9.6 Output Scratch Variables

In FLASH4 a user can allocate space for a scratch or temporary variable with grid scope using one of the Config keywords SCRATCHVAR, SCRATCHCENTERVAR, SCRATCHFACEXVAR,SCRATCHFACEYVAR or SCRATCHFACEZVAR (see Sec:ConfigFileSyntax). To output these scratch variables, the user only needs to set the values of the runtime parameters plot_grid_var_1, plot_grid_var_2, etc., by setting them in the flash.par file. For example to output the magnitude of vorticity with a declaration in a Config file of SCRATCHVAR mvrt:  
plot_grid_var_1 = "mvrt"
Note that the post-processing routines like fidlr do not display these variables, although they are present in the output file. Future implementations may support this visualization.

Generic Flash Docs User 2019-10-18