# 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, , of each fluid element could be treated as the summation of a relative velocity, , and a velocity due to the rotating frame, . The "VelocityRelative" means the :

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:

  1. VelocityRelative – Relative velocity with respect to the rotating reference frame (non-dimensional).

  2. AlphaRadians – Local angle of attack in radians.

  3. CfAxial – Axial aerodynamic force coefficient.

  4. CfCircumferential – Circumferential aerodynamic force coefficient.

  5. TipLossFactor – Factor to model the effect of blade tip.

  6. 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:

  1. 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.

  2. r_d – A modified ratio of the modeled length scale to the wall distance, from which f_d is derived.

  3. DDES_lengthRANS – The wall distance from the computational cell to the nearest solid boundary.

  4. DDES_lengthScale – The characteristic DES length scale:

  5. DDES_lengthLES – The characteristic LES length scale:

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:

  1. 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.

  2. ZDES_fd – Original DDES shielding function used in computing ZDES_fp.

  3. 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.

  4. 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.

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