Space-time

varying boundary condition

class TimeVaryingBC : public pfc::FieldModifier {
  double m_frequency;
public:
  TimeVaryingBC(double freq) : m_frequency(freq) {}
 
  void apply(pfc::Model& model, double time) override {
    auto& field = model.get_real_field(get_field_name());
    const auto& world = model.get_world();
    const auto& fft = model.get_fft();
    auto inbox = pfc::fft::get_inbox(fft);
 
    // Time-varying amplitude
    double amplitude = std::sin(pfc::two_pi * m_frequency * time);
 
    double dx = pfc::world::get_spacing(world, 0);
    int idx = 0;
    for (int k = inbox.low[2]; k <= inbox.high[2]; k++) {
      for (int j = inbox.low[1]; j <= inbox.high[1]; j++) {
        for (int i = inbox.low[0]; i <= inbox.high[0]; i++) {
          if (i == 0) {  // Left boundary
            field[idx] = amplitude;
          }
          idx++;
        }
      }
    }
  }
};