sv0D unit conversion factor

Code/Source/solver/ComMod.cpp

@@ -213,6 +213,14 @@ void svZeroDSolverInterfaceType::set_data(const svZeroDSolverInterfaceParameters
     initial_pressures = params.initial_pressures();
   }
 
+  // Copy unit conversion factors if provided
+  if (params.pressure_conversion_factor.defined()) {
+    pressure_conversion = params.pressure_conversion_factor();
+  }
+  if (params.flowrate_conversion_factor.defined()) {
+    flowrate_conversion = params.flowrate_conversion_factor();
+  }
+
   has_data = true;
 }
 

Code/Source/solver/ComMod.h

@@ -795,6 +795,12 @@ class svZeroDSolverInterfaceType
     // the svZeroDSolver_interface XML parameter has been defined.
     bool has_data = false;
 
+    // Unit conversion factors between 3D (svMultiPhysics) and 0D (svZeroD)
+    // When sending values to 0D, multiply by these; when receiving from 0D,
+    // divide by these. Defaults are 1.0 (no conversion).
+    double pressure_conversion = 1.0;
+    double flowrate_conversion = 1.0;
+
     void set_data(const svZeroDSolverInterfaceParameters& params);
     void add_block_face(const std::string& block_name, const std::string& face_name);
 };

Code/Source/solver/Parameters.cpp

@@ -1103,6 +1103,10 @@ svZeroDSolverInterfaceParameters::svZeroDSolverInterfaceParameters()
 
   set_parameter("Shared_library", "", required, shared_library);
 
+  // Unit conversion factors (default 1.0 means no scaling).
+  set_parameter("Pressure_conversion_factor", 1.0, !required, pressure_conversion_factor);
+  set_parameter("Flowrate_conversion_factor", 1.0, !required, flowrate_conversion_factor);
+
 };
 
 void svZeroDSolverInterfaceParameters::set_values(tinyxml2::XMLElement* xml_elem)

Code/Source/solver/Parameters.h

@@ -671,6 +671,13 @@ class svZeroDSolverInterfaceParameters : public ParameterLists
 
     Parameter<std::string> shared_library;
 
+    // Unit conversion factors between 3D and 0D models
+    // Pressure and flowrate values will be multiplied by these factors before 
+    // being sent to the 0D model, and the inverse factors will be applied to 
+    // 0D outputs before returning to 3D.
+    Parameter<double> pressure_conversion_factor;
+    Parameter<double> flowrate_conversion_factor;
+
     bool value_set = false;
 };
 

Code/Source/solver/svZeroD_subroutines.cpp

@@ -352,11 +352,13 @@ void init_svZeroD(ComMod& com_mod, const CmMod& cm_mod)
     interface->return_ydot(last_state_ydot);
     for (int s = 0; s < numCoupledSrfs; ++s) {
       if (init_flow_flag == 1) {
-        lpn_state_y[sol_IDs[2 * s]] = init_flow;
+        // Apply flowrate conversion when initializing state
+        lpn_state_y[sol_IDs[2 * s]] = init_flow * solver_interface.flowrate_conversion;
         cplBC.fa[s].y = lpn_state_y[sol_IDs[2 * s]];
       }
       if (init_press_flag == 1) {
-        lpn_state_y[sol_IDs[2 * s + 1]] = init_press;
+        // Apply pressure conversion when initializing state
+        lpn_state_y[sol_IDs[2 * s + 1]] = init_press * solver_interface.pressure_conversion;
         cplBC.fa[s].y = lpn_state_y[sol_IDs[2 * s + 1]];
       }
     }
@@ -434,14 +436,14 @@ void calc_svZeroD(ComMod& com_mod, const CmMod& cm_mod, char BCFlag) {
 
       total_flow = 0.0;
 
-      // Update pressure and flow in the zeroD model
+      // Update pressure and flow in the zeroD model (apply unit conversions)
       for (int i = 0; i < numCoupledSrfs; ++i) {
         if (i < nDir) {
-          params[0] = PCoupled[i];
-          params[1] = PnCoupled[i];
+          params[0] = PCoupled[i] * cplBC.svzerod_solver_interface.pressure_conversion;
+          params[1] = PnCoupled[i] * cplBC.svzerod_solver_interface.pressure_conversion;
         } else {
-          params[0] = in_out_sign[i] * QCoupled[i];
-          params[1] = in_out_sign[i] * QnCoupled[i];
+          params[0] = in_out_sign[i] * QCoupled[i] * cplBC.svzerod_solver_interface.flowrate_conversion;
+          params[1] = in_out_sign[i] * QnCoupled[i] * cplBC.svzerod_solver_interface.flowrate_conversion;
           total_flow += QCoupled[i];
         }
         update_svZeroD_block_params(svzd_blk_names[i], times, params);
@@ -455,10 +457,12 @@ void calc_svZeroD(ComMod& com_mod, const CmMod& cm_mod, char BCFlag) {
 
       for (int i = 0; i < numCoupledSrfs; ++i) {
         if (i < nDir) {
-          QCoupled[i] = in_out_sign[i] * lpn_state_y[sol_IDs[2 * i]];
+          // Convert 0D flow back to 3D units
+          QCoupled[i] = (in_out_sign[i] * lpn_state_y[sol_IDs[2 * i]]) / cplBC.svzerod_solver_interface.flowrate_conversion;
           cplBC.fa[i].y = QCoupled[i];
         } else {
-          PCoupled[i] = lpn_state_y[sol_IDs[2 * i + 1]];
+          // Convert 0D pressure back to 3D units
+          PCoupled[i] = lpn_state_y[sol_IDs[2 * i + 1]] / cplBC.svzerod_solver_interface.pressure_conversion;
           cplBC.fa[i].y = PCoupled[i];
         }
       }

tests/cases/fluid/pipe_RCR_sv0D/svzerod_3Dcoupling.json

@@ -10,6 +10,7 @@
             "bc_name": "RCR",
             "bc_type": "RCR",
             "bc_values": {
+                "_comment": "cgs units. R: (dyn/cm^2).s/cm^3, C: cm^3/(dyn/cm^2), Pd: (dyn/cm^2)",
                 "Rp": 121.0,
                 "Rd": 1212.0,
                 "C": 1.5e-4,

tests/cases/fluid/pipe_RCR_sv0D_different_units/README.md

@@ -0,0 +1,14 @@
+# pipe_RCR_sv0D_units
+
+This test is identical to `fluid/pipe_RCR_sv0D` but uses mixed units:
+
+- solver.xml: cgs units (dynes/cm^2, cm^3/s)
+- svZeroD JSON: clinical units (mmHg, mL/s)
+
+The `svZeroDSolver_interface` specifies conversion factors so that values are converted automatically:
+
+- `Pressure_conversion_factor =  0.00075006157584566` (dynes/cm^2 -> mmHg)
+- `Flowrate_conversion_factor = 1.0` (cm^3/s -> mL/s)
+
+Mesh and inflow files are referenced from the original test directory `pipe_RCR_sv0D/` to avoid duplication.
+Also, the reference result `result_002.vtu` in `pipe_RCR_sv0D/` is used for comparison.

tests/cases/fluid/pipe_RCR_sv0D_different_units/solver.xml

@@ -0,0 +1,111 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<svMultiPhysicsFile version="0.1">
+
+<GeneralSimulationParameters>
+
+  <Continue_previous_simulation> false </Continue_previous_simulation>
+  <Number_of_spatial_dimensions> 3 </Number_of_spatial_dimensions> 
+  <Number_of_time_steps> 2 </Number_of_time_steps> 
+  <Time_step_size> 0.005 </Time_step_size> 
+  <Spectral_radius_of_infinite_time_step> 0.50 </Spectral_radius_of_infinite_time_step> 
+  <Searched_file_name_to_trigger_stop> STOP_SIM </Searched_file_name_to_trigger_stop> 
+
+  <Save_results_to_VTK_format> 1 </Save_results_to_VTK_format> 
+  <Name_prefix_of_saved_VTK_files> result </Name_prefix_of_saved_VTK_files> 
+  <Increment_in_saving_VTK_files> 1 </Increment_in_saving_VTK_files> 
+  <Start_saving_after_time_step> 1 </Start_saving_after_time_step> 
+
+  <Increment_in_saving_restart_files> 200 </Increment_in_saving_restart_files> 
+  <Convert_BIN_to_VTK_format> 0 </Convert_BIN_to_VTK_format> 
+
+  <Verbose> 1 </Verbose> 
+  <Warning> 0 </Warning> 
+  <Debug> 0 </Debug> 
+
+</GeneralSimulationParameters>
+
+<Add_mesh name="msh" > 
+
+  <Mesh_file_path> ../pipe_RCR_sv0D/mesh-complete/mesh-complete.mesh.vtu </Mesh_file_path>
+
+  <Add_face name="lumen_inlet">
+      <Face_file_path> ../pipe_RCR_sv0D/mesh-complete/mesh-surfaces/lumen_inlet.vtp </Face_file_path>
+  </Add_face>
+
+  <Add_face name="lumen_outlet">
+      <Face_file_path> ../pipe_RCR_sv0D/mesh-complete/mesh-surfaces/lumen_outlet.vtp </Face_file_path>
+  </Add_face>
+
+  <Add_face name="lumen_wall">
+      <Face_file_path> ../pipe_RCR_sv0D/mesh-complete/mesh-surfaces/lumen_wall.vtp </Face_file_path>
+  </Add_face>
+
+</Add_mesh>
+
+<Add_equation type="fluid" > 
+   <Coupled> 1 </Coupled>
+   <Min_iterations> 3 </Min_iterations>  
+   <Max_iterations> 10 </Max_iterations> 
+   <Tolerance> 1e-3 </Tolerance> 
+   <Backflow_stabilization_coefficient> 0.2 </Backflow_stabilization_coefficient>
+
+   <Density> 1.06 </Density> <!-- g/cm^3 -->
+   <Viscosity model="Constant" >
+     <Value> 0.04 </Value> <!-- poise -->
+   </Viscosity>
+
+   <Output type="Spatial" >
+      <Velocity> true </Velocity>
+      <Pressure> true </Pressure>
+      <Traction> true </Traction>
+     <WSS> true </WSS>
+      <Vorticity> true </Vorticity>
+      <Divergence> true </Divergence>
+   </Output>
+
+   <LS type="NS" >
+      <Linear_algebra type="fsils" >
+         <Preconditioner> fsils </Preconditioner>
+      </Linear_algebra> 
+      <Max_iterations> 10 </Max_iterations> 
+      <NS_GM_max_iterations> 3 </NS_GM_max_iterations>
+      <NS_CG_max_iterations> 500 </NS_CG_max_iterations>
+      <Tolerance> 1e-3 </Tolerance>
+      <NS_GM_tolerance> 1e-3 </NS_GM_tolerance>
+      <NS_CG_tolerance> 1e-3 </NS_CG_tolerance>
+      <Krylov_space_dimension> 50 </Krylov_space_dimension>
+   </LS>
+
+   <svZeroDSolver_interface> 
+     <Coupling_type> semi-implicit </Coupling_type>
+     <Configuration_file> svzerod_3Dcoupling.json </Configuration_file>
+     <Shared_library> ../../../../svZeroDSolver/build/src/interface/libsvzero_interface.dylib </Shared_library>  
+     <Initial_flows> 0.0 </Initial_flows>
+     <Initial_pressures> 0.0 </Initial_pressures>
+     <Pressure_conversion_factor> 0.00075006157584566 </Pressure_conversion_factor> <!-- dyn/cm^2 to mmHg -->
+     <Flowrate_conversion_factor> 1.0 </Flowrate_conversion_factor> <!-- cm^3/s to ml/s -->
+   </svZeroDSolver_interface> 
+
+   <Add_BC name="lumen_inlet" > 
+      <Type> Dir </Type> 
+      <Time_dependence> Unsteady </Time_dependence> 
+      <Temporal_values_file_path> ../pipe_RCR_sv0D/lumen_inlet.flw</Temporal_values_file_path> 
+      <Zero_out_perimeter> true </Zero_out_perimeter> 
+      <Impose_flux> true </Impose_flux> 
+   </Add_BC>
+
+   <Add_BC name="lumen_outlet" > 
+      <Type> Neu </Type> 
+      <Time_dependence> Coupled </Time_dependence> 
+      <svZeroDSolver_block> RCR_coupling </svZeroDSolver_block>  
+   </Add_BC> 
+
+   <Add_BC name="lumen_wall" > 
+      <Type> Dir </Type> 
+      <Time_dependence> Steady </Time_dependence> 
+      <Value> 0.0 </Value>
+   </Add_BC> 
+
+</Add_equation>
+
+</svMultiPhysicsFile>

tests/cases/fluid/pipe_RCR_sv0D_different_units/svzerod_3Dcoupling.json

@@ -0,0 +1,36 @@
+{
+    "simulation_parameters": {
+        "coupled_simulation": true,
+        "number_of_time_pts": 100,
+        "output_all_cycles": true,
+        "steady_initial": false
+    },
+    "boundary_conditions": [
+        {
+            "bc_name": "RCR",
+            "bc_type": "RCR",
+            "bc_values": {
+                "_comment": "Clinical units. R: mmHg.s/mL, C: mL/mmHg, Pd: mmHg",
+                "Rp": 0.09075745067,
+                "Rd": 0.90907462992,
+                "C": 0.19998358112,
+                "Pd": 0.0
+            }
+        }
+    ],
+    "external_solver_coupling_blocks": [
+        {
+            "name": "RCR_coupling",
+            "type": "FLOW",
+            "location": "inlet",
+            "connected_block": "RCR",
+            "periodic": false,
+            "values": {
+                "t": [0.0, 1.0],
+                "Q": [1.0, 1.0]
+            }
+        }
+    ],
+    "junctions": [],
+    "vessels": []
+}

tests/test_fluid.py

@@ -64,6 +64,10 @@ def test_pipe_RCR_sv0D(n_proc):
     t_max = 2
     run_with_reference(base_folder, test_folder, fields, n_proc, t_max)
 
+def test_pipe_RCR_sv0D_different_units(n_proc):
+    test_folder = "pipe_RCR_sv0D_different_units"
+    t_max = 2
+    run_with_reference(base_folder, test_folder, fields, n_proc, t_max, name_ref="../pipe_RCR_sv0D/result_002.vtu")
 
 def test_driven_cavity_2d(n_proc):
     test_folder = "driven_cavity_2d"