ComponentNeBem2d.hh

Go to the documentation of this file.

#ifndef G_COMPONENT_NEBEM_2D_H
#define G_COMPONENT_NEBEM_2D_H
 
#include "ComponentBase.hh"
 
namespace Garfield {
 
/// Two-dimensional implementation of the nearly exact Boundary %Element Method.
 
class ComponentNeBem2d : public ComponentBase {
 public:
  /// Constructor
  ComponentNeBem2d();
  /// Destructor
  ~ComponentNeBem2d() {}
 
  Medium* GetMedium(const double x, const double y, const double z) override;
 
  void ElectricField(const double x, const double y, const double z, double& ex,
                     double& ey, double& ez, Medium*& m, int& status) override;
  void ElectricField(const double x, const double y, const double z, double& ex,
                     double& ey, double& ez, double& v, Medium*& m,
                     int& status) override;
  bool GetVoltageRange(double& vmin, double& vmax) override;
 
  bool GetBoundingBox(double& xmin, double& ymin, double& zmin,
                      double& xmax, double& ymax, double& zmax) override;
 
  bool IsWireCrossed(const double x0, const double y0, const double z0,
                     const double x1, const double y1, const double z1,
                     double& xc, double& yc, double& zc, const bool centre,
                     double& rc) override;
  bool IsInTrapRadius(const double q0, const double x0, const double y0,
                      const double z0, double& xw, double& yx,
                      double& rw) override;
 
  /// Set the "background" medium.
  void SetMedium(Medium* medium) { m_medium = medium; }
 
  /** Add a conducting straight-line segment.
    * \param x0,y0,x1,y1 coordinates of start and end point.
    * \param v applied potential.
    * \param ndiv number of elements in which to split the segment.
    */
  bool AddSegment(const double x0, const double y0, const double x1,
                  const double y1, const double v, const int ndiv = -1);
  /** Add a wire.
    * \param x,y centre of the wire.
    * \param d wire diameter.
    * \param v applied potential.
    * \param ntrap multiple of the wire radius within which a particle is 
             considered to be trapped by the wire. 
    */
  bool AddWire(const double x, const double y, const double d, const double v,
               const int ntrap = 5);
  /** Add a region bounded by a polygon.
    * \param xp,yp x/y-coordinates of the vertices of the polygon.
    * \param medium pointer to the medium associated to the region. 
    * \param bctype 1: fixed voltage, 4: dielectric-dielectric interface.
    * \param v applied potential.
    * \param ndiv number of elements on each edge segment.
    */ 
  bool AddRegion(const std::vector<double>& xp,
                 const std::vector<double>& yp, Medium* medium,
                 const unsigned int bctype = 4, const double v = 0.,
                 const int ndiv = -1);
  /// Set the extent of the drift region along z.
  void SetRangeZ(const double zmin, const double zmax);
 
  /// Discretise the geometry and compute the solution.
  bool Initialise();
 
  /// Set the default number of elements per segment.
  void SetNumberOfDivisions(const unsigned int ndiv);
 
  void SetNumberOfCollocationPoints(const unsigned int ncoll);
  void EnableAutoResizing(const bool on = true) { m_autoSize = on; }
  void EnableRandomCollocation(const bool on = true) {
    m_randomCollocation = on;
  }
  void SetMaxNumberOfIterations(const unsigned int niter);
 
  /// Return the number of regions.
  unsigned int GetNumberOfRegions() const { return m_regions.size(); }
  /// Return the properties of a given region.
  bool GetRegion(const unsigned int i,
                 std::vector<double>& xv, std::vector<double>& yv,
                 Medium*& medium, unsigned int& bctype, double& v);
  /// Return the number of conducting straight-line segments.
  unsigned int GetNumberOfSegments() const { return m_segments.size(); }
  /// Return the coordinates and voltage of a given straight-line segment.
  bool GetSegment(const unsigned int i, double& x0, double& y0, 
                  double& x1, double& x2, double& v) const;
  /// Return the number of wires.
  unsigned int GetNumberOfWires() const { return m_wires.size(); }
  /// Return the coordinates, diameter, potential and charge of a given wire.
  bool GetWire(const unsigned int i, double& x, double& y, double& d,
               double& v, double& q) const; 
  /// Return the number of boundary elements.
  unsigned int GetNumberOfElements() const { return m_elements.size(); }
  /// Return the coordinates and charge of a given boundary element.
  bool GetElement(const unsigned int i, double& x0, double& y0,
                  double& x1, double& y1, double& q) const;
 private:
  static const double InvEpsilon0;
  static const double InvTwoPiEpsilon0;
 
  /// Default number elements per segment.
  unsigned int m_nDivisions = 5;
  unsigned int m_nCollocationPoints = 1;
  bool m_autoSize = false;
  bool m_randomCollocation = false;
  unsigned int m_nMaxIterations = 3;
 
  /// Background medium.
  Medium* m_medium = nullptr;
  /// Flag whether a z-range has been defined by the user.
  bool m_useRangeZ = false;
  /// Lower z limit. 
  double m_zmin = -1.;
  /// Upper z limit.
  double m_zmax =  1.;
  /// Boundary condition type.
  enum BC {
    Voltage = 1, //< Fixed potential.
    Charge,      //< Fixed charge density (not implemented).
    Floating,    //< Floating conductor (not implemented).
    Dielectric   //< Dielectric-dielectric interface.
  };
  struct Region {
    std::vector<double> xv;    //< x-coordinates of the vertices.
    std::vector<double> yv;    //< y-coordinates of the vertices.
    Medium* medium;            //< Medium associated to the region.
    std::pair<BC, double> bc;  //< Applied boundary condition.
    unsigned int depth;        //< Level in the hierarchy.
    int ndiv;                  //< Number of elements per edge segment.
  };
  /// Regions.
  std::vector<Region> m_regions;
 
  struct Segment {
    std::array<double, 2> x0;  //< Coordinates of the start point.
    std::array<double, 2> x1;  //< Coordinates of the end point.
    int region1;               //< Inner region. 
    int region2;               //< Outer region.
    std::pair<BC, double> bc;  //< Applied boundary condition.
    int ndiv;                  //< Number of elements.
  };
  /// User-specified conducting straight-line segments.
  std::vector<Segment> m_segments;
 
  struct Wire {
    double x, y; //< Coordinates of the centre.
    double r;    //< Radius.
    double v;    //< Potential.
    double q;    //< Charge.
    int ntrap;   //< Trap radius (in units of the wire radius).
  };
  /// Wires.
  std::vector<Wire> m_wires;
 
  struct Element {
    double x, y; //< Coordinates of the element centre (collocation point).
    double a;    //< Half-length.
    double cphi; //< Rotation.
    double sphi; //< Rotation.
    double q;    //< Charge density (solution).
    std::pair<BC, double> bc; //< Boundary condition.
    double lambda;            //< Ratio of dielectric permittivities.
  };
  /// Straight-line boundary elements.
  std::vector<Element> m_elements;
 
  /// Split/merge overlapping segments.
  void EliminateOverlaps(std::vector<Segment>& segments);
  /// Create elements from a straight-line segment.
  bool Discretise(const Segment& segment, std::vector<Element>& elements,
                  const double lambda, const unsigned int ndiv);
 
  bool ComputeInfluenceMatrix(std::vector<std::vector<double> >& infmat) const;
  bool InvertMatrix(std::vector<std::vector<double> >& influenceMatrix,
                    std::vector<std::vector<double> >& inverseMatrix) const;
  bool LUDecomposition(std::vector<std::vector<double> >& mat,
                       std::vector<int>& index) const;
  void LUSubstitution(const std::vector<std::vector<double> >& mat,
                      const std::vector<int>& index,
                      std::vector<double>& col) const;
 
  bool Solve(const std::vector<std::vector<double> >& inverseMatrix,
             const std::vector<double>& bc);
  bool CheckConvergence(const double tol, std::vector<bool>& ok);
  void SplitElement(Element& oldElement, std::vector<Element>& elements);
 
  /// Potential of a line segment (half-width a) in local coordinates.
  double LinePotential(const double a, const double x, const double y) const;
  /// Potential of a thin wire with radius r0.
  double WirePotential(const double r0, const double x, const double y) const;
  /// Field of a line segment (half-width a) in local coordinates.
  void LineFlux(const double a, const double x, const double y, double& ex,
                double& ey) const;
  /// Field of a thin wire with radius r0.
  void WireFlux(const double r0, const double x, const double y, double& ex,
                double& ey) const;
 
  void Reset() override;
  void UpdatePeriodicity() override;
  /// Rotation from global to local coordinates.
  void ToLocal(const double xIn, const double yIn,
               const double cphi, const double sphi,
               double& xOut, double& yOut) const;
  /// Rotation from local to global coordinates.
  void ToGlobal(const double xIn, const double yIn, 
                const double cphi, const double sphi,
                double& xOut, double& yOut) const;
 
};
}
 
#endif