nikuradse.hh

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#ifndef DUMUX_MATERIAL_FLUIDMATRIX_FRICTIONLAW_NIKURADSE_HH
#define DUMUX_MATERIAL_FLUIDMATRIX_FRICTIONLAW_NIKURADSE_HH
 
#include <algorithm>
#include <cmath>
#include <dune/common/math.hh>
#include "frictionlaw.hh"
 
namespace Dumux {
template <typename VolumeVariables>
class FrictionLawNikuradse : public FrictionLaw<VolumeVariables>
{
    using Scalar = typename VolumeVariables::PrimaryVariables::value_type;
public:
    FrictionLawNikuradse(const Scalar ks)
        : ks_(ks) {}
 
    Dune::FieldVector<Scalar, 2> shearStress(const VolumeVariables& volVars) const final
    {
        using Dune::power;
        using std::log;
        using std::hypot;
 
        Dune::FieldVector<Scalar, 2> shearStress(0.0);
 
        Scalar roughnessHeight = ks_;
        roughnessHeight = this->limitRoughH(roughnessHeight, volVars.waterDepth());
        const Scalar ustarH = power(0.41,2)/power(log((12*(volVars.waterDepth() + roughnessHeight))/ks_),2);
        const Scalar uv = hypot(volVars.velocity(0),volVars.velocity(1));
 
        shearStress[0] = -ustarH * volVars.velocity(0) * uv;
        shearStress[1] = -ustarH * volVars.velocity(1) * uv;
 
        return shearStress;
    }
private:
    Scalar ks_;
};
 
} // end namespace Dumux
 
#endif