fsi.cc

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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
// LIC// modify it under the terms of the GNU Lesser General Public
// LIC// License as published by the Free Software Foundation; either
// LIC// version 2.1 of the License, or (at your option) any later version.
// LIC//
// LIC// This library is distributed in the hope that it will be useful,
// LIC// but WITHOUT ANY WARRANTY; without even the implied warranty of
// LIC// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// LIC// Lesser General Public License for more details.
// LIC//
// LIC// You should have received a copy of the GNU Lesser General Public
// LIC// License along with this library; if not, write to the Free Software
// LIC// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
// LIC// 02110-1301  USA.
// LIC//
// LIC// The authors may be contacted at oomph-lib@maths.man.ac.uk.
// LIC//
// LIC//====================================================================
#include "fsi.h"
#include "integral.h"
#include "algebraic_elements.h"
 
namespace oomph
{
  //======================================================================
  /// Namespace for "global" FSI functions
  //======================================================================
  namespace FSI_functions
  {
    /// Strouhal number St = a/(UT) for application of no slip condition.
    /// Initialised to 1.0.
    double Strouhal_for_no_slip = 1.0;
 
    /// Apply no-slip condition for N.St. on a moving wall node
    /// u = St dR/dt, where the Strouhal number St = a/(UT) is defined by
    /// FSI_functions::Strouhal_for_no_slip and is initialised to 1.0.
    /// Note: This requires the x,y,[z] velocity components to be stored
    /// in nodal values 0,1,[2]. This is the default for all currently
    /// existing Navier-Stokes elements. If you use any others,
    /// use this function at your own risk.
    void apply_no_slip_on_moving_wall(Node* node_pt)
    {
      // Find out spatial dimension of node
      unsigned ndim = node_pt->ndim();
      // Assign velocity
      for (unsigned i = 0; i < ndim; i++)
      {
        node_pt->set_value(i,
                           Strouhal_for_no_slip * (node_pt->dposition_dt(i)));
      }
    }
 
  } // namespace FSI_functions
 
 
  //====================================================================
  /// Flag that allows the suppression of warning messages
  //====================================================================
  bool FSIWallElement::Dont_warn_about_missing_adjacent_fluid_elements = false;
 
  //====================================================================
  /// Function to describe the local dofs of the element. The ostream
  /// specifies the output stream to which the description
  /// is written; the string stores the currently
  /// assembled output that is ultimately written to the
  /// output stream by Data::describe_dofs(...); it is typically
  /// built up incrementally as we descend through the
  /// call hierarchy of this function when called from
  /// Problem::describe_dofs(...)
  //====================================================================
  void FSIWallElement::describe_local_dofs(
    std::ostream& out, const std::string& current_string) const
  {
    // Call the standard finite element classification.
    FiniteElement::describe_local_dofs(out, current_string);
    describe_solid_local_dofs(out, current_string);
    // Find the number of external field data
    const unsigned n_external_field_data = nexternal_interaction_field_data();
    // Now loop over the field data again to assign local equation numbers
    for (unsigned i = 0; i < n_external_field_data; i++)
    {
      std::stringstream conversion;
      conversion << " of External Interaction Field Data " << i
                 << current_string;
      std::string in(conversion.str());
      External_interaction_field_data_pt[i]->describe_dofs(out, in);
    }
 
    // Find the number of external geometric data
    unsigned n_external_geom_data = nexternal_interaction_geometric_data();
 
    // Now loop over the field data again assign local equation numbers
    for (unsigned i = 0; i < n_external_geom_data; i++)
    {
      std::stringstream conversion;
      conversion << " of External Interaction Geometric Data " << i
                 << current_string;
      std::string in(conversion.str());
      External_interaction_geometric_data_pt[i]->describe_dofs(out, in);
    }
  }
 
  //================================================================
  /// Compete build of element: Assign storage -- pass the Eulerian
  /// dimension of the "adjacent" fluid elements and the
  /// number of local coordinates required to parametrise
  /// the wall element. E.g. for a FSIKirchhoffLoveBeam,
  /// bounding a 2D fluid domain ndim_fluid=2 and nlagr_solid=1.
  /// Note that, by default, we're only providing storage for fluid
  /// loading on the "front" of the element. Call
  /// FSIWallElement::enable_fluid_loading_on_both_sides()
  /// to enable fluid loading on the back, too.
  //====================================================================
  void FSIWallElement::setup_fsi_wall_element(const unsigned& nlagr_solid,
                                              const unsigned& ndim_fluid)
  {
    // Set storage for underlying GeomObject
    set_nlagrangian_and_ndim(nlagr_solid, ndim_fluid);
 
    // Set source element storage - one interaction
    this->set_ninteraction(1);
  }
 
 
  //==================================================================
  /// Allow element to be loaded by fluid on both
  /// sides. (Resizes containers for lookup schemes and initialises
  /// data associated with elements at the "back" of the FSIWallElement
  /// to NULL.
  //==================================================================
  void FSIWallElement::enable_fluid_loading_on_both_sides()
  {
    // Both faces are loaded
    Only_front_is_loaded_by_fluid = false;
 
    // Set source element storage - two interactions
    this->set_ninteraction(2);
  }
 
 
  //==================================================================
  /// Get the contribution to the load vector provided by
  /// the adjacent fluid element: Pass number of integration point
  /// in solid element,
  /// and the unit normal vector (pointing into the fluid on the "front"
  /// of the FSIWallElement) and return the load vector.
  /// Note that the load is non-dimensionalised on the wall-stress scale,
  /// i.e. it is obtained by computing the traction (on the fluid stress-scale)
  /// from the adjacent fluid element and then multiplying it by
  /// the stress-scale-ratio \f$ Q. \f$.
  /// If element is loaded on both sides, the fluid load computed
  /// from the reverse element is \b subtracted, because it's
  /// computed with the same normal vector.
  //==================================================================
  void FSIWallElement::fluid_load_vector(const unsigned& intpt,
                                         const Vector<double>& N,
                                         Vector<double>& load)
  {
    // Size of load vector
    unsigned n_load = load.size();
 
    // Initialise
    for (unsigned i = 0; i < n_load; i++) load[i] = 0.0;
 
    // Create vector for fluid load
    Vector<double> fluid_load(n_load);
 
    // Loop over front and back if required: Get number of fluid-loaded faces
    unsigned n_loaded_face = 2;
    if (Only_front_is_loaded_by_fluid) n_loaded_face = 1;
 
    for (unsigned face = 0; face < n_loaded_face; face++)
    {
      // Get the local coordinate in the fluid element (copy
      // operation for Vector)
      Vector<double> s_adjacent(external_element_local_coord(face, intpt));
 
      // Call the load function for adjacent element
      FSIFluidElement* el_f_pt =
        dynamic_cast<FSIFluidElement*>(external_element_pt(face, intpt));
      if (el_f_pt != 0)
      {
        el_f_pt->get_load(s_adjacent, N, fluid_load);
      }
      else
      {
#ifdef PARANOID
        if (!Dont_warn_about_missing_adjacent_fluid_elements)
        {
          std::ostringstream warning_stream;
          warning_stream
            << "Info: No adjacent element set in FSIWallElement.\n\n"
            << "Note: you can disable this message by setting \n      "
            << "FSIWallElement::Dont_warn_about_missing_adjacent_fluid_elements"
            << "\n      to true or recompiling without PARANOID.\n";
          OomphLibWarning(warning_stream.str(),
                          "FSIWallElement::fluid_load_vector()",
                          OOMPH_EXCEPTION_LOCATION);
        }
#endif
      }
 
      // Adjust sign of fluid traction. If normal on the front
      // points into the fluid, the normal at the back points away
      // from it.
      double sign = 1.0;
      if (face == 1) sign = -1.0;
 
      // The load is scaled by the stress-scale ratio Q
      for (unsigned i = 0; i < n_load; i++)
      {
        load[i] += fluid_load[i] * sign * q();
      }
 
    } // end of loop over faces
  }
 
 
  //==================================================================
  /// Update the nodal positions in all fluid elements that affect
  /// the traction on this FSIWallElement
  //==================================================================
  void FSIWallElement::node_update_adjacent_fluid_elements()
  {
    // Don't update elements repeatedly
    std::map<FSIFluidElement*, bool> done;
 
    // Number of integration points
    unsigned n_intpt = integral_pt()->nweight();
 
    // Loop over front and back if required: Get number of fluid-loaded faces
    unsigned n_loaded_face = 2;
    if (Only_front_is_loaded_by_fluid) n_loaded_face = 1;
    for (unsigned face = 0; face < n_loaded_face; face++)
    {
      // Loop over all integration points in wall element
      for (unsigned iint = 0; iint < n_intpt; iint++)
      {
        // Get fluid element that affects this integration point
        FSIFluidElement* el_f_pt =
          dynamic_cast<FSIFluidElement*>(external_element_pt(face, iint));
 
        // Is there an adjacent fluid element?
        if (el_f_pt != 0)
        {
          // Have we updated its positions yet?
          if (!done[el_f_pt])
          {
            // Update nodal positions
            el_f_pt->node_update();
            done[el_f_pt] = true;
          }
        }
      }
    }
  }
 
 
  //=================================================================
  /// Static default value for the ratio of stress scales
  /// used in the fluid and solid equations (default is 1.0)
  //=================================================================
  double FSIWallElement::Default_Q_Value = 1.0;
 
 
  //=======================================================================
  /// Overload the function that must return all field data involved
  /// in the interactions from the external (fluid) element. It allows
  /// the velocity degrees of freedom to be ignored if we want to
  /// ignore the shear stresses when computing the Jacobian.
  //=======================================================================
  void FSIWallElement::identify_all_field_data_for_external_interaction(
    Vector<std::set<FiniteElement*>> const& external_elements_pt,
    std::set<std::pair<Data*, unsigned>>& paired_interaction_data)
  {
    // Loop over each inteaction
    const unsigned n_interaction = this->ninteraction();
    for (unsigned i = 0; i < n_interaction; i++)
    {
      // Loop over each element in the set
      for (std::set<FiniteElement*>::const_iterator it =
             external_elements_pt[i].begin();
           it != external_elements_pt[i].end();
           it++)
      {
        // Cast the element  the specific fluid element
        FSIFluidElement* external_fluid_el_pt =
          dynamic_cast<FSIFluidElement*>(*it);
 
        // Only add pressure load if so desired
        if (Ignore_shear_stress_in_jacobian)
        {
          // Add the "pressure" load data
          external_fluid_el_pt->identify_pressure_data(paired_interaction_data);
        }
        else
        {
          // Add the "direct" load data (usually velocities and pressures)
          // to the set
          external_fluid_el_pt->identify_load_data(paired_interaction_data);
        }
      }
    } // End of loop over interactions
  }
 
  //===================================================================
  /// Function that must return all geometric data involved
  /// in the desired interactions from the external element
  //===================================================================
  void FSIWallElement::identify_all_geometric_data_for_external_interaction(
    Vector<std::set<FiniteElement*>> const& external_elements_pt,
    std::set<Data*>& external_geometric_data_pt)
  {
    // If we are ignoring the shear stress, then we can ignore all
    // external geometric data
    if (Ignore_shear_stress_in_jacobian)
    {
      return;
    }
    else
    {
      // Loop over each inteaction
      const unsigned n_interaction = this->ninteraction();
      for (unsigned i = 0; i < n_interaction; i++)
      {
        // Loop over each element in the set
        for (std::set<FiniteElement*>::const_iterator it =
               external_elements_pt[i].begin();
             it != external_elements_pt[i].end();
             it++)
        {
          (*it)->identify_geometric_data(external_geometric_data_pt);
        }
      }
    }
  }
 
 
} // namespace oomph