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22.16.8 Summary Reporting of Current Particles

For many mass-transfer and flow processes, it is desirable to know the mean diameter of the particles. A mean diameter, $D_{jk}$, is calculated from the particle size distribution using the following general expression [ 188]:


 \left(D_{jk}\right)^{j-k} \equiv \frac{ {\displaystyle \int_... ...} D^j f(D) dD}{ {\displaystyle \int_{0}^{\infty}} D^k f(D) dD} (22.16-1)

where $j$ and $k$ are integers and $f(D)$ is the distribution function (e.g., Rosin-Rammler). $D_{10}$, for example, is the average (arithmetic) particle diameter. The Sauter mean diameter (SMD), $D_{32}$, 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  22.16.1.


Table 22.16.1: Common Mean Diameters and Their Fields of Application
${j}$ ${k}$ Order
${j + k}$
Name Field of Application
1 0 1 Mean diameter, $D_{10}$ Comparisons, evaporation
2 0 2 Mean surface diameter, $D_{20}$ Absorption
3 0 3 Mean volume diameter, $D_{30}$ Hydrology
2 1 3 Overall surface diameter, $D_{21}$ Adsorption
3 1 4 Overall volume diameter, $D_{31}$ Evaporation, molecular diffusion
3 2 5 Sauter mean diameter, $D_{32}$ Combustion, mass transfer, and
efficiency studies
4 3 7 De Brouckere diameter, $D_{43}$ Combustion equilibrium

Summary information (number, mass, average diameter) for particles currently in the computational domain can be reported using the Particle Summary panel (Figure  22.16.4) .

Report $\rightarrow$ Discrete Phase $\rightarrow$ Summary...

Figure 22.16.4: The Particle Summary Panel
figure

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

1.   Select the particle injection(s) for which you want to generate a summary in the Injections list.

FLUENT provides a shortcut for selecting injections with names that match a specified pattern. To use this shortcut, enter the pattern under Injection Name Pattern and then click Match to select the injections with names that match the specified pattern. For example, if you specify drop*, all injections that have names beginning with drop (e.g., drop-1, droplet) will be selected automatically. If they are all selected already, they will be deselected. If you specify drop?, all surfaces with names consisting of drop followed by a single character will be selected (or deselected, if they are all selected already).

2.   Click Summary to display the injection summary in the console window.

           (*)- 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)


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