BuskeCompressionForce.cpp

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#include "BuskeCompressionForce.hpp"
#include "NodeBasedCellPopulation.hpp"

template<unsigned DIM>
BuskeCompressionForce<DIM>::BuskeCompressionForce()
    : AbstractForce<DIM>(),
      mCompressionEnergyParameter(5.0)
{
}

template<unsigned DIM>
double BuskeCompressionForce<DIM>::GetCompressionEnergyParameter()
{
    return mCompressionEnergyParameter;
}

template<unsigned DIM>
void BuskeCompressionForce<DIM>::SetCompressionEnergyParameter(double compressionEnergyParameter)
{
    mCompressionEnergyParameter = compressionEnergyParameter;
}

template<unsigned DIM>
void BuskeCompressionForce<DIM>::AddForceContribution(AbstractCellPopulation<DIM>& rCellPopulation)
{
    // This force class is defined for NodeBasedCellPopulations only
    assert(dynamic_cast<NodeBasedCellPopulation<DIM>*>(&rCellPopulation) != NULL);

    NodeBasedCellPopulation<DIM>* p_static_cast_cell_population = static_cast<NodeBasedCellPopulation<DIM>*>(&rCellPopulation);


    c_vector<double, DIM> unit_vector;

    // Loop over cells in the population
    for (typename AbstractCellPopulation<DIM>::Iterator cell_iter = rCellPopulation.Begin();
         cell_iter != rCellPopulation.End();
         ++cell_iter)
    {
        // Get the node index corresponding to this cell
        unsigned node_index = rCellPopulation.GetLocationIndexUsingCell(*cell_iter);

        Node<DIM>* p_node_i = rCellPopulation.GetNode(node_index);

        // Get the location of this node
        c_vector<double, DIM> node_i_location = p_node_i->rGetLocation();

        // Get the radius of this cell
        double radius_of_cell_i = p_node_i->GetRadius();

        double delta_V_c = 0.0;
        c_vector<double, DIM> dVAdd_vector = zero_vector<double>(DIM);

        // Get the set of node indices corresponding to this cell's neighbours
        std::set<unsigned> neighbouring_node_indices = p_static_cast_cell_population->GetNeighbouringNodeIndices(node_index);

        // Loop over this set
        for (std::set<unsigned>::iterator iter = neighbouring_node_indices.begin();
             iter != neighbouring_node_indices.end();
             ++iter)
        {
            Node<DIM>* p_node_j = rCellPopulation.GetNode(*iter);

            // Get the location of this node
            c_vector<double, DIM> node_j_location = p_node_j->rGetLocation();

            // Get the unit vector parallel to the line joining the two nodes (assuming no periodicities etc.)
            unit_vector = node_j_location - node_i_location;

            // Calculate the distance between the two nodes
            double dij = norm_2(unit_vector);

            unit_vector /= dij;

            // Get the radius of the cell corresponding to this node
            double radius_of_cell_j = p_node_j->GetRadius();

            // If the cells are close enough to exert a force on each other...
            if (dij < radius_of_cell_i + radius_of_cell_j)
            {
                // ...then compute the adhesion force and add it to the vector of forces...
                double xij = 0.5*(radius_of_cell_i*radius_of_cell_i - radius_of_cell_j*radius_of_cell_j + dij*dij)/dij;
                double dxijdd = 1.0 - xij/dij;
                double dVAdd = M_PI*dxijdd*(5.0*pow(radius_of_cell_i,2.0) + 3.0*pow(xij,2.0) - 8.0*radius_of_cell_i*xij)/3.0;

                dVAdd_vector += dVAdd*unit_vector;

                // ...and add the contribution to the compression force acting on cell i
                delta_V_c += M_PI*pow(radius_of_cell_i - xij,2.0)*(2*radius_of_cell_i - xij)/3.0;
            }
        }

        double V_A = 4.0/3.0*M_PI*pow(radius_of_cell_i,3.0) - delta_V_c;

        double V_T = 5.0;

        // Note: the sign in force_magnitude is different from the one in equation (A3) in the Buske paper
        c_vector<double, DIM> applied_force = -mCompressionEnergyParameter/V_T*(V_T - V_A)*dVAdd_vector;
        p_node_i->AddAppliedForceContribution(applied_force);
    }
}

template<unsigned DIM>
void BuskeCompressionForce<DIM>::OutputForceParameters(out_stream& rParamsFile)
{
    *rParamsFile << "\t\t\t<CompressionEnergyParameter>" << mCompressionEnergyParameter << "</CompressionEnergyParameter>\n";

    // Call method on direct parent class
    AbstractForce<DIM>::OutputForceParameters(rParamsFile);
}

// Explicit instantiation

template class BuskeCompressionForce<1>;
template class BuskeCompressionForce<2>;
template class BuskeCompressionForce<3>;

// Serialization for Boost >= 1.36
#include "SerializationExportWrapperForCpp.hpp"
EXPORT_TEMPLATE_CLASS_SAME_DIMS(BuskeCompressionForce)