young_laplace_contact_angle_elements.h

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// LIC// ====================================================================
// LIC// This file forms part of oomph-lib, the object-oriented,
// LIC// multi-physics finite-element library, available
// LIC// at http://www.oomph-lib.org.
// LIC//
// LIC// Copyright (C) 2006-2025 Matthias Heil and Andrew Hazel
// LIC//
// LIC// This library is free software; you can redistribute it and/or
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// LIC// License as published by the Free Software Foundation; either
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// LIC// Lesser General Public License for more details.
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// LIC//====================================================================
// Header file for elements that are used to apply contact angle
// BC for Young Laplace eqns
 
#ifndef OOMPH_YOUNGLAPLACE_FLUX_ELEMENTS_HEADER
#define OOMPH_YOUNGLAPLACE_FLUX_ELEMENTS_HEADER
 
 
// Config header
#ifdef HAVE_CONFIG_H
#include <oomph-lib-config.h>
#endif
 
 
// oomph-lib ncludes
#include "generic/Qelements.h"
 
namespace oomph
{
  //======================================================================
  /// A class for elements that allow the imposition of an
  /// contact angle bcs for Young Laplace elements.
  /// The element geometry is obtained from the  FaceGeometry<ELEMENT>
  /// policy class. Jacobian is evaluated by finite differencing.
  //======================================================================
  template<class ELEMENT>
  class YoungLaplaceContactAngleElement : public virtual FaceGeometry<ELEMENT>,
                                          public virtual FaceElement
  {
  public:
    /// Constructor, takes the pointer to the "bulk" element and the
    /// index of the face to which the element is attached.
    YoungLaplaceContactAngleElement(FiniteElement* const& bulk_el_pt,
                                    const int& face_index);
 
    /// Broken empty constructor
    YoungLaplaceContactAngleElement()
    {
      throw OomphLibError(
        "Don't call empty constructor for YoungLaplaceContactAngleElement",
        OOMPH_CURRENT_FUNCTION,
        OOMPH_EXCEPTION_LOCATION);
    }
 
    /// Broken copy constructor
    YoungLaplaceContactAngleElement(
      const YoungLaplaceContactAngleElement& dummy) = delete;
 
    /// Broken assignment operator
    void operator=(const YoungLaplaceContactAngleElement&) = delete;
 
    /// Access function for the pointer to the prescribed contact angle
    /// (const version)
    double* prescribed_cos_gamma_pt() const
    {
      return Prescribed_cos_gamma_pt;
    }
 
 
    /// Access function for the pointer to the prescribed contact angle
    double*& prescribed_cos_gamma_pt()
    {
      return Prescribed_cos_gamma_pt;
    }
 
 
    /// Add the element's contribution to its residual vector
    void fill_in_contribution_to_residuals(Vector<double>& residuals);
 
    /// Get the local equation number of the (one and only) unknown
    /// stored at local node n (returns -1 if value is pinned).
    /// Can be overloaded in derived multiphysics elements.
    inline int u_local_eqn(const unsigned& n)
    {
      // Local equation number is the first value stored at the node
      return nodal_local_eqn(n, 0);
    }
 
 
    /// Specify the value of nodal zeta from the face geometry
    /// The "global" intrinsic coordinate of the element when
    /// viewed as part of a geometric object should be given by
    /// the FaceElement representation, by default (needed to break
    /// indeterminacy if bulk element is SolidElement)
    double zeta_nodal(const unsigned& n,
                      const unsigned& k,
                      const unsigned& i) const
    {
      return FaceElement::zeta_nodal(n, k, i);
    }
 
    /// Output function -- forward to broken version in FiniteElement
    /// until somebody decides what exactly they want to plot here...
    void output(std::ostream& outfile)
    {
      FiniteElement::output(outfile);
    }
 
    /// Output function -- forward to broken version in FiniteElement
    /// until somebody decides what exactly they want to plot here...
    void output(std::ostream& outfile, const unsigned& n_plot)
    {
      FiniteElement::output(outfile, n_plot);
    }
 
    /// C-style output function -- forward to broken version in FiniteElement
    /// until somebody decides what exactly they want to plot here...
    void output(FILE* file_pt)
    {
      FiniteElement::output(file_pt);
    }
 
    /// C-style output function -- forward to broken version in
    /// FiniteElement until somebody decides what exactly they want to plot
    /// here...
    void output(FILE* file_pt, const unsigned& n_plot)
    {
      FiniteElement::output(file_pt, n_plot);
    }
 
    /// Compute cosinus of actual contact angle
    double actual_cos_contact_angle(const Vector<double>& s);
 
    /// Get unit tangent and normal vectors to contact line
    void contact_line_vectors(const Vector<double>& s,
                              Vector<double>& tangent,
                              Vector<double>& normal)
    {
      // Dummy
      double norm_of_drds;
      Vector<double> spine(3);
      contact_line_vectors(s, tangent, normal, spine, norm_of_drds);
    }
 
    /// Get unit tangent and normal vectors to contact line. Final
    /// argument gives the norm of dR/ds where R is the vector to the
    /// contact line and s the local coordinate in the element.
    void contact_line_vectors(const Vector<double>& s,
                              Vector<double>& tangent,
                              Vector<double>& normal,
                              double& norm_of_drds)
    {
      // Dummy
      Vector<double> spine(3);
      contact_line_vectors(s, tangent, normal, spine, norm_of_drds);
    }
 
 
    /// Get tangent and normal vectors to contact line and spine vector
    /// (wall normal can then be obtained by cross-product). Final
    /// argument gives the norm of dR/ds where R is the vector to the
    /// contact line and s the local coordinate in the element.
    void contact_line_vectors(const Vector<double>& s,
                              Vector<double>& tangent,
                              Vector<double>& normal,
                              Vector<double>& spine,
                              double& norm_of_drds);
 
  protected:
    /// Define an access function to the first data value stored
    /// at each node. In a more general "Equation" element, such abstraction
    /// is essential, because different Elements will store the same variables
    /// in different locations.
    double& u(const unsigned int& n)
    {
      return *this->node_pt(n)->value_pt(0);
    }
 
    /// Function to calculate the cos of the prescribed contact angle
    double prescribed_cos_gamma()
    {
      // If the function pointer is zero return zero
      if (Prescribed_cos_gamma_pt == 0)
      {
        return 0.0;
      }
      // Otherwise de-reference pointer
      else
      {
        return *Prescribed_cos_gamma_pt;
      }
    }
 
 
  private:
    /// Pointer to prescribed cos gamma
    double* Prescribed_cos_gamma_pt;
  };
 
 
} // namespace oomph
 
#endif