Iteration archival: solve on master model, archive outputs to studies/iterations/iterNNN/

- Each iteration gets: params.json, results.json, OP2, F06, mass files
- Model directory stays clean (no solver output buildup)
- Study folder is self-contained with full trial history

projects/hydrotech-beam/studies/01_doe_landscape/nx_interface.py

@@ -153,15 +153,18 @@ class AtomizerNXSolver:
         if not model_dir.exists():
             raise FileNotFoundError(f"Model directory not found: {model_dir}")
 
-        self.model_dir = model_dir
+        self.model_dir = model_dir.resolve()
         self.nx_version = nx_version
         self.timeout = timeout
         self.use_iteration_folders = use_iteration_folders
         self._iteration = 0
 
-        # Set up iteration base directory
-        self.iterations_dir = model_dir.parent / "2_iterations"
+        # Iteration outputs go inside the study folder, not models/
+        # study_dir = the directory where run_doe.py lives
+        self.study_dir = Path(__file__).parent.resolve()
+        self.iterations_dir = self.study_dir / "iterations"
         self.iterations_dir.mkdir(parents=True, exist_ok=True)
+        logger.info("Iterations dir: %s", self.iterations_dir)
 
         # Find the .sim file
         sim_files = list(model_dir.glob("*.sim"))
@@ -277,25 +280,34 @@ class AtomizerNXSolver:
             trial.hole_count,
         )
 
-        try:
-            # Step 1: Create iteration folder with fresh model copies + .exp file
-            if self.use_iteration_folders:
-                iter_dir = self._nx_solver.create_iteration_folder(
-                    iterations_base_dir=self.iterations_dir,
-                    iteration_number=self._iteration,
-                    expression_updates=expressions,
-                )
-                sim_file = iter_dir / self.sim_file.name
-                prt_file = iter_dir / self.prt_file.name
-            else:
-                iter_dir = self.model_dir
-                sim_file = self.sim_file
-                prt_file = self.prt_file
+        # Create iteration output folder inside the study
+        iter_dir = self.iterations_dir / f"iter{self._iteration:03d}"
+        iter_dir.mkdir(parents=True, exist_ok=True)
 
-            # Step 2: Run NX journal (update expressions + solve)
+        try:
+            # Step 1: Solve directly on master model (no file copying)
+            # NX file references stay intact — expressions updated in-place by journal
+            sim_file = self.sim_file
+            prt_file = self.prt_file
+
+            # Save trial params to iteration folder
+            import json
+            params_file = iter_dir / "params.json"
+            params_file.write_text(json.dumps({
+                "iteration": self._iteration,
+                "expressions": expressions,
+                "trial_input": {
+                    "beam_half_core_thickness": trial.beam_half_core_thickness,
+                    "beam_face_thickness": trial.beam_face_thickness,
+                    "holes_diameter": trial.holes_diameter,
+                    "hole_count": trial.hole_count,
+                },
+            }, indent=2))
+
+            # Step 2: Run NX journal (update expressions + solve) on master model
             solve_result = self._nx_solver.run_simulation(
                 sim_file=sim_file,
-                working_dir=iter_dir,
+                working_dir=self.model_dir,
                 expression_updates=expressions,
             )
 
@@ -348,6 +360,9 @@ class AtomizerNXSolver:
                 logger.warning("Stress extraction failed: %s", e)
                 max_vm_stress = float("nan")
 
+            # Step 6: Copy solver outputs to iteration folder for archival
+            self._archive_iteration(iter_dir, op2_path, mass_kg, tip_displacement, max_vm_stress)
+
             elapsed = time.time() - start_time
             logger.info(
                 "Trial %d complete: mass=%.2f kg, disp=%.3f mm, stress=%.1f MPa (%.1fs)",
@@ -373,6 +388,52 @@ class AtomizerNXSolver:
                 iteration_dir=str(iter_dir) if 'iter_dir' in locals() else None,
             )
 
+    def _archive_iteration(
+        self,
+        iter_dir: Path,
+        op2_path: Path,
+        mass: float,
+        displacement: float,
+        stress: float,
+    ) -> None:
+        """Copy solver outputs to iteration folder for archival.
+
+        Keeps the models/ directory clean — solver outputs go to the study's
+        iterations/ folder. Each iteration gets: OP2, F06, mass file, and
+        a results summary JSON.
+        """
+        import json
+        import shutil
+
+        # Copy OP2 and F06 files
+        for suffix in [".op2", ".f06", ".log"]:
+            src = op2_path.with_suffix(suffix)
+            if src.exists():
+                try:
+                    shutil.copy2(src, iter_dir / src.name)
+                except Exception as e:
+                    logger.warning("Could not copy %s: %s", src.name, e)
+
+        # Copy mass temp file if it exists
+        for fname in ["_temp_mass.txt", "_temp_part_properties.json"]:
+            src = self.model_dir / fname
+            if src.exists():
+                try:
+                    shutil.copy2(src, iter_dir / fname)
+                except Exception as e:
+                    logger.warning("Could not copy %s: %s", fname, e)
+
+        # Write results summary
+        results_file = iter_dir / "results.json"
+        results_file.write_text(json.dumps({
+            "mass_kg": mass,
+            "tip_displacement_mm": displacement,
+            "max_von_mises_mpa": stress,
+            "op2_file": op2_path.name,
+        }, indent=2))
+
+        logger.info("Archived iteration %d to %s", self._iteration, iter_dir.name)
+
     def close(self) -> None:
         """Clean up NX solver resources."""
         logger.info("AtomizerNXSolver closed. %d iterations completed.", self._iteration)