Control the Variables that are Written to the FV-UNS Files

AcuTrans can be used to restrict the number of variables that are written into each FV-UNS file.

This feature provides you with a high level of control over the size of the FV-UNS files that are created. By default, AcuSolve will write all variables associated with the NODAL_OUTPUT command. However, you can add to this list by turning on additional command line options, or reduce the size of this list by specifying the desired variables individually. Consider, for example, a turbulent thermal flow simulation. The simplest AcuTrans command: acuTrans -out -to fieldview.

produces the following output:
...
acuTrans:            Nodal output vars = velocity,pressure,temperature,eddy_viscosity,surface_y_plus,surface_film_coefficient,wall_shear_stress
This list represents the nodal output variables that are written to disk as a result of the NODAL_OUTPUT command. However, there are also a number of additional variables that can be computed based on this list. For example, AcuTrans can compute the spatial derivatives of these variables and other quantities such as the CFL number. To trigger this behavior, the extended nodal output should be toggled on using the -extout command line option. When this is done, the list of variables grows. For example:
acuTrans -out -to fieldview -extout
produces the following output:
...
acuTrans:            Nodal output vars = velocity,pressure,temperature,eddy_viscosity,surface_y_plus,surface_film_coefficient,wall_shear_stress,grad_velocity,grad_pressure,grad_temperature,grad_eddy_viscosity,volume,strain_rate_invariant_2,velocity_magnitude,vorticity,cfl_number
When other output commands are present in the input file, such as DERIVED_QUANTITY_OUTPUT and NODAL_RESIDUAL_OUTPUT, these values are also added to the list of variables that are written to the FV-UNS file when the -extout option is active. For the case of a turbulent thermal simulation with DERIVED_QUANTITY_OUTPUT and NODAL_RESIDUAL_OUTPUT active, the list of extended output variables increases to the following:
acuTrans:            Nodal output vars = velocity,pressure,temperature,eddy_viscosity,surface_y_plus,surface_film_coefficient,wall_shear_stress,grad_velocity,grad_pressure,grad_temperature,grad_eddy_viscosity,volume,strain_rate_invariant_2,velocity_magnitude,vorticity,cfl_number,density,viscosity,material_viscosity,gravity,specific_heat,conductivity,heat_source,turbulence_y,turbulence_y_plus,residual_velocity,residual_pressure,residual_temperature,residual_eddy_viscosity
This list of variables is very large and becomes even larger when more types of output and additional physics are present. Accepting this list of variables can lead to extremely large FV-UNS files. In many cases, this is not desirable and you are only interested in a small subset of the variables that are shown in the list. AcuTrans provides the -outv command line option to control the number of variables that are converted. For example:
acuTrans -out -to fieldview -extout -outv velocity,pressure,residual_velocity,residual_pressure
produces the following output:
...
acuTrans:            Nodal output vars = velocity,pressure,residual_velocity,residual_pressure

This command sequence produces FV-UNS files that are greatly reduced in size and contain only the variables that you are interested in. This preserves disk space and increases both the conversion and file reading time. Note that if you request a variable that is not available in the output database, AcuTrans gives an error and exits. This behavior can be overridden by providing the -imv or -ignore_missing_variables command line option. In this case, the missing variables are simply skipped and the remaining variables are converted.