Solid to solid conjugate heat transfer

Common/include/option_structure.hpp

@@ -409,6 +409,7 @@ enum ENUM_TRANSFER {
   CONJUGATE_HEAT_WEAKLY_FS          = 17,   /*!< \brief Conjugate heat transfer (between incompressible fluids and solids). */
   CONJUGATE_HEAT_SF                 = 18,   /*!< \brief Conjugate heat transfer (between solids and compressible fluids). */
   CONJUGATE_HEAT_WEAKLY_SF          = 19,   /*!< \brief Conjugate heat transfer (between solids and incompressible fluids). */
+  CONJUGATE_HEAT_SS                 = 20,   /*!< \brief Conjugate heat transfer (between two solids). */
 };
 
 /*!

SU2_CFD/src/drivers/CDriver.cpp

@@ -2494,19 +2494,22 @@ void CDriver::InitializeInterface(CConfig **config, CSolver***** solver, CGeomet
           if (rank == MASTER_NODE) cout << "sliding interface." << endl;
         }
         else if (heat_donor || heat_target) {
-          if (heat_donor && heat_target)
-            SU2_MPI::Error("Conjugate heat transfer between solids is not implemented.", CURRENT_FUNCTION);
+          if (heat_donor && heat_target){
+            interface_type = CONJUGATE_HEAT_SS;
 
-          const auto fluidZone = heat_target? donor : target;
+          } else {
 
-          if (config[fluidZone]->GetEnergy_Equation() || (config[fluidZone]->GetKind_Regime() == ENUM_REGIME::COMPRESSIBLE) 
-              || (config[fluidZone]->GetKind_FluidModel() == ENUM_FLUIDMODEL::FLUID_FLAMELET))
-            interface_type = heat_target? CONJUGATE_HEAT_FS : CONJUGATE_HEAT_SF;
-          else if (config[fluidZone]->GetWeakly_Coupled_Heat())
-            interface_type = heat_target? CONJUGATE_HEAT_WEAKLY_FS : CONJUGATE_HEAT_WEAKLY_SF;
-          else
-            interface_type = NO_TRANSFER;
+            const auto fluidZone = heat_target? donor : target;
 
+            if (config[fluidZone]->GetEnergy_Equation() || (config[fluidZone]->GetKind_Regime() == ENUM_REGIME::COMPRESSIBLE) 
+                || (config[fluidZone]->GetKind_FluidModel() == ENUM_FLUIDMODEL::FLUID_FLAMELET))
+              interface_type = heat_target? CONJUGATE_HEAT_FS : CONJUGATE_HEAT_SF;
+            else if (config[fluidZone]->GetWeakly_Coupled_Heat())
+              interface_type = heat_target? CONJUGATE_HEAT_WEAKLY_FS : CONJUGATE_HEAT_WEAKLY_SF;
+            else
+              interface_type = NO_TRANSFER;
+          }
+
           if (interface_type != NO_TRANSFER) {
             auto nVar = 4;
             interface[donor][target] = new CConjugateHeatInterface(nVar, 0);

SU2_CFD/src/drivers/CMultizoneDriver.cpp

@@ -585,6 +585,9 @@ bool CMultizoneDriver::TransferData(unsigned short donorZone, unsigned short tar
         BroadcastData(SPECIES_SOL, SPECIES_SOL);
       }
       break;
+    case CONJUGATE_HEAT_SS:
+      BroadcastData(HEAT_SOL, HEAT_SOL);
+      break;
     case CONJUGATE_HEAT_FS:
       BroadcastData(FLOW_SOL, HEAT_SOL);
       break;

SU2_CFD/src/interfaces/cht/CConjugateHeatInterface.cpp

@@ -133,7 +133,10 @@
         (donor_config->GetKind_CHT_Coupling() == CHT_COUPLING::AVERAGED_TEMPERATURE_ROBIN_HEATFLUX)) {
 
       const su2double rho_cp_solid = donor_config->GetSpecific_Heat_Cp()*donor_config->GetMaterialDensity(0);
-      conductivity_over_dist  = thermal_diffusivity*rho_cp_solid/dist;
+      const su2double thermal_conductivity = thermal_diffusivity * rho_cp_solid;
+      // TODO: add proper contact resistance here.
+      const su2double R_c = 0.0;
+      conductivity_over_dist  = thermal_conductivity/(dist + thermal_conductivity * R_c);
     }
   }