abstract = "The drag coefficient plays a vital role in the
modeling of gas-solid flows. Its knowledge is essential
for understanding the momentum exchange between the gas
and solid phases of a fluidization system, and
correctly predicting the related hydrodynamics. There
exists a number of models for predicting the magnitude
of the drag coefficient. However, their major
limitation is that they predict widely differing drag
coefficient values over same parameter ranges. The
parameter ranges over which models possess a good drag
prediction accuracy are also not specified explicitly.
Accordingly, the present investigation employs Geldart
group B particles fluidization data from various
studies covering wide ranges of Re and epsilons to
propose a new unified drag coefficient model. A novel
artificial intelligence based formalism namely genetic
programming (GP) has been used to obtain this model. It
is developed using the pressure drop approach, and its
performance has been assessed rigorously for predicting
the bed height, pressure drop, and solid volume
fraction at different magnitudes of Reynolds number, by
simulating a 3D bubbling fluidised bed. The new drag
model has been found to possess better prediction
accuracy and applicability over a much wider range of
Re and epsilon than a number of existing models. Owing
to the superior performance of the new drag model, it
has a potential to gainfully replace the existing drag
models in predicting the hydrodynamic behaviour of
fluidized beds.",