GeometricField< Type, fvPatchField, volMesh > &field, const dimensionSet &ds)

template<class Type , class ... AlphaRhoFieldTypes>
Foam::tmp< Foam::fvMatrix< Type > >	source (const GeometricField< Type, fvPatchField, volMesh > &field, const word &fieldName, const dimensionSet &ds, const AlphaRhoFieldTypes &... alphaRhos) const

template<class Type >
Foam::tmp< Foam::fvMatrix< Type > >	source (const GeometricField< Type, fvPatchField, volMesh > &field) const

template<class Type >
Foam::tmp< Foam::fvMatrix< Type > >	source (const GeometricField< Type, fvPatchField, volMesh > &field, const word &fieldName) const

template<class Type >
Foam::tmp< Foam::fvMatrix< Type > >	source (const volScalarField &rho, const GeometricField< Type, fvPatchField, volMesh > &field) const

template<class Type >
Foam::tmp< Foam::fvMatrix< Type > >	source (const volScalarField &rho, const GeometricField< Type, fvPatchField, volMesh > &field, const word &fieldName) const

template<class Type >
Foam::tmp< Foam::fvMatrix< Type > >	source (const volScalarField &alpha, const volScalarField &rho, const GeometricField< Type, fvPatchField, volMesh > &field) const

template<class Type >
Foam::tmp< Foam::fvMatrix< Type > >	source (const volScalarField &alpha, const volScalarField &rho, const GeometricField< Type, fvPatchField, volMesh > &field, const word &fieldName) const

Additional Inherited Members
Static Public Member Functions inherited from fvModel
template<class Type , class AlphaRhoFieldType , class ... AlphaRhoFieldTypes>
static dimensionSet	sourceDims (const GeometricField< Type, fvPatchField, volMesh > &field, const dimensionSet &ds, const AlphaRhoFieldType &alphaRho, const AlphaRhoFieldTypes &... alphaRhos)
	Return the dimensions of the matrix of a source term. More...

template<class Type >
static dimensionSet	sourceDims (const GeometricField< Type, fvPatchField, volMesh > &field, const dimensionSet &ds)
	Return the dimensions of the matrix of a source term (base. More...

static autoPtr< fvModel >	New (const word &name, const dictionary &dict, const fvMesh &mesh)
	Return a reference to the selected fvModel. More...

Protected Member Functions inherited from damping
void	readCoeffs ()
	Non-virtual read. More...

tmp< volScalarField::Internal >	forceCoeff () const
	Return the force coefficient. More...

Protected Member Functions inherited from fvModel
template<class Type >
void	addSupType (fvMatrix< Type > &eqn, const word &fieldName) const
	Add a source term to an equation. More...

template<class Type >
void	addSupType (const volScalarField &rho, fvMatrix< Type > &eqn, const word &fieldName) const
	Add a source term to a compressible equation. More...

template<class Type >
void	addSupType (const volScalarField &alpha, const volScalarField &rho, fvMatrix< Type > &eqn, const word &fieldName) const
	Add a source term to a phase equation. More...

template<class Type , class ... AlphaRhoFieldTypes>
tmp< fvMatrix< Type > >	source (const GeometricField< Type, fvPatchField, volMesh > &field, const word &fieldName, const dimensionSet &ds, const AlphaRhoFieldTypes &... alphaRhos) const
	Return source for equation with specified name and dimensions. More...

Protected Attributes inherited from damping
word	UName_
	Name of the velocity field. More...

dimensionedScalar	lambda_
	Damping coefficient [1/s]. More...

autoPtr< Function1< scalar > >	scale_
	The scaling function. More...

vectorField	origins_
	Origins of the scaling coordinate. More...

vectorField	directions_
	Directions of increasing scaling coordinate. More...

Detailed Description

This fvModel applies an explicit damping force to components of the vector field in the direction of gravity. Its intended purpose is to damp the vertical motions of an interface in the region approaching an outlet so that no reflections are generated.

Damping is achieved by applying a force to the momentum equation proportional to the momentum of the flow in the direction of gravity. The constant of proportionality is given by a coefficient $\lambda$ which has units of inverse-time. In the absence of any other forces this would generate an exponential decay of the vertical velocity.

$\frac{d (m u_z)}{d t} = - \lambda m u_z$

$u_z = u_{z0} e^{- \lambda t}$

The coefficient $\lambda$ should be set based on the desired level of damping and the residence time of a perturbation through the damping zone. For example, if waves moving at 2 [m/s] are travelling through a damping zone 8 [m] in length, then the residence time is 4 [s]. If it is deemed necessary to damp for 5 time-scales, then $\lambda$ should be set to equal 5/(4 [s]) = 1.2 [1/s].

Usage

Example usage:

verticalDamping1
{
    type            verticalDamping;

    // Define the line along which to apply the graduation
    origin          (1200 0 0);
    direction       (1 0 0);

    // Or, define multiple lines
    // origins         ((1200 0 0) (1200 -300 0) (1200 300 0));
    // directions      ((1 0 0) (0 -1 0) (0 1 0));

    scale
    {
        type        halfCosineRamp;
        start       0;
        duration    600;
    }

    lambda          [0 0 -1 0 0 0 0] 1; // Damping coefficient

    timeStart       0;
    duration        1e6;
}