Stokes.hpp

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#pragma once
 
#include <polyfem/assembler/MatParams.hpp>
#include <polyfem/assembler/Assembler.hpp>
 
#include <polyfem/utils/AutodiffTypes.hpp>
 
namespace polyfem::assembler
{
    // stokes local assembler for velocity
    class StokesVelocity : public LinearAssembler
    {
    public:
        using LinearAssembler::assemble;
 
        StokesVelocity();
 
        VectorNd compute_rhs(const AutodiffHessianPt &pt) const override;
        // res is R^{dim²}
        Eigen::Matrix<double, Eigen::Dynamic, 1, 0, 9, 1>
        assemble(const LinearAssemblerData &data) const override;
 
        void add_multimaterial(const int index, const json &params, const Units &units) override;
 
        const GenericMatParam &viscosity() const { return viscosity_; }
 
        virtual std::string name() const override { return "Stokes"; }
        std::map<std::string, ParamFunc> parameters() const override;
 
        bool is_fluid() const override { return true; }
        bool is_tensor() const override { return true; }
 
    private:
        GenericMatParam viscosity_;
    };
 
    // stokes mixed assembler (velocity phi and pressure psi)
    class StokesMixed : public MixedAssembler
    {
    public:
        std::string name() const override { return "StokesMixed"; }
 
        // res is R^{dim}
        Eigen::Matrix<double, Eigen::Dynamic, 1, 0, 3, 1>
        assemble(const MixedAssemblerData &data) const override;
 
        inline int rows() const override { return size(); }
        inline int cols() const override { return 1; }
    };
 
    // pressure only for stokes is zero
    class StokesPressure : public LinearAssembler
    {
    public:
        using LinearAssembler::assemble;
 
        std::string name() const override { return "StokesPressure"; }
        std::map<std::string, ParamFunc> parameters() const override { return std::map<std::string, ParamFunc>(); }
 
        // res is R^{dim²}
        Eigen::Matrix<double, Eigen::Dynamic, 1, 0, 9, 1>
        assemble(const LinearAssemblerData &data) const override
        {
            return Eigen::Matrix<double, 1, 1>::Zero(1, 1);
        }
 
        bool is_fluid() const override { return true; }
 
        void set_size(const int) override { size_ = 1; }
    };
 
    class OperatorSplitting : public StokesVelocity
    {
    public:
        OperatorSplitting() = default;
        ~OperatorSplitting() = default;
 
        std::string name() const override { return "OperatorSplitting"; }
    };
} // namespace polyfem::assembler