NavierStokes.hpp

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#pragma once
 
#include <polyfem/assembler/MatParams.hpp>
#include <polyfem/assembler/Assembler.hpp>
 
#include <polyfem/utils/AutodiffTypes.hpp>
 
// Navier-Stokes local assembler
namespace polyfem::assembler
{
    class NavierStokesVelocity : public NLAssembler
    {
    public:
        using NLAssembler::assemble_energy;
        using NLAssembler::assemble_gradient;
        using NLAssembler::assemble_hessian;
 
        NavierStokesVelocity();
 
        std::string name() const override { return "NavierStokes"; }
        std::map<std::string, ParamFunc> parameters() const override;
 
        // navier stokes is not energy based
        double compute_energy(const NonLinearAssemblerData &data) const override
        {
            // not used, this formulation is gradient based!
            assert(false);
            return 0;
        }
 
        // res is R^{dim²}
        // pde
        Eigen::VectorXd
        assemble_gradient(const NonLinearAssemblerData &data) const override;
 
        Eigen::MatrixXd
        // gradient of pde, this returns full gradient or partil depending on the template
        assemble_hessian(const NonLinearAssemblerData &data) const override;
 
        // rhs for fabbricated solution
        VectorNd compute_rhs(const AutodiffHessianPt &pt) const override;
 
        // set viscosity
        void add_multimaterial(const int index, const json &params, const Units &units) override;
 
        bool is_fluid() const override { return true; }
        bool is_tensor() const override { return true; }
 
        void set_picard(const bool val) { full_gradient_ = !val; }
 
    private:
        GenericMatParam viscosity_;
 
        // not full graidnet used for Picard iteration
        bool full_gradient_ = true;
 
        Eigen::MatrixXd compute_N(const NonLinearAssemblerData &data) const;
        Eigen::MatrixXd compute_W(const NonLinearAssemblerData &data) const;
    };
 
} // namespace polyfem::assembler