Add BC_Periodic to HeatSolver.

Author: TobiKattmann

SU2_CFD/include/solvers/CHeatSolver.hpp

@@ -247,6 +247,15 @@ class CHeatSolver final : public CSolver {
                                   CConfig *config,
                                   unsigned short val_marker) override;
 
+  /*!
+   * \brief Impose a periodic boundary condition by summing contributions from the complete control volume.
+   * \param[in] geometry - Geometrical definition of the problem.
+   * \param[in] solver_container - Container vector with all the solutions.
+   * \param[in] numerics - Description of the numerical method.
+   * \param[in] config - Definition of the particular problem.
+   */
+  void BC_Periodic(CGeometry* geometry, CSolver** solver_container, CNumerics* numerics, CConfig* config) final;
+
   /*!
    * \brief Set the conjugate heat variables.
    * \param[in] val_marker        - marker index

SU2_CFD/src/solvers/CHeatSolver.cpp

@@ -893,6 +893,20 @@ void CHeatSolver::BC_ConjugateHeat_Interface(CGeometry *geometry, CSolver **solv
   }
 }
 
+void CHeatSolver::BC_Periodic(CGeometry* geometry, CSolver** solver_container, CNumerics* numerics,
+                                           CConfig* config) {
+  /*--- Complete residuals for periodic boundary conditions. We loop over
+   the periodic BCs in matching pairs so that, in the event that there are
+   adjacent periodic markers, the repeated points will have their residuals
+   accumulated corectly during the communications. For implicit calculations
+   the Jacobians and linear system are also correctly adjusted here. ---*/
+
+  for (unsigned short iPeriodic = 1; iPeriodic <= config->GetnMarker_Periodic() / 2; iPeriodic++) {
+    InitiatePeriodicComms(geometry, config, iPeriodic, PERIODIC_RESIDUAL);
+    CompletePeriodicComms(geometry, config, iPeriodic, PERIODIC_RESIDUAL);
+  }
+}
+
 void CHeatSolver::Heat_Fluxes(CGeometry *geometry, CSolver **solver_container, CConfig *config) {
 
   unsigned long iPointNormal;