Reference / Output variables

Output variables

Every variable zCFD can write, grouped by family. Name volume variables in volume variables and surface variables in surface variables, both under output settings › solution. Each row says whether the variable is written to volume output, surface output or both.

Written to

Flow

Primitive solution variables.

Name	What it is	Written to	Also accepted as
`pressure`	Static pressure (Pa)	volume and surface	`p`
`density`	Density (kg/m^3)	volume and surface	`rho`
`velocity`	Velocity vector (m/s)	volume and surface	`V`, `v`
`temperature`	Temperature (K)	volume and surface	`T`, `t`
`mach`	Mach number	volume and surface	`m`
`gauge_pressure`	Pressure relative to the reference value (Pa)	volume and surface
`V_avg`	Running average of the velocity vector (m/s)	volume and surface
`V_rms`	RMS of the velocity vector (m/s)	volume and surface
`p_avg`	Running average of the static pressure (Pa)	volume and surface
`p_rms`	RMS of the static pressure (Pa)	volume and surface
`T_avg`	Running average of the temperature (K)	volume and surface
`T_rms`	RMS of the temperature (K)	volume and surface

Derived

Quantities computed from the solution.

Name	What it is	Written to	Also accepted as
`potentialtemperature`	Potential temperature (K)	volume and surface
`cp`	Pressure coefficient	volume and surface
`totalcp`	Total pressure coefficient	volume and surface
`ek`	Kinetic energy contained in the cell, 0.5 rho \|V\|^2 times the cell volume (non-dimensional)	volume and surface
`enstrophy`	Enstrophy - squared magnitude of vorticity	volume and surface
`velocitynd`	Non-dimensional velocity	volume and surface
`vorticity`	Vorticity vector (1/s)	volume
`vorticitynd`	Non-dimensional vorticity	volume
`Qcriterion`	Q criterion - vortex core identification	volume
`Qcriterionnd`	Non-dimensional Q criterion	volume
`helicity`	Helicity	volume
`helicitynd`	Non-dimensional helicity	volume
`viscosity`	Dynamic viscosity (Pa.s)	volume and surface	`mu`
`nu`	Kinematic viscosity (m^2/s)	volume and surface

Gradients

Gradient vectors and tensors.

Name	What it is	Written to
`pressuregrad`	Pressure gradient vector	volume and surface
`densitygrad`	Density gradient vector	volume and surface
`velocitygrad`	Velocity gradient tensor	volume and surface
`temperaturegrad`	Temperature gradient vector	volume and surface
`turbulencekineticenergygrad`	Turbulence kinetic energy gradient	volume
`turbulenceeddyfrequencygrad`	Turbulence eddy frequency gradient	volume

Turbulence

Turbulence model quantities.

Name	What it is	Written to
`eddy`	Eddy viscosity (Pa.s)	volume and surface
`reynoldstress`	Reynolds stress tensor	volume
`ti`	Turbulence intensity	volume
`turbulencekineticenergy`	Turbulence kinetic energy (J/kg)	volume and surface
`turbulenceeddyfrequency`	Turbulence eddy frequency (1/s)	volume and surface
`nuTilde`	Spalart-Allmaras working variable	volume and surface
`menterf1`	Menter SST blending function	volume
`lesregion`	DES/DDES/IDDES region flag	volume and surface
`viscouslengthscale`	Minimum distance between a cell and its neighbours	volume
`turbulenceintermittency`	Transition model intermittency	volume
`transitionreynoldsnumber`	Transition momentum-thickness Reynolds number	volume

Wall

Wall and boundary-layer quantities.

Name	What it is	Written to
`walldist`	Distance to the nearest wall (m)	volume and surface
`walldistancezone`	Wall-distance zone id	volume and surface
`yplus`	Non-dimensional wall distance	surface
`ut`	Friction velocity at the wall	surface
`cf`	Skin friction coefficient	surface
`roughness`	Wall roughness height	surface
`heatflux`	Wall heat flux (W/m^2), positive into the fluid	surface
`twall`	Wall temperature (K)	surface
`velocitynearnd`	Non-dimensional velocity at the near-wall cell	volume and surface

Forces & moments

Per-face force and moment contributions.

Name	What it is	Written to
`pressureforce`	Pressure component of force on a face	surface
`pressuremoment`	Pressure component of moment on a face	surface
`pressuremoment<axis>`	Pressure moment about the `<axis>` axis Replace `<axis>` with x, y or z.	surface
`frictionforce`	Skin friction component of force on a face	surface
`frictionmoment`	Skin friction component of moment on a face	surface
`frictionmoment<axis>`	Skin friction moment about the `<axis>` axis Replace `<axis>` with x, y or z.	surface

Mesh & geometry

Cell and zone geometry.

Name	What it is	Written to
`zone`	Boundary/mesh zone identifier	volume and surface
`centre`	Cell or face centre location	volume and surface
`cell_centre`	Cell centre location	volume and surface
`cellvolume`	Cell volume	volume
`cell_volupdate`	Cell volume update rate (moving mesh)	volume
`cellcolour`	Partition/colouring index used by the mesh partitioner	volume
`cell_velocity`	Velocity of the mesh at each cell centre from mesh motion (m/s)	volume
`cellzone`	Cell zone number of each cell, as stored in the mesh file	volume
`GlobalCellId`	Global cell index, as named in the invalid-cell log lines	volume

Solver

Residuals, limiters and numerical diagnostics.

Name	What it is	Written to
`timestep`	Local timestep	volume and surface
`turbulencetimestep`	Local turbulence timestep	volume
`densitylimiter`	Density limiter value	volume and surface
`klimiter`	Turbulence kinetic energy limiter value	volume and surface
`omegalimiter`	Turbulence eddy frequency limiter value	volume and surface
`sagradientlimiter`	Spalart-Allmaras gradient limiter value	volume
`celllimiter`	Cell-based reconstruction limiter value for density (1 = unlimited); written by the 'barth jespersen', 'michalak gooch' and 'venkatakrishnan' limiters	volume
`celllimiterpressure`	Cell-based reconstruction limiter value for pressure (1 = unlimited); written by the 'barth jespersen', 'michalak gooch' and 'venkatakrishnan' limiters	volume
`roelowdissipation`	Roe low-dissipation blending factor	volume
`FailCell`	1 in a cell whose solution is invalid, 0 elsewhere	volume
`badcells`	Largest non-orthogonality among the cell's first-order faces under mesh quality remediation	volume
`sponge`	Sponge layer damping coefficient	volume
`MomentumSource`	Momentum source term (fluid zone sources)	volume
`timestepratio`	Local time step ratio	volume and surface
`artificial_viscosity`	Artificial viscosity applied	volume
`cellorder`	Spatial order used in each cell	volume
`lambdavariable`	Spectral radius of the flux Jacobian	volume
`lescfl`	CFL on the LES length scale used by the DES CFL shield: the larger of the grid relative transport CFL and the eddy turnover CFL	volume and surface
`lesturnover`	Eddy turnover contribution to lescfl on its own, so the binding mechanism is visible	volume and surface
`fdshield`	DES/DDES/IDDES shielding function f_d: 1 in resolved LES, 0 in the shielded RANS region	volume and surface
`var_<n>`	Solution value of solved equation `<n>` Replace `<n>` with the number of a solved equation, counting from 1. A case solves 5 equations with euler, viscous, les, incomp viscous or incomp les, 7 with rans or incomp rans, 6 with the `sa-neg` turbulence model and 9 with the `sst-transition` turbulence model.	volume and surface
`resvar_<n>`	Residual of solved equation `<n>` Replace `<n>` with the number of a solved equation, counting from 1. A case solves 5 equations with euler, viscous, les, incomp viscous or incomp les, 7 with rans or incomp rans, 6 with the `sa-neg` turbulence model and 9 with the `sst-transition` turbulence model.	volume and surface
`resshare_<n>`	Share of the total squared residual held by each cell, equation `<n>`. Sums to one over the mesh; threshold at 1/Neff (reported when output settings › report › residual statistics is on) to isolate the cells carrying the residual Replace `<n>` with the number of a solved equation, counting from 1. A case solves 5 equations with euler, viscous, les, incomp viscous or incomp les, 7 with rans or incomp rans, 6 with the `sa-neg` turbulence model and 9 with the `sst-transition` turbulence model.	volume and surface
`vargrad_<n>`	Gradient of solved equation `<n>` Replace `<n>` with the number of a solved equation, counting from 1. A case solves 5 equations with euler, viscous, les, incomp viscous or incomp les, 7 with rans or incomp rans, 6 with the `sa-neg` turbulence model and 9 with the `sst-transition` turbulence model.	volume and surface

Overset

Overset data.

Name	What it is	Written to	Also accepted as
`overset`	Overset blanking/donor status	volume and surface
`parent`	Parent cell/zone id (overset)	volume

Modal deformation and mesh motion.

Name	What it is	Written to
`modaldeformation`	Modal deformation of the surface	surface
`meshvelocity`	Mesh velocity from mesh motion (m/s)	volume and surface
`modeshapedisplacement_<n>`	Displacement of mode shape `<n>` Replace `<n>` with a number from 1 to 14.	surface
`modeshaperotation_<n>`	Rotation of mode shape `<n>` Replace `<n>` with a number from 1 to 10.	surface