Add Base Units and Unit System as SimulationParams's property

flow360/component/simulation/conversion.py

@@ -136,34 +136,22 @@ def unit_converter(dimension, params, required_by: List[str] = None) -> u.UnitSy
 
     def get_base_length():
         require(["private_attribute_asset_cache", "project_length_unit"], required_by, params)
-        base_length = params.private_attribute_asset_cache.project_length_unit.to("m").v.item()
+        base_length = params.base_length.v.item()
         return base_length
 
     def get_base_temperature():
-        if params.operating_condition.type_name == "LiquidOperatingCondition":
+        if params.operating_condition.type_name != "LiquidOperatingCondition":
             # Temperature in this condition has no effect because the thermal features will be disabled.
             # Also the viscosity will be constant.
             # pylint:disable = no-member
-            return 273 * u.K
-        require(["operating_condition", "thermal_state", "temperature"], required_by, params)
-        base_temperature = params.operating_condition.thermal_state.temperature.to("K").v.item()
+            require(["operating_condition", "thermal_state", "temperature"], required_by, params)
+        base_temperature = params.base_temperature.v.item()
         return base_temperature
 
     def get_base_velocity():
-        if params.operating_condition.type_name == "LiquidOperatingCondition":
-            # Provides an imaginary "speed of sound"
-            # Resulting in a hardcoded freestream mach of `LIQUID_IMAGINARY_FREESTREAM_MACH`
-            # To ensure incompressible range.
-            if params.operating_condition.velocity_magnitude.value != 0:
-                return (
-                    params.operating_condition.velocity_magnitude / LIQUID_IMAGINARY_FREESTREAM_MACH
-                )
-            return (
-                params.operating_condition.reference_velocity_magnitude
-                / LIQUID_IMAGINARY_FREESTREAM_MACH
-            )
-        require(["operating_condition", "thermal_state", "temperature"], required_by, params)
-        base_velocity = params.operating_condition.thermal_state.speed_of_sound.to("m/s").v.item()
+        if params.operating_condition.type_name != "LiquidOperatingCondition":
+            require(["operating_condition", "thermal_state", "temperature"], required_by, params)
+        base_velocity = params.base_velocity.v.item()
         return base_velocity
 
     def get_base_time():
@@ -179,11 +167,9 @@ def get_base_angular_velocity():
         return base_angular_velocity
 
     def get_base_density():
-        if params.operating_condition.type_name == "LiquidOperatingCondition":
-            return params.operating_condition.material.density
-        require(["operating_condition", "thermal_state", "density"], required_by, params)
-        base_density = params.operating_condition.thermal_state.density.to("kg/m**3").v.item()
-
+        if params.operating_condition.type_name != "LiquidOperatingCondition":
+            require(["operating_condition", "thermal_state", "density"], required_by, params)
+        base_density = params.base_density.v.item()
         return base_density
 
     def get_base_viscosity():
@@ -262,6 +248,10 @@ def get_base_thermal_conductivity():
         base_length = get_base_length()
         flow360_conversion_unit_system.base_length = base_length
 
+    elif dimension == u.dimensions.mass:
+        base_mass = params.base_mass
+        flow360_conversion_unit_system.base_mass = base_mass
+
     elif dimension == u.dimensions.temperature:
         base_temperature = get_base_temperature()
         flow360_conversion_unit_system.base_temperature = base_temperature

flow360/component/simulation/simulation_params.py

@@ -7,8 +7,12 @@
 from typing import Annotated, List, Optional, Union
 
 import pydantic as pd
+import unyt as u
 
-from flow360.component.simulation.conversion import unit_converter
+from flow360.component.simulation.conversion import (
+    LIQUID_IMAGINARY_FREESTREAM_MACH,
+    unit_converter,
+)
 from flow360.component.simulation.framework.base_model import Flow360BaseModel
 from flow360.component.simulation.framework.entity_registry import EntityRegistry
 from flow360.component.simulation.framework.param_utils import (
@@ -52,10 +56,15 @@
 )
 from flow360.component.simulation.time_stepping.time_stepping import Steady, Unsteady
 from flow360.component.simulation.unit_system import (
+    AbsoluteTemperatureType,
+    DensityType,
     DimensionedTypes,
     LengthType,
+    MassType,
+    TimeType,
     UnitSystem,
     UnitSystemType,
+    VelocityType,
     is_flow360_unit,
     unit_system_manager,
     unyt_quantity,
@@ -533,6 +542,70 @@ def _update_entity_private_attrs(self, registry: EntityRegistry) -> EntityRegist
 
         return registry
 
+    @property
+    def base_length(self) -> LengthType:
+        """Get base length unit for non-dimensionalization"""
+        # pylint:disable=no-member
+        return self.private_attribute_asset_cache.project_length_unit.to("m")
+
+    @property
+    def base_temperature(self) -> AbsoluteTemperatureType:
+        """Get base temperature unit for non-dimensionalization"""
+        # pylint:disable=no-member
+        if self.operating_condition.type_name == "LiquidOperatingCondition":
+            # Temperature in this condition has no effect because the thermal features will be disabled.
+            # Also the viscosity will be constant.
+            # pylint:disable = no-member
+            return 273 * u.K
+        return self.operating_condition.thermal_state.temperature.to("K")
+
+    @property
+    def base_velocity(self) -> VelocityType:
+        """Get base velocity unit for non-dimensionalization"""
+        # pylint:disable=no-member
+        if self.operating_condition.type_name == "LiquidOperatingCondition":
+            # Provides an imaginary "speed of sound"
+            # Resulting in a hardcoded freestream mach of `LIQUID_IMAGINARY_FREESTREAM_MACH`
+            # To ensure incompressible range.
+            if self.operating_condition.velocity_magnitude.value != 0:
+                return (
+                    self.operating_condition.velocity_magnitude / LIQUID_IMAGINARY_FREESTREAM_MACH
+                ).to("m/s")
+            return (
+                self.operating_condition.reference_velocity_magnitude
+                / LIQUID_IMAGINARY_FREESTREAM_MACH
+            ).to("m/s")
+        return self.operating_condition.thermal_state.speed_of_sound.to("m/s")
+
+    @property
+    def base_density(self) -> DensityType:
+        """Get base density unit for non-dimensionalization"""
+        # pylint:disable=no-member
+        if self.operating_condition.type_name == "LiquidOperatingCondition":
+            return self.operating_condition.material.density.to("kg/m**3")
+        return self.operating_condition.thermal_state.density.to("kg/m**3")
+
+    @property
+    def base_mass(self) -> MassType:
+        """Get base mass unit for non-dimensionalization"""
+        return self.base_density * self.base_length**3
+
+    @property
+    def base_time(self) -> TimeType:
+        """Get base time unit for non-dimensionalization"""
+        return self.base_length / self.base_velocity
+
+    @property
+    def flow360_unit_system(self) -> u.UnitSystem:
+        """Get the unit system for non-dimensionalization"""
+        return u.UnitSystem(
+            name="flow360_nondim",
+            length_unit=self.base_length,
+            mass_unit=self.base_mass,
+            time_unit=self.base_time,
+            temperature_unit=self.base_temperature,
+        )
+
     @property
     def used_entity_registry(self) -> EntityRegistry:
         """

tests/simulation/framework/test_entities_v2.py

@@ -211,6 +211,10 @@ class TempSimulationParam(_ParamModelBase):
     udd: Optional[TempUserDefinedDynamic] = pd.Field(None)
     private_attribute_asset_cache: AssetCache = pd.Field(AssetCache(), frozen=True)
 
+    @property
+    def base_length(self) -> LengthType:
+        return self.private_attribute_asset_cache.project_length_unit.to("m")
+
     def preprocess(self):
         """
         Supply self._supplementary_registry to the construction of