Engine mass-flow rate coupling for zero-thrust simulation

Common/include/CConfig.hpp

@@ -932,6 +932,7 @@ class CConfig {
   Pressure_Thermodynamic,          /*!< \brief Thermodynamic pressure of the fluid. */
   Temperature_FreeStream,          /*!< \brief Total temperature of the fluid.  */
   Temperature_ve_FreeStream;       /*!< \brief Total vibrational-electronic temperature of the fluid.  */
+  bool out2in_mdot_engine;         /*!< \brief Flag to use engine outlet mass flow as engine inlet mass flow. */
   unsigned short wallModel_MaxIter; /*!< \brief maximum number of iterations for the Newton method for the wall model */
   su2double wallModel_Kappa,        /*!< \brief von Karman constant kappa for turbulence wall modeling */
   wallModel_B,                      /*!< \brief constant B for turbulence wall modeling */
@@ -2118,6 +2119,12 @@ class CConfig {
    */
   su2double GetNuFactor_Engine(void) const { return NuFactor_Engine; }
 
+  /*!
+   * \brief Get the flag to use exhaust mass flow as inlet mass flow.
+   * \return TRUE if exhaust mass flow is used as inlet mass flow.
+   */
+  bool GetExhaustToInlet_Engine(void) const { return out2in_mdot_engine; }
+
   /*!
    * \brief Get the value of the non-dimensionalized actuator disk turbulence intensity.
    * \return Non-dimensionalized actuator disk intensity.

Common/src/CConfig.cpp

@@ -1793,6 +1793,8 @@ void CConfig::SetConfig_Options() {
   addEnumOption("ENGINE_INFLOW_TYPE", Kind_Engine_Inflow, Engine_Inflow_Map, FAN_FACE_MACH);
   /* DESCRIPTION: Evaluate a problem with engines */
   addBoolOption("ENGINE", Engine, false);
+  /* DESCRIPTION: Use exhaust mass flow as inlet mass flow. */
+  addBoolOption("ENGINE_EXHAUST_TO_INLET", out2in_mdot_engine, false);
 
   /* DESCRIPTION:  Sharpness coefficient for the buffet sensor */
   addDoubleOption("BUFFET_K", Buffet_k, 10.0);

SU2_CFD/src/solvers/CEulerSolver.cpp

@@ -7622,6 +7622,17 @@ void CEulerSolver::BC_Engine_Inflow(CGeometry *geometry, CSolver **solver_contai
 
     Target_Inflow_MassFlow = config->GetEngineInflow_Target(Marker_Tag) / (config->GetDensity_Ref() * config->GetVelocity_Ref());
 
+    if (config->GetExhaustToInlet_Engine()) {
+      su2double Outlet_MF = 0.0;
+      unsigned short nMarker_Global = config->GetnMarker_CfgFile();
+      for (unsigned short iMarker_Global = 0; iMarker_Global < nMarker_Global; iMarker_Global++) {
+        if (config->GetMarker_CfgFile_KindBC(config->GetMarker_CfgFile_TagBound(iMarker_Global)) == ENGINE_EXHAUST) {
+          Outlet_MF = Outlet_MF + config->GetExhaust_MassFlow(config->GetMarker_CfgFile_TagBound(iMarker_Global));
+        }
+      }
+      Target_Inflow_MassFlow = Outlet_MF;
+    }
+
     if (config->GetSystemMeasurements() == US) Target_Inflow_MassFlow /= 32.174;
 
     if (Engine_HalfModel) Target_Inflow_MassFlow /= 2.0;

config_template.cfg

@@ -1183,6 +1183,9 @@ MARKER_ENGINE_INFLOW= ( NONE )
 % Format: (engine exhaust marker, total nozzle temp, total nozzle pressure, ... )
 MARKER_ENGINE_EXHAUST= ( NONE )
 %
+% Flag to allow mass-flow rate coupling between all exhaust surfaces and the engine inlet (YES, NO)
+ENGINE_EXHAUST_TO_INLET= NO
+%
 % Displacement boundary marker(s) (NONE = no marker)
 % Format: ( displacement marker, displacement value normal to the surface, ... )
 MARKER_NORMAL_DISPL= ( NONE )