Development of a dual serial-parallel multiphase CFD code for application to industrial combustor/reactor systems. Page: 5 of 9
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For droplet and solid phases, the Eulerian approach is employed, and the formulation is:
axnd~kud.kJ axJ )St
in which 4 is a general droplet or particle property; nk is droplet or particle number density of k*tl size group; udkj are
droplet or particle velocity components of kh size group in the x, r is droplet or particle diffusivity resulting from
interaction with turbulence in the gas phase ; and S is the sum of source terms.
A control volume approach is used to convert these governing equations to algebraic equations on a staggered,
discretized grid system. The algebraic equations are solved iteratively with proper boundary conditions. In the
calculations, Patankar's SIMPLER computational scheme  is used to solve the pressure linked momentum
An example of computed multiphase reacting flow result with large scale features is shown in Figure 1. The
figure includes three plots: (a) catalyst volume fraction, (b) feed oil droplet volume fraction, and (c) gasoline mass
fraction with gas phase velocity vectors. Figure la show how the catalyst is distributed in the reactor. Figure lb
shows how the feed oil is injected into the reactor and mixed with the catalyst. Figure Ic shows where the feed oil is
vaporized and cracked by the catalyst into gasoline. This information can lead to the optimization of the unit
performance and the development of advanced systems.
(a) Catalyst Volume Fraction
i L 0.00
(b) Feed Oil Droplet Volume Fraction
(c) Gasoline Mass Fraction
and Vapor Velocity
Figure 1 Computed Flow Properties of an Industrial Size FCC Riser
ELEMENTS OF MULTIPHASE REACTING FLOW ANALYSIS THAT RELATE TO PARALLELISM
The primary motivation for developing parallel computing capability for multiphase reacting flow analysis of
industrial size systems lies in the wide variety of phenomena, spanning different time and length scales or different
virtual spaces (for example, droplet size space) that are being modeled in these types of CFD codes [4-8].
Adequately resolving the scales of the interacting processes in these systems easily reaches the limits of the fastest
serial computers. One goal for practical engineering computations is to be able to complete a computation in four to
eight hours. If this goal is met, then a computation with one set of parameter values can be completed within one
work day, checked for convergence and reasonableness, and restarted to run overnight if necessary. The elements of
multiphase reacting flow analysis that place large demands on computing resources and make parallel computing a
good candidate for achieving the one day computation time goal are briefly outlined in the following paragraphs.
Often these large-scale systems cannot be well modeled experimentally by scaling them down to a laboratory
scale. Also, these systems frequently have harsh operating environments in which experimental data gathering may
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Lottes, S. A.; Fischer, P. F. & Chang, S. L. Development of a dual serial-parallel multiphase CFD code for application to industrial combustor/reactor systems., article, May 16, 2000; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc712529/m1/5/: accessed May 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.