CFD coupling particle statistics is a module introduced in Rocky v4.5. It collects instantaneous values from particle-fluid interaction variables and calculates with them average values that then are associated to the particles. This originates new particle properties that users may visualize in a 3D view window and post-process at their convenience.
Table 4.6: Available CFD coupling particle statistics, as of v4.5
|
Property |
Calculation |
|---|---|
| Drag Force | Equation 4–36 with  from equation
of the DEM-CFD Coupling
Technical Manual |
| Lift Force | Equation 4–36 with  from equation of
the DEM-CFD Coupling Technical Manual |
| Vitrtual Mass Force | Equation 4–36 with  from equation
of the DEM-CFD Coupling
Technical Manual |
| Pressure Gradient Force | Equation 4–36 with  from equation
of the DEM-CFD
Coupling Technical Manual |
| Flow Induced Torque | Equation 4–38 with  from equation of
the DEM-CFD Coupling Technical Manual |
| Convective Heat Transfer Rate | Equation 4–39 with  from equation
of the DEM-CFD Coupling
Technical Manual |
The currently available statistics are listed in Table 4.6: Available CFD coupling particle statistics, as of v4.5. All of them are integral-based statistics that represent average values of particle-fluid interaction magnitudes measured during an output interval. For instance, the average CFD interaction forces are calculated as:
 | (4–36) |
where 
is the impulse associated to the interaction force 
, which, in turn, is approximated as indicated in Equation 4–17
. The time interval 
is the time of residence of the particle p during the
output interval. Normally it will be equal to the output interval itself, 
, except in the case in which the particle entered the simulation at some
point within that interval. In that case 
will be equal to 
, where 
is the output time which the statistics are associated to, while
is the time at which the particle was released into the simulation. The
previous definition can be condensed into the expression:
 | (4–37) |
Equivalent expressions are used to calculate the average values of the flow-induced torque and the convective heat transfer rate. In the case of the flow-induced torque, the average value is calculated as:
 | (4–38) |
where 
is the instantaneous value of the flow-induced torque and 
is the simulation timestep.
For the convective heat transfer rate, its average is calculated using the expression:
 | (4–39) |
where 
is the instantaneous value of the convective heat transfer rate.
The expressions that define the instantaneous values of each one of the interaction magnitudes mentioned above are indicated in Table 4.6: Available CFD coupling particle statistics, as of v4.5. All of them are included in the DEM-CFD Coupling Technical Manual; for further details about how those magnitudes are calculated please refer to that manual.
Each one of the statistics offered by the CFD coupling particle statistics module can be enabled individually in the Rocky UI. A given statistics may be enabled even if the related interaction variable is not active in the CFD coupling calculations performed by Rocky. If that is the case, the related statistics will have zero values for all particles at all output times. However, users must be aware that those statistics still will occupy memory and disk space, for that reason they must be careful and enable only statistics related to active variables.