displacement_control_element.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//
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// LIC//====================================================================
// Header file for classes that define element objects
 
// Include guard to prevent multiple inclusions of the header
#ifndef OOMPH_DISPLACEMENT_CONTROL_ELEMENT_HEADER
#define OOMPH_DISPLACEMENT_CONTROL_ELEMENT_HEADER
 
 
// Config header
#ifdef HAVE_CONFIG_H
#include <oomph-lib-config.h>
#endif
 
#include <deque>
 
// oomph-lib includes
#include "elements.h"
 
namespace oomph
{
  //======================================================================
  /// Displacement control element: In the "normal" formulation
  /// of solid mechanics problems, the external load is given and the
  /// displacement throughout the solid body is computed.
  /// For highly nonlinear problems it is sometimes helpful to
  /// re-formulate the problem by prescribing the position of a
  /// selected control point and treating the (scalar) load level
  /// required to achieve this deformation as an unknown.
  /// As an example consider the buckling of pressure-loaded,
  /// thin-walled elastic shells.
  /// The load-displacement characteristics of such structures tend to be highly
  /// nonlinear and bifurcations from the structure's pre-buckling state
  /// often occur via sub-critical bifurcations. If we have some
  /// a-priori knowledge of the expected deformation (for example, during the
  /// non-axisymmetric buckling of a circular cylindrical shell certain
  /// material points will be displaced radially inwards), it
  /// is advantageous to prescribe the radial displacement of a carefully
  /// selected control point and treat the external pressure as an unknown.
  ///
  /// \c DisplacementControlElements facilitate the use of
  /// such methods. They require the specification of
  /// - the control point at which the displacement is prescribed. This is
  ///   done by specifying:
  ///   - a pointer, \c controlled_element_pt, to a \c SolidFiniteElement and
  ///   - the vector \c controlled_point which contains the local
  ///     coordinates of the control point in that \c SolidFiniteElement.
  ///   .
  /// - the coordinate direction. \c controlled_direction. in which
  ///   the displacement is controlled.
  /// - a pointer to a double, \c  control_position_value_pt,
  ///   that specifies the desired value of the prescribed
  ///   coordinate after the deformation (i.e. if \c controlled_direction=1
  ///   then \c *control_position_value_pt specifies
  ///   the \f$ x_1 \f$ coordinate of the control point in the deformed
  ///   configuration.)
  /// .
  /// The \c DisplacementControlElement has two constructors:
  /// - In the first version, we pass the pointer to the \c Data object whose
  ///   one-and-only value contains the scalar load level that is "traded"
  ///   for the displacement constraint. This is appropriate if the
  ///   load \c Data has already been created (and is included in the
  ///   overall equation numbering procedure) by some other element. In that
  ///   case the  \c DisplacementControlElement treats the (already existing)
  ///   \c Data object external \c Data.
  /// - In the second version, a \c Data object (with a single value)
  ///   is created by the constructor of the \c DisplacementControlElement
  ///   and stored in its internal \c Data. Once the
  ///   \c DisplacementControlElement has been included in one of the
  ///   \c Problem's meshes, it is therefore automatically included
  ///   in the equation numbering procedure. The (pointer to) the
  ///   newly created \c Data is accessible via the access function
  ///   \c displacement_control_load_pt(). It can be used to make
  ///   make the unknown load level accessible to the load function
  ///   that drives the deformation.
  /// .
  /// \b Note: The element inherits from the BlockPreconditionableElementBase
  /// and can be used in the block-preconditioning context. The element
  /// is "in charge" of the control load (if it's been created internally)
  /// and classifies it as its one-and-only "DOF type"
  //======================================================================
  class DisplacementControlElement : public virtual GeneralisedElement
  {
  public:
    /// Constructor. Pass:
    /// - Pointer to \c SolidFiniteElement that contains the control point
    /// - Vector that contains the local coordinates of the control point
    ///   in that element.
    /// - the coordinate direction in which the position of the control
    ///   point is prescribed
    /// - pointer to double that specifies the prescribed coordinate
    ///   of the control point
    /// - Pointer to Data item whose one-and-only  value
    ///   contains the load value that is being adjusted
    ///   to allow displacement control.
    /// .
    /// The load \c Data is treated as external \c Data for this
    /// element.
    DisplacementControlElement(SolidFiniteElement* controlled_element_pt,
                               const Vector<double>& controlled_point,
                               const unsigned& controlled_direction,
                               double* control_position_value_pt,
                               Data* displacement_control_load_pt)
      : Displacement_control_load_pt(displacement_control_load_pt),
        Control_position_value_pt(control_position_value_pt),
        Controlled_direction(controlled_direction),
        Controlled_element_pt(controlled_element_pt),
        Controlled_point(controlled_point)
    {
#ifdef PARANOID
      if (displacement_control_load_pt->nvalue() != 1)
      {
        throw OomphLibError(
          "Displacement control data must only contain a single value!\n",
          OOMPH_CURRENT_FUNCTION,
          OOMPH_EXCEPTION_LOCATION);
      }
#endif
 
      // The displacement control load is external Data for this element;
      // add it to the container and and store its index in that container.
      Load_data_index = add_external_data(Displacement_control_load_pt);
 
      // Store flag
      Load_data_created_internally = false;
 
      // The positional degrees of freedom of all the nodes in the
      // controlled SolidFiniteElement are external Data
      // for this element
      unsigned nnode = Controlled_element_pt->nnode();
      for (unsigned j = 0; j < nnode; j++)
      {
        add_external_data(
          static_cast<SolidNode*>(Controlled_element_pt->node_pt(j))
            ->variable_position_pt());
      }
    }
 
    /// Constructor. Pass:
    /// - Pointer to \c SolidFiniteElement that contains the control point
    /// - Vector that contains the local coordinates of the control point
    ///   in that element.
    /// - the coordinate direction in which the position of the control
    ///   point is prescribed
    /// - pointer to double that specifies the prescribed coordinate
    ///   of the control point
    /// .
    /// The pointer to a Data item whose one-and-only  value
    /// contains the load value that is being adjusted
    /// to allow displacement control is created internally (and stored
    /// in the element's internal \c Data. It is accessible (for use
    /// the load function) via the access function
    /// \c displacement_control_load_pt()
    DisplacementControlElement(SolidFiniteElement* controlled_element_pt,
                               const Vector<double>& controlled_point,
                               const unsigned& controlled_direction,
                               double* control_position_value_pt)
      : Control_position_value_pt(control_position_value_pt),
        Controlled_direction(controlled_direction),
        Controlled_element_pt(controlled_element_pt),
        Controlled_point(controlled_point)
    {
      // Create displacement control load internally (below, we'll store it
      // in the element's internal data so it'll be killed automatically --
      // no need for a destructor)
      Displacement_control_load_pt = new Data(1);
 
      // The displacement control load is internal Data for this element
      Load_data_index = add_internal_data(Displacement_control_load_pt);
 
      // Store flag
      Load_data_created_internally = true;
 
      // The positional degrees of freedom of all the nodes in the
      // controlled SolidFiniteElement are external Data
      // for this element
      unsigned nnode = Controlled_element_pt->nnode();
      for (unsigned j = 0; j < nnode; j++)
      {
        add_external_data(
          static_cast<SolidNode*>(Controlled_element_pt->node_pt(j))
            ->variable_position_pt());
      }
    }
 
    /// Broken copy constructor
    DisplacementControlElement(const DisplacementControlElement&) = delete;
 
 
    /// Broken assignment operator
    void operator=(const DisplacementControlElement&) = delete;
 
 
    /// Pointer to Data object whose one-and-only value represents the
    /// load that is adjusted to allow displacement control
    Data* displacement_control_load_pt() const
    {
      return Displacement_control_load_pt;
    }
 
 
    /// Store local equation number of displacement control equation
    void assign_additional_local_eqn_numbers()
    {
      if (Load_data_created_internally)
      {
        // Local equation number is the local equation number of the
        // one and only (i.e. the zero-th value stored in the
        // load data (which is stored in the internal data)
        Displ_ctrl_local_eqn = internal_local_eqn(Load_data_index, 0);
      }
      else
      {
        // Local equation number is the local equation number of the
        // one and only (i.e. the zero-th value stored in the
        // load data (which is stored in the external data)
        Displ_ctrl_local_eqn = external_local_eqn(Load_data_index, 0);
      }
    }
 
 
    /// Add the element's contribution to its residual vector:
    /// The displacement constraint. [Note: Jacobian is computed
    /// automatically by finite-differencing]
    void fill_in_contribution_to_residuals(Vector<double>& residuals)
    {
      if (Displ_ctrl_local_eqn >= 0)
      {
        residuals[Displ_ctrl_local_eqn] =
          Controlled_element_pt->interpolated_x(Controlled_point,
                                                Controlled_direction) -
          *Control_position_value_pt;
      }
    }
 
    /// The number of "DOF" that degrees of freedom in this element
    /// are sub-divided into: Just the control pressure.
    unsigned ndof_types() const
    {
      return 1;
    }
 
    /// Create a list of pairs for all unknowns in this element,
    /// so that the first entry in each pair contains the global equation
    /// number of the unknown, while the second one contains the number
    /// of the "DOF type" that this unknown is associated with.
    /// (Function can obviously only be called if the equation numbering
    /// scheme has been set up.) The only dof this element is in charge
    /// of is the control load, provided it's been created as
    /// internal Data.
    void get_dof_numbers_for_unknowns(
      std::list<std::pair<unsigned long, unsigned>>& dof_lookup_list) const
    {
      if (Load_data_created_internally)
      {
        // temporary pair (used to store dof lookup prior to being
        // added to list)
        std::pair<unsigned long, unsigned> dof_lookup;
 
        // determine local eqn number for displacement control eqn
        int local_eqn_number = Displ_ctrl_local_eqn;
 
        // Is it a dof or is it pinned?
        if (local_eqn_number >= 0)
        {
          // store dof lookup in temporary pair: First entry in pair
          // is global equation number; second entry is dof type
          dof_lookup.first = this->eqn_number(local_eqn_number);
          dof_lookup.second = 0;
 
          // Add to list
          dof_lookup_list.push_front(dof_lookup);
        }
      }
    }
 
  protected:
    /// Pointer to Data item whose one-and-only  value
    /// contains the load value that is being adjusted
    /// to allow displacement control.
    Data* Displacement_control_load_pt;
 
    /// Pointer to the value that stores the prescribed coordinate
    /// of the control point
    double* Control_position_value_pt;
 
    /// Coordinate direction in which the displacement of the
    /// control point is controlled
    unsigned Controlled_direction;
 
    /// Pointer to SolidFiniteElement at which control displacement is applied
    SolidFiniteElement* Controlled_element_pt;
 
    /// Vector of local coordinates of point at which control
    /// displacement is applied
    Vector<double> Controlled_point;
 
    /// Flag to indicate if load data was created internally or
    /// externally (and is therefore stored in the element's internal or
    /// external Data)
    bool Load_data_created_internally;
 
    /// In which component (in the vector of the element's internal or
    /// external Data) is the load stored?
    unsigned Load_data_index;
 
    /// Local equation number of the control-displacement equation
    int Displ_ctrl_local_eqn;
  };
 
} // namespace oomph
 
#endif