Available Output Fields

Available Output Fields#

This section provides a comprehensive overview of all output fields (flow variables) available in Flow360 simulations, organized by their availability across different output types.

Note: All output fields are non-dimensional by default unless otherwise specified. See Scaling Values and Nondimensionalization for information on converting to dimensional values.

Universal Fields#

These fields are available for all output types.

Field Name	Description	Units
`Cp`	Coefficient of pressure	Non-dimensional
`Cpt`	Coefficient of total pressure	Non-dimensional
`gradW`	Gradient of primitive solution	Non-dimensional
`kOmega`	k and omega (turbulence variables)	Non-dimensional
`Mach`	Mach number	Non-dimensional
`mut`	Turbulent viscosity	Non-dimensional
`mutRatio`	Turbulent viscosity and freestream dynamic viscosity ratio	Non-dimensional
`nuHat`	Spalart-Almaras variable	Non-dimensional
`primitiveVars`	Density, velocities (u,v,w), and pressure	Non-dimensional
`qcriterion`	Q criterion for vortex identification	Non-dimensional
`residualNavierStokes`	Navier-Stokes residual	Non-dimensional
`residualTransition`	Transition residual	Non-dimensional
`residualTurbulence`	Turbulence residual	Non-dimensional
`s`	Entropy	Non-dimensional
`solutionNavierStokes`	Navier-Stokes solution	Non-dimensional
`solutionTransition`	Transition solution	Non-dimensional
`solutionTurbulence`	Turbulence solution	Non-dimensional
`T`	Temperature	Non-dimensional
`velocity`	Velocity vector	Non-dimensional
`velocity_magnitude`	Magnitude of velocity vector	Non-dimensional
`pressure`	Pressure	Non-dimensional
`vorticity`	Vorticity	Non-dimensional
`vorticityMagnitude`	Vorticity magnitude	Non-dimensional
`wallDistance`	Wall distance	Grid unit length
`numericalDissipationFactor`	Numerical dissipation factor sensor	Non-dimensional
`residualHeatSolver`	Heat equation residual	Non-dimensional
`VelocityRelative`	Velocity with respect to non-inertial frame	Non-dimensional
`lowMachPreconditionerSensor`	Low-Mach preconditioner factor	Non-dimensional

VelocityRelative#

This is the relative velocity with respect to the volume zone reference frame. In a rotational domain, the absolute velocity, \(\overrightarrow{\boldsymbol{U}}_\text{absolute}\), of each fluid element could be treated as the summation of a relative velocity, \(\overrightarrow{\boldsymbol{U}}_\text{relative}\), and a velocity due to the rotating frame, \(\overrightarrow{\Omega}\times \overrightarrow{r}\). The “VelocityRelative” means the \(\overrightarrow{\boldsymbol{U}}_\text{relative}\):

\[\overrightarrow{\boldsymbol{U}}_\text{absolute} = \overrightarrow{\boldsymbol{U}}_\text{relative} + \overrightarrow{\Omega}\times \overrightarrow{r}\]

It should be noted that the relative velocity is zero on no-slip walls that are part of the rotating frame (i.e., rotating walls) within rotational blocks. When a wall function is used, this velocity is near zero.

Volume and Slice Specific Fields#

These fields are available only for Volume Output and Slice Output types.

Field Name	Description	Units
`betMetrics`	BET Metrics	Non-dimensional
`betMetricsPerDisk`	BET Metrics per Disk	Non-dimensional
`linearResidualNavierStokes`	Linear residual of Navier-Stokes solver	Non-dimensional
`linearResidualTurbulence`	Linear residual of turbulence solver	Non-dimensional
`linearResidualTransition`	Linear residual of transition solver	Non-dimensional
`SpalartAllmaras_hybridModel`	Hybrid RANS-LES output for Spalart-Allmaras solver (supports both DDES and ZDES)	Non-dimensional
`kOmegaSST_hybridModel`	Hybrid RANS-LES output for kOmegaSST solver (supports both DDES and ZDES)	Non-dimensional
`localCFL`	Local CFL number	Non-dimensional

BET Metrics Output Variables#

The betMetrics and betMetricsPerDisk output fields provide Blade Element Theory (BET) metrics for analyzing rotor and propeller performance. These fields are available when using BET models in volume zones. The betMetrics field includes data from all BET disks with possible overlapping, while betMetricsPerDisk provides separate outputs for each disk to avoid overlap.

The following variables are included in the betMetrics output:

VelocityRelative – Relative velocity with respect to the rotating reference frame (non-dimensional).
AlphaRadians – Local angle of attack in radians.
CfAxial – Axial aerodynamic force coefficient.
CfCircumferential – Circumferential aerodynamic force coefficient.
TipLossFactor – Factor to model the effect of blade tip.
LocalSolidityIntegralWeight – Local solidity multiplied by the integral weight.

Hybrid RANS-LES Output Variables#

The SpalartAllmaras_hybridModel and kOmegaSST_hybridModel output fields provide diagnostic variables for hybrid RANS-LES simulations. The specific variables included depend on whether you’re using DDES (Delayed Detached Eddy Simulation) or ZDES (Zonal Detached Eddy Simulation) as the shielding function.

DDES Variables (when `shielding_function="DDES"`)#

When using DDES, the hybrid model output includes five key variables:

f_d – The shielding function that delineates the RANS and LES regions. When f_d = 0, the RANS model is fully applied; when f_d = 1, the LES model is used. Intermediate values represent a smooth transition between the two regimes.
r_d – A modified ratio of the modeled length scale to the wall distance, from which f_d is derived.
DDES_lengthRANS – The wall distance from the computational cell to the nearest solid boundary.
DDES_lengthScale – The characteristic DES length scale: \(\tilde{d} \equiv d - f_d \max(0, d - C_{DES}*\Delta)\)
DDES_lengthLES – The characteristic LES length scale: \(C_{DES}*\Delta\)

Among these variables, f_d is the most significant, as it enables users to identify and visualize the regions dominated by RANS and DES behavior within the computational domain.

ZDES Variables (when `shielding_function="ZDES"`)#

When using ZDES, the hybrid model output includes four key variables:

ZDES_fp – The enhanced shielding function that determines whether RANS or LES is used. When ZDES_fp = 0, RANS is active; when ZDES_fp = 1, LES is active. This function is computed from ZDES_fd, ZDES_fR, and ZDES_fp2.
ZDES_fd – Original DDES shielding function used in computing ZDES_fp.
ZDES_fR – Component used in computing ZDES_fp. This is included to disable or inhibit the second shielding function in regions where vorticity magnitude is increasing away from walls - this is designed to disable the secondary shielding function where a shear layer is detected above a wall.
ZDES_fp2 – Causes the model to revert to RANS mode in the outer portion of boundary layers, used in computing ZDES_fp.

Surface Specific Fields#

These fields are available only for Surface Output and Surface Probe Output types.

Field Name	Description	Units
`CfVec`	Skin friction coefficient vector	Non-dimensional
`Cf`	Magnitude of skin friction coefficient	Non-dimensional
`heatFlux`	Non-dimensional heat flux	Non-dimensional
`nodeNormals`	Wall normals	Non-dimensional
`nodeForcesPerUnitArea`	Forces per unit area	Non-dimensional
`yPlus`	Non-dimensional wall distance	Non-dimensional
`wallFunctionMetric`	Wall function metrics	Non-dimensional
`heatTransferCoefficientStaticTemperature`	Surface heat transfer coefficient (static temperature as reference)	Non-dimensional
`heatTransferCoefficientTotalTemperature`	Surface heat transfer coefficient (total temperature as reference)	Non-dimensional
`wall_shear_stress_magnitude`	Wall shear stress magnitude	Non-dimensional
`wall_shear_stress_magnitude_pa`	Wall shear stress magnitude	Pascals (Pa) - Available since version 25.2

Isosurface Specific Fields#

These fields are available only for Isosurface Output types.

Visualization Tips#

Isosurface outputs support all universal fields listed above. The most commonly used fields for isosurface visualization are:

qcriterion - For vortex identification
Mach - For shock wave visualization
pressure - For pressure-based isosurfaces
Cpt - For total pressure loss visualization

Custom Variables#

User-defined expressions with dimensions. These can be created using the Variable Settings tool or Python API.

By default, the following expressions are available:

Variable Name	Expression	Description
`velocity_with_units`	`solution.velocity`	Velocity in physical units
`velocity_magnitude_with_units`	`math.magnitude(solution.velocity)`	Velocity magnitude in physical units
`pressure_with_units`	`solution.pressure`	Pressure in physical units
`wall_shear_stress_magnitude_with_units`	`solution.wall_shear_stress_magnitude`	Wall shear stress magnitude in physical units

Note: You can create additional custom variables using the Variable Settings tool or through the Python API. Custom variables can access multiple solver variables and undergo mathematical operations.