Static Body¶

The Static Body statistics provide time-resolved, surface-integrated quantities describing the interaction between the fluid and stationary geometry. These outputs capture forces, torques, stresses, and geometric properties associated with each Static Body in the simulation, enabling detailed analysis of fluid-induced loading and surface behavior. A tab-separated ASCII .txt file is created for each Static Body in the model. The name of this file is StaticBody_{DynamicName}.txt, where the dynamic name corresponds to the name of the Static Body in the Model Tree. The output files are updated at the Statistics Output Write Interval.

The reported quantities fall into several categories:

Forces and Torques: Force and torque components quantify the total fluid-induced loading on the body, obtained by integrating surface stresses over all triangles in the static body family.
Surface Quantities: Pressure, shear stress, and related metrics represent spatial averages (or extrema) over the body surface, providing insight into how loading is distributed.
Geometric Properties: Area, wetted area, and non-wetted area describe the effective surface interacting with the fluid, including phase-dependent coverage in multiphase systems.
Wetting and Phase Interaction: Quantities such as wetted area by fluid and fluid-adjacent area describe how different phases interact with the surface and how much of the body is actively engaged with each phase.
Scalar Transport: Scalar field flux terms describe the transfer of scalar quantities between the static body and the surrounding fluid, including time-averaged fluxes.
Thermal Quantities: Heat flux and heat transfer rate terms describe energy exchange between the static body and the fluid, including both instantaneous and time-averaged contributions, as well as boundary condition–driven heat transfer.
Interior and Boundary Contributions: Terms such as conduction boundary condition heat flux and custom variable rates capture contributions from boundary conditions or surface reactions applied to the body.
Time-Averaged Quantities: Time-averaged forces, torques, pressures, temperatures, and fluxes provide smoothed representations of system behavior and are useful for steady-state analysis.
Wall Modeling Metrics: Quantities such as y+ provide information about near-wall resolution and boundary layer modeling quality.

Statistics Table¶

The index table below shows the statistics that can appear in the Static Body Output file. Within this table, each statistic corresponds to a column in the output table that evolves with the time column.

Statistics	Units	Details
Time	s	simulation time
[dynamic]	K
[dynamic]	K
[dynamic] Wetted Area	m^2	total surface area wetted by fluid 1
[dynamic] Wetted Area	m^2	total surface area wetted by fluid 2
Area Adjacent to Fluid	m^2	total surface area adjacent to active region where fluid is present or can possibly be present, does not consider current VOF state for free surface models
Conduction Boundary Condition Heat Flux	W	total heat transfer rate to static body from conduction boundary condition
Custom Static Body Variable Rate	[dynamic]	rate of change for custom static body variable in surface reaction
Custom Variable	[dynamic]	spatial mean of custom variable magnitude
Fluid Temperature	K	spatial mean of fluid temperature adjacent to static body surface
Fluid Wetted Area	m^2	total surface area wetted by fluid
Force X	N	total force on static body from fluid
Force Y	N	total force on static body from fluid
Force Z	N	total force on static body from fluid
Layer	K
Non Wetted Area	m^2	total surface area not wetted by fluid
Scalar Field Flux	[dynamic]	total scalar field flux from static body to fluid
Scalar Field Time-Avg Flux	[dynamic]	time-averaged total scalar field flux from static body to fluid
Shear Stress	Pa	spatial mean of shear stress from fluid
Thermal Field Heat Flux	W/m^2	total heat transfer flux from static body to fluid
Thermal Field Heat Transfer Rate	W	total heat transfer rate from static body to fluid
Thermal Field Time-Avg Heat Flux	W/m^2	time-averaged total heat transfer flux from static body to fluid
Thermal Field Time-Avg Heat Transfer Rate	W	time-averaged total heat transfer rate from static body to fluid
Time-Avg Fluid Temperature	K	time-averaged spatial mean of fluid temperature adjacent to static body surface
Time-Avg Force X	N	time-averaged total force on static body from fluid
Time-Avg Force Y	N	time-averaged total force on static body from fluid
Time-Avg Force Z	N	time-averaged total force on static body from fluid
Time-Avg Torque X	N-m	time-averaged total torque on static body from fluid
Time-Avg Torque Y	N-m	time-averaged total torque on static body from fluid
Time-Avg Torque Z	N-m	time-averaged total torque on static body from fluid
Time-Avg Total Pressure	Pa	time-averaged spatial mean of pressure from fluid, positive indicates pressure in direction of triangle normal
Torque X	N-m	total torque on static body from fluid
Torque Y	N-m	total torque on static body from fluid
Torque Z	N-m	total torque on static body from fluid
Total Area	m^2	total surface area
Total Pressure	Pa	spatial mean of pressure from fluid, positive indicates pressure in direction of triangle normal
y+	Dimensionless	spatial mean of y+ value

Usage and Interpretation¶

Forces and Torques

The force and torque quantities (e.g., Force X/Y/Z, Torque X/Y/Z) represent the total fluid-induced loading on the static body. These are computed by integrating fluid stresses over all surface triangles belonging to the static body family.

The total force is given by

\[\mathbf{F} = \sum_k \left( -p_k \mathbf{n}_k + \boldsymbol{\tau}_k \right) A_k.\]

Torque is computed about the static body mount point

\[\mathbf{T} = \sum_k \mathbf{r}_k \times \left[ \left( -p_k \mathbf{n}_k + \boldsymbol{\tau}_k \right) A_k \right],\]

where \(r_k=x_k−x_{mount}\). As with moving bodies, torque depends on the chosen reference point.

Surface Quantities

Surface quantities (e.g., Total Pressure, Shear Stress, Total Stress) represent spatial averages over the body surface and are computed as area-weighted averages,

\[\langle \phi \rangle = \frac{1}{A_{\text{tot}}} \sum_k \phi_k A_k.\]

These metrics describe how fluid loading is distributed across the surface and provide a direct connection between local stresses and integrated force and torque.

Geometric Properties

Geometric quantities (e.g., Total Area, Wetted Area, Non-Wetted Area) describe the effective surface interacting with the fluid,

\[A_{\text{total}} = \sum_k A_k.\]

The wetted area represents the portion of the surface in contact with the fluid and is computed as

\[A_{\text{wetted}} = \sum_k \phi_k A_k,\]

where \(\phi_k\) is the fluid volume fraction adjacent to the surface triangles.

These quantities are used to normalize forces and stresses and to interpret how much of the body is actively engaged with the flow.

Wetting and Phase Interaction

Wetting-related quantities (e.g., Wetted Area by Fluid, Fluid Wetted Area, Area Adjacent to Fluid) describe how different phases interact with the surface.

These metrics are particularly important in multiphase simulations, where the fraction of the surface in contact with each phase may vary over time. They provide insight into phase coverage, interfacial exposure, and which portions of the geometry are actively participating in transport processes.

Scalar Transport

Scalar transport quantities (e.g., Scalar Field Flux, Scalar Field Time-Avg Flux) describe the transfer of scalar quantities between the static body and the surrounding fluid.

The total scalar flux is computed as a surface integral

\[\dot{m}_{\phi} = \sum_k J_{\phi,k} \, A_k\]

where \(Jϕ,k\) is the local scalar flux at triangle \(k\).

These quantities are useful for tracking mass transfer across boundaries—including dissolution, deposition, or reactive fluxes.

Thermal Quantities

Thermal quantities (e.g., Thermal Field Heat Flux, Thermal Field Heat Transfer Rate, Conduction Boundary Condition Heat Flux) describe energy transfer between the static body and the fluid.

The total heat transfer rate is computed as

\[\dot{Q} = \sum_k q_k \, A_k\]

where \(qk\) is the local heat flux.

Heat flux quantities represent per-area transfer rates, while heat transfer rate quantities represent total integrated energy transfer. Time-averaged values provide a smoothed view of thermal behavior under steady or quasi-steady conditions.

Interior and Boundary Contributions

Interior and boundary-related quantities (e.g., Conduction Boundary Condition Heat Flux, Custom Variable Rate) represent contributions from boundary conditions or surface reactions applied to the static body.

These terms allow separation of externally imposed effects (e.g., fixed heat flux, reaction rates) from fluid-driven transport processes, and are important for closing energy and mass balances.

Time-Averaged Quantities

Time-averaged quantities (e.g., Time-Avg Force, Time-Avg Torque, Time-Avg Pressure, Time-Avg Heat Flux) represent running averages over time.

These are particularly useful for steady-state analysis, reducing noise from transient fluctuations and providing stable values for comparison, reporting, and design decisions.

Wall Modeling Metrics

Wall-related quantities (e.g., \(y+\)) provide information about near-wall resolution and turbulence modeling fidelity.

These metrics are used to assess whether the boundary layer is adequately resolved and whether wall-model assumptions are appropriate for the given simulation.

Important

All Static Body statistics are computed at the family level, including forces, torques, fluxes, and other derived quantities. Each reported value represents the total or average obtained by integrating over all surface triangles associated with the static body family.

If a family contains multiple child geometries, the reported quantities reflect the combined contribution of all child surfaces within that family. To obtain statistics for individual geometries, each must be assigned to its own moving body family.