When you have defined discrete phase particle injections, as described in Setting Initial Conditions for the Discrete Phase, you can display the trajectories of these discrete particles using the Particle Tracks Dialog Box (Figure 24.59: The Particle Tracks Dialog Box).

You can create named particle track definitions and save them for later use. See Creating and Using Contour Plot Definitions for additional information on graphics object definitions.

Note that particle track definitions can be included in scenes as long as the XY Plot option is not enabled. See Displaying a Scene for additional information on scenes.

 Results → Graphics → Particle Tracks  Edit...

You can also create a named particle track plot definition and save it for later use.

 Results → Graphics → Particle Tracks  New...

Figure 24.59: The Particle Tracks Dialog Box

The procedure for drawing trajectories for particle injections is as follows:

 

24.9.1.3. Controlling the Vector Style of Particle Tracks

You can choose to have the particle tracks displayed as vectors. Choose the Vector Style from the drop-down list in the Particle Tracks dialog box:

• If you select vector, the vector will be generated starting in the center of the particle, as shown in Figure 24.62: Particles with the Vector Style.

• If you select centered-vector, the midpoint of the vector will appear in the center of the particle, as shown in Figure 24.63: Particles with the Centered Vector Style.

• If you select centered-cylinder, the midpoint of the cylinder will appear in the center of the particle, as shown in Figure 24.64: Particles with the Centered Cylinder Style.

Figure 24.62: Particles with the Vector Style

Figure 24.63: Particles with the Centered Vector Style

Figure 24.64: Particles with the Centered Cylinder Style

Click the Attributes... button to specify how you would like to display the particle tracks. In the Particle Vector Style Attributes dialog box (Figure 24.65: The Particle Vector Style Attributes Dialog Box) you will set the Length, Scale, and Length to Head Ratio. The direction of the vectors is displayed for the selected variable under Vectors of. You have the option of specifying a Constant Length or a Variable Length, which is based on the variable selected under Length by. If Constant Color is enabled, then all vectors/cylinders are colored by the color selected in the Color drop-down list. Otherwise, it is the color selected in the Particle Tracks dialog box (seen in the Mesh Colors dialog box when Draw Mesh is enabled).

Vectors can be scaled by the factor given in the Scale entry box. The ratio of vector length to vector head size can be changed in the box Length to Head Ratio. In the case of a cylinder, the ratio of the length to the diameter is affected.

Figure 24.65: The Particle Vector Style Attributes Dialog Box

 

24.9.1.4. Importing Particle Data

For transient simulations, you can use the Import Particle Data dialog box (Figure 24.66: The Import Particle Data Dialog Box) to import particle data to display in the graphics window.

 Results → Model Specific → Discrete Phase → Import Particle Data...

Figure 24.66: The Import Particle Data Dialog Box

1. Click Read... to display a file selection dialog box where you can enter a file name and a directory that contains the imported data.

2. Choose from the available import options by selecting Auto Range and/or Draw Mesh under Options. If you prefer to restrict the range of the scalar field, disable the Auto Range option and set the Min and Max values manually beneath the Color by list.

3. Choose to color the particle pathlines by any of the scalar fields in the Color by list. If you select COLORBY, the pathlines will be colored by the quantity that was chosen when the particle data file was created. (See Exporting Steady-State Particle History Data)

4. Select a pathline style under Style. To set pathline style attributes, click the Attributes... button. For more information about the pathline style types, see Controlling the Pathline Style.

5. The value of Steps sets the maximum number of steps a particle can advance. A particle will stop when it has traveled this number of steps or when it leaves the domain.

6. If your pathline plot is difficult to understand because there are too many paths displayed, you can “thin out” the pathlines by changing the Skip value.

7. Click the Display button to draw the pathlines, or click the Pulse button to animate the particle positions. The Pulse button will become the Stop ! button during the animation, and you must click Stop ! to stop the pulsing.

 

24.9.1.5. Particle Filtering

You can specify how you would like to filter the particles being displayed, by first enabling the Filter option in the Options group of the Particle Tracks dialog box, then clicking the Filter by... button. In the Particle Filter Attributes dialog box, select the field variable by which you want to filter, then specify whether you would like to display all the particle tracks Inside or Outside the Filter-Min and Filter-Max range, as shown in Figure 24.67: The Particle Filter Attributes Dialog Box.

---

Note:  All particle variables as well as any field variable except for Custom Field Functions... can be used as a filter variable.

---

Figure 24.67: The Particle Filter Attributes Dialog Box

During two-way coupled DPM calculations or when you do graphical postprocessing of steady particle trajectories (as described in Displaying of Trajectories), Ansys Fluent prints tracking statistics in the console. For example:

 DPM Iteration ....
  number tracked = 7, escaped = 4, aborted = 0, trapped = 0, evaporated = 3
 Done.

The above numbers report events that the numerical parcels may have undergone. They should not be taken for any physically meaningful information since numerical parcels may represent different amounts (particle counts) of the particulate phase.

The description of particle statuses can be found in Trajectory Fates.

By default, only those events that have occurred at least once are reported. This can be changed using the define/models/dpm/numerics/tracking-statistics text command.

You can also track particles through the domain without displaying the trajectories by clicking the Track button at the bottom of the Particle Tracks dialog box. This allows the listing of reports without also displaying the tracks.

You can request additional detail about the trajectory fates as the particles exit the domain, including the mass flow rates through each boundary zone, mass flow rate of evaporated droplets, and composition of the particles.

A detailed report similar to the following example will appear in the console window. (You may also choose to write this report to a file by selecting File as the Report to option, clicking the Write... button (which was originally the Display button), and specifying a file name for the summary report file in The Select File Dialog Box.)

 number  tracked  =  10,  escaped  =  3,  aborted  =  0,  trapped  =  5,  evaporated  =  2,

 Fate          Zone Zone Number                  Elapsed Time (s)     Injection, Index Injection, Index
               Name   Id             Min       Max       Avg   Std Dev             Min              Max
 ---------- ------- ---- ----- --------- --------- --------- --------- ----------- --- ----------- ----
 Evaporated                  2 1.770e-03 1.114e-02 6.456e-03 4.686e-03 injection-0   2 injection-0   76
 Escaped    outflow    6     3 6.043e-01 7.037e-01 6.471e-01 4.172e-02 injection-1   4 injection-1   72
 Trapped       wall    7     5 8.486e-03 1.767e-01 5.030e-02 6.421e-02 injection-1   8 injection-1   75

                                  (*)- Mass Transfer Summary -(*) 

 Fate           Zone   Zone       Mass Flow (kg/s)
                Name     Id    Initial      Final     Change
 ----------- ------- ------ ---------- ---------- ----------
 Evaporated                  8.333e-02  0.000e+00 -8.333e-02
 Escaped     outflow      6  1.167e-01  5.144e-02 -6.523e-02
 Trapped        wall      7  2.000e-01  2.400e-02 -1.760e-01
 -----------                ---------- ---------- ----------
 Net                         4.000e-01  7.544e-02 -3.246e-01

                                  (*)- Energy Transfer Summary -(*) 

 Fate           Zone   Zone      Heat Rate (W)          Change of Heat (W)
                Name     Id    Initial      Final   Sensible     Latent      Total
 ----------- ------- ------ ---------- ---------- ---------- ---------- ----------
 Evaporated                 -3.180e+04  0.000e+00 -3.382e+02  3.214e+04      1.107
 Escaped     outflow      6  5.272e+05  6.519e+05 -3.487e+03  1.282e+05      1.523
 Trapped        wall      7  4.954e+05  6.993e+05 -1.173e+03  2.051e+05      1.737
 -----------                ---------- ---------- ---------- ---------- ----------
 Net                         9.908e+05  1.351e+06 -4.998e+03  3.654e+05      4.367

                                  (*)- Combusting Particles -(*) 

 Fate           Zone   Zone   Volatile Content (kg/s)        Char Content (kg/s)    
                Name     Id    Initial      Final   %Conv    Initial      Final   %Conv
 ----------- ------- ------ ---------- ---------- ------- ---------- ---------- -------
 Evaporated                  0.000e+00  0.000e+00    0.00  0.000e+00  0.000e+00     100
 Escaped     outflow      6  9.333e-03  9.333e-03    0.00  2.133e-02  2.133e-02       0
 Trapped        wall      7  9.333e-03  7.485e-01  100.00  2.133e-02  2.133e-02      98
 -----------                ---------- ---------- ------- ---------- ---------- -------
 Net                         1.867e-02  9.333e-03  50.00  4.267e-02  4.267e-02      198

                                  (*)- Multicomponent Droplet -(*) 

 Fate           Zone   Zone               Species      Species Content (kg/s)  
                Name     Id                 Names    Initial      Final   %Conv
 ----------- ------- ------ --------------------- ---------- ---------- -------
 Evaporated                      c5h12-droplet<l>  1.667e-02  0.000e+00  100.00
 Evaporated                      c7h16-droplet<l>  3.333e-02  0.000e+00  100.00
 Evaporated                                h2o<l>  0.000e+00  0.000e+00    0.00
 Escaped    outflow       6      c5h12-droplet<l>  1.667e-02  2.585e-04   98.45
 Escaped    outflow       6      c7h16-droplet<l>  0.000e+00  0.000e+00    0.00
 Escaped    outflow       6                h2o<l>  3.333e-02  1.134e-02   65.99
 Trapped       wall       7      c5h12-droplet<l>  3.333e-02  0.000e+00  100.00
 Trapped       wall       7      c7h16-droplet<l>  3.333e-02  0.000e+00  100.00
 Trapped       wall       7                h2o<l>  3.333e-02  0.000e+00  100.00

The report groups together particles with each possible fate, and reports the number of particles, the time elapsed during trajectories, and the mass and energy transfer This information can be very useful for obtaining information such as where particles are escaping from the domain, where particles are colliding with surfaces, and the extent of heat and mass transfer to/from the particles within the domain. Additional information is reported for combusting particles and multicomponent particles.

For cases with multiple injections, note the following:

Note that for cases with unsteady particle tracking, information about particle parcels still residing within the computational domain is only reported if you use the Display button (not the Track button). If you require this information but are not interested in the graphical display, you can use the Display button but set the Skip entry to a very large number and make sure Draw Mesh is cleared.

 

24.9.3.2. Elapsed Time

The number of particles with each fate is listed under the Number heading. (Particles that escape through different zones or are trapped at different zones are considered to have different fates, and are therefore listed separately.) The minimum, maximum, and average time elapsed during the trajectories of these particles, as well as the standard deviation about the average time, are listed in the Min, Max, Avg, and Std Dev columns. This information indicates how much time the particle(s) spent in the domain before they escaped, aborted, evaporated, or were trapped. Also, on the right side of the report, the injection name and index of the trajectories with the minimum and maximum elapsed times. (You may need to use the scroll bar to view this information.)

                           (*)- Mass Transfer Summary -(*)

 Fate              Zone   Zone       Mass Flow (kg/s)
                   Name     Id    Initial      Final     Change
 ----------- ---------- ------ ---------- ---------- ----------
 Incomplete                     1.388e-03  1.943e-04  1.194e-03
 Escaped        outflow      7  1.683e-01  7.124e-02 -9.709e-02

 

24.9.3.5. Heat Rate and Energy Reporting

For all particles with each fate, the total initial and final heat content are reported in the Initial and Final columns. The particle heat content is defined as follows:

Inert Particles:

(24–15)

where:
	= mass flow rate of particles (kg/s)
	= temperature of particles (K)
	= heat capacity of particles (J/kg/K)
	= reference temperature for enthalpy (K)

Droplet Particles:

(24–16)

where:
	= heat of pyrolysis (J/kg)
	= latent heat of evaporation at reference conditions (J/kg)

The latent heat at the reference conditions is defined in Equation 12–509 in the Theory Guide.

Combusting Particles:

(24–17)

is the heat content of the evaporating/boiling liquid material if Wet Combustion is selected (otherwise = 0).

(24–18)

where:
	is the mass fraction of the liquid in the combusting particle
	, , and are properties of the evaporating liquid material

is the heat content of the dry combusting particle and is calculated as

(24–19)

where:
	is the volatile fraction
	is the combustible fraction

---

Important:  The Heat Rate section of the report is not provided for the multiple surface reactions model.

---

Multicomponent Particles:

(24–20)

where:
	= mass fraction of component i in particle
	= heat content of component i

and

(24–21)

where:
	= heat of pyrolysis for component i (J/kg)
	= latent heat of evaporation at reference conditions for component i (J/kg)
	= specific heat of component i (J/kg/K)

 

24.9.3.5.1. Change of Heat and Change of Energy Reporting

This section reports the total heat transferred from the particle to the continuous phase and is analyzed in components of Sensible heat, Latent heat and heat of Reaction. The Total change reported equals the difference between the Initial and Final states of the particle streams. The sensible heat component is reported for all particle types, the latent heat for the droplet, combusting and multicomponent particle, while the heat of reaction is reported for the combusting particle type only. A positive Change of Heat denotes that heat is expelled from the continuous phase and absorbed by the particle, while a negative Change of Heat denotes heat is released by the particle to the continuous phase.

Steady and Transient Simulations

For steady simulations the report lists the heat rate , while for unsteady tracking the time integrated energy from time 0 to current flow time is reported.

(24–22)

Below is an example of an Energy Transfer Summary report for evaporating droplets:

                                     (*)- Energy Transfer Summary -(*) 

 Fate               Zone   Zone         Heat Rate (W)             Change of Heat (W)
                    Name     Id     Initial       Final    Sensible      Latent       Total
 ----------- ------------ ------ ---------- ----------- ----------- ----------- -----------
 Evaporated                      -4.530e+04   0.000e+00  -4.750e+02   4.577e+04   4.530e+04
 Escaped          utflow      6  -2.339e+05  -1.559e+05  -7.085e+03   8.505e+04   7.797e+04
 Trapped            wall      7  -2.176e+05   0.000e+00  -1.058e+03   2.187e+05   2.176e+05
 -----------                     ---------- ----------- ----------- ----------- -----------
 Net                             -4.353e+05  -4.670e+04  -4.085e+03   3.927e+05   3.886e+05

Below is an example of an Energy Transfer Summary report for combusting particles:

   (*)- Energy Transfer Summary -(*) 

 Fate           Zone   Zone      Heat Rate (W)          Change of Heat (W)
                Name     Id    Initial      Final   Sensible     Latent   Reaction      Total
 ----------- ------- ------ ---------- ---------- ---------- ---------- ---------- ----------
 Escaped        wall      5  1.697e+05  2.555e+04  3.166e+03  1.034e+00 -1.473e+05      -1.44
 Trapped     outflow      6  1.886e+04  1.938e+04  5.731e+02  1.149e-01 -5.370e+01       5.19
 -----------                ---------- ---------- ---------- ---------- ---------- ----------
 Net                         1.886e+05  4.493e+04  3.739e+03  1.149e+00 -1.474e+05      -1.43

---

Important:  In a coupled calculation, for all types of steady flows, the Total Net Change of Heat reported in the Energy Transfer Summary should balance with the opposite of the Sum over all fluid cells of the DPM Sensible Enthalpy Source. If this is not the case, this means that the coupled discrete-continuous phase calculation has not converged, and more DPM phase iterations are required. For more information on coupled calculations, see Performing Trajectory Calculations.

---

                               Sum
   DPM  Sensible  Enthalpy  Source                        (w)
  --------------------------------       --------------------
                           fluid-1                 -388937.41  

                  (*)-  Combusting  Particles  -(*)
 Fate          Zone   Zone   Volatile Content (kg/s)        Char Content (kg/s)    
               Name     Id    Initial      Final   %Conv    Initial      Final   %Conv
 ----------- ------ ------ ---------- ---------- ------- ---------- ---------- -------
 Incomplete                 6.247e-04  0.000e+00  100.00  5.691e-04  0.000e+00  100.00
 Escaped    outflow      7  6.758e-04  0.000e+00  100.00  6.158e-04  3.782e-05   93.86

(*)- Multiple Surface Reactions -(*) 

 Fate         Zone   Zone   Species      Species Content (kg/s)  
              Name     Id     Names    Initial      Final   %Conv
 --------- ------- ------ --------- ---------- ---------- -------
 Escaped   outflow      6      c<s>  6.080e-02  1.487e-06  100.00
 Escaped   outflow      6      s<s>  3.200e-03  5.077e-06   99.84
 Escaped   outflow      6       cao   0.000e+00  1.153e-03   0.00
 Escaped   outflow      6     caso4  9.266e-04  7.776e-03    0.00
 Escaped   outflow      6     caco3  8.000e-03  5.260e-03   34.25

                                              (*)- Multicomponent Droplet -(*) 

 Fate           Zone   Zone              Species   Species Content (kg/s)    
                Name     Id                Names    Initial      Final   %Conv
 ----------- ------- ------ -------------------- ---------- ---------- -------
 Evaporated                     c5h12-droplet<l>  1.667e-02  0.000e+00  100.00
 Evaporated                     c7h16-droplet<l>  3.333e-02  0.000e+00  100.00
 Evaporated                               h2o<l>  0.000e+00  0.000e+00    0.00
 Escaped     outflow       6    c5h12-droplet<l>  1.667e-02  2.585e-04   98.45
 Escaped     outflow       6    c7h16-droplet<l>  0.000e+00  0.000e+00    0.00
 Escaped     outflow       6              h2o<l>  3.333e-02  1.134e-02   65.99
 Trapped        wall       7    c5h12-droplet<l>  3.333e-02  0.000e+00  100.00
 Trapped        wall       7    c7h16-droplet<l>  3.333e-02  0.000e+00  100.00
 Trapped        wall       7              h2o<l>  3.333e-02  0.000e+00  100.00

report> enable-exch-details-in-dpm-summ-rep?
Details about exchange per zone to be given in DPM summary reports? [yes] no

At times, you may want to obtain a detailed, step-by-step report of the particle trajectory/trajectories. Such reports can be obtained in alphanumeric format. This capability allows you to monitor the particle position, velocity, temperature, or diameter as the trajectory proceeds.

The procedure for generating files containing step-by-step reports is listed below:

A detailed report similar to the following example will be saved to the specified file before the trajectories are plotted. (You may also choose to print the report in the console by choosing Console as the Report to option and clicking Display or Track, but the report is very long that it is unlikely to be of use to you in that form.)

 FILE  TYPE: 1  
 COLUMNS:  11  
 TITLE: TRACK  HISTORY

 COLUMN  TYPE  VARIABLE                          (UNITS)
 ------  ----  --------                          -------
      1     2  ParticleResidenceTime             (s)
      2    10  ParticleXPosition                 (m)
      3    10  ParticleYPosition                 (m)
      4    10  ParticleZPosition                 (m)
      5    10  ParticleXVelocity                 (m/s)
      6    10  ParticleYVelocity                 (m/s)
      7    10  ParticleZVelocity                 (m/s)
      8    10  ParticleDiameter                  (m)
      9    10  ParticleTemperature               (K)
     10    10  ParticleDensity                   (kg/m3)
     11    10  ParticleMass                      (kg)
---------------------------------------------
  
  0.00000e+00   5.00000e-02   5.00000e-02   5.00000e-02   2.00000e+01   0.0000  .  .  .
  1.07087e-07   5.00000e-02   5.00000e-02   5.00000e-02   1.23339e+01   2.6696  .  .  .
  2.51617e-07   5.00000e-02   5.00000e-02   5.00000e-02   1.04417e+01   3.3286  .  .  .
 .              .             .             .             .            .
 .              .             .             .             .            .
 .              .             .             .             .            .

The default step-by-step report lists the position, velocity, diameter, temperature, density and mass of the particle at selected time steps along the trajectory. In addition, the variable you have selected in the Color by list is also included. If you choose Console as the Report to option, the variable names are written as the header of each column. (You may need to use the scroll bar to view all variables in this column.)

Time       X-Position   Y-Position   Z-Position    X-Velocity   Y-Velocity    Z-Veloc  
0.000e+00  1.000e-03    3.120e-02    0.000e+00    1.000e+01     5.000e+00     0.000e  
1.672e-05  1.168e-03    3.128e-02    0.000e+00    1.010e+01     4.988e+00     0.000e  
3.342e-05  1.337e-03    3.137e-02    0.000e+00    1.019e+01     4.977e+00     0.000e  
5.010e-05  1.508e-03    3.145e-02    0.000e+00    1.028e+01     4.965e+00     0.000e  
6.675e-05  1.680e-03    3.153e-02    0.000e+00    1.038e+01     4.954e+00     0.000e  
8.338e-05  1.854e-03    3.161e-02    0.000e+00    1.047e+01     4.942e+00     0.000e
.          .            .            .            .             .             .
.          .            .            .            .             .             .
.          .            .            .            .             .             .

If you change the reporting variables, only those selected will appear in the report. The particle time is always reported in the first column. Note that it is possible to select one variable in the Reporting Variables dialog box and a variable from the Color by drop-down list in the Particle Tracks dialog box, however, each variable is reported only once.

When the report is written to a file, a table at the beginning of the file lists all variables selected with the corresponding unit. Thus you can display or export any variable along a particle trajectory to the console or to a file.

Note that the Coarsen option affects the step-by-step report.

In transient cases, when using unsteady tracking, you may want to obtain a report of the current positions and states of the particles. Selecting Current Positions under Report Type in the Particle Tracks Dialog Box enables the export of the current positions of the particles.

The procedure for generating files containing current position reports is listed below:

The default current position report lists the position, velocity, diameter, temperature, density, mass and number in parcel of the particle at selected time steps along the trajectory. In addition, the variable you have selected in the Color by list is also included. If you change the reporting variables, only those selected will appear in the report. The particle time is always reported in the first column. It is possible to select one variable in the Reporting Variables dialog box and a variable from the Color by drop-down list in the Particle Tracks dialog box, however, each variable is reported only once.

The output to a file or to the console has the same format as the step-by-step report for steady-state cases.

Time       X-Position  Y-Position  Z-Position   X-Velocity   Y-Velocity  Z-Velocity
0.000e+00  1.000e-03   3.120e-02   0.000e+00    1.000e+01    5.000e+00    0.000e+00
1.672e-05  1.168e-03   3.128e-02   0.000e+00    1.010e+01    4.988e+00    0.000e+00
3.342e-05  1.337e-03   3.137e-02   0.000e+00    1.019e+01    4.977e+00    0.000e+00
5.010e-05  1.508e-03   3.145e-02   0.000e+00    1.028e+01    4.965e+00    0.000e+00
6.675e-05  1.680e-03   3.153e-02   0.000e+00    1.038e+01    4.954e+00    0.000e+00
8.338e-05  1.854e-03   3.161e-02   0.000e+00    1.047e+01    4.942e+00    0.000e+00
.          .            .          .            .            .            .
.          .            .          .            .            .            .
.          .            .          .            .            .            .

Also listed are the diameter, temperature, density, mass of the particles, number in parcel and the variable selected from the Color by list. (You may need to use the scroll bar to view this information.)

Time       Diameter    Temperature   Density     Mass        Number      ColorBy
9.999e-04  9.352e-05   3.710e+02     6.840e+02   2.929e-10   2.792e+02   4.783e-02  
1.999e-03  7.952e-05   3.710e+02     6.840e+02   1.801e-10   2.792e+02   3.834e-02  
3.000e-03  6.660e-05   3.710e+02     6.840e+02   1.058e-10   2.792e+02   2.989e-02  
4.001e-03  5.425e-05   3.710e+02     6.840e+02   5.719e-11   2.792e+02   3.719e-02  
5.001e-03  4.184e-05   3.710e+02     6.840e+02   2.624e-11   2.792e+02   2.978e-02
.          .           .             .           .           .           .
.          .           .             .           .           .           .
.          .           .             .           .           .           .

If you selected Sample File Format, then the report file also includes the flow-time column. This column contains the current simulated time at which the report was written. When using the file to transfer a population of particle parcels into another simulation, you can use the Start Time and Start Flow-Time in File file injection point properties in the Set Injection Properties dialog box to control the particle injection time. For example, if you set Start Flow-Time in File to a value that is only minimally lower than the flow-time, then the particle parcels will be injected into the domain at the specified Start Time.

Ansys Fluent reports the magnitudes of the interphase exchange of momentum, heat, and mass in each control volume in your Ansys Fluent model. You can display these variables graphically, by drawing contours, profiles, and so on. They are all contained in the Discrete Phase Sources... category of the variable selection drop-down list that appears in postprocessing dialog boxes:

See Field Function Definitions for definitions of these variables.

Note that these exchange terms are updated and displayed only when coupled calculations are performed. Displaying and reporting particle trajectories (as described in Displaying of Trajectories and Particle Tracking Statistics) will not affect the values of these exchange terms.

The exchange terms are reported as the rate occurring in each cell. A unit cell depth is used for 2D cases, and a reference cell depth of 1 radian is used for 2D axisymmetric cases.

In Ansys Fluent, the discrete phase variables listed in the tables below can be used for:

The following variables are available for all DPM simulations.

Table 24.7: General Particle Variables

Name	Symbol Name in Journals	Units	Description
Particle Residence Time	particle-resid-time	time	Time since the moment of particle injection.
Particle ID	particle-id	-	Unique (global) particle ID.
Surface ID	surface-id	-	ID of the surface from which the particle was released; else -1.
Particle X Position	particle-x-position	length	Particle position in the global X-direction.
Particle Y Position	particle-y-position	length	Particle position in the global Y-direction.
Particle Z Position	particle-z-position	length	(3d only) Particle position in the global Z-direction.
Particle Radial Position	particle-radial-position	length	(3d only) Particle radial coordinate w.r.t. the cylindrical coordinate system defined for the reference thread.
Particle Theta Position	particle-theta-position	angle	(3d only) Particle theta coordinate w.r.t. the cylindrical coordinate system defined for the reference thread, angle counted starting from a plane containing the Y axis.
Particle X Velocity	particle-x-velocity	velocity	Particle velocity component in the global X-direction.
Particle Y Velocity	particle-y-velocity	velocity	Particle velocity component in the global Y-direction.
Particle Z Velocity	particle-z-velocity	velocity	(3d only) Particle velocity component in the global Z-direction.
Particle Radial Velocity	particle-radial-velocity	velocity	(3d only) Particle radial velocity component w.r.t. the cylindrical coordinate system defined for the reference thread.
Particle Swirl Velocity	particle-swirl-velocity	velocity	(3d only) Particle swirl velocity component w.r.t. the cylindrical coordinate system defined for the reference thread.
Particle Velocity Magnitude	particle-velocity-mag	velocity
Particle Diameter	particle-diameter	length	Particle diameter, .
Particle Density	particle-density	density	Particle mass density, . The density may be defined as a function of temperature. For multicomponent particles, it can be calculated as a volume-weighted value of the density of the droplet components.
Particle Specific Heat	particle-Cp	specific-heat	Particle-specific heat capacity defined in material settings for the current particle temperature (or at the reference temperature if physical property averaging is used).
Particle Binary Diffusivity	particle-binary-diffusivity	diffusivity	For droplet and multicomponent particles: Binary diffusivity of the vapor species at the particle temperature (or at the reference temperature if physical property averaging is used). For combusting particles: Binary diffusivity of the oxidant at the continuous-phase temperature.
Particle Mass	particle-mass	mass
Particle Temperature	particle-temperature	temperature	Particle temperature, (300 K if particle temperature is not solved).
Particle Law Index	particle-law-index	-	Current law index number: 1: Inert Heating 2: Droplet Vaporization 3: Droplet Boiling 4: Devolatilization 5: Surface Combustion 6: Inert Cooling 7: Multicomponent Particle Definition
Particle On Wall Flag	particle-on-wall	-	True (1) if the particle is a film particle.
Particle Reynolds Number	particle-reynolds-number	-
Particle Time Step	particle-time-step	time	Time step used by the numerical integration scheme.
Particle Number in Parcel	particle-number-in-parcel	mass per time / non-dimensional	Steady tracking: Mass of particles per time. Unsteady tracking: Number of particles in parcel (not available for steady tracking).
Tracking Scheme	tracking-scheme	-	0: (Euler) implicit 1: (Euler) trapezoidal 2: (Exponential) analytic 3: Runge-Kutta (explicit)
Number of Refinements	number-of-refinements	-	Number of times by which the integration time step size was reduced in the adaptive integration scheme.
Particle Penetration	particle-penetration	length	Distance traveled by the parcel from the injection reference position.
Parcel Mass	parcel-mass	mass	(Unsteady tracking only) Mass of Parcel = Mass of Particle x Number of Particles per Parcel.
Parcel Diameter	parcel-diameter	length	(Unsteady tracking only) Parcel diameter computed from parcel mass and parcel density.
Parcel Volume	parcel-volume	volume	(Unsteady tracking only) Volume of Parcel = Volume of Particle x Number of Particles per Parcel.
Particle Current Time	particle-current-time	time	(Unsteady tracking only) Particle time (identical to the current flow time).

The following variables are available if particle heat/mass transfer is enabled.

Table 24.8: Particle Variables with Heat and Mass Transfer

Name	Symbol Name in Journals	Units	Description
Latent Heat	latent-heat	specific-energy	Particle latent heat at the current particle temperature.
Vaporization Limiting Time	vaporization-limiting-time	time	Time scale for achieving fractional changes in both particle mass and temperature according to the Vaporization Limiting Factors specified in the Discrete Phase Model dialog box. This is available when Droplet or Multicomponent particles are not enabled in the Coupled Heat-Mass Solution group box in the Discrete Phase Model dialog box (Numerics tab).
Particle Lewis Number	particle-lewis-number	-	(Droplet particles only)
Particle Nusselt Number	particle-nusselt-number	-	Nusselt Number: Ranz-Marshall
Bt Heat Transfer Number	bt-heat-transfer-number	-	(Droplet particles only) Spalding heat transfer number (Equation 12–96 in the Fluent Theory Guide).
Bm Mass Transfer Number	bt-mass-transfer-number	-	(Droplet particles only) Spalding mass transfer number (Equation 12–86 in the Fluent Theory Guide).
Mass Fraction of species-n		-	(Combusting particles with multiple surface reactions only) Mass fraction of the solid species as defined in the Selected Solid Species list in the Species dialog box.
Particle Mass Fraction of species-n		-	(Multicomponent particles only) Mass fraction of the liquid component.
Particle Enthalpy		specific-energy	Particle enthalpy at the current particle temperature. For multicomponent particles, it is calculated as a mass-weighted value of the enthalpies of the droplet components.
Particle Liquid Mass Fraction	particle-liquid-mass-fraction	-	Wet combusting particles: Liquid mass fraction. Droplet particles: Volatile component fraction.
Particle Volatile Mass Fraction	particle-volatile-fraction	-	Combusting particles: Mass fraction of volatiles Droplet particles: Volatile component fraction.
Particle Char Mass Fraction	particle-char-fraction	-	(Combusting particles only) Mass fraction of the char component of the particle.

The following variables are available if the DEM model is enabled.

Table 24.9: Particle Variables with the DEM model

Name	Symbol Name in Journals	Units	Description
Total X Force	force-x-total	force	X component of the total force (body force and volume force) acting on the DEM particle during the DEM collision: Shows the value from last time step . Not stored in the .dat file.
Total Y Force	force-y-total	force	Y component of the total force (body force and volume force) acting on the DEM particle during the DEM collision: Shows the value from last time step . Not stored in the .dat file.
Total Z Force	force-z-total	force	Z component of the total force (body force and volume force) acting on the DEM particle during the DEM collision: Shows the value from last time step . Not stored in the .dat file.
Total Force Magnitude	force-total-mag	force
Collision X Force	force-x-coll	force	X component of the body force acting on the DEM particle during the DEM collision: Shows the value from last time step. Not stored in the .dat file.
Collision Y Force	force-y-coll	force	Y component of the body force acting on the DEM particle during the DEM collision: Shows the value from last time step. Not stored in the .dat file.
Collision Z Force	force-z-coll	force	Z component of the body force acting on the DEM particle during the DEM collision: Shows the value from last time step. Not stored in the .dat file.
Collision Force Magnitude	force-coll-mag	force
Total X Acceleration	acc-x-total	acceleration	X component of total acceleration due to the total force during the DEM collision: Shows the value from last time step. Not stored in the .dat file.
Total Y Acceleration	acc-y-total	acceleration	Y component of total acceleration due to total Force during DEM collision: Shows the value from last time step. Not stored in the .dat file.
Total Z Acceleration	acc-z-total	acceleration	Z component of total acceleration due to the total force during the DEM collision: Shows the value from last time step. Not stored in the .dat file.
Total Acceleration Magnitude	acc-total-mag	acceleration

The following variables are available if particle rotation is enabled.

Table 24.10: Particle Variables with Particle Rotation

Name	Symbol Name in Journals	Units	Description
Angular X Velocity	x-angular-velocity	angular velocity	Particle rotation rate about the X-axis.
Angular Y Velocity	y-angular-velocity	angular velocity	Particle rotation rate about the Y-axis.
Angular Z Velocity	z-angular-velocity	angular velocity	Particle rotation rate about the Z-axis.
Angular Velocity Magnitude	angular-velocity-mag	angular velocity

The following variables are available if user define particles are enabled.

The following variables are available if particle breakup is enabled.

Table 24.12: Particle Variables with Particle Breakup

Name	Symbol Name in Journals	Units	Description
Particle Breakup Type	particle-breakup-type	-	0: None 1: Levich 2: TAB 3: WAVE 4: KHRT 5: SSD 6: Madabhushi 7: Schmehl
Particle Weber Number Gas	particle-weber-number-gas	-	Liquid Weber number based on gas density
Particle Weber Number Liquid	particle-weber-number-liquid	-	Liquid Weber number based on particle density
SSD break up time	ssd-break-up-time	time	Equation 12–445 in the Fluent Theory Guide
Normalized TAB displacement	normalized-TAB-displacement	-	Equation 12–405 in the Fluent Theory Guide
Normalized TAB velocity	normalized-TAB-velocity	1/time	Equation 12–409 in the Fluent Theory Guide
WAVE break up time	WAVE-break-up-time	time	Equation 12–437 in the Fluent Theory Guide
WAVE mass in shed drops	WAVE-mass-in-shed-drops	mass	Mass of the shed-off droplet during the WAVE breakup process.
WAVE shed drops cutoff mass	WAVE-shed-drops-cutoff-mass	mass	Cut-off mass for the shed particles. During WAVE breakup, a new parcel will be created if the particle shed mass becomes larger than the cutoff mass.
Accumulated break up time	accumulated-break-up-time	time	Equation 12–442 in the Fluent Theory Guide
PILCH_ERDMAN deformation time	PILCH_ERDMAN-deformation-time	time	Equation 12–448 in the Fluent Theory Guide
PILCH_ERDMAN break up time	PILCH_ERDMAN-break-up-time	time	Equation 12–449 in the Fluent Theory Guide
PILCH_ERDMAN total break up time	PILCH_ERDMAN-total-break-up-time	time	Equation 12–455 in the Fluent Theory Guide
PILCH_ERDMAN initial weber number	PILCH_ERDMAN-initial-weber-number	-	Particle Weber number at the beginning of the Pilch-Erdman breakup process. It is used to compute the deformation and breakup time of the droplets.
PILCH_ERDMAN initial diameter	PILCH_ERDMAN-initial-diameter	length	Particle diameter at the beginning of the Pilch-Erdman breakup process.
MADABHUSHI column break up time	MADABHUSHI-column-break-up-time	time	Equation 12–447 in the Fluent Theory Guide

Ansys Fluent reports various discrete phase particle/parcel quantities including erosion/accretion rates, radiation quantities, and (optionally) cell-averaged particle size, velocity, temperature, and so on. You can display these variables graphically, by drawing contours, profiles, and so on. They are accessed in the Discrete Phase Variables... category of the variable selection drop-down list that appears in postprocessing dialog boxes.

Several quantities are automatically available depending on the models being used in the simulation. For the cell-averaged quantities to be available, you must first enable Mean Values under Contour Plots for DPM Variables in the Discrete Phase Model dialog box, Discrete Phase Model Dialog Box. RMS quantities are also available for particle velocity and temperature by enabling RMS Values.

The following lists specify those variables that are available automatically and those that require you to enable them

For the discrete phase variable , the event-based time average (mean) in a cell is calculated as:

(24–23)

where

= number of parcels in the cell

= number of particles in the th parcel

= residence time of the parcel

The RMS value of the discrete phase variable is calculated as:

(24–24)

See Field Function Definitions for definitions of these variables.

Note that these variables are updated and displayed only when coupled calculations are performed. Displaying and reporting particle trajectories (as described in Displaying of Trajectories and Particle Tracking Statistics) will not affect the values of these variables.

If you are performing a transient simulation, you can include the computation of unsteady time statistics (mean and RMS) for the discrete phase(s) of the transient flow. These are computed on a per-phase basis by event-based time averaging over the discrete phase parcels in the domain. This means that the sampling of the discrete phase particle quantity in a given cell occurs when (and only when) a parcel passes through the cell.

To calculate the unsteady DPM time statistics, enable Data Sampling for Time Statistics in the Run Calculation task page and enable DPM Variables in the Sampling Options dialog box when preparing to run your simulation (see Inputs for Time-Dependent Problems).

For a discrete phase variable, , the event-based time average (mean) in a cell is calculated from Equation 24–25.

(24–25)

where is the number of parcels in the cell, and

(24–26)

Here is the number of particles in the ^th parcel and is the residence time of the ^th parcel in the cell. The weighting by residence time is necessary because a parcel may pass through more than one cell within a computational time step and therefore its contribution to the averaged cell quantities depends on the fraction of the time step spent in each cell.

The time-averaged DPM volume fraction is calculated from the individual number of particles in the parcel, the particle volume, and its residence time in the cell in relation to the individual time step.

The RMS value is also available and is computed from Equation 24–27.

(24–27)

Note that these quantities are averaged over all parcels that have passed through the cell and are therefore different from the instantaneous cell-averaged values described in Reporting of Discrete Phase Variables.

Below is a list of the available unsteady statistics when DPM Variables is enabled in the Sampling Options dialog box. These are accessible by selecting the Unsteady DPM Statistics... category in postprocessing or reporting dialog boxes. Note that the availability of some quantities depends on the physics models being used. For definitions of these quantities, refer to the definitions of the instantaneous quantities from which they are derived (see Alphabetical Listing of Field Variables and Their Definitions).

Explanations for the Accum... variables are provided in Alphabetical Listing of Field Variables and Their Definitions.

Particle states (position, velocity, diameter, temperature, and mass flow rate) can be written to files at various boundaries and planes (lines in 2D) using the Sample Trajectories Dialog Box (Figure 24.69: The Sample Trajectories Dialog Box).

 Results → Reports → Discrete Phase → Sample Edit...

Figure 24.69: The Sample Trajectories Dialog Box

The procedure for generating files containing the particle samples is listed below:

For unsteady particle tracking, clicking the Start button will open the files and write the file header sections. If the solution is advanced in time by computing some time steps, the particle trajectories will be updated and the particle states will be written to the files as they cross the selected planes or boundaries. Clicking the Stop button will close the files and end the sampling.

For stochastic tracking, it may be useful to repeat this process multiple times and append the results to the same file, while monitoring the sample statistics at each update. To do this, enable the Append Files option before repeating the calculation (clicking Compute). Similarly, you can cause erosion and accretion rates to be accumulated for repeated trajectory calculations by turning on the Accumulate Erosion/Accretion Rates option. (See also Postprocessing of Erosion/Accretion Rates.)

The format and the information written for the sample output can also be controlled through a user-defined function, which can be selected in the Output drop-down list. See DEFINE_DPM_OUTPUT in the Fluent Customization Manual for more information.

The generated sample files can be used as injection file in a file injection. Both files use the same file formats which differ between steady and unsteady particle tracking. For details, see Point Properties for File Injections.

If the number of lines in the sampling file is large, you can reduce it by combining sets of similar line entries into one single entry per such set. The mass represented by that entry will be increased accordingly to ensure mass conservation. For details, see Data Reduction of Samples.

DPM sample files can be created using the Sample Trajectories Dialog Box (as described in Sampling of Trajectories) or by the VOF-to-DPM model transition mechanism. Such a file contains multiple records, each consisting of values for the same set of variables. You can postprocess probability distributions and simple correlation analyses of these variables using the Trajectory Sample Histograms Dialog Box (Figure 24.70: The Trajectory Sample Histograms Dialog Box).

 Results → Reports → Discrete Phase → Histogram Edit...

Figure 24.70: The Trajectory Sample Histograms Dialog Box

You can create contour plots of the spatial distribution of certain particle phase properties from DPM particle sampling on a specific planar surface (cut plane or planar domain boundary face zone). For example, you can create a contour plot of the droplet Sauter mean diameter on a plane orthogonal to the liquid spray direction. In this feature, the planar surface at which the DPM parcel samples are written to a file is divided into squares of a user-specified edge length. The DPM sampling events, which occur when particles cross the plane, are counted in each square. The weighted averages of different quantities are calculated based on the DPM particles sampled in that square. The results are then automatically interpolated into the CFD mesh and made available for graphical postprocessing as named expressions.

The procedural steps for using this feature are shown below.

For many mass-transfer and flow processes, it is desirable to know the mean diameter of the particles. A mean diameter, , is calculated from the particle size distribution using the following general expression  [83]:

(24–28)

where and are integers and is the distribution function (for example, Rosin-Rammler). , for example, is the average (arithmetic) particle diameter. The Sauter mean diameter (SMD), , is the diameter of a particle whose ratio of volume to surface area is equal to that of all particles in the computation. A summary of common mean diameters is given in Table 24.13: Common Mean Diameters and Their Fields of Application.

Table 24.13: Common Mean Diameters and Their Fields of Application

		Order	Name	Field of Application
1	0	1	Mean diameter,	Comparisons, evaporation
2	0	2	Mean surface diameter,	Absorption
3	0	3	Mean volume diameter,	Hydrology
2	1	3	Overall surface diameter,	Adsorption
3	1	4	Overall volume diameter,	Evaporation, molecular diffusion
3	2	5	Sauter mean diameter,	Combustion, mass transfer, and efficiency studies
4	3	7	De Brouckere diameter,	Combustion equilibrium

Summary information (number, mass, average diameter) for particles currently in the computational domain can be reported using the Particle Summary Dialog Box (Figure 24.73: The Particle Summary Dialog Box)

 Results → Reports → Discrete Phase → Summary Edit...

Figure 24.73: The Particle Summary Dialog Box

The procedure for reporting a summary for particle injections is as follows:

   (*)-  Summary  for  Injection:  injection-0  -(*)
  
  Total  number  of  parcels              :  1862  
  Total  number  of  particles            :  1.196710e+05  
  Total  mass                             :  1.128303e-05 (kg)
  Maximum  RMS  distance  from  injector  :  7.372527e-01 (m)
  Maximum  particle  diameter             :  3.072739e-04 (m)
  Minimum  particle  diameter             :  1.756993e-06 (m)
  Overall  RR  Spread  Parameter          :  1.446806e+00  
  Maximum  Error  in  RR  fit             :  1.071220e-01  
  Overall  RR  diameter             (D_RR):  9.051303e-05 (m)
  Overall  mean  diameter           (D_10):  4.663269e-05 (m)
  Overall  mean  surface  area      (D_20):  5.344694e-05 (m)
  Overall  mean  volume             (D_30):  6.121478e-05 (m)
  Overall  surface  diameter        (D_21):  6.125692e-05 (m)
  Overall  volume  diameter         (D_31):  7.013570e-05 (m)
  Overall  Sauter  diameter         (D_32):  8.030141e-05 (m)
  Overall  De  Brouckere  diameter  (D_43):  1.082971e-04 (m)

You can calculate the erosion and accretion rates in a cumulative manner (over a series of injections) by using the Sample Trajectories dialog box. First select an injection in the Release From Injections list and compute its trajectory. Then enable the Accumulate Erosion/Accretion Rates option, select the next injection (after deselecting the first one), and click Compute again. The rates will accumulate at the surfaces each time you click Compute.

Ansys Fluent provides functionality for assessing the solids deposition risk in the Selective Catalytic Reduction (SCR) process. The computation involves several chemical and hydrodynamic risk factors that are based on thermodynamic data and known chemical pathways, as well as on experimental evidence reported in the literature ([149], [156], [22], [133], and [176]). The risk assessment calculation should be invoked after the initial liquid film formation on the surfaces of the SCR device, and should cover a time period over one or more urea injection cycles. The risk variables are defined as dimensionless quantities that vary from 0 to 1, where 0 corresponds to no risk and 1 corresponds to maximum risk. Note that the risk assessment calculation is not a predictive model for urea deposit formation, and the obtained results should be considered only as rough guidance in exploring urea deposit formation trends.

The implementation takes into account the following chemistry risk factors:

In addition, the following hydrodynamic factors have been shown to affect solids deposit formation trends:

Accordingly, Ansys Fluent uses the following definitions to quantify the hydrodynamic risk factors:

Equation 24–31 and Equation 24–32 use the following nomenclature:

= (Wall Film Height) / (Maximum Film Height)

=(Wall Film Velocity) / (Maximum Wall Film Velocity)

= (Wall Film Heat Flux) / (Maximum Wall Film Heat Flux)

Finally, averaging over the period from to and applying appropriate weighting factors, the total risk is calculated as:

(24–33)

where:

(24–34)

(24–35)

The weighting factors . , , and are user-specified values.

You can access the functionality for assessing the risk of solids deposit formation via the following text commands:

define/models/dpm/options/scr-urea-deposition/enable-risk-analysis? yes

You will be asked to define the wall zones where the risk assessment should be performed, for example:

Wall face zones(1) [()] 8

The implementation uses the data sampling and custom field functions in Ansys Fluent, and after enabling the risk assessment capability, the following steps are automatically performed:

Once the SCR urea deposition risk analysis is enabled, you can set the following parameters and weighting factors (available under define/models/dpm/options/scr-urea-deposition):

After the time-dependent calculation is completed, the following variables will be available under Custom Field Functions... category for post-processing:

Additional field variables reported under the Custom Field Functions... and SCR Urea Deposition Risk Analysis... categories are the following:

You may ignore the additional variables with the scr-urea-depo- prefix in the Custom Field Functions... category as they are intermediate quantities with no meaningful values.