Designing
supervised classifiers for multiphase flow data classification
Chemical Engineering Science, 2004, accepted
Laurentiu A. Tarca, Bernard P.A. Grandjean and Faїçal Larachi
Department of Chemical Engineering & CERPIC
Laval University - Québec, Canada G1K 7P4
Abstract
There is a great deal of instances in
multiphase reactor engineering where the system’s state is labeled using
categorical indices to depict class memberships. Remarkable examples encompass
the labeling of flow patterns and regime transitions in multiphase porous media
flows, the macro and microscale fluidization states
in fluid-solid or fluid-fluid-solid reactors, the bubble wake morphologies, the
bed initial contraction/expansion in fluidization, etc. The design of
general-purpose flow pattern recognizers for multiphase reactors requires
implementation of feature selection algorithms and classifier design methods.
Feature selection algorithms enables extracting the most informative feature
sets to be included in the data-driven inference engine (or classifier). In
this work, supervised classifiers were built by modeling the class-conditional
probability functions of class memberships. The discriminant
functions yielding the best class separation were searched using the following
statistical and neural network based classifiers: Gaussian (quadratic
discrimination rule), linear (normal based), nearest mean class, nearest
neighbor, k-nearest neighbor, binary decision tree, radial basis functions and
multilayer perceptron neural networks. These
approaches were benchmarked using, as an example, the three-class trickle-bed
flow-regimes problem (Low interaction regime [LIR], high interaction regime
[HIR], transition regime [TR]) for which a comprehensive knowledge-referenced
database is available (5,061 flow regime observation records). For a given
model complexity, the multilayer perceptron (MLP)
neural network outperformed the other approaches in terms of accuracy. Enhanced
phenomenological consistency and immunity against overfitting
of the MLP model were achieved by embedding specific domain prior knowledge.
The model captured with success the hierarchical linking nature of the categories
during monotonic increase (respectively, decrease) of fluid throughputs
(respectively, gas density) from LIR to HIR through TR. Misclassification
between the non-adjacent LIR and HIR classes was kept to a minimum and the
model yielded cross-validated error of 16% for the 5,061 database records.
Keywords
Classification, RBF, perceptron neural
networks, decision tree, trickle bed, flow regime
You can get the FlowRegClassifier.xls
file that contains the simulator to identify the flow regime in trickle beds.