levelSetDesignVariables.H

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    Copyright (C) 2022-2023 PCOpt/NTUA
    Copyright (C) 2022-2023 FOSS GP
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License
    This file is part of OpenFOAM.
 
    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
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Class
    Foam::levelSetDesignVariables
 
Description
    Signed distance field design variables for level-set based topology
    optimization (topO).
 
    A great reference for various aspects of level-set-based topO can be found
    in
 
    Reference:
    \verbatim
        van Dijk, N.P., Maute, K., Langelaar, M., & & van Keulen, F. (2013).
        Level-set methods for structural topology optimization: a review.
        Structural and Multidisciplinary Optimization, 48, 437–472.
        https://doi.org/10.1007/s00158-013-0912-y
    \endverbatim
 
    The implemented approach borrows from the references therein, but does not
    follow any of them exactly. The underlying field of the design variables
    is not the level-set field but affects the latter through:
    a) a regularisation approach similar to that used in porosity-based topO
    (see the regularisation class and references therein) and
    b) a re-initialisation strategy. Since solving a modified Hamilton-Jacobi
    equation poses a number of numerical challenges, the signed distance field
    is obtained by identifying the zero level-set contour using the
    cutFaceIso, cutCellIso infrastructure (see references therein for the
    methodology) and using these "cut-faces" as seeds for meshWave.
 
SourceFiles
    levelSetDesignVariables.C
 
\*---------------------------------------------------------------------------*/
 
#ifndef levelSetDesignVariables_H
#define levelSetDesignVariables_H
 
#include "topOVariablesBase.H"
#include "designVariables.H"
#include "regularisationRadius.H"
#include "regularisationPDE.H"
#include "topOInterpolationFunction.H"
#include "adjointSensitivity.H"
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
namespace Foam
{
 
/*---------------------------------------------------------------------------*\
                   Class levelSetDesignVariables Declaration
\*---------------------------------------------------------------------------*/
 
class levelSetDesignVariables
:
    public topOVariablesBase,
    public designVariables
{
protected:
 
    // Protected Data Members
 
        //- The regularisation radius
        autoPtr<regularisationRadius> radius_;
 
        //- Regularisation mechanism
        autoPtr<regularisationPDE> regularisation_;
 
        //- The regularised field
        volScalarField aTilda_;
 
        //- The signed distances field
        volScalarField signedDistances_;
 
        //- Function to transorm signed distances to the indicator field beta_
        autoPtr<topOInterpolationFunction> interpolation_;
 
        //- The indicator field
        volScalarField beta_;
 
        //- Fix aTilda values in fixed{Zero}PorousZones and IOcells
        bool fixATildaValues_;
 
        //- Write all fields related to the distance calculation (debugging)
        bool writeAllDistanceFields_;
 
        //- Mesh faces acting as the source of MeshWave
        labelList changedFaces_;
 
        //- Seed distances to MeshWave and cell distances
        //  The data carried by each wallPoints corresponds to the origin
        //  mesh face ID
        List<wallPointData<label>> changedFacesInfo_;
        List<wallPointData<label>> allCellInfo_;
 
 
    // Protected Member Functions
 
        //- Read the design variables field
        void readField();
 
        //- Apply fixed values in certain zones
        void applyFixedPorosityValues();
 
        //- Determine which design variables are active
        void setActiveDesignVariables(bool activeIO = false);
 
        //- Make aTilda a signed distance field based on the zero iso-surface
        //- of the current aTilda field
        void updateSignedDistances();
 
        //- Update the beta field
        void updateBeta();
 
 
private:
 
    // Private Member Functions
 
        //- No copy construct
        levelSetDesignVariables(const levelSetDesignVariables&) = delete;
 
        //- No copy assignment
        void operator=(const levelSetDesignVariables&) = delete;
 
 
public:
 
    //- Runtime type information
    TypeName("levelSet");
 
 
    // Constructors
 
        //- Construct from dictionary
        levelSetDesignVariables
        (
            fvMesh& mesh,
            const dictionary& dict
        );
 
 
    // Selectors
 
        //- Return a reference to the selected turbulence model
        static autoPtr<levelSetDesignVariables> New
        (
            fvMesh& mesh,
            const dictionary& dict
        );
 
 
    //- Destructor
    virtual ~levelSetDesignVariables() = default;
 
 
    // Member Functions
 
        //- Const reference to the beta field
        virtual const volScalarField& beta() const;
 
        //- Update design variables based on a given correction
        virtual void update(scalarField& correction);
 
        //- Compute eta if not set in the first step
        virtual scalar computeEta(scalarField& correction);
 
        //- Whether to use global sum when computing matrix-vector products
        //- in update methods
        virtual bool globalSum() const;
 
        //- Add contributions from the adjoint to the regularization PDE,
        //- the derivative of the interpolation function and the mesh volume
        //- to the final sensitivities
        virtual tmp<scalarField> assembleSensitivities
        (
            adjointSensitivity& adjointSens
        );
 
        //- Write useful quantities to files
        virtual void writeDesignVars();
 
        //- The writeData function required by the regIOobject write operation
        virtual bool writeData(Ostream&) const;
};
 
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
} // End namespace Foam
 
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
#endif
 
// ************************************************************************* //