refactor(FXC-6541): default SurfaceOutput.name to None and write empty string to solver JSON

Change SurfaceOutput.name and TimeAverageSurfaceOutput.name default from
a string label to None. The translator writes an empty string to the solver
JSON when name is None, so the C++ solver falls back to the standard
"surface" prefix. Non-None names are written as-is for disambiguation.

Made-with: Cursor

Author: NasserFlexCompute

flow360/component/simulation/outputs/outputs.py

@@ -470,9 +470,10 @@ class SurfaceOutput(_AnimationAndFileFormatSettings, _OutputBase):
     # TODO: entities is None --> use all surfaces. This is not implemented yet.
 
     name: Optional[FileNameString] = pd.Field(
-        "Surface output",
-        description="Name of the `SurfaceOutput`. Must be unique across all `SurfaceOutput` "
-        "instances that share the same surface entity.",
+        None,
+        description="Name of the `SurfaceOutput`. Used as a suffix in output filenames to "
+        "disambiguate when multiple outputs share the same surface entity. "
+        "Must be unique across all instances that share the same surface.",
     )
     entities: EntityList[  # pylint: disable=duplicate-code
         Surface,
@@ -499,9 +500,8 @@ class SurfaceOutput(_AnimationAndFileFormatSettings, _OutputBase):
 
     @property
     def has_default_name(self) -> bool:
-        """Whether this output still carries its Pydantic-defined default name."""
-        # pylint: disable=unsubscriptable-object
-        return self.name is None or self.name == type(self).model_fields["name"].default
+        """Whether this output has no custom name assigned."""
+        return self.name is None
 
     @contextual_field_validator("entities", mode="after")
     @classmethod
@@ -546,9 +546,10 @@ class TimeAverageSurfaceOutput(SurfaceOutput):
     """
 
     name: Optional[FileNameString] = pd.Field(
-        "Time average surface output",
-        description="Name of the `TimeAverageSurfaceOutput`. Must be unique across all "
-        "`TimeAverageSurfaceOutput` instances that share the same surface entity.",
+        None,
+        description="Name of the `TimeAverageSurfaceOutput`. Used as a suffix in output filenames "
+        "to disambiguate when multiple outputs share the same surface entity. "
+        "Must be unique across all instances that share the same surface.",
     )
 
     start_step: Union[pd.NonNegativeInt, Literal[-1]] = pd.Field(

flow360/component/simulation/translator/solver_translator.py

@@ -597,7 +597,7 @@ def _translate_single_surface_output(
         ),
     )
     surface_output["writeSingleFile"] = output_instance.write_single_file
-    surface_output["name"] = output_instance.name
+    surface_output["name"] = output_instance.name if output_instance.name is not None else ""
     return surface_output
 
 

tests/ref/simulation/service_init_geometry.json

@@ -372,7 +372,7 @@
             },
             "frequency": -1,
             "frequency_offset": 0,
-            "name": "Surface output",
+            "name": null,
             "output_fields": {
                 "items": [
                     "Cp",

tests/ref/simulation/service_init_surface_mesh.json

@@ -372,7 +372,7 @@
             },
             "frequency": -1,
             "frequency_offset": 0,
-            "name": "Surface output",
+            "name": null,
             "output_fields": {
                 "items": [
                     "Cp",

tests/ref/simulation/service_init_volume_mesh.json

@@ -327,7 +327,7 @@
             },
             "frequency": -1,
             "frequency_offset": 0,
-            "name": "Surface output",
+            "name": null,
             "output_fields": {
                 "items": [
                     "Cp",

tests/simulation/ref/entity_expansion_service_ref_outputs.json

@@ -44,7 +44,7 @@
         },
         "frequency": -1,
         "frequency_offset": 0,
-        "name": "Surface output",
+        "name": null,
         "output_fields": {
             "items": [
                 "Cp",

tests/simulation/translator/ref/Flow360_CHT_three_cylinders.json

@@ -97,7 +97,7 @@
             "animationFrequencyOffset": 0,
             "animationFrequencyTimeAverage": -1,
             "animationFrequencyTimeAverageOffset": 0,
-            "name": "Surface output",
+            "name": "",
             "outputFields": [],
             "outputFormat": "paraview",
             "startAverageIntegrationStep": -1,
@@ -137,7 +137,7 @@
             "animationFrequencyOffset": 0,
             "animationFrequencyTimeAverage": -1,
             "animationFrequencyTimeAverageOffset": 0,
-            "name": "Surface output",
+            "name": "",
             "outputFields": [],
             "outputFormat": "paraview",
             "startAverageIntegrationStep": -1,

tests/simulation/translator/ref/Flow360_NestedCylindersSRF.json

@@ -69,7 +69,7 @@
             "animationFrequencyOffset": 0,
             "animationFrequencyTimeAverage": -1,
             "animationFrequencyTimeAverageOffset": 0,
-            "name": "Surface output",
+            "name": "",
             "outputFields": [],
             "outputFormat": "paraview",
             "startAverageIntegrationStep": -1,

tests/simulation/translator/ref/Flow360_TurbFlatPlate137x97_BoxTrip.json

@@ -78,7 +78,7 @@
             "animationFrequencyOffset": 0,
             "animationFrequencyTimeAverage": -1,
             "animationFrequencyTimeAverageOffset": 0,
-            "name": "Surface output",
+            "name": "",
             "outputFields": [],
             "outputFormat": "paraview",
             "startAverageIntegrationStep": -1,

tests/simulation/translator/ref/Flow360_XV15HoverMRF.json

@@ -60,7 +60,7 @@
             "animationFrequencyOffset": 0,
             "animationFrequencyTimeAverage": -1,
             "animationFrequencyTimeAverageOffset": 0,
-            "name": "Surface output",
+            "name": "",
             "outputFields": [],
             "outputFormat": "paraview",
             "startAverageIntegrationStep": -1,