### 3.2.11. CFX-Solver Output File (Particle Runs)

#### 3.2.11.1. Particle Transport Equations

This section lists the particle transport equations solved during the solver run for each independent domain.

     +--------------------------------------------------------------------+
     |      Particle Transport Equations Solved in This Calculation       |
     +--------------------------------------------------------------------+
    Domain Type : Default Domain
       x-Mom-Sand Fully Coupled
       y-Mom-Sand Fully Coupled
       z-Mom-Sand Fully Coupled
       x-Mom-Sand One Way Coupled
       y-Mom-Sand One Way Coupled
       z-Mom-Sand One Way Coupled

For additional information, see Solved Equations.

#### 3.2.11.2. Particle Fate Diagnostics

Within the particle transport model, each particle is tracked until one of the abort criteria is satisfied or the particle escapes the domain. Particles may also be aborted if a tracking error is found. Because each particle is tracked from its injection point until some abort criteria is met, it does not influence other particles. Thus, a tracking error for one particle does not necessarily stop the execution of the CFX-Solver run. However, if some fundamental problem is found during tracking, then the flow calculations terminates after printing an error message.

At the end of each particle integration step, a diagnostic summary is generated that indicates the fate of all injected particles as outlined below:

     +--------------------------------------------------------------------+
     |                      Particle Fate Diagnostics                     |
     +--------------------------------------------------------------------+
     | Particle type          | Fate type                       Particles |
     +--------------------------------------------------------------------+
     | Sand Fully Coupled     | Entered domain                :       200 |
     |                        | Left domain                   :       200 |
     +--------------------------------------------------------------------+

The following fate types may be encountered during particle tracking:

##### 3.2.11.2.1. Absorbed by Porous Media

This message indicates the number of particle that have been absorbed by the porous media and is determined by the Absorption Diameter setting. For details, see Particle Absorption in the CFX-Pre User's Guide.

##### 3.2.11.2.2. Continue from Last Time Step (Transient Only)

See Waiting for Next Time Step (Transient only).

##### 3.2.11.2.3. Collected on Walls

This message indicates that particles are trapped at the wall because both the parallel and perpendicular restitution coefficients are zero. As a result, the particle tracking is terminated and the remaining momentum of the particles is transferred to the wall as a force. For details, see Restitution Coefficients for Particles in the CFX-Solver Modeling Guide.

##### 3.2.11.2.4. Entered Domain

This message indicates the number of particles that were injected into the domain either at a boundary or particle injection region.

##### 3.2.11.2.5. Exceeded Distance Limit

This message indicates that these particles have exceeded the maximum tracking distance with respect to the particle traveling distance. If a large number of particles show this fate, you may need to increase the maximum tracking distance. For details, see Maximum Tracking Distance. Any remaining mass, momentum, and energy that must be exchanged with the fluid to equilibrate the aborted particle with the local fluid properties, is exchanged in the current control volume.

##### 3.2.11.2.6. Exceeded Integration Limit

This message indicates that these particles have exceeded the maximum number of integration steps with respect to the total number of particle integration steps. If a large number of particles show this fate, you may need to increase the maximum number of integration steps. For details, see Maximum Number of Integration Steps. Any remaining mass, momentum, and energy that must be exchanged with the fluid to equilibrate the aborted particle with the local fluid properties, is exchanged in the current control volume.

##### 3.2.11.2.7. Exceeded Time Limit

This message indicates that these particles have exceeded the maximum tracking time with respect to the particle traveling time. If a large number of particles show this fate, you may need to increase the maximum tracking time. For details, see Maximum Tracking Time. Any remaining mass, momentum, and energy that must be exchanged with the fluid to equilibrate the aborted particle with the local fluid properties, is exchanged in the current control volume.

##### 3.2.11.2.8. Fell Below Minimum Diameter

This message indicates that evaporating or reacting particles are not tracked below a diameter of 1.0E-8 [m] because they are too small to have any effect. The minimum diameter can be controlled by expert parameter `pt minimum diameter`, see Particle Tracking Parameters.

##### 3.2.11.2.9. Integration Error

This message indicates that the tracking of these particles was terminated due to an unexpected error in the particle tracking integration. If a small number of particles terminate in this way, it is not generally a cause for concern. Any remaining mass, momentum, and energy of the particle is neglected.

##### 3.2.11.2.10. Left Domain

This message indicates the number of particles that have escaped from the domain and are no longer tracked. Any remaining particle mass, momentum and energy also escapes the domain with particles. This is the normal abort criterion for particles traveling through inlets, openings, and outlets.

##### 3.2.11.2.11. Sliding along Walls

This message indicates that particles have stopped as they were hitting the wall below the minimum specified impact angle. For details, see Fluid Values for Walls in the CFX-Pre User's Guide.

##### 3.2.11.2.12. Waiting for Next Time Step (Transient only)

All particles that are alive at the end of a fluid time step get the fate `Waiting for Next Time Step`. When the next fluid time step is performed, then these particles are continued to be tracked and their fate is changed to `Continue from Last Time Step`. So across two time steps, both numbers should be the same.

#### 3.2.11.3. Transient Particle Diagnostics

The transient particle diagnostics enable you to monitor various quantities, like total mass of particles in the domain, penetration of particles from a given PIR (Particle Injection Region), or user-defined location. For details, see Transient Particle Diagnostics in the CFX-Solver Modeling Guide. A typical diagnostics output that is recorded in the CFX-Solver Output file is shown below:

     +--------------------------------------------------------------------+
     |                   Transient Particle Diagnostics                   |
     +--------------------------------------------------------------------+

     Water Droplets

      Total Particle Mass
         Total Particle Mass                       2.0000E-02
      Penetration from PIR
         Axial Penetration                         1.7655E-01
         Radial Penetration                        1.8561E-01
         Normal Penetration                        6.6197E-02
         Spray Angle                               1.9856E+01
      Penetration from Location
         Axial Penetration                         1.7655E-01
         Radial Penetration                        1.8561E-01
         Normal Penetration                        6.6197E-02
         Spray Angle                               4.1836E+01

#### 3.2.11.4. Particle Convergence History

Coupled particles are solved several times during the simulation and each particle tracking step leads to updated sources for the transport equations of the coupled continuous phase. A convergence criterion for the particle solver is the relative change of the generated sources of two successive particle tracking steps. Therefore, a table containing summary of all coupled particle equations, separately listed for each particle type, is generated at the end of each particle tracking step. This table contains the information on integrated sources as well as the source change rate as outlined below.

     +--------------------------------------------------------------------+
     |   Particle Equation    |  Total source and source change rates     |
     +--------------------------------------------------------------------+
     |                        | Equation            Source      Rate      |
     +--------------------------------------------------------------------+
     | Domain: PipeValve                                                  |
     +--------------------------------------------------------------------+
     | Sand Fully Coupled     | x-Mom               4.016E-02   0.0085    |
     |                        | y-Mom               7.765E-02   0.0062    |
     |                        | z-Mom               1.261E-01   0.0035    |
     +--------------------------------------------------------------------+

The `Source` column refers to the new particle source to the equation, which is calculated as the sum over all vertices of the absolute particle source values to that equation. For details, see Particle Source Change Target and Particle Under-Relaxation Factors in the CFX-Solver Modeling Guide.

The `Rate` column shows the fractional change in the source between the current and the previous injection. The source change rate can also be graphically monitored in the CFX-Solver Manager.

For additional information, see Convergence Control for Particle Transport in the CFX-Solver Modeling Guide.

#### 3.2.11.5. Integrated Particle Flows

At the end of a run, the integrated particle mass, momentum and energy flows over all boundaries and at all particle injection regions are printed to the CFX-Solver Output file. If the expert parameter MONITOR TOTALS is set to `T`, the same information is printed at the end of each particle tracking step. In a transient run, the time integrated total particle flows are also listed at the end of a run.

#### 3.2.11.6. CPU Requirements of Numerical Solution

At the end of the run, a summary of the CPU time spent inside of the particle tracking routine is given as outlined in the table below. This information may be used to determine the time spent per particle.

    +--------------------------------------------------------------------+
    |               CPU Requirements of Numerical Solution               |
    +--------------------------------------------------------------------+

     Subsystem Name                  Discretization       Linear Solution
                                    (secs.   %total)     (secs.   %total)
     ----------------------------------------------------------------------
     Momentum and Mass              1.00E+02  48.2 %     1.79E+01   8.6 %
     TurbKE and Diss.K              3.46E+01  16.6 %     2.17E+01  10.4 %
                                    -------- -------     --------  ------
     Subsystem Summary              1.35E+02  64.9 %     3.96E+01  19.1 %

     Particle Tracking              2.18E+01   10.5 %
     Variable Updates               5.91E+00    2.8 %
     File Reading                   6.25E-02    0.0 %
     Miscellaneous                  5.72E+00    2.7 %
                                    --------
     Total                          2.08E+02

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