fixing jacobian contribution energy equation for radiation model

Author: Cristopher-Morales

SU2_CFD/src/numerics/flow/flow_sources.cpp

@@ -823,8 +823,7 @@ CNumerics::ResidualType<> CSourceRadiation::ComputeResidual(const CConfig *confi
 
     /*--- Jacobian is set to zero on initialization. ---*/
 
-    jacobian[nDim+1][nDim+1] = -RadVar_Source[1]*Volume;
-
+    jacobian[nDim + 1][nDim + 1] = -RadVar_Source[1] * Volume / Cp_i;
   }
 
   return ResidualType<>(residual, jacobian, nullptr);

SU2_CFD/src/solvers/CIncEulerSolver.cpp

@@ -1661,6 +1661,10 @@ void CIncEulerSolver::Source_Residual(CGeometry *geometry, CSolver **solver_cont
 
       second_numerics->SetVolume(geometry->nodes->GetVolume(iPoint));
 
+      /*--- Set Cp (for implicit) ---*/
+
+      if (implicit) second_numerics->SetSpecificHeat(nodes->GetSpecificHeatCp(iPoint), 0.0);
+
       /*--- Compute the residual ---*/
 
       auto residual = second_numerics->ComputeResidual(config);