integrate_river_outflow.h

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#ifndef INTEGRATE_RIVER_OUTFLOW_H
#define INTEGRATE_RIVER_OUTFLOW_H
 
#include "common/common.h"
#include "lib_disc/function_spaces/grid_function.h"
 
namespace ug {
namespace d3f {
 
template <typename TGridFunction>
number IntegrateRiverOutflow(
    SmartPtr<CplUserData<MathVector<TGridFunction::dim>, TGridFunction::dim>> velocityField,
    SmartPtr<CplUserData<number, TGridFunction::dim>> scalarField,
    SmartPtr<TGridFunction> gridFunction,
    const char* bndSubsets,
    const char* innerSubsets = "",
    int quadOrder = 1)
{
    // --- Subset Preparation ---
    SubsetGroup bndSSGrp(gridFunction->domain()->subset_handler());
    bndSSGrp.add(TokenizeString(bndSubsets));
 
    number totalFlux = 0.0;
    std::vector<DoFIndex> ind;
 
    // --- Nodal Integration ---
    // We iterate over all requested subsets.
    for (size_t i = 0; i < bndSSGrp.size(); ++i) {
        const int subsetIndex = bndSSGrp[i];
        if (subsetIndex == -1) continue;
 
        auto iter    = gridFunction->template begin<Vertex>(subsetIndex);
        auto iterEnd = gridFunction->template end<Vertex>(subsetIndex);
 
        for (; iter != iterEnd; ++iter) {
            Vertex* v = *iter;
 
            // Retrieve Velocity (v) - Component 1
            gridFunction->dof_indices(v, 1, ind);
            const number velocityValue = DoFRef(*gridFunction, ind[0]);
 
            // Retrieve Area (A) - Component 0
            gridFunction->dof_indices(v, 0, ind);
            const number areaValue = DoFRef(*gridFunction, ind[0]);
 
            // Sum the absolute flux (v * A)
            totalFlux += std::fabs(velocityValue * areaValue);
        }
    }
 
    return totalFlux;
}
 
} // namespace d3f
} // namespace ug
 
#endif // INTEGRATE_RIVER_OUTFLOW_H