Post-Processing Lagrangian Data

Direct Data on Boundaries

The following field functions are available on boundaries:

• Incident mass flux (particle flux for massless particle): computes the instantaneous mass flux (or particle flux) of one Lagrangian phase interacting with a boundary (hitting it or escaping through it).
• Erosion rate: computes the estimated loss of mass material per second due to particle impact. This field function is available only if erosion is activated in Lagrangian models. See Modeling Erosion.

See Lagrangian Multiphase Field Functions Reference.

Local Instantaneous Data

To analyze the particle field at an instant, the Lagrangian phase is available as a part for the scalar or geometry displayer. The data available on this field are Particle and Parcel field functions. The parcels are shown as small spheres, whose size and color can both be field function dependent.

As an example of how you can use local instantaneous data, consider the following steps for counting the number of particles in a particular set of regions:

1. Open the Regions node and select the regions for which you want the parcel counts.
2. In the properties for each region, note the value of the Index property, an integer n.
3. Right-click Derived Parts and select New Part > Threshold... to create a Threshold node under Derived Parts.
4. Select the new threshold node, set the following values:

   Property	Value
   Parts	Lagrangian Phases
   Scalar Field	Region Index
   Mode	Between In the special case of Index = 0, use Below Min.
   Range	Enter [a, b], a range that includes the indices of the regions for which you want the parcel count. For example, for parcel counts of regions 2, 3, and 4, enter [2, 4].

   The threshold now passes all and only the parcels with Region Index values in the specified range.

5. Right-click Reports and select New Report > Element Count to create an Element Count node under Reports.
6. In the Element Count node properties, edit the Parts property, open Derived Parts, and select the threshold node that was created earlier.
7. Right-click the Element Count node and select Run Report. The number of parcels in each region is displayed in the Output window.

The above steps are based on a set of regions with consecutive indices. Regions with non-consecutive indices require multiple reports.

Particle Track Data

The Lagrangian track file is an object which stores the field function values for Lagrangian particles as the calculation proceeds. It can be used as a post-processing part and data source. Post-processing is set up as follows:

1. Activate the Track File in the Lagrangian models selection box. Select the desired field function: the values available are particle and parcels relative field functions.
2. Run the calculation. The track data is stored in a temporary file that is named <simname>.trk.tmp, where <simname> is the simulation name.
3. Save the simulation. This action appends the temporary track file to the existing one, or creates a permanent track file with name <simname>.trk. (Check the output.)
4. Load the track file in the simulation by right-clicking on the node Tools > Track Files. This action generates a new object in the Particle Track node.
5. You can now use the particle track as a part in a Geometry, Scalar, or Streamline displayer. The data available from the field functions with names beginning with “Track.”

Boundary Sampling

The Boundary Sampling model, available in the Lagrangian selection box, allows the storage of field function values on a boundary during a calculation. This feature is similar to the Track Files feature but with these differences:

• Data is not stored in an external file, so you do not need to save the simulation, nor to load a track file to use the tracks from the Boundary Sampling.
• The stored data is for one Lagrangian step, so it is necessary to monitor the desired values during the calculation. However, unlike the track file, you can monitor the evolution of this data during the calculation, as with every Eulerian scalar or vector field.
• This data is only available at a local position, so if Boundary Sampling tracks are used in a Streamline displayer, it is not possible to see trajectories.

Use the following workflow:

1. Select the Boundary Sampling physics model.
2. In the Boundary Sampling node properties:
   1. Edit the Scalars property and select the field functions that you want to track on the parcels.
   2. Edit the Boundaries property and select the boundaries that you want to sample.
3. Create a sum report and give it an appropriate name. (See Sum.)
4. In the sum report properties:
   1. Edit the Scalar Field Function property and select the Track functions for the functions that are selected for the Boundary Sampling physics model.
   2. Edit the Parts property and select the Particle Tracks you want to sample.
5. Run the simulation, then right-click the report and select Run report.

See Modeling with Boundary Sampling.

Simulation History Phase Data

Use simulation history files to save scalar and vector data on selected Lagrangian phases.

By default, simulation history files record data from the following field functions when one of their inputs is a Lagrangian phase:

• Parcel Centroid
• Parcel Orientation
• Parcel Size

When the Export for reporting property is On and one of the inputs is a Lagrangian phase, simulation history files record data from the following field functions by default:

• Particle Count (for the Unsteady model)
• Particle Diameter
• Particle Flow Rate (for the Steady model)
• Particle Mass
• Particle Surface Area
• Particle Volume