Postprocessing

Overview

When using m-AIA with a Cartesian solver, you have the possibility to use Postprocessing.

The postprocessing is activated by setting:

postProcessing = true

Multiple postprocessing instances can be created to do Post-Processing for a multi-solver simulation. The number of postprocessing instances is specifies by the property

noPostProcessing

The assignment of a postprocessing instance with the corresponding physics solver is done by the property

postProcessingSolverIds

The postprocessing type specifying the type of physics solver and the postprocessing operations of a postprocessing instance is specified by the property

postProcessingType

Possible Post-Processing types are

"POSTPROCESSING_FV"
"POSTPROCESSING_LS"
"POSTPROCESSING_LB"  
"POSTPROCESSING_DG"
"POSTPROCESSING_FVLPT"  
"POSTPROCESSING_LBLPT"

The Post-Processing operations are specified by

postProcessingOps

The list of Post-Processing operations is given below.

Average
Moving Average
Point Probing
Line Probing
Arbitrary Line Probing
Slice Probing
Abritrary Slice Probing
Reduce Level
Spatial Average

Every Postprocessing functionality can be labeled in three different ways
PRE PreSolve: Call of postprocessing operations before simulation is started (performs postprocessing on restartFiles that are loaded)
IN InSolve: Call of postprocessing operations during simulation
POST PostSolve: Call of postprocessing operations after simulation (i.e. probing on averaged variables)

Here the number of the postprocessing instance is specified by appending _<postprocessinginstanceId>.

Depending on whether an additional postdata solver is called, the Post-Processing practice can be classified into two general types:

1. Post-Processing with an additional Postdata solver
2. Post-Processing without the Postdata solver for special IO

Post-Processing with an additional Postdata solver

The first type of Post-Processing calculates additional flow properties (i.e. temporal average, moving average...), which are stored in a separate output file. For that a seperate solver has to be created in the grid file, see Mesh Generation. This allows the Postdata solver to be a subset of the global grid, such that postprocessing operations can be performed on a subset of the global grid (i.e. calculation of average in a specific region). Ideally, the postdata solver should be the solver with the highest solverId.

Additionally, the following properties have to be specified to configure the Postdata solver:

solvertype.<postdatasolverId> = "MAIA_POST_DATA"
noVariables.<postdatasolverId> = 5   # for example 

The variable postdatasolverId is set to the solver-ID of the Postdata solver in the grid file.

Make sure, that multiSolverGrid = true.

Post-Processing for special IO

The second type allows the output of reduced solver data (i.e. line probing, slice probing...). For that, a separate Postdata solver is not required, unless the probing is performed on averaged variables (PostSolve).

Working Example

The following example shows how to set up the Post-Processing instance for a coupled FV-LB simulation (FV-Solver solverId = 0, LB-Solver solverId = 1, Postdata solverId = 2).

postProcessing          = true
noPostProcessing        = 2
postProcessingSolverIds = [0,1]
postProcessingType_0    = ["POSTPROCESSING_FV"]
postProcessingOps_0     = ["PP_AVERAGE_IN", "PP_PROBE_LINE_IN"]
postProcessingType_1    = ["POSTPROCESSING_LB"]
postProcessingOps_1     = ["PP_AVERAGE_IN"]
 
solvertype.2            = "MAIA_POST_DATA"
# number of variables (5 primitive variables + 7 additional variables for pp_square calculation)
noVariables.2           = 12 
 
# Properties for PP_AVERAGE_IN
pp_square               = true
pp_averageStartTimestep = 1
pp_averageStopTimestep  = 10
pp_averageInterval      = 1
pp_averageRestart       = false
 
# Properties for PP_PROBE_LINE_IN
pp_probeLineDirection   = [0, 2]
pp_probeLineCoordinates = [-0.1, -0.1, 0.0, 0.0]

postprocessingOp

MString* PostProcessing::m_postprocessingOps
default = empty

This property is a list of postprocessing operations to be performed

• PP_AVERAGE_PRE
• PP_AVERAGE_IN
• PP_AVERAGE_POST
• PP_COMPUTE_DIVERGENCEVELOCITY_PRE
• PP_COMPUTE_DIVERGENCEVELOCITY_IN
• PP_COMPUTE_DIVERGENCEVELOCITY_POST
• PP_MOVING_AVERAGE_PRE
• PP_MOVING_AVERAGE_IN
• PP_MOVING_AVERAGE_POST
• PP_PROBE_POINT_PRE
• PP_PROBE_POINT_IN
• PP_PROBE_POINT_POST
• PP_PROBE_LINE_PRE
• PP_PROBE_LINE_IN
• PP_PROBE_LINE_POST
• PP_PROBE_LINE_PERIODIC_IN
• PP_PROBE_LINE_PERIODIC_POST
• PP_PROBE_ARB_LINE_PRE
• PP_PROBE_ARB_LINE_IN
• PP_PROBE_ARB_LINE_POST
• PP_PROBE_SLICE_PRE
• PP_PROBE_SLICE_POST
• PP_PROBE_SLICE_IN
• PP_PROBE_ARB_SLICE_PRE
• PP_PROBE_ARB_SLICE_IN
• PP_PROBE_ARB_SLICE_POST
• PP_AVERAGE_SLICE_PRE
• PP_REDUCE_TO_LEVEL_PRE
• PP_REDUCE_TO_LEVEL_POST
• PP_REDUCE_TO_LEVEL_AVERAGES_PRE
• PP_SPATIAL_AVERAGE_PRE
• PP_SPATIAL_AVERAGE_POST
• PP_SPATIAL_AVERAGE_IN
• PP_AVERAGE_REYNOLDS_STRESSES_AND_AVERAGES_IN

Keywords: GENERAL, GLOBAL, POSTPROCESSING