manning.hh

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#ifndef DUMUX_MATERIAL_FLUIDMATRIX_FRICTIONLAW_MANNING_HH
#define DUMUX_MATERIAL_FLUIDMATRIX_FRICTIONLAW_MANNING_HH
 
#include <algorithm>
#include <cmath>
#include <dune/common/math.hh>
#include "frictionlaw.hh"
 
namespace Dumux {
template <typename VolumeVariables>
class FrictionLawManning : public FrictionLaw<VolumeVariables>
{
    using Scalar = typename VolumeVariables::PrimaryVariables::value_type;
public:
    FrictionLawManning(const Scalar gravity, const Scalar manningN)
    : gravity_(gravity), manningN_(manningN) {}
 
    Dune::FieldVector<Scalar, 2> bottomShearStress(const VolumeVariables& volVars) const final
    {
        using std::pow;
        using Dune::power;
        using std::hypot;
 
        Dune::FieldVector<Scalar, 2> shearStress(0.0);
 
        Scalar roughnessHeight = power(25.68/(1.0/manningN_), 6);
        roughnessHeight = this->limitRoughH(roughnessHeight, volVars.waterDepth());
        // c has units of m^(1/2)/s so c^2 has units of m/s^2
        const Scalar c = pow(volVars.waterDepth() + roughnessHeight, 1.0/6.0) * 1.0/(manningN_);
        const Scalar uv = hypot(volVars.velocity(0), volVars.velocity(1));
 
        const Scalar dimensionlessFactor = gravity_/(c*c);
        shearStress[0] = dimensionlessFactor * volVars.velocity(0) * uv * volVars.density();
        shearStress[1] = dimensionlessFactor * volVars.velocity(1) * uv * volVars.density();
 
        return shearStress;
    }
 
private:
    Scalar gravity_;
    Scalar manningN_;
};
 
} // end namespace Dumux
 
#endif