Computes the Obukhov length field and associated friction velocity field. More...

Inheritance diagram for ObukhovLength:

Collaboration diagram for ObukhovLength:

Public Member Functions
	TypeName ("ObukhovLength")
	Run-time type information. More...

	ObukhovLength (const word &name, const Time &runTime, const dictionary &dict)
	Construct from Time and dictionary. More...

	ObukhovLength (const ObukhovLength &)=delete
	No copy construct. More...

void	operator= (const ObukhovLength &)=delete
	No copy assignment. More...

virtual	~ObukhovLength ()=default
	Destructor. More...

void	removeObukhovLength ()
	Remove (checkOut) the output fields from the object registry. More...

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

virtual bool	execute ()
	Calculate the output fields. More...

virtual bool	write ()
	Write the output fields. More...

virtual void	updateMesh (const mapPolyMesh &mpm)
	Update for changes of mesh. More...

virtual void	movePoints (const polyMesh &m)
	Update for mesh point-motion. More...

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

	fvMeshFunctionObject (const word &name, const Time &runTime, const dictionary &dict)
	Construct from Time and dictionary. More...

	fvMeshFunctionObject (const word &name, const objectRegistry &obr, const dictionary &dict)
	Construct from the region objectRegistry and dictionary. More...

virtual	~fvMeshFunctionObject ()=default
	Destructor. More...

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

	regionFunctionObject (const word &name, const Time &runTime, const dictionary &dict)
	Construct from Time and dictionary. More...

	regionFunctionObject (const word &name, const objectRegistry &obr, const dictionary &dict)
	Construct from the region objectRegistry and dictionary. More...

virtual	~regionFunctionObject ()=default
	Destructor. More...

template<class ObjectType >
const ObjectType *	lookupObjectPtr (const word &fieldName) const
	Deprecated(2018-10) More...

template<class ObjectType >
ObjectType *	lookupObjectRefPtr (const word &fieldName) const
	Deprecated(2018-10) More...

Public Member Functions inherited from stateFunctionObject
	stateFunctionObject (const word &name, const Time &runTime)
	Construct from components. More...

virtual	~stateFunctionObject ()=default
	Destructor. More...

dictionary &	propertyDict ()
	Return access to the property dictionary. More...

bool	foundProperty (const word &entryName) const
	Return true if the property exists. More...

void	clearTrigger ()
	Remove the trigger index from the properties. More...

label	getTrigger () const
	Get the current trigger index. More...

bool	setTrigger (const label triggeri, bool increaseOnly=true)
	Set the trigger index. Normally only if greater than current. More...

bool	getDict (const word &entryName, dictionary &dict) const
	Set dictionary, return true if set. More...

bool	getObjectDict (const word &objectName, const word &entryName, dictionary &dict) const
	Set dictionary from named object, return true if set. More...

template<class Type >
Type	getProperty (const word &entryName, const Type &defaultValue=Type(Zero)) const
	Retrieve generic property. More...

template<class Type >
bool	getProperty (const word &entryName, Type &value) const
	Set generic property, return true if set. More...

template<class Type >
void	setProperty (const word &entryName, const Type &value)
	Add generic property. More...

template<class Type >
Type	getObjectProperty (const word &objectName, const word &entryName, const Type &defaultValue=Type(Zero)) const
	Retrieve generic property from named object. More...

template<class Type >
bool	getObjectProperty (const word &objectName, const word &entryName, Type &value) const
	Set generic property from named object, return true if set. More...

template<class Type >
void	setObjectProperty (const word &objectName, const word &entryName, const Type &value)
	Add generic property from named object. More...

template<class Type >
void	setResult (const word &entryName, const Type &value)
	Add result. More...

template<class Type >
void	setObjectResult (const word &objectName, const word &entryName, const Type &value)
	Add result from named object. More...

template<class Type >
Type	getResult (const word &entryName, const Type &defaultValue=Type(Zero)) const
	Retrieve result. More...

template<class Type >
Type	getObjectResult (const word &objectName, const word &entryName, const Type &defaultValue=Type(Zero)) const
	Retrieve result from named object. More...

template<class Type >
bool	getObjectResult (const word &objectName, const word &entryName, Type &value) const
	Set result from named object, return true if set. More...

word	resultType (const word &entryName) const
	Retrieve the result type. More...

word	objectResultType (const word &objectName, const word &entryName) const
	Return the type of result. More...

wordList	objectResultEntries () const
	Retrieve the result entries. More...

wordList	objectResultEntries (const word &objectName) const
	Return result entries for named object. More...

void	writeResultEntries (Ostream &os) const
	Write the results entries for all objects to stream. More...

void	writeResultEntries (const word &objectName, Ostream &os) const
	Write the results entries for named object to stream. More...

void	writeAllResultEntries (Ostream &os) const
	Write the results entries for all objects to stream. More...

Public Member Functions inherited from timeFunctionObject
	timeFunctionObject (const word &name, const Time &runTime)
	Construct from Time. More...

virtual	~timeFunctionObject ()=default
	Destructor. More...

const Time &	time () const
	Return time database. More...

objectRegistry &	storedObjects ()

const objectRegistry &	storedObjects () const

Public Member Functions inherited from functionObject
	declareRunTimeSelectionTable (autoPtr, functionObject, dictionary,(const word &name, const Time &runTime, const dictionary &dict),(name, runTime, dict))

	functionObject (const word &name, const bool withNamePrefix=defaultUseNamePrefix)
	Construct from components. More...

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

virtual	~functionObject ()=default
	Destructor. More...

virtual const word &	type () const =0
	Runtime type information. More...

const word &	name () const noexcept
	Return the name of this functionObject. More...

bool	useNamePrefix () const noexcept
	Return the flag for adding a scoping name prefix. More...

bool	useNamePrefix (bool on) noexcept
	Modify the flag for adding a scoping name prefix. More...

virtual bool	execute (const label subIndex)
	Execute using the specified subIndex. More...

virtual bool	end ()
	Called when Time::run() determines that the time-loop exits. More...

virtual bool	adjustTimeStep ()
	Called at the end of Time::adjustDeltaT() if adjustTime is true. More...

virtual bool	filesModified () const
	Did any file get changed during execution? More...

Protected Member Functions
bool	calcOL ()
	Hard-coded Obukhov length field and friction velocity. More...

Protected Member Functions inherited from fvMeshFunctionObject
	fvMeshFunctionObject (const fvMeshFunctionObject &)=delete
	No copy construct. More...

void	operator= (const fvMeshFunctionObject &)=delete
	No copy assignment. More...

Protected Member Functions inherited from regionFunctionObject
virtual const objectRegistry &	obr () const
	The region or sub-region registry being used. More...

template<class ObjectType >
bool	foundObject (const word &fieldName) const
	Find object (eg, a field) in the (sub) objectRegistry. More...

template<class ObjectType >
const ObjectType *	cfindObject (const word &fieldName) const

template<class ObjectType >
const ObjectType *	findObject (const word &fieldName) const

template<class ObjectType >
ObjectType *	findObject (const word &fieldName)

template<class ObjectType >
ObjectType *	getObjectPtr (const word &fieldName) const

template<class ObjectType >
const ObjectType &	lookupObject (const word &fieldName) const
	Lookup and return object (eg, a field) from the (sub) objectRegistry. More...

template<class ObjectType >
ObjectType &	lookupObjectRef (const word &fieldName) const
	Lookup and return object (eg, a field) from the (sub) objectRegistry. More...

template<class ObjectType >
bool	store (word &fieldName, const tmp< ObjectType > &tfield, bool cacheable=false)
	Store the field in the (sub) objectRegistry under the given name. More...

template<class ObjectType >
bool	storeInDb (const word &fieldName, const tmp< ObjectType > &tfield, const objectRegistry &obr)
	Store the field in an optional objectRegistry under the given name. More...

bool	writeObject (const word &fieldName)
	Write field if present in the (sub) objectRegistry. More...

bool	clearObject (const word &fieldName)
	Clear field from the (sub) objectRegistry if present. More...

void	clearObjects (const wordList &objNames)
	Clear fields from the (sub) objectRegistry if present. More...

	regionFunctionObject (const regionFunctionObject &)=delete
	No copy construct. More...

void	operator= (const regionFunctionObject &)=delete
	No copy assignment. More...

Protected Member Functions inherited from stateFunctionObject
const functionObjects::properties &	stateDict () const
	Return a const reference to the state dictionary. More...

functionObjects::properties &	stateDict ()
	Return non-const access to the state dictionary. More...

	stateFunctionObject (const stateFunctionObject &)=delete
	No copy construct. More...

void	operator= (const stateFunctionObject &)=delete
	No copy assignment. More...

Protected Member Functions inherited from timeFunctionObject
void	clearOutputObjects (const wordList &objNames)
	Remove specified items from "functionObjectObjects". More...

	timeFunctionObject (const timeFunctionObject &)=delete
	No copy construct. More...

void	operator= (const timeFunctionObject &)=delete
	No copy assignment. More...

Protected Member Functions inherited from functionObject
word	scopedName (const word &name) const
	Return a scoped (prefixed) name. More...

Protected Attributes
word	UName_
	Name of velocity field. More...

word	resultName1_
	Name of the output field for ObukhovLength. More...

word	resultName2_
	Name of the output field for Ustar. More...

scalar	rhoRef_
	Reference density (to convert from kinematic to static pressure) More...

scalar	kappa_
	von Kármán constant [-] More...

dimensionedScalar	beta_
	Thermal expansion coefficient [1/K]. More...

const dimensionedVector	g_
	Gravitational acceleration vector [m/s2]. More...

Protected Attributes inherited from fvMeshFunctionObject
const fvMesh &	mesh_
	Reference to the fvMesh. More...

Protected Attributes inherited from regionFunctionObject
word	subRegistryName_
	Name for alternative object registry. More...

const objectRegistry &	obr_
	Reference to the region objectRegistry. More...

const objectRegistry *	obrPtr_
	Pointer to alternative (eg, sub-region) objectRegistry. More...

Protected Attributes inherited from timeFunctionObject
const Time &	time_
	Reference to the time database. More...

Additional Inherited Members
Static Public Member Functions inherited from functionObject
static autoPtr< functionObject >	New (const word &name, const Time &runTime, const dictionary &dict)
	Select from dictionary, based on its "type" entry. More...

Public Attributes inherited from functionObject
bool	log
	Flag to write log into Info. More...

Static Public Attributes inherited from functionObject
static int	debug
	Flag to execute debug content. More...

static bool	postProcess
	Global post-processing mode switch. More...

static bool	defaultUseNamePrefix
	Global default for useNamePrefix. More...

static word	outputPrefix
	Directory prefix. More...

Detailed Description

Computes the Obukhov length field and associated friction velocity field.

When scaled by the ground-normal height, i.e. z, the Obukhov length becomes a dimensionless stability parameter, i.e. z/L, for atmospheric boundary layer modelling, expressing the relative roles of buoyancy and shear in the production and dissipation of turbulent kinetic energy.

\[ u^* = \sqrt{\max (\nu_t \sqrt{2 |\symm{\grad{u}}|^2}, VSMALL)} \]

\[ L_o = - \frac{(u^*)^3}{sign(B) \kappa \max (|B|, VSMALL)} \]

with

\[ B = \alpha_t \beta \frac{\grad{T} \cdot \vec{g}}{\rho} \]

where

$ u^* $	=	Friction velocity [m/s]
$ \nu_t $	=	Turbulent viscosity [m2/s]
$ u $	=	Velocity [m/s]
$ L_o $	=	Obukhov length [m]
$ B $	=	Buoyancy production term [m2/s3]
$ \alpha_t $	=	Kinematic turbulent thermal conductivity [m2/s]/[kg/m/s]
$ \rho $	=	Density of fluid [-]/[kg/m3]
$ \beta $	=	Thermal expansion coefficient [1/K]
$ T $	=	Temperature [K]
$ g $	=	Gravitational acceleration [m/s2]
$ VSMALL $	=	A very small number to avoid floating point exceptions

References:

    Definition of the Obukhov length (tag:O):
        Obukhov, A. M. (1946).
        Turbulentnost'v temperaturnoj-neodnorodnoj atmosfere.
        Trudy Inst. Theor. Geofiz. AN SSSR, 1, 95-115.

        Obukhov, A. M. (1971).
        Turbulence in an atmosphere with a non-uniform temperature.
        Boundary-layer meteorology, 2(1), 7-29.
        DOI:10.1007/BF00718085

        Obukhov length. (2016).
        In American Meteorological Society - Glossary of meteorology.
        Retrieved Apr 1, 2020, from glossary.ametsoc.org/wiki/Obukhov_length

Required fields:

      U           | Velocity                                 [m/s]
      T           | Temperature                              [K]
      nut         | Turbulent viscosity                      [m2/s]
      alphat      | Kinematic turbulent thermal conductivity [m2/s]/[kg/m/s]
      g           | Gravitational acceleration               [m/s2]

Operand	Type	Location
`input`	-	-
`output` file	-	-
`output` field 1	volScalarField	$FOAM_CASE/<time>/<ObukhovLength>
`output` field 2	volScalarField	$FOAM_CASE/<time>/<Ustar>

Usage

Minimal example by using system/controlDict.functions:

ObukhovLength1
{
    // Mandatory entries (unmodifiable)
    type            ObukhovLength;
    libs            (fieldFunctionObjects);

    // Optional entries (runtime modifiable)
    U               U;
    result1         ObukhovLength;
    result2         Ustar;
    rhoRef          1.0;
    kappa           0.4;
    beta            3e-3;

    // Optional (inherited) entries
    ...
}

where the entries mean:

Property	Description	Type	Req'd	Dflt
`type`	Type name: ObukhovLength	word	yes	-
`libs`	Library name: fieldFunctionObjects	word	yes	-
`U`	Name of the velocity field	word	no	U
`result1`	Name of the output field for ObukhovLength	word	no	ObukhovLength
`result2`	Name of the output field for Ustar	word	no	Ustar
`rhoRef`	Reference density (to convert from kinematic to static pressure)	scalar	no	1.0
`kappa`	von Kármán constant	scalar	no	0.40
`beta`	Thermal expansion coefficient	scalar	no	3e-3

The inherited entries are elaborated in:

functionObject.H

Minimal example by using the postProcess utility:

        postProcess -func "ObukhovLength(<UField>)"

See also

Foam::functionObjects::fvMeshFunctionObject
ExtendedCodeGuide::atmosphericModels::functionObjects::ObukhovLength

Source files

Definition at line 297 of file ObukhovLength.H.

Constructor & Destructor Documentation

◆ ObukhovLength() [1/2]

ObukhovLength	(	const word &	name,
		const Time &	runTime,
		const dictionary &	dict
	)

Construct from Time and dictionary.

Definition at line 144 of file ObukhovLength.C.

References dict, and Foam::read().

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◆ ObukhovLength() [2/2]

ObukhovLength ( const ObukhovLength & )

delete

No copy construct.

◆ ~ObukhovLength()

virtual ~ObukhovLength ( )

virtualdefault

Destructor.

Member Function Documentation

◆ calcOL()

bool calcOL ( )

protected

Hard-coded Obukhov length field and friction velocity.

Returns: true if fields did not previously exist

Definition at line 51 of file ObukhovLength.C.

References B, ObukhovLength::beta_, dimensioned< Type >::dimensions(), Foam::dimLength, Foam::dimless, Foam::dimVelocity, objectRegistry::findObject(), ObukhovLength::g_, objectRegistry::getObjectPtr(), Foam::fvc::grad(), ObukhovLength::kappa_, objectRegistry::lookupObject(), Foam::mag(), Foam::magSqr(), Foam::max(), fvMeshFunctionObject::mesh_, Foam::min(), IOobject::NO_READ, IOobject::NO_WRITE, nut, Foam::pow3(), ObukhovLength::resultName1_, ObukhovLength::resultName2_, rho, rhoPtr, ObukhovLength::rhoRef_, Foam::sign(), Foam::sqr(), Foam::sqrt(), Foam::symm(), Foam::T(), fvMesh::time(), Time::timeName(), U, and ObukhovLength::UName_.

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◆ TypeName()

TypeName ( "ObukhovLength" )

Run-time type information.

◆ operator=()

void operator= ( const ObukhovLength & )

delete

No copy assignment.

◆ removeObukhovLength()

void removeObukhovLength ( )

Remove (checkOut) the output fields from the object registry.

Definition at line 241 of file ObukhovLength.C.

◆ read()

bool read ( const dictionary & dict )

virtual

Read the data.

Reimplemented from regionFunctionObject.

Definition at line 182 of file ObukhovLength.C.

References dict, Foam::constant::electromagnetic::e, and regionFunctionObject::read().

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◆ execute()

bool execute ( )

virtual

Calculate the output fields.

Implements functionObject.

Definition at line 208 of file ObukhovLength.C.

References Foam::endl(), Log, Foam::name(), Foam::nl, and Foam::type().

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◆ write()

bool write ( )

virtual

Write the output fields.

Implements functionObject.

Definition at line 222 of file ObukhovLength.C.

References Foam::endl(), Log, Foam::name(), IOobject::name(), Foam::nl, Foam::type(), Ostream::write(), and regIOobject::write().

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◆ updateMesh()

void updateMesh ( const mapPolyMesh & mpm )

virtual

Update for changes of mesh.

Reimplemented from functionObject.

Definition at line 248 of file ObukhovLength.C.

References mapPolyMesh::mesh().

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◆ movePoints()

void movePoints ( const polyMesh & m )

virtual

Update for mesh point-motion.

Reimplemented from functionObject.

Definition at line 257 of file ObukhovLength.C.

Member Data Documentation

◆ UName_

word UName_

protected

Name of velocity field.

Definition at line 306 of file ObukhovLength.H.

Referenced by ObukhovLength::calcOL().

◆ resultName1_

word resultName1_

protected

Name of the output field for ObukhovLength.

Definition at line 309 of file ObukhovLength.H.

Referenced by ObukhovLength::calcOL().

◆ resultName2_

word resultName2_

protected

Name of the output field for Ustar.

Definition at line 312 of file ObukhovLength.H.

Referenced by ObukhovLength::calcOL().

◆ rhoRef_

scalar rhoRef_

protected

Reference density (to convert from kinematic to static pressure)

Definition at line 315 of file ObukhovLength.H.

Referenced by ObukhovLength::calcOL().

◆ kappa_

scalar kappa_

protected

von Kármán constant [-]

Definition at line 318 of file ObukhovLength.H.

Referenced by ObukhovLength::calcOL().

◆ beta_

dimensionedScalar beta_

protected

Thermal expansion coefficient [1/K].

Definition at line 321 of file ObukhovLength.H.

Referenced by ObukhovLength::calcOL().

◆ g_

const dimensionedVector g_

protected

Gravitational acceleration vector [m/s2].

Definition at line 324 of file ObukhovLength.H.

Referenced by ObukhovLength::calcOL().

The documentation for this class was generated from the following files:

src/atmosphericModels/functionObjects/ObukhovLength/ObukhovLength.H
src/atmosphericModels/functionObjects/ObukhovLength/ObukhovLength.C

\( u^* \)	=	Friction velocity [m/s]
\( \nu_t \)	=	Turbulent viscosity [m2/s]
\( u \)	=	Velocity [m/s]
\( L_o \)	=	Obukhov length [m]
\( B \)	=	Buoyancy production term [m2/s3]
\( \alpha_t \)	=	Kinematic turbulent thermal conductivity [m2/s]/[kg/m/s]
\( \rho \)	=	Density of fluid [-]/[kg/m3]
\( \beta \)	=	Thermal expansion coefficient [1/K]
\( T \)	=	Temperature [K]
\( g \)	=	Gravitational acceleration [m/s2]
\( VSMALL \)	=	A very small number to avoid floating point exceptions

Public Member Functions

Protected Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ ObukhovLength() [1/2]

◆ ObukhovLength() [2/2]

◆ ~ObukhovLength()

Member Function Documentation

◆ calcOL()

◆ TypeName()

◆ operator=()

◆ removeObukhovLength()

◆ read()

◆ execute()

◆ write()

◆ updateMesh()

◆ movePoints()

Member Data Documentation

◆ UName_

◆ resultName1_

◆ resultName2_

◆ rhoRef_

◆ kappa_

◆ beta_

◆ g_