23.7.2 Reporting of Trajectory Fates

When you perform trajectory calculations by displaying the trajectories (as described in Section  23.7.1), ANSYS FLUENT will provide information about the trajectories as they are completed. By default, the number of trajectories with each possible fate (escaped, aborted, evaporated, etc.) is reported:

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

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

Trajectory Fates

The possible fates for a particle trajectory are as follows:

• "Escaped'' trajectories are those that terminate at a flow boundary for which the "escape'' condition is set.

• "Incomplete'' trajectories are those that were terminated when the maximum allowed number of time steps--as defined by the Max. Number of Steps input in the Discrete Phase Model dialog box (see Section  23.2.8)--was exceeded.

• "Trapped'' trajectories are those that terminate at a flow boundary where the "trap'' condition has been set.

• "Evaporated'' trajectories include those trajectories along which the particles were evaporated within the domain.

• "Aborted'' trajectories are those that fail to complete due to roundoff reasons. You may want to retry the calculation with a modified length scale and/or different initial conditions.

• "Shed'' trajectories are newly generated particles during the breakup of a larger droplet. They appear only if a breakup model is enabled.

• "Coalesced'' trajectories are removed particles which have coalesced after particle-particle collisions. They appear only if the coalescence model is enabled.

• "Splashed'' trajectories are particles which are newly generated when a particle touches a wall-film. Those trajectories appear only if the wall-film model is enabled.

Summary Reports

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.

1.   Follow steps 1 and 2 in Section  23.7.1 for displaying trajectories.

2.   Select Summary as the Report Type and click Display or Track.

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 resulting Select File dialog box (see Section  2.1.6).)

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

Fate                   Number           Elapsed Time (s)                                    
                                       Min        Max        Avg    Std Dev                  Min                  Max
 ----                   ------  ---------- ---------- ---------- ---------- 
Evaporated                  2  1.770e-003 1.114e-002 6.456e-003 4.686e-003
Escaped - Zone 6            3  6.043e-001 7.037e-001 6.471e-001 4.172e-002
Trapped - Zone 7            5  8.486e-003 1.767e-001 5.030e-002 6.421e-0021

                    (*)- Mass Transfer Summary -(*) 

 Fate                        Mass Flow (kg/s)
                           Initial      Final     Change
 ----                   ---------- ---------- ----------
 Evaporated             8.333e-002 0.000e+000 -8.333e-002
 Escaped - Zone 6       1.167e-001 5.144e-002 -6.523e-002
 Trapped - Zone 7       2.000e-001 2.400e-002 -1.760e-001
 ----                   ---------- ---------- ----------
 Net                    4.000e-001 7.544e-002 -3.246e-001

                    (*)- Energy Transfer Summary -(*) 

 Fate                       Heat Rate (W)          Change of Heat (W)
                           Initial      Final     Sensible     Latent   React
 ----                   ---------- ----------   ---------- ---------- -------
 Evaporated             -3.180e+004 0.000e+000  -3.382e+002 3.214e+004 1.107
 Escaped - Zone 6        5.272e+005 6.519e+005  -3.487e+003 1.282e+005 1.523
 Trapped - Zone 7        4.954e+005 6.993e+005  -1.173e+003 2.051e+005 1.737
 ----                   ---------- ----------   ---------- ---------- ------
 Net                     9.908e+005 1.351e+006  -4.998e+003 3.654e+005 4.367

                    (*)- Combusting Particles -(*) 

 Fate                     Volatile Content (kg/s)        Char Content (kg/s)    
                           Initial      Final   \%Conv    Initial      Final
 ----                   ---------- ---------- -------  ---------- ---------- 
 Evaporated             0.000e+000 0.000e+000    0.00  0.000e+000 0.000e+000  
 Escaped - Zone 6       9.333e-003 9.333e-003    0.00  2.133e-002 2.133e-002  
 Trapped - Zone 7       9.333e-003 7.485e-010  100.00  2.133e-002 2.133e-002   
 ----                   ---------- ---------- -------  ---------- ---------- 
 Net                    1.867e-002 9.333e-003   50.00  4.267e-002 4.267e-002  

 
 
                 (*) - Multicomponent Droplet -(*) 

 Fate                                  Species      Species Content (kg/s)    
                                       Names     Initial      Final   \%Conv
 ----                                 -------  ---------- ---------- -------
 Evaporated                 c5h12-droplet<l>  1.667e-002 0.000e+000  100.00
 Evaporated                 c7h16-droplet<l>  3.333e-002 0.000e+000  100.00
 Evaporated                           h2o<l>  0.000e+000 0.000e+000    0.00
 Escaped - Zone 6           c5h12-droplet<l>  1.667e-002 2.585e-004   98.45
 Escaped - Zone 6           c7h16-droplet<l>  0.000e+000 0.000e+000    0.00
 Escaped - Zone 6                     h2o<l>  3.333e-002 1.134e-002   65.99
 Trapped - Zone 7           c5h12-droplet<l>  3.333e-002 0.000e+000  100.00
 Trapped - Zone 7           c7h16-droplet<l>  3.333e-002 0.000e+000  100.00
 Trapped - Zone 7                     h2o<l>  3.333e-002 0.000e+000  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.

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.

 Fate                 Number           Elapsed Time (s)
                                     Min        Max        Avg    Std Dev
 ----                 ------  ---------- ---------- ---------- ---------- ---
 Incomplete                2   1.485e+01  2.410e+01  1.947e+01  4.623e+00
 Escaped - Zone 7          8   4.940e+00  2.196e+01  1.226e+01  4.871e+00

Also, on the right side of the report are listed 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.)

   Elapsed Time (s)                       Injection, Index
 Min        Max        Avg    Std Dev                  Min                Max
 --- ---------- ---------- ---------- -------------------- ------------------
 +01  2.410e+01  1.947e+01  4.623e+00     injection-0    1   injection-0    0
 +00  2.196e+01  1.226e+01  4.871e+00     injection-0    9   injection-0    2

Mass Transfer Summary

For all droplet or combusting particles with each fate, the total initial and final mass flow rates and the change in mass flow rate are reported in the Initial, Final, and Change columns. With this information, you can determine how much mass was transferred to the continuous phase from the particles.

For unsteady tracking, the report lists the time-integrated mass flow rate of the particle streams that have reached a particular fate at the current flow time. In other words, the report does not include particles that are still being tracked in the domain.

                   (*)- Mass Transfer Summary -(*)

 Fate                        Mass Flow (kg/s)
                           Initial      Final     Change
 ----                   ---------- ---------- ----------
 Incomplete              1.388e-03  1.943e-04 -1.194e-03
 Escaped - Zone 7        1.502e-03  2.481e-04 -1.254e-03

Energy Transfer Summary

This report tells you how much heat was transferred from the particles to the continuous phase. The report is organized in two sections. For steady simulations, there is a Heat Rate and a Change of Heat section. For unsteady particle tracking, there is an Energy and a Change of Energy section. The Heat Rate and Energy sections are the same for all particle types, while the other sections report the change of heat due to the various transfer processes, which differ for each particle type. For steady simulations, the report lists the rate and the change of heat for the particle streams organized according to the particle stream fates. For unsteady tracking, the report lists the time integrated heat rate and change of the particle streams that have reached a particular fate at the current flow time. Note that the report does not include particles that are still being tracked in the domain.

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 $H_p$ is defined as follows:

Inert Particles:

where:	$m_p$	=	mass flow rate of particles (kg/s)
	$T_p$	=	temperature of particles (K)
	${C_p}_p$	=	heat capacity of particles (J/kg/K)
	$T_{ref}$	=	reference temperature for enthalpy (K)

Droplet Particles:

where:	$H_{pyrol}$	=	heat of pyrolysis (J/kg)
	$H_{lat_{ref}}$	=	latent heat of evaporation at reference conditions (J/kg)

The latent heat at the reference conditions $H_{lat_{ref}}$ is defined in this equation in the separate Theory Guide.

Combusting Particles:

where:	$H_{comb}$	=	heat of reaction (J/kg)
	$H_{lat_{ref}}$	=	latent heat of devolatilization adjusted to account for the difference in
			heat capacities between the particle and the devolatilizing species (J/kg)

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

Multicomponent Particles:

where:	$y_i$	=	mass fraction of component i in particle
	$H_{p_i}$	=	heat content of component i

and

ïƒµ

where:	$H_{{pyrol}_i}$	=	heat of pyrolysis for component i (J/kg)
	$H_{{lat_{ref}}_i}$	=	latent heat of evaporation at reference conditions
			for component i (J/kg)
	${C_p}_{p_i}$	=	specific heat of component i (J/kg/K)

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 $H_p$, while for unsteady tracking the time integrated energy $E_p$ from time 0 to current flow time $ts$ is reported.

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

                    (*)- Energy Transfer Summary -(*) 

 Fate               Heat Rate (W)          Change of Heat (W)
                    Initial      Final     Sensible     Latent      Total
 ----             ----------  ----------   ----------  ----------  ----------
 Evaporated      -4.530e+004  0.000e+000  -4.750e+002  4.577e+004  4.530e+004
 Escaped-Zone 6  -1.723e+005 -4.670e+004  -2.552e+003  1.282e+005  1.256e+005
 Trapped-Zone 7  -2.176e+005  0.000e+000  -1.058e+003  2.187e+005  2.176e+005
 ----             ---------- ----------   ---------- ---------- ----------
 Net             -4.353e+005 -4.670e+004  -4.085e+003  3.927e+005  3.886e+005

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

             (*)- Energy Transfer Summary -(*) 

Fate                Heat Rate (W)         Change of Heat (W)
                   Initial      Final    Sensible     Latent   Reaction   Tot
----            ---------- ----------  ---------- ---------- ---------- ------
Escaped-Zone 5  1.697e+005 2.555e+004  3.166e+003 1.034e+000 -1.473e+005 -1.44
Trapped-Zone 6  1.886e+004 1.938e+004  5.731e+002 1.149e-001 -5.370e+001  5.19
----            ---------- ----------  ---------- ---------- ---------- ------
Net             1.886e+005 4.493e+004  3.739e+003 1.149e+000 -1.474e+005 -1.43

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 Section  23.6.1.

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

Combusting Particles

If combusting particles are present, ANSYS FLUENT will include additional reporting on the volatiles and char converted. These reports are intended to help you identify the composition of the combusting particles as they exit the computational domain.

               (*)- Combusting Particles -(*)

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

The total volatile content at the start and end of the trajectory is reported in the Initial and Final columns under Volatile Content. The percentage of volatiles that has been devolatilized is reported in the %Conv column.

The total reactive portion (char) at the start and end of the trajectory is reported in the Initial and Final columns under Char Content. The percentage of char that reacted is reported in the %Conv column.

Combusting Particles with the Multiple Surface Reaction Model

If the multiple surface reaction model is used with combusting particles, ANSYS FLUENT will include additional reporting on the mass of the individual solid species that constitute the particle mass.

               (*)- Multiple Surface Reactions -(*)

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

The total mass of each solid species in the particles at the start and end of the trajectory is reported in the Initial and Final columns, respectively. The percentage of each species that is reacted is reported in the %Conv column. Note that for the solid reaction products (e.g., if the mass of a solid species has increased in the particle), the conversion is reported to be 0.

Multicomponent Particles

If your simulation includes multicomponent particles, ANSYS FLUENT generates an additional report for the particle components.

                 (*) - Multicomponent Droplet -(*) 

 Fate                                  Species      Species Content (kg/s)    
                                       Names     Initial      Final   \%Conv
 ----                                 -------  ---------- ---------- -------
 Evaporated                 c5h12-droplet<l>  1.667e-002 0.000e+000  100.00
 Evaporated                 c7h16-droplet<l>  3.333e-002 0.000e+000  100.00
 Evaporated                           h2o<l>  0.000e+000 0.000e+000    0.00
 Escaped - Zone 6           c5h12-droplet<l>  1.667e-002 2.585e-004   98.45
 Escaped - Zone 6           c7h16-droplet<l>  0.000e+000 0.000e+000    0.00
 Escaped - Zone 6                     h2o<l>  3.333e-002 1.134e-002   65.99
 Trapped - Zone 7           c5h12-droplet<l>  3.333e-002 0.000e+000  100.00
 Trapped - Zone 7           c7h16-droplet<l>  3.333e-002 0.000e+000  100.00
 Trapped - Zone 7                     h2o<l>  3.333e-002 0.000e+000  100.00