Enable periodic BC in Legacy Mesher

flow360/component/simulation/meshing_param/volume_params.py

@@ -354,7 +354,7 @@ class AutomatedFarfield(Flow360BaseModel):
 
     type: Literal["AutomatedFarfield"] = pd.Field("AutomatedFarfield", frozen=True)
     name: Optional[str] = pd.Field("Automated Farfield")  # Kept optional for backward compatibility
-    method: Literal["auto", "quasi-3d"] = pd.Field(
+    method: Literal["auto", "quasi-3d", "quasi-3d-periodic"] = pd.Field(
         default="auto",
         frozen=True,
         description="""
@@ -364,6 +364,7 @@ class AutomatedFarfield(Flow360BaseModel):
             - -Y semi sphere if min{Y} < 0 and max{Y} = 0.
         - quasi-3d: Thin disk will be generated for quasi 3D cases.
                     Both sides of the farfield disk will be treated as "symmetric plane"
+        - quasi-3d-periodic: The two sides of the quasi-3d disk will be conformal
         Note: For quasi-3d, please do not group patches from both sides of the farfield disk into a single surface.
         """,
     )
@@ -372,6 +373,11 @@ class AutomatedFarfield(Flow360BaseModel):
         frozen=True,
         exclude=True,
     )
+    relative_size: pd.PositiveFloat = pd.Field(
+        default=50.0,
+        description="Radius of the far-field (semi)sphere/cylinder relative to "
+        "the max dimension of the geometry bounding box.",
+    )
 
     @property
     def farfield(self):
@@ -392,6 +398,19 @@ def symmetry_planes(self):
             ]
         raise ValueError(f"Unsupported method: {self.method}")
 
+    @pd.field_validator("method", mode="after")
+    @classmethod
+    def _validate_quasi_3d_periodic_only_in_legacy_mesher(cls, values):
+        """
+        Check mesher and AutomatedFarfield method compatibility
+        """
+        validation_info = get_validation_info()
+        if validation_info is None:
+            return values
+        if validation_info.is_beta_mesher and values == "quasi-3d-periodic":
+            raise ValueError("Only legacy mesher can support quasi-3d-periodic")
+        return values
+
 
 class UserDefinedFarfield(Flow360BaseModel):
     """

flow360/component/simulation/translator/volume_meshing_translator.py

@@ -265,9 +265,13 @@ def get_volume_meshing_json(input_params: SimulationParams, mesh_units):
 
         if isinstance(zone, AutomatedFarfield):
             translated["farfield"] = {
-                "type": zone.method,
-                "planarFaceTolerance": meshing_params.defaults.planar_face_tolerance,
+                "planarFaceTolerance": meshing_params.defaults.planar_face_tolerance
             }
+            if zone.method == "quasi-3d-periodic":
+                translated["farfield"]["type"] = "quasi-3d"
+                translated["farfield"]["periodic"] = {"type": "translational"}
+            else:
+                translated["farfield"]["type"] = zone.method
             break
 
     if "farfield" not in translated:

tests/ref/simulation/service_init_geometry.json

@@ -23,7 +23,8 @@
             {
                 "type": "AutomatedFarfield",
                 "name": "Farfield",
-                "method": "auto"
+                "method": "auto",
+                "relative_size": 50.0
             }
         ]
     },

tests/ref/simulation/service_init_surface_mesh.json

@@ -23,7 +23,8 @@
             {
                 "type": "AutomatedFarfield",
                 "name": "Farfield",
-                "method": "auto"
+                "method": "auto",
+                "relative_size": 50.0
             }
         ]
     },

tests/simulation/params/meshing_validation/test_meshing_param_validation.py

@@ -440,3 +440,17 @@ def test_box_entity_enclosed_only_in_beta_mesher():
                 spacing_circumferential=20,
                 enclosed_entities=[box_entity],
             )
+
+
+def test_quasi_3d_periodic_only_in_legacy_mesher():
+    # raises when legacy mesher is off
+    with pytest.raises(
+        pd.ValidationError,
+        match=r"Only legacy mesher can support quasi-3d-periodic",
+    ):
+        with ValidationContext(VOLUME_MESH, beta_mesher_context):
+            my_farfield = AutomatedFarfield(method="quasi-3d-periodic")
+
+    # does not raise with legacy mesher on
+    with ValidationContext(VOLUME_MESH, non_beta_mesher_context):
+        my_farfield = AutomatedFarfield(method="quasi-3d-periodic")