Control Volume

Control Volume statistics record time-evolving quantities extracted from user-defined control volumes. The results are written to tab-separated ASCII .txt files inside an output directory named ./ControlVolume_{DynamicName}, where the dynamic name corresponds to the control volume feature in the model tree. Within this output directory, two files are generated: FieldData.txt and ParticleData.txt. These files store the selected field and particle-based statistics introduced below. These files are appended with new data at the Statistics Output Write Interval.

Jump to: FieldData.txt | ParticleData.txt

FieldData.txt

This file contains statistics computed from voxel-based field variables within the control volume. These statistics are based on the combined selections of the Planes/Probes Output Control and Volume Output Control, as well as other variables used internally by the solver. In addition, the file will include fluid volume and fluid fluxes through control-volume faces.

The reported quantities fall into several categories:

• Extrema and Statistical Metrics: Maximum, mean, and minimum values (Max/Mean/Min) describe the range and distribution of quantities within the control volume.

• Kinematic Metrics: Velocity and vorticity (including component-wise values) describe the motion and rotation of the fluid within the region.

• Turbulence and Dissipation Metrics: Energy dissipation rate, turbulent kinetic energy, and sub-grid turbulent viscosity characterize turbulence behavior.

• Stress and Deformation Metrics: Strain rate and resolved shear stress quantify deformation and internal stresses in 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 and particle volume fractions, particle-set kLa, and total fluid volume describe phase distribution and interphase transport within the region.

• Scalar and Custom Variable Metrics: Scalar fields and user-defined variables provide additional transported or user-defined quantities.

• Flux Metrics: Face-resolved fluxes (e.g., ±X, ±Y, ±Z, or cylindrical faces) quantify volumetric flow entering and leaving the control volume.

• Age Metrics: Mean age and its extrema characterize residence time behavior within the control volume.

• Time-Averaged Metrics: Time-averaged quantities provide smoothed representations of system behavior for steady-state or statistically converged analysis.

Statistics Table

The index table below shows all possible statistics that may appear in the output file. Within this table, each statistic corresponds to a column in the output table that evolves with the time column. The units described are the engineering output units. The Output Condition specifies which model component must be present for this data column to be written.

Tip

You can preview the exact data that will be written for your system using Preview Output Files.

Note

While the output is primarily determined by the selections in Planes/Probes Output Control and Volume Output Control, additional quantities may be written if they are already computed internally by the solver.

Statistics	Units	Details	Output Condition
Time	s	simulation time
Age Max	s	fluid mean age	Mean Age
Age Mean	s	fluid mean age	Mean Age
Age Min	s	fluid mean age	Mean Age
Avg Turb KE Max	J/kg	time-averaged turbulent kinetic energy
Avg Turb KE Mean	J/kg	time-averaged turbulent kinetic energy
Avg Turb KE Min	J/kg	time-averaged turbulent kinetic energy
Custom Variable Max	[dynamic]	custom variable magnitude
Custom Variable Max	[dynamic]	custom variable magnitude
Custom Variable Mean	[dynamic]	custom variable magnitude
Custom Variable Mean	[dynamic]	custom variable magnitude
Custom Variable Min	[dynamic]	custom variable magnitude
Custom Variable Min	[dynamic]	custom variable magnitude
Custom Variable X Max	[dynamic]	custom variable value
Custom Variable X Mean	[dynamic]	custom variable value
Custom Variable X Min	[dynamic]	custom variable value
Custom Variable Y Max	[dynamic]	custom variable value
Custom Variable Y Mean	[dynamic]	custom variable value
Custom Variable Y Min	[dynamic]	custom variable value
Custom Variable Z Max	[dynamic]	custom variable value
Custom Variable Z Mean	[dynamic]	custom variable value
Custom Variable Z Min	[dynamic]	custom variable value
Density Max	kg/m^3	density after accounting for multiphase, particles, bubbles, and scalar fields
Density Mean	kg/m^3	density after accounting for multiphase, particles, bubbles, and scalar fields
Density Min	kg/m^3	density after accounting for multiphase, particles, bubbles, and scalar fields
Energy Dissipation Rate Max	W/kg	energy dissipation rate including both resolved and unresolved components
Energy Dissipation Rate Mean	W/kg	energy dissipation rate including both resolved and unresolved components
Energy Dissipation Rate Min	W/kg	energy dissipation rate including both resolved and unresolved components
Fluid Viscosity Max	m^2/s	fluid kinematic viscosity
Fluid Viscosity Mean	m^2/s	fluid kinematic viscosity
Fluid Viscosity Min	m^2/s	fluid kinematic viscosity
Fluid Volume	m^3	total fluid volume contained in control volume
Fluid Volume Fraction Max	vf	fluid volume fraction
Fluid Volume Fraction Mean	vf	fluid volume fraction
Fluid Volume Fraction Min	vf	fluid volume fraction
Flux +X	m^3/s	fluid flux through +X face of box, positive flux indicates flowing out of control volume
Flux +Y	m^3/s	fluid flux through +Y face of box, positive flux indicates flowing out of control volume
Flux +Z	m^3/s	fluid flux through +Z face of box, positive flux indicates flowing out of control volume
Flux -X	m^3/s	fluid flux through -X face of box, positive flux indicates flowing out of control volume
Flux -Y	m^3/s	fluid flux through -Y face of box, positive flux indicates flowing out of control volume
Flux -Z	m^3/s	fluid flux through -Z face of box, positive flux indicates flowing out of control volume
Flux Bottom	m^3/s	fluid flux through bottom face of cylinder, positive flux indicates flowing out of control volume
Flux Side	m^3/s	fluid flux through side face of cylinder, positive flux indicates flowing out of control volume
Flux Top	m^3/s	fluid flux through top face of cylinder, positive flux indicates flowing out of control volume
Pressure Max	Pa	pressure
Pressure Mean	Pa	pressure
Pressure Min	Pa	pressure
Resolved Shear Stress Max	Pa	resolved shear stress magnitude
Resolved Shear Stress Mean	Pa	resolved shear stress magnitude
Resolved Shear Stress Min	Pa	resolved shear stress magnitude
Resolved Strain Rate Max	1/s	strain rate magnitude not including unresolved strain
Resolved Strain Rate Mean	1/s	strain rate magnitude not including unresolved strain
Resolved Strain Rate Min	1/s	strain rate magnitude not including unresolved strain
Scalar Field Max	[dynamic]	scalar field value
Scalar Field Mean	[dynamic]	scalar field value
Scalar Field Min	[dynamic]	scalar field value
Sub-Grid Turbulent Viscosity Max	m^2/s	sub-grid turbulent viscosity from LES model
Sub-Grid Turbulent Viscosity Mean	m^2/s	sub-grid turbulent viscosity from LES model
Sub-Grid Turbulent Viscosity Min	m^2/s	sub-grid turbulent viscosity from LES model
Temperature Max	K	fluid temperature
Temperature Mean	K	fluid temperature
Temperature Min	K	fluid temperature
Time-Avg Energy Dissipation Rate Max	W/kg	time-averaged energy dissipation rate including both resolved and unresolved components
Time-Avg Energy Dissipation Rate Mean	W/kg	time-averaged energy dissipation rate including both resolved and unresolved components
Time-Avg Energy Dissipation Rate Min	W/kg	time-averaged energy dissipation rate including both resolved and unresolved components
Time-Avg Pressure Max	Pa	time-averaged pressure
Time-Avg Pressure Mean	Pa	time-averaged pressure
Time-Avg Pressure Min	Pa	time-averaged pressure
Time-Avg Resovled Shear Stress Max	Pa	time-averaged resolved shear stress magnitude
Time-Avg Resovled Shear Stress Mean	Pa	time-averaged resolved shear stress magnitude
Time-Avg Resovled Shear Stress Min	Pa	time-averaged resolved shear stress magnitude
Time-Avg Strain Rate Max	1/s	time-averaged strain rate magnitude
Time-Avg Strain Rate Mean	1/s	time-averaged strain rate magnitude
Time-Avg Strain Rate Min	1/s	time-averaged strain rate magnitude
Time-Avg Velocity Magnitude Max	m/s	time-averaged fluid velocity magnitude
Time-Avg Velocity Magnitude Mean	m/s	time-averaged fluid velocity magnitude
Time-Avg Velocity Magnitude Min	m/s	time-averaged fluid velocity magnitude
Time-Avg Velocity Max	m/s	time-averaged fluid velocity magnitude
Time-Avg Velocity Mean	m/s	time-averaged fluid velocity magnitude
Time-Avg Velocity Min	m/s	time-averaged fluid velocity magnitude
Time-Avg Velocity X Max	m/s	time-averaged fluid velocity
Time-Avg Velocity X Mean	m/s	time-averaged fluid velocity
Time-Avg Velocity X Min	m/s	time-averaged fluid velocity
Time-Avg Velocity Y Max	m/s	time-averaged fluid velocity
Time-Avg Velocity Y Mean	m/s	time-averaged fluid velocity
Time-Avg Velocity Y Min	m/s	time-averaged fluid velocity
Time-Avg Velocity Z Max	m/s	time-averaged fluid velocity
Time-Avg Velocity Z Mean	m/s	time-averaged fluid velocity
Time-Avg Velocity Z Min	m/s	time-averaged fluid velocity
Velocity Magnitude Max	m/s	magnitude of fluid velocity
Velocity Magnitude Mean	m/s	magnitude of fluid velocity
Velocity Magnitude Min	m/s	magnitude of fluid velocity
Velocity Max	m/s	magnitude of fluid velocity
Velocity Mean	m/s	magnitude of fluid velocity
Velocity Min	m/s	magnitude of fluid velocity
Velocity X Max	m/s	fluid velocity
Velocity X Mean	m/s	fluid velocity
Velocity X Min	m/s	fluid velocity
Velocity Y Max	m/s	fluid velocity
Velocity Y Mean	m/s	fluid velocity
Velocity Y Min	m/s	fluid velocity
Velocity Z Max	m/s	fluid velocity
Velocity Z Mean	m/s	fluid velocity
Velocity Z Min	m/s	fluid velocity
Vorticity Magnitude Max	1/s	vorticity magnitude
Vorticity Magnitude Mean	1/s	vorticity magnitude
Vorticity Magnitude Min	1/s	vorticity magnitude
Vorticity Max	1/s	vorticity magnitude
Vorticity Mean	1/s	vorticity magnitude
Vorticity Min	1/s	vorticity magnitude
Vorticity X Max	1/s	vorticity
Vorticity X Mean	1/s	vorticity
Vorticity X Min	1/s	vorticity
Vorticity Y Max	1/s	vorticity
Vorticity Y Mean	1/s	vorticity
Vorticity Y Min	1/s	vorticity
Vorticity Z Max	1/s	vorticity
Vorticity Z Mean	1/s	vorticity
Vorticity Z Min	1/s	vorticity
Particle Set kLa Max	1/s	kLa for particle set
Particle Set kLa Mean	1/s	kLa for particle set
Particle Set kLa Min	1/s	kLa for particle set
Particle Set Volume Fraction Max	vf	volume fraction for particle set
Particle Set Volume Fraction Mean	vf	volume fraction for particle set
Particle Set Volume Fraction Min	vf	volume fraction for particle set

ParticleData.txt

This file contains statistics computed from particle-based quantities within the control volume. In addition to ensemble statistics for particle diameter, count, and velocity, the file reports the mean, minimum, and maximum particle residence times within the control volume. Each statistic listed below corresponds to a column in the time-evolving output table. Data is written separately for each particle set.

The reported quantities fall into several categories:

• Population Metrics: Particle count and parcel count describe the total number of particles and parcels within the control volume, including effects of number scaling.

• Size Metrics: Mean particle diameter characterizes the representative particle size within the control volume.

• Residence Time Metrics: Maximum and mean residence times describe how long particles remain within the control volume, providing insight into retention and transport behavior.

• Kinematic Metrics: Mean particle velocity (magnitude and components) describes the motion of particles within the region.

Statistics Table

The index table below shows all possible statistics that may appear in the output file. Within this table, each statistic corresponds to a column in the output table which evolves with the time column. The units described are the engineering output units. The Output Condition specifies which model component must be present for this data column to be written.

Tip

You can preview the exact data that will be written for your system using the Output Preview Panel. This preview shows everything that will be printed, including quantities selected through checkboxes, as well as internally computed variables.

Statistics	Units	Details	Output Condition
Time	s	simulation time
Count	Dimensionless	total number of particles including number scaling in control volume
Diameter Mean	m	particle diameter mean over particles not including number scale
Parcel Count	Dimensionless	total number of parcels in control volume
Residence Time Max	s	max particle residence time
Residence Time Mean	s	particle residence time mean over particles not including number scale
Velocity Mean	m/s	particle velocity magnitude mean over particles not including number scale
Velocity X Mean	m/s	particle velocity mean over particles not including number scale
Velocity Y Mean	m/s	particle velocity mean over particles not including number scale
Velocity Z Mean	m/s	particle velocity mean over particles not including number scale

Usage and Interpretation

The Control Volume statistics provide a region-based, time-resolved reduction of simulation data by computing volume-averaged, extremal, and flux-based quantities over a user-defined control volume, \(V_{cv}\), and its enclosing surface, \(S_{cv}\). These outputs include both field-based variables (defined on the Eulerian mesh) and particle-based variables (defined on Lagrangian particles within the region), enabling a complete characterization of fluid, turbulence, and dispersed phase behavior within localized regions of interest. For any scalar field quantity \(ϕ(x,t)\), the control volume statistics are defined as

\[\phi_{\max}(t) = \max_{x \in V_{cv}} \phi(x,t)\]

with analogous definitions applied component-wise for vector quantities such as velocity. Time-averaged quantities are additionally reported and are defined as

\[\bar{\phi}(t) = \frac{1}{\Delta t} \int_{t - \Delta t}^{t} \phi(\tau)\, d\tau\]

In addition to volumetric statistics, surface fluxes quantify transport across the control volume boundary.

\[Q(t) = \int_{S_{cv}} \mathbf{u} \cdot \mathbf{n}\, dA\]

In practice, fluxes are reported per control volume face (e.g., \(+X,−X,+Y,−Y,+Z,−Z\), or cylindrical faces), with positive values indicating flow out of the control volume. These fluxes are used to quantify exchange between regions, evaluate feed and discharge behavior, and support residence time analysis. The fluid properties are computed using the same formulations as the Volume Output statistics

An additional diagnostic is the particle residence time, defined for each particle as the time spent within the control volume. The reported statistics include

\[\langle t_{\mathrm{res}} \rangle (t) = \frac{1}{N_{cv}} \sum_{i=1}^{N_{cv}} t_i\]

\[t_{\mathrm{res,max}}(t) = \max_i (t_i)\]

where residence time is reset when a particle exits the control volume. These metrics are used to identify recirculation zones, stagnation regions, and non-uniform particle transport.

Additional particle-derived quantities, such as particle-set volume fraction and particle-set \(k_La\), provide insight into dispersed phase behavior and interphase mass transfer. The \(k_La\) metric represents the volumetric mass transfer coefficient associated with the particle phase and is particularly relevant in gas–liquid or reactive systems. The properties are computed using the same formulations as the Bubbles/Particle Output statistics.

Taken together, the Control Volume are used to analyze localized flow behavior. By combining volume-averaged quantities, spatial extremes, surface fluxes, turbulence and stress measures, scalar transport diagnostics, and particle-based statistics, users can quantify mixing performance, transport processes, and mechanical environments within specific regions of interest.