Output Configuration

Outputs control what data Flow360 writes during and after a simulation. You can export flow field data on volumes, surfaces, slices, isosurfaces, and at probe points—each with configurable fields and save frequency. Additionally, you can configure force and moment outputs, including total forces on specific models and custom force distributions along arbitrary directions. Results are saved in ParaView (.vtu/.vtp), Tecplot (.szplt), or CSV formats.

Important

Outputs must be configured before running the simulation. Data that was not requested in the output configuration cannot be retrieved after the simulation completes. You would need to re-run the case with the desired outputs enabled.

Available Outputs

The table below lists all available output types. It also contains links to the documentation of each type for both the GUI and the Python API interfaces. The File column shows the path to the file that contains the data produced by each output for custom post-processing. All of the files can be found in the assets menu in the WebUI. The API Access column shows the property on the Case object used to access each result programmatically (see Download Results for how to retrieve a case from cloud).

Available Output Types

Output Type	Data	Availability	File	API Access
Volume Output	Flow field data throughout the computational volume	GUI, API	volumes.tar.gz → volume	case.results.volumes
Time-averaging Volume Output	Time-averaged flow field data throughout the volume	GUI, API	volumes.tar.gz → volume_time_avg	case.results.volumes
Surface Output	Flow field data on geometry or volume mesh boundaries	GUI, API	surfaces.tar.gz → surface_<boundary_name>	case.results.surfaces
Time-averaging Surface Output	Time-averaged flow field data on surfaces	GUI, API	surfaces.tar.gz → surface_<boundary_name>_time_avg	case.results.surfaces
Slice Output	Flow field data on user-defined slice planes	GUI, API	slices.tar.gz → slice_<slice_name>	case.results.slices
Time-averaging Slice Output	Time-averaged flow field data on slice planes	GUI, API	slices.tar.gz → slice_<slice_name>_time_avg	case.results.slices
Probe Output	Flow field data monitoring during simulation	GUI, API	monitor_<output_name>_v2.csv	case.results.monitors
Time-averaging Probe Output	Time-averaged monitoring data	GUI, API	monitor_<output_name>_v2.csv	case.results.monitors
Surface Probe Output	Flow field data at specific points projected onto surfaces	GUI, API	monitor_<output_name>_v2.csv	case.results.monitors
Time-average Surface Probe Output	Time-averaged data at specific surface points	API	monitor_<output_name>_v2.csv	case.results.monitors
Surface Slice Output	Flow field data on slices of surfaces	API	surfaces.tar.gz → surface_slice_<slice_name>	case.results.surfaces
Isosurface Output	Flow field data on surfaces of constant variable value	GUI, API	isosurfaces.tar.gz → isosurface_<isosurface_name>	case.results.isosurfaces
Time-averaging Isosurface Output	Time-averaged flow field data on isosurfaces	GUI, API	isosurfaces.tar.gz → isosurface_<isosurface_name>_time_avg	case.results.isosurfaces
Surface Integral Output	Surface integral data	GUI, API	monitor_<output_name>_v2.csv	case.results.monitors
Aeroacoustic Output	Data for aeroacoustic analysis at observer positions	GUI, API	total_acoustics_v3.csv	case.results.aeroacoustics
Force Output	Force and moment coefficient outputs with optional statistics	GUI, API	force_output_<output_name>_v2.csv force_output_<output_name>_moving_statistic_v2.csv	case.results.custom_forces
Force Distribution Output	Custom force and moment distribution along a specified direction	GUI, API	<output_name>_forceDistribution.csv	case.results.force_distributions
Time-averaging Force Distribution Output	Time-averaged custom force and moment distribution	GUI, API	<output_name>_forceDistribution.csv	case.results.force_distributions
BET Disk Forces	Per-disk integrated forces and moments (automatic when a BET disk is present)	User guide, API	bet_forces_v2.csv	case.results.bet_forces
BET Disk Coefficients	Per-disk non-dimensional force, moment, lift and drag coefficients	User guide, API	bet_force_coefficients_v2.csv	case.results.bet_forces.compute_coefficients(params)
BET Forces Radial Distribution	Sectional thrust and torque coefficients along the blade radius, per blade	User guide, API	bet_forces_radial_distribution_v2.csv	case.results.bet_forces_radial_distribution
Streamline Output	Streamline visualization data	GUI, API	N/A	N/A
Time-averaging Streamline Output	Time-averaged streamline visualization data	GUI, API	N/A	N/A
Render Output	Automatically rendered animations for unsteady simulations	API	Rendered animation frames	N/A

Multiple Outputs for the Same Surface

The same surface can be assigned to more than one surface output. This is useful for unsteady and aeroacoustic simulations, where the same surface is often needed at more than one cadence or in more than one format. A typical pattern pairs a detailed output (which saves a full set of fields at a high frequency for flow-field and noise-source analysis, kept on the cloud and downloaded only when needed because of its size) with a lightweight output (which saves a compact set of fields less often for quick download and comparison in third-party tools such as ParaView or Tecplot).

When several surface outputs share a surface, each one must be given a unique name. The name is appended as a suffix to that output’s filenames, so the data from each output is written to separate files and never overwrites the others.

Note

The uniqueness requirement applies only between outputs of the same type. An instantaneous surface output and a time-averaged surface output may share a surface without unique names, because they already write to separate files. When several outputs of the same type are combined into a single file, their names must still resolve to distinct suffixes.

To configure this in each interface, see the Surface Output page of the WebUI guide and the output configuration section of the Python API reference.

Output Fields

Note

The fields listed below are the default output fields provided by Flow360. All values are non-dimensional unless otherwise noted. See Non-Dimensional Outputs for dimensionalization formulas.

Important

Custom and Dimensional Outputs: Use User Variables to define custom output expressions or to output existing fields in dimensional units (e.g., velocity_m_per_s, pressure_pa, wall_shear_stress_magnitude_pa). See Units & Expressions for details.

Universal Fields

Available for all output types (Volume, Surface, Slice, Isosurface, Probe):

Name	Description
Cp	Coefficient of pressure Eq.(5)
Cpt	Coefficient of total pressure Eq.(7)
gradW	Gradient of primitive solution
kOmega	k and omega when using the kOmegaSST model
Mach	Mach number
mut	Turbulent viscosity
mutRatio	Ratio between turbulent viscosity and freestream dynamic viscosity \(\mu_t/\mu_\infty\)
nuHat	Spalart-Allmaras variable, nuHat
primitiveVars	Primitive solution: rho, u, v, w, p (density, 3 velocities and pressure)
qcriterion	Q criterion
residualNavierStokes	5 components of the N-S residual
residualTransition	Residual for the transition model
residualTurbulence	Residual for the turbulence model
s	Entropy
solutionNavierStokes	Solution for the N-S equation in conservative form
solutionTransition	Solution for the transition model
solutionTurbulence	Solution for the turbulence model
T	Temperature
velocity	Velocity vector
velocity_magnitude	Velocity magnitude
pressure	Pressure
vorticity	Vorticity vector
vorticityMagnitude	Vorticity magnitude
wallDistance	Wall distance
numericalDissipationFactor	Sensor showing where the numericalDissipationFactor has been increased
residualHeatSolver	Residual for the heat equation solver
VelocityRelative	Velocity vector from which velocity of a non-inertial frame is subtracted. Equals 0 on any no-slip walls within rotational blocks.
lowMachPreconditionerSensor	Low-Mach preconditioner factor

Surface-Specific Fields

Available only for Surface Output and Surface Probe Output:

Name	Description
Cf	Skin friction coefficient magnitude
CfVec	Skin friction coefficient vector Eq.(3)
yPlus	Non-dimensional wall distance (y⁺)
nodeForcesPerUnitArea	Total force per unit area (pressure + friction)
nodeNormals	Wall normal direction
heatFlux	Heat flux
heatTransferCoefficientStaticTemperature	Heat transfer coefficient (static T reference)
heatTransferCoefficientTotalTemperature	Heat transfer coefficient (total T reference)
wallFunctionMetric	Wall model quality indicator (beta)
wall_shear_stress_magnitude	Wall shear stress magnitude

Volume and Slice-Specific Fields

Available only for Volume Output and Slice Output:

Name	Description
betMetrics	BET disk metrics for all BET disks. See BET Metrics Output Variables below for details.
betMetricsPerDisk	BET disk metrics per disk (no overlapping)
linearResidualNavierStokes	Linear residual of Navier-Stokes solver
linearResidualTurbulence	Linear residual of turbulence solver
linearResidualTransition	Linear residual of transition solver
SpalartAllmaras_hybridModel	Hybrid RANS-LES output for Spalart-Allmaras solver (supports both DDES and ZDES)
kOmegaSST_hybridModel	Hybrid RANS-LES output for kOmegaSST solver (supports both DDES and ZDES)
localCFL	Local CFL number

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.

Note

Detailed explanations of these variables, including their mathematical formulations, are available in the BET disk section of the Formulations documentation.

Hybrid RANS-LES Model Outputs

The SpalartAllmaras_hybridModel and kOmegaSST_hybridModel output fields provide diagnostic variables for hybrid RANS-LES simulations (DDES and ZDES). These fields are available for Volume Output and Slice Output only.

Important

Requirements:

• SpalartAllmaras_hybridModel can only be specified when using the Spalart-Allmaras turbulence model with hybrid RANS-LES enabled (DDES or ZDES).

• kOmegaSST_hybridModel can only be specified when using the kOmegaSST turbulence model with hybrid RANS-LES enabled (DDES or ZDES).

• Hybrid models require unsteady simulations—they are not available for steady-state cases.

The specific variables included in each hybrid model output depend on the shielding function used:

DDES Variables

When shielding_function="DDES", the hybrid model output includes five variables:

1. f_d: The shielding function that delineates RANS and LES regions. When f_d = 0, RANS is fully applied; when f_d = 1, LES is used. Intermediate values represent a smooth transition between 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: \(\tilde{d} \equiv d - f_d \max(0, d - C_{DES}*\Delta)\)

5. DDES_lengthLES: The characteristic LES length scale: \(C_{DES}*\Delta\)

Among these variables, f_d is the most significant for identifying and visualizing regions dominated by RANS vs. LES behavior.

ZDES Variables

When shielding_function="ZDES", the hybrid model output includes four 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 that disables or inhibits the secondary shielding function in regions where vorticity magnitude increases away from walls (designed to disable the secondary shielding where a shear layer is detected above a wall). Used in computing ZDES_fp.

4. ZDES_fp2: Causes the model to revert to RANS mode in the outer portion of boundary layers. Used in computing ZDES_fp.

BET Coefficient Distributions

For any case that includes one or more BET disks, Flow360 automatically writes tabular (CSV) summaries of the blade-element loading alongside the field outputs. These tables let you analyze rotor and propeller performance directly. They are produced whenever a BET model is present, so no additional output configuration is required.

All coefficients in these tables are non-dimensional (see Non-Dimensional Outputs). Force coefficients are normalized by \(q_\infty \, S_{ref}\) and moment coefficients by \(q_\infty \, S_{ref} \, L_{ref}\), where \(q_\infty\) is the freestream dynamic pressure and \(S_{ref}\), \(L_{ref}\) are the reference area and reference length.

Per-disk force and moment coefficients

The file bet_force_coefficients_v2.csv contains the integrated force and moment coefficients of each BET disk at every recorded step. The first two columns are physical_step and pseudo_step; the remaining columns repeat for each disk i:

Column	Quantity
Disk<i>_CFx, Disk<i>_CFy, Disk<i>_CFz	Force coefficient components along the global x, y, z axes.
Disk<i>_CMx, Disk<i>_CMy, Disk<i>_CMz	Moment coefficient components about the global x, y, z axes, taken about the case moment center.
Disk<i>_CL	Lift coefficient (force projected onto the lift direction).
Disk<i>_CD	Drag coefficient (force projected onto the freestream/drag direction).

By default each disk is identified by its global index (Disk<i>). When the table is retrieved through the Python API the column headers can be renamed to use the BET model and cylinder names defined in the simulation (for example Disk0 becomes <BETName>_<CylinderName>).

Sectional (radial) distribution

The file bet_forces_radial_distribution_v2.csv contains the spanwise loading distribution. Each row corresponds to one radial station (loading node) along the blade, so the number of rows matches the number of loading nodes used to resolve the disk (the n_loading_nodes value from the BET disk setup). For each disk i the columns are:

Column	Quantity
Disk<i>_All_Radius	Radial position of the station.
Disk<i>_Blade<b>_All_ThrustCoeff	Sectional thrust coefficient at that radius for blade b.
Disk<i>_Blade<b>_All_TorqueCoeff	Sectional torque coefficient at that radius for blade b.

Because the thrust and torque coefficients are reported separately for each blade, the table resolves the radial (spanwise) variation of the loading and, for time-accurate BET Line simulations where the blades occupy distinct azimuthal positions, the per-blade (azimuthal) variation as well.

Accessing the tables

Both files are written to the case output and can be downloaded from the assets menu in the WebUI, together with the other result files. They can also be retrieved and processed programmatically through the case.results interface (case.results.bet_forces and case.results.bet_forces_radial_distribution). See Download Results and the Results API reference for the available models and methods.

See also

• Outputs API Reference — Python API classes for all output types

• Non-Dimensional Outputs — formulas to convert non-dimensional values to physical units

• Converting to Physical Units (N, N·m) — step-by-step conversion of force/moment coefficients and raw BET/AD/PM outputs to Newtons and Newton-meters

• User Variables — define custom expressions and dimensional outputs

• Units & Expressions — unit-aware variable system

• Results Processing — processing the results after the simulation

• BET Coefficient Distributions (tabular BET force, moment and sectional-loading exports)