Static Bodies¶
The Static Bodies Output Panel specifies which surface-resolved and surface-derived quantities are calculated and exported on static geometry during a simulation. Static body outputs include both local surface variables defined on the geometry, and reduced statistical quantities derived from those variables.
Surface-resolved outputs retain spatially distributed information on the static body surface, including fluid stresses, heat flux, scalar flux, temperature, and wall-function diagnostics such as \(y+\). Integrated outputs include quantities such as total force, time-averaged force, wetted area, and surface-averaged transport metrics. Together, these datasets enable detailed analysis of hydrodynamic loading, heat transfer, and scalar transport at solid boundaries.
All static body visualization outputs are written to the existing binary VTK surface datasets and are synchronized with the Plane/Probe Write Interval as well as the Volume Write Interval. The names of these output file are SliceStaticBody_{StaticBody}.pvd and VolumeStaticBody_{StaticBody}.pvd, where {StaticBody} is the Dynamic Name of the Static Body. This output ensures frame-consistent visualization alongside fluid, particle, and scalar fields. Each Static Body family is written to its own output dataset. Data is written at each face of the static body output surface. The resolution of this spatially varying output data is directly correlated the static body mesh quality.
In parallel with spatial outputs, the static body output system generates time-dependent statistics written to the standard ASCII statistics files. These include integrated and time-averaged quantities such as total force, wetted area, mean surface temperature, and total scalar or heat flux. These statistics are written at the Statistics Write Interval and are intended for plotting, regression, and quantitative analysis of wall-level transport and loading behavior.
Output Panel¶
General¶
- ▢ Enable Output with Slices
When enabled, static body output is written together with the slice (Plane/Interface) datasets, allowing static body surface data to be visualized and analyzed alongside fluid and scalar fields within the same output frames. When disabled, static body data are written only with the volume outputs. This option is provided to reduce disk storage requirements.
Output Control¶
Local Properties¶
These quantities describe the local hydrodynamic state at the static body surface.
- ▢ Fluid Volume Fractions
This writes the local fluid phase volume fractions along static body surface. This output is useful for inspecting wetting, phase coverage, and multiphase contact behavior.
- ▢ Fluid Stresses
Pa | This exports the local stress tensor acting on the surface, including pressure, shear stress, and total stress. For an incompressible fluid, the stress tensor is defined as
\[\boldsymbol{\sigma} = -p\,\mathbf{I} + 2\mu\mathbf{S},\]where
\[S_{ij} = \frac{1}{2}\left(\frac{\partial v_i}{\partial x_j} + \frac{\partial v_j}{\partial x_i}\right)\]is the resolved strain-rate tensor, \(p\) is the pressure, and \(\mu\) is the effective dynamic viscosity.
The following quantities are directly available from the fluid stress evaluation at the static body surface:
Total Pressure
The static pressure is the isotropic normal force per unit area exerted by the fluid on the surface and contributes the normal component of the surface traction,
\[\mathbf{t}_p = -p\,\mathbf{n}.\]In addition to the static pressure, the solver also reports the total pressure, defined as
\[p_{\mathrm{tot}} = p + \frac{1}{2}\rho \left| \mathbf{u} \right|^{2},\]which includes both the static and dynamic contributions associated with the local fluid velocity at the wall.
Total Stress
The total surface stress is obtained by projecting the full stress tensor onto the surface normal,
\[t = \sigma \cdot n = -p\,n + 2\mu\, S \cdot n.\]This quantity includes both the normal (pressure) and tangential (viscous shear) contributions and represents the complete force per unit area exerted by the fluid on the surface.
Shear Stress
The shear stress is the tangential component of the viscous traction acting parallel to the surface. The viscous contribution to the surface traction is
\[t_{\mathrm{visc}} = 2\mu\, S \cdot n,\]and the wall shear stress vector is given by the tangential projection
\[\tau_w = t_{\mathrm{visc}} - \left( t_{\mathrm{visc}} \cdot n \right) n.\]This represents the shear force per unit area acting along the surface of the static body.
- ▢ Time-Averaged Fluid Stresses
Pa | This writes the fluid stresses associated with the time-averaged surface stress tensor, providing a smoothed representation of the loading on the static body. The time-averaged stress tensor \(\bar{\boldsymbol{\sigma}}\) is computed from the instantaneous stress tensor \({\boldsymbol{\sigma}}\) using the averaging scheme specified in Time Averaging within Simulation Parameters. The corresponding time-averaged surface traction is
\[\bar{\mathbf{t}} = \bar{\boldsymbol{\sigma}} \cdot \mathbf{n},\]which includes both averaged pressure and shear contributions.
- ▢ \(y+\)
dimensionless | This outputs the non-dimensional wall distance used in wall-function modeling, enabling verification of near-wall resolution and wall-function validity. This value is calculated using the Musker profile, as discussed in the Static Body Wall Function. This output option will only appear if at least one static body has a Boundary Type set to Wall Function.
If a thermal property is present, the following section will launch:
Thermal¶
These quantities describe heat transfer between the fluid and the static body surface, including local temperatures and heat fluxes at the fluid–solid interface. Outputs are available only when the Thermal Field is active and when appropriate thermal boundary conditions are defined.
- ▢ Fluid Temperature
K | This writes the instantaneous fluid temperature evaluated at the static body surface. This output is only available when the Thermal Field is present.
- ▢ Time-Averaged Fluid Temperature
K | This writes the time-averaged local fluid temperature along the static body surface. The averaging is performed using the scheme specified in Time Averaging within Simulation Parameters. This output is only available when the Thermal Field is active.
- ▢ Heat Flux
W/\(m^2\) | This exports the instantaneous heat flux across the static body surface. This output appears only when one or more static body-fluid thermal boundary conditions are specified as non-adiabatic.
- ▢ Time-Averaged Heat Flux
W/\(m^2\) | This writes the time-averaged local heat flux along the static body surface, suitable for steady-state or cycle-averaged analysis. The averaging is performed using the scheme specified in Time Averaging within Simulation Parameters. This output appears only when one or more static body-fluid thermal boundary conditions are specified as non-adiabatic.
If a Scalar Field is present, the following section will launch:
Scalar Fields¶
These quantities describe scalar transport between the fluid and the static body surface, reporting fluxes of species or other scalar quantities at the fluid–solid interface. Outputs are available for each defined scalar field and reflect transport into or out of the surface.
- ▢ Instantaneous Scalar Flux
Base Unit/( \(m^2\) -s) | This writes the instantaneous local scalar flux across the static body surface. The units correspond to the base units defined for the scalar field. This output appears only when one or more static body-fluid thermal boundary conditions is set to a flux boundary condition.
- ▢ Time-Averaged Scalar Flux
Base Unit/( \(m^2\) -s) | This writes the time-averaged local scalar flux across the static body surface, enabling evaluation of net scalar transfer to or from the surface. The averaging is performed using the scheme specified in Time Averaging within Simulation Parameters. This output appears only when one or more static body-fluid thermal boundary conditions is set to a flux boundary condition.
If a Static Body Variable is present, the following section will launch:
Static Body Variables¶
- ▢ {Static Body Variable}
This describes the current value of the local Static Body Variable. The selection name is the dynamic name given to the variable. This option only appears if a Static Body Variable is defined on one or more static bodies. The Static Body Variable will be calculated and printed along all surfaces of all Children Geometry associated with the family. The smoothness of the output is directly linked to the child geometry mesh resolution.