AverageGradShapeFunction.h

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include <Eigen/Core>
#include <vector>
 
#include "MeshLib/Elements/Element.h"
#include "NumLib/Fem/InitShapeMatrices.h"
#include "NumLib/Fem/Integration/GenericIntegrationMethod.h"
 
namespace NumLib
{
template <int DisplacementDim,
          typename ShapeFunction,
          typename ShapeMatricesType,
          typename IpData>
Eigen::Vector3d averageGradShapeFunction(
    int const local_node_id,
    MeshLib::Element const& element,
    NumLib::GenericIntegrationMethod const& integration_method,
    std::vector<IpData, Eigen::aligned_allocator<IpData>> const& ip_data,
    const bool is_axially_symmetric)
{
    Eigen::Vector3d bar_gradN = Eigen::Vector3d::Zero();
    unsigned const n_integration_points =
        integration_method.getNumberOfPoints();
    assert(n_integration_points == ip_data.size());
    for (unsigned ip = 0; ip < n_integration_points; ip++)
    {
        auto const& N = ip_data[ip].N_u;
        auto const& dNdx = ip_data[ip].dNdx_u;
 
        auto const dNidx = dNdx.col(local_node_id);
 
        auto const& w = ip_data[ip].integration_weight;
        bar_gradN.template segment<DisplacementDim>(0) += dNidx * w;
 
        if (is_axially_symmetric)
        {
            auto const x_coord =
                NumLib::interpolateXCoordinate<ShapeFunction,
                                               ShapeMatricesType>(element, N);
            bar_gradN[2] += w * N(local_node_id) / x_coord;
        }
    }
    return bar_gradN;
}
}  // namespace NumLib