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292 lines
8.8 KiB
C++
292 lines
8.8 KiB
C++
/*---------------------------------------------------------------------------*\
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========= |
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\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
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\\ / O peration |
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\\ / A nd | www.openfoam.com
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\\/ M anipulation |
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-------------------------------------------------------------------------------
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Copyright (C) 2020-2021 OpenCFD Ltd.
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-------------------------------------------------------------------------------
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License
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This file is part of OpenFOAM.
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OpenFOAM is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
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Class
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Foam::functionObjects::DMD
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Group
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grpFieldFunctionObjects
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Description
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Computes a dynamic mode decomposition model on a specified field.
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Dynamic mode decomposition (i.e. DMD) is a data-driven
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dimensionality reduction method. DMD is being used as a mathematical
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processing tool to reveal dominant modes out of a given field (or dataset)
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each of which is associated with a constant frequency and decay rate,
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so that dynamic features of a given flow may become interpretable,
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tractable, and even reproducible without computing simulations.
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DMD only relies on input data, therefore it is an equation-free approach.
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References:
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\verbatim
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DMD characteristics:
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Brunton S. L. (2018).
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Dynamic mode decomposition overview.
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Seattle, Washington: University of Washington.
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youtu.be/sQvrK8AGCAo (Retrieved:24-04-20)
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\endverbatim
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Operands:
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\table
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Operand | Type | Location
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input | {vol,surface}\<Type\>Field(s) <!--
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--> | \<time\>/\<inputField\>(s)
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output file | dat | postProcessing/\<FO\>/\<time\>/\<file\>(s)
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output field | volVectorField(s) | \<time\>/\<outputField\>(s)
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\endtable
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where \c \<Type\>=Scalar/Vector/SphericalTensor/SymmTensor/Tensor.
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Output fields:
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\verbatim
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modeRe_<modeIndex>_<field>_<FO> | Real part of a mode field
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modeIm_<modeIndex>_<field>_<FO> | Imaginary part of a mode field
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\endverbatim
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Output files:
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\verbatim
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dynamics_<field>.dat | Dynamics data for each mode
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filtered_dynamics_<field>.dat | Filtered dynamics data for each mode
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\endverbatim
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wherein for each mode, the following quantities are output into files:
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\vartable
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freq | Frequency
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mag | Magnitude
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ampRe | Amplitude coefficients (real part)
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ampIm | Amplitude coefficients (imaginary part)
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evalRe | Eigenvalue (real part)
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evalIm | Eigenvalue (imaginary part)
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\endvartable
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Usage
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Minimal example by using \c system/controlDict.functions:
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\verbatim
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DMD1
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{
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// Mandatory entries (unmodifiable)
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type DMD;
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libs (fieldFunctionObjects);
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DMDModel <DMDModel>;
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field <inputField>;
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// Optional entries (unmodifiable)
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patch <patchName>;
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// Mandatory/Optional (inherited) entries
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...
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}
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\endverbatim
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where the entries mean:
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\table
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Property | Description | Type | Reqd | Deflt
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type | Type name: DMD | word | yes | -
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libs | Library name: fieldFunctionObjects | word | yes | -
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DMDModel | Name of specified DMD model | word | yes | -
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field | Name of operand field | word | yes | -
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patch | Name of operand patch | word | no | null
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\endtable
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Options for the \c DMDModel entry:
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\verbatim
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STDMD | Streaming total dynamic mode decomposition
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\endverbatim
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The inherited entries are elaborated in:
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- \link functionObject.H \endlink
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- \link writeFile.H \endlink
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Minimal example by using the \c postProcess utility:
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\verbatim
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<solver> -postProcess -fields '(U p)' -time '10:'
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\endverbatim
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Note
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- Warning: DMD is an active research area at the time of writing;
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therefore, there could be cases whereat oddities can be seen.
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See also
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- Foam::functionObjects::fvMeshFunctionObject
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- Foam::functionObjects::writeFile
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- Foam::DMDModel
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- Foam::DMDModels::STDMD
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SourceFiles
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DMD.C
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DMDTemplates.C
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\*---------------------------------------------------------------------------*/
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#ifndef functionObjects_DMD_H
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#define functionObjects_DMD_H
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#include "fvMeshFunctionObject.H"
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#include "RectangularMatrix.H"
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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namespace Foam
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{
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// Forward Declarations
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class DMDModel;
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namespace functionObjects
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{
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/*---------------------------------------------------------------------------*\
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Class DMD Declaration
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\*---------------------------------------------------------------------------*/
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class DMD
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:
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public fvMeshFunctionObject
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{
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typedef RectangularMatrix<scalar> RMatrix;
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// Private Data
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//- Dynamic mode decomposition model
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autoPtr<DMDModel> DMDModelPtr_;
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//- Augmented snapshot matrix (effectively a column vector)
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// Upper half = current-time snapshot slot
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// Lower half = previous-time snapshot slot
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// A snapshot is an input dataset to be processed per execution step
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// A single snapshot is usually referred to as the snapshot of a single
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// time step, an augmented snapshot is constructed of two snapshots
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RMatrix z_;
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//- Name of operand field
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const word fieldName_;
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//- Name of operand patch
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const word patch_;
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//- Number of elements in a snapshot
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label nSnap_;
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//- Current execution-step index of DMD,
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//- not necessarily that of the simulation
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label step_;
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// Private Member Functions
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// Evaluation
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//- Initialise snapshot at the first-execution step
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// Initialisation at the ctor or read level is not possible
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// since the operand field is not available in the database
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void initialise();
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//- Create operand snapshot by using
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//- current-time and previous-time operand fields
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void snapshot();
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//- Get operand field based on its base type
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template<class Type>
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bool getSnapshot();
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//- Store operand field based on its geometric
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//- field type after few manipulations
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// Move previous-time field into previous-time slot in snapshot
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// copy new current-time field into current-time slot in snapshot
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template<class GeoFieldType>
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bool storeSnapshot();
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// Access
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//- Return number of components of the base type of a given field
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label nComponents(const word& fieldName) const;
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//- Get the number of components of the base type of a given field
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template<class Type>
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bool nComponents(const word& fieldName, label& nComps) const;
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public:
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//- Runtime type information
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TypeName("DMD");
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// Constructors
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//- Construct from Time and dictionary
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DMD
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(
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const word& name,
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const Time& runTime,
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const dictionary& dict
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);
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//- No copy construct
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DMD(const DMD&) = delete;
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//- No copy assignment
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void operator=(const DMD&) = delete;
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//- Destructor
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virtual ~DMD() = default;
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// Member Functions
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//- Read DMD settings
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virtual bool read(const dictionary& dict);
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//- Execute DMD
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virtual bool execute();
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//- Write DMD results
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virtual bool write();
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//- Write DMD results
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virtual bool end();
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};
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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} // End namespace functionObjects
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} // End namespace Foam
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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#ifdef NoRepository
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#include "DMDTemplates.C"
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#endif
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// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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#endif
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// ************************************************************************* //
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