Output Line¶

The Output Line statistics provide spatially resolved, time-dependent data sampled along a user-defined output line within the simulation domain. These outputs capture the variation of flow properties along the line at discrete points, enabling detailed analysis of spatial gradients, profiles, and transport behavior. A directory is created for each Output Line with the name ./outputLine_{DynamicName}, where the dynamic name corresponds to the name of the Output Line in the model tree. Within this directory, a separate file is written for each statistics output time, using the format time_{PrintTime}.txt where PrintTime is the physical simulation time. Each file contains the full set of sampled data along the output line at that specific time. Output files are generated at the Statistics Output Write Interval.

Within each file, data is organized such that each row corresponds to a sampling point along the line, and each column corresponds to a statistic listed in the table below.

The position of each sampling point is defined by both the Linear Position and the Absolution Position. The linear position is the distance along the output line (from the line origin). The absolute position is the position relative to the world origin. All reported quantities (velocity, pressure, scalar fields, turbulence metrics, etc.) are evaluated at these discrete locations along the line.

The reported quantities fall into several categories:

Spatial Position Metrics: Linear position and absolute position (X, Y, Z) define the location of each sampling point along the output line.
Kinematic Metrics: Velocity and vorticity (including component-wise values) describe the motion and rotation of the fluid along the line.
Turbulence and Dissipation Metrics: Energy dissipation rate, turbulent kinetic energy, and sub-grid turbulent viscosity characterize turbulence behavior along the line.
Stress and Deformation Metrics: Strain rate and resolved shear stress quantify local deformation and stress within the fluid.
Thermodynamic and Material Properties: Pressure, density, viscosity, and temperature describe the physical state of the fluid, including multiphase effects.
Multiphase and Particle Metrics: Fluid volume fraction, particle-set volume fraction, and particle-set kLa describe phase distribution and interphase transport along the line.
Scalar and Custom Variable Metrics: Scalar fields and user-defined variables provide additional transported or user-defined quantities.
Age Metrics: Mean age characterizes residence time behavior of the fluid along the line.
Time-Averaged Metrics: Time-averaged quantities provide smoothed representations of behavior for steady-state or statistically converged analysis.

Statistics Table¶

The index table below shows the statistics that will appear in the Output Line output file. Within this table, each statistic corresponds to a column in the output table that evolves with the position column.

Statistics	Units	Details	When Appears
Time	s	simulation time
Age	s	fluid mean age	Mean Age
Avg Turb KE	J/kg	time-averaged turbulent kinetic energy
Custom Variable	[dynamic]	custom variable magnitude
Custom Variable	[dynamic]	custom variable magnitude
Custom Variable X	[dynamic]	custom variable value
Custom Variable Y	[dynamic]	custom variable value
Custom Variable Z	[dynamic]	custom variable value
Density	kg/m^3	density after accounting for multiphase, particles, bubbles, and scalar fields
Energy Dissipation Rate	W/kg	energy dissipation rate including both resolved and unresolved components
Fluid Viscosity	m^2/s	fluid kinematic viscosity
Fluid Volume Fraction	vf	fluid volume fraction
Linear Position	m	linear position along output line
Particle Set kLa	1/s	kLa for particle set
Particle Set Volume Fraction	vf	volume fraction for particle set
Position X	m	position of point along output line
Position Y	m	position of point along output line
Position Z	m	position of point along output line
Pressure	Pa	pressure
Resolved Shear Stress	Pa	resolved shear stress magnitude
Resolved Strain Rate	1/s	strain rate magnitude not including unresolved strain
Scalar Field	[dynamic]	scalar field value
Sub-Grid Turbulent Viscosity	m^2/s	sub-grid turbulent viscosity from LES model
Temperature	K	fluid temperature
Time-Avg Energy Dissipation Rate	W/kg	time-averaged energy dissipation rate including both resolved and unresolved components
Time-Avg Pressure	Pa	time-averaged pressure
Time-Avg Resovled Shear Stress	Pa	time-averaged resolved shear stress magnitude
Time-Avg Strain Rate	1/s	time-averaged strain rate magnitude
Time-Avg Velocity	m/s	time-averaged fluid velocity magnitude
Time-Avg Velocity Magnitude	m/s	time-averaged fluid velocity magnitude
Time-Avg Velocity X	m/s	time-averaged fluid velocity
Time-Avg Velocity Y	m/s	time-averaged fluid velocity
Time-Avg Velocity Z	m/s	time-averaged fluid velocity
Velocity	m/s	magnitude of fluid velocity
Velocity Magnitude	m/s	magnitude of fluid velocity
Velocity X	m/s	fluid velocity
Velocity Y	m/s	fluid velocity
Velocity Z	m/s	fluid velocity
Vorticity	1/s	vorticity magnitude
Vorticity Magnitude	1/s	vorticity magnitude
Vorticity X	1/s	vorticity
Vorticity Y	1/s	vorticity
Vorticity Z	1/s	vorticity

Usage and Interpretation¶

The Output Line statistics provide a spatially resolved, time-dependent sampling of flow variables along a user-defined line, enabling analysis of gradients, profiles, and transport behavior within the simulation. At each statistics output time, a file is written that represents a snapshot of the CFD solution along the line, where each row corresponds to a discrete sampling location and each column corresponds to a physical quantity evaluated at that point. The position along the line is parameterized by the linear coordinate \(s\), defined as the distance from the line origin, with spatial location

\[\mathbf{x}(s) = \mathbf{x}_0 + s\, \hat{\mathbf{t}}\]

where \(x_0\) is the line origin and \(\hat{\mathbf{t}}\) is the unit tangent vector. All reported quantities (velocity, pressure, scalars, etc.) are evaluated as

\[\phi(s,t) = \phi(\mathbf{x}(s), t)\]

providing a one-dimensional slice through the full 3D solution. The fluid properties are computed using the same formulations as the Volume Output statistics. Properties associated with particles are computed using the same formulations as the Bubbles/Particle Output statistics.