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Fix bug that dimensionalization used wrong velocity scale #1361

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benflexcompute merged 2 commits into from
Aug 15, 2025
Merged

Fix bug that dimensionalization used wrong velocity scale #1361

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ba9e5dc
Fix bug that dimensionalization used wrong velocity scale
benflexcompute Aug 15, 2025
e5e3881
Fix unit test
benflexcompute Aug 15, 2025
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36 changes: 33 additions & 3 deletions flow360/component/simulation/conversion.py
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Original file line number Diff line number Diff line change
Expand Up @@ -362,15 +362,45 @@ def get_base_thermal_conductivity():
return flow360_conversion_unit_system.conversion_system


def get_flow360_unit_system_liquid(params) -> u.UnitSystem:
def get_flow360_unit_system_liquid(params, to_flow360_unit: bool = False) -> u.UnitSystem:
"""
Returns the flow360 unit system when liquid operating condition is used
Returns the flow360 unit system when liquid operating condition is used.

Parameters
----------
params : SimulationParams
The parameters needed for unit conversion.
to_flow360_unit : bool, optional
If True, return the flow360 unit system.

Returns
-------
u.UnitSystem
The flow360 unit system.

##-- When to_flow360_unit is True,
##-- time unit should be changed such that it takes into consideration
##-- the fact that solver output already multiplied by "velocityScale"
"""

if to_flow360_unit:
base_velocity = params.base_velocity
else:
# For dimensionalization of Flow360 output
# The solver output is already re-normalized by `reference velocity` due to "velocityScale"
# So we need to find the `reference velocity`.
# `reference_velocity_magnitude` takes precedence, consistent with how "velocityScale" is computed.
if params.operating_condition.reference_velocity_magnitude is not None:
base_velocity = (params.operating_condition.reference_velocity_magnitude).to("m/s")
else:
base_velocity = params.base_velocity.to("m/s") * LIQUID_IMAGINARY_FREESTREAM_MACH

time_unit = params.base_length / base_velocity
return u.UnitSystem(
name="flow360_liquid",
length_unit=params.base_length,
mass_unit=params.base_mass,
time_unit=params.base_time / LIQUID_IMAGINARY_FREESTREAM_MACH,
time_unit=time_unit,
temperature_unit=params.base_temperature,
)

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16 changes: 16 additions & 0 deletions tests/simulation/translator/ref/Flow360_liquid_rotation_dd.json
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,10 @@
}
},
"userDefinedFields": [
{
"expression": "double ___velocity[3];___velocity[0] = primitiveVars[1] * velocityScale;___velocity[1] = primitiveVars[2] * velocityScale;___velocity[2] = primitiveVars[3] * velocityScale;velocity_SI[0] = (___velocity[0] * 10.0); velocity_SI[1] = (___velocity[1] * 10.0); velocity_SI[2] = (___velocity[2] * 10.0);",
"name": "velocity_SI"
},
{
"expression": "double velocity[3];velocity[0] = primitiveVars[1];velocity[1] = primitiveVars[2];velocity[2] = primitiveVars[3];velocity_magnitude = magnitude(velocity) * velocityScale;",
"name": "velocity_magnitude",
Expand All @@ -99,6 +103,18 @@
"outputRescale": {
"velocityScale": 20.0
},
"volumeOutput": {
"animationFrequency": -1,
"animationFrequencyOffset": 0,
"animationFrequencyTimeAverage": -1,
"animationFrequencyTimeAverageOffset": 0,
"computeTimeAverages": false,
"outputFields": [
"velocity_SI"
],
"outputFormat": "paraview",
"startAverageIntegrationStep": -1
},
"volumeZones": {
"zone_zone_1": {
"referenceFrame": {
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138 changes: 138 additions & 0 deletions tests/simulation/translator/ref/Flow360_liquid_rotation_dd_with_ref_vel.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1,138 @@
{
"freestream": {
"alphaAngle": 5.0,
"betaAngle": 2.0,
"Mach": 0.05,
"Temperature": -1,
"muRef": 4.554545454545455e-09,
"MachRef": 0.1
},
"timeStepping": {
"CFL": {
"type": "adaptive",
"min": 0.1,
"max": 1000000.0,
"maxRelativeChange": 50.0,
"convergenceLimitingFactor": 1.0
},
"physicalSteps": 100,
"orderOfAccuracy": 2,
"maxPseudoSteps": 20,
"timeStepSize": 80.0
},
"navierStokesSolver": {
"absoluteTolerance": 1e-10,
"relativeTolerance": 0.0,
"orderOfAccuracy": 2,
"linearSolver": {
"maxIterations": 30
},
"CFLMultiplier": 1.0,
"kappaMUSCL": -1.0,
"numericalDissipationFactor": 1.0,
"limitVelocity": false,
"limitPressureDensity": false,
"lowMachPreconditioner": true,
"updateJacobianFrequency": 4,
"maxForceJacUpdatePhysicalSteps": 0,
"lowMachPreconditionerThreshold": 0.05,
"modelType": "Compressible",
"equationEvalFrequency": 1
},
"turbulenceModelSolver": {
"absoluteTolerance": 1e-08,
"relativeTolerance": 0.0,
"orderOfAccuracy": 2,
"linearSolver": {
"maxIterations": 20
},
"CFLMultiplier": 2.0,
"reconstructionGradientLimiter": 0.5,
"quadraticConstitutiveRelation": false,
"updateJacobianFrequency": 4,
"maxForceJacUpdatePhysicalSteps": 0,
"rotationCorrection": false,
"equationEvalFrequency": 4,
"modelType": "SpalartAllmaras",
"modelConstants": {
"C_DES": 0.72,
"C_d": 8.0,
"C_cb1": 0.1355,
"C_cb2": 0.622,
"C_sigma": 0.6666666666666666,
"C_v1": 7.1,
"C_vonKarman": 0.41,
"C_w2": 0.3,
"C_t3": 1.2,
"C_t4": 0.5,
"C_min_rd": 10.0
},
"DDES": false,
"ZDES": false,
"gridSizeForLES": "maxEdgeLength"
},
"initialCondition": {
"type": "initialCondition",
"rho": "rho",
"u": "u",
"v": "v",
"w": "w",
"p": "p"
},
"boundaries": {
"fluid/body": {
"type": "NoSlipWall",
"heatFlux": 0.0,
"roughnessHeight": 0.0
},
"fluid/farfield": {
"type": "Freestream"
}
},
"userDefinedFields": [
{
"expression": "double ___velocity[3];___velocity[0] = primitiveVars[1] * velocityScale;___velocity[1] = primitiveVars[2] * velocityScale;___velocity[2] = primitiveVars[3] * velocityScale;velocity_SI[0] = (___velocity[0] * 20.0); velocity_SI[1] = (___velocity[1] * 20.0); velocity_SI[2] = (___velocity[2] * 20.0);",
"name": "velocity_SI"
},
{
"expression": "double velocity[3];velocity[0] = primitiveVars[1];velocity[1] = primitiveVars[2];velocity[2] = primitiveVars[3];velocity_magnitude = magnitude(velocity) * velocityScale;",
"name": "velocity_magnitude",
"from_user_variables": false
}
],
"usingLiquidAsMaterial": true,
"outputRescale": {
"velocityScale": 10.0
},
"volumeOutput": {
"animationFrequency": -1,
"animationFrequencyOffset": 0,
"animationFrequencyTimeAverage": -1,
"animationFrequencyTimeAverageOffset": 0,
"computeTimeAverages": false,
"outputFields": [
"velocity_SI"
],
"outputFormat": "paraview",
"startAverageIntegrationStep": -1
},
"volumeZones": {
"zone_zone_1": {
"referenceFrame": {
"axisOfRotation": [
0.6,
0.8,
0.0
],
"centerOfRotation": [
0.01,
0.01,
0.01
],
"thetaRadians": "-180/pi * atan(2 * 3.00 * 20.00 * 2.00/180*pi * cos(2.00/180*pi * sin(0.05877271 * (0.005 * t))) * cos(0.05877271 * (0.005 * t)) / 200.00) + 2 * 2.00 * sin(0.05877271 * (0.005 * t)) - 2.00 * sin(0.05877271 * (0.005 * t))"
},
"modelType": "FluidDynamics",
"isRotatingReferenceFrame": false
}
}
}
16 changes: 8 additions & 8 deletions tests/simulation/translator/test_output_translation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1351,7 +1351,7 @@ def test_dimensioned_output_fields_translation(vel_in_km_per_hr):
},
{
"name": "pressure_pa",
"expression": "double pressure;double gamma = 1.4;pressure = (usingLiquidAsMaterial) ? (primitiveVars[4] - 1.0 / gamma) * (velocityScale * velocityScale) : primitiveVars[4];pressure_pa = pressure * 2500000.0;",
"expression": "double pressure;double gamma = 1.4;pressure = (usingLiquidAsMaterial) ? (primitiveVars[4] - 1.0 / gamma) * (velocityScale * velocityScale) : primitiveVars[4];pressure_pa = pressure * 10000000.0;",
"from_user_variables": False,
},
{
Expand All @@ -1361,11 +1361,11 @@ def test_dimensioned_output_fields_translation(vel_in_km_per_hr):
},
{
"name": "velocity_in_km_per_hr",
"expression": "double ___velocity[3];___velocity[0] = primitiveVars[1] * velocityScale;___velocity[1] = primitiveVars[2] * velocityScale;___velocity[2] = primitiveVars[3] * velocityScale;velocity_in_km_per_hr[0] = (___velocity[0] * 180.0); velocity_in_km_per_hr[1] = (___velocity[1] * 180.0); velocity_in_km_per_hr[2] = (___velocity[2] * 180.0);",
"expression": "double ___velocity[3];___velocity[0] = primitiveVars[1] * velocityScale;___velocity[1] = primitiveVars[2] * velocityScale;___velocity[2] = primitiveVars[3] * velocityScale;velocity_in_km_per_hr[0] = (___velocity[0] * 360.0); velocity_in_km_per_hr[1] = (___velocity[1] * 360.0); velocity_in_km_per_hr[2] = (___velocity[2] * 360.0);",
},
{
"name": "velocity_m_per_s",
"expression": "double velocity[3];velocity[0] = primitiveVars[1] * velocityScale;velocity[1] = primitiveVars[2] * velocityScale;velocity[2] = primitiveVars[3] * velocityScale;velocity_m_per_s[0] = velocity[0] * 50.0;velocity_m_per_s[1] = velocity[1] * 50.0;velocity_m_per_s[2] = velocity[2] * 50.0;",
"expression": "double velocity[3];velocity[0] = primitiveVars[1] * velocityScale;velocity[1] = primitiveVars[2] * velocityScale;velocity[2] = primitiveVars[3] * velocityScale;velocity_m_per_s[0] = velocity[0] * 100.0;velocity_m_per_s[1] = velocity[1] * 100.0;velocity_m_per_s[2] = velocity[2] * 100.0;",
"from_user_variables": False,
},
{
Expand All @@ -1375,22 +1375,22 @@ def test_dimensioned_output_fields_translation(vel_in_km_per_hr):
},
{
"name": "velocity_magnitude_m_per_s",
"expression": "double velocity_magnitude;double velocity[3];velocity[0] = primitiveVars[1];velocity[1] = primitiveVars[2];velocity[2] = primitiveVars[3];velocity_magnitude = magnitude(velocity) * velocityScale;velocity_magnitude_m_per_s = velocity_magnitude * 50.0;",
"expression": "double velocity_magnitude;double velocity[3];velocity[0] = primitiveVars[1];velocity[1] = primitiveVars[2];velocity[2] = primitiveVars[3];velocity_magnitude = magnitude(velocity) * velocityScale;velocity_magnitude_m_per_s = velocity_magnitude * 100.0;",
"from_user_variables": False,
},
{
"name": "velocity_x_m_per_s",
"expression": "double velocity_x;velocity_x = primitiveVars[1] * velocityScale;velocity_x_m_per_s = velocity_x * 50.0;",
"expression": "double velocity_x;velocity_x = primitiveVars[1] * velocityScale;velocity_x_m_per_s = velocity_x * 100.0;",
"from_user_variables": False,
},
{
"name": "velocity_y_m_per_s",
"expression": "double velocity_y;velocity_y = primitiveVars[2] * velocityScale;velocity_y_m_per_s = velocity_y * 50.0;",
"expression": "double velocity_y;velocity_y = primitiveVars[2] * velocityScale;velocity_y_m_per_s = velocity_y * 100.0;",
"from_user_variables": False,
},
{
"name": "velocity_z_m_per_s",
"expression": "double velocity_z;velocity_z = primitiveVars[3] * velocityScale;velocity_z_m_per_s = velocity_z * 50.0;",
"expression": "double velocity_z;velocity_z = primitiveVars[3] * velocityScale;velocity_z_m_per_s = velocity_z * 100.0;",
"from_user_variables": False,
},
{
Expand All @@ -1405,7 +1405,7 @@ def test_dimensioned_output_fields_translation(vel_in_km_per_hr):
},
{
"name": "wall_shear_stress_magnitude_pa",
"expression": "double wall_shear_stress_magnitude;wall_shear_stress_magnitude = magnitude(wallShearStress) * (velocityScale * velocityScale);wall_shear_stress_magnitude_pa = wall_shear_stress_magnitude * 2500000.0;",
"expression": "double wall_shear_stress_magnitude;wall_shear_stress_magnitude = magnitude(wallShearStress) * (velocityScale * velocityScale);wall_shear_stress_magnitude_pa = wall_shear_stress_magnitude * 10000000.0;",
"from_user_variables": False,
},
]
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16 changes: 16 additions & 0 deletions tests/simulation/translator/test_solver_translator.py
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,7 @@
from flow360.component.simulation.user_code.core.types import UserVariable
from flow360.component.simulation.user_code.functions import math
from flow360.component.simulation.user_code.variables import solution
from flow360.component.simulation.utils import model_attribute_unlock
from tests.simulation.translator.utils.actuator_disk_param_generator import (
actuator_disk_create_param,
)
Expand Down Expand Up @@ -659,13 +660,28 @@ def test_liquid_simulation_translation():
),
],
time_stepping=Unsteady(steps=100, step_size=0.4),
outputs=[
VolumeOutput(
name="output",
output_fields=[solution.velocity],
)
],
)
# Derivation:
# Solver speed of sound = 10m/s / 0.05 = 200m/s
# Flow360 time to seconds = 1m/(200m/s) = 0.005 s
# t_seconds = (0.005 s * t)
translate_and_compare(param, mesh_unit=1 * u.m, ref_json_file="Flow360_liquid_rotation_dd.json")

with model_attribute_unlock(param.operating_condition, "reference_velocity_magnitude"):
param.operating_condition.reference_velocity_magnitude = 20 * u.m / u.s
translate_and_compare(
param,
mesh_unit=1 * u.m,
ref_json_file="Flow360_liquid_rotation_dd_with_ref_vel.json",
debug=True,
)


def test_param_with_user_variables():
some_dependent_variable_a = UserVariable(
Expand Down
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