  Wall channeling is a phenomena of interest for Pebble Bed Reactors (PBRs)
where flow is diverted into high-porosity regions near the wall. This diversion
of flow can have a significant impact on maximum fuel temperatures and core
bypass flow. Porous media models that are currently used to model PBRs for
design scoping and transient simulation are lacking in their capabilities to
model the wall channel effect. Recent efforts at Penn State have produced an
improved porous media pressure drop equation that is more capable of modeling
the velocity variations caused by the wall channel effect in a porous media
model. Several pebble beds were divided into concentric rings of $0.05D_{peb}$,
and average flow quantities and porosities were extracted for the ring. A
correlation between the form loss coefficient and the local ring porosity was
found, allowing for the addition of a correction factor to the form loss term
of the KTA equation. The developed correlation was purely empirical, and thus a
more thorough understanding of the underlying flow phenomena is desired. This
study investigates geometric and flow features that can explain the observed
correlation between the form coefficient and the local porosity that was used
to generate the improved pressure drop equation. The solid surface area to
volume ratio $S_v$ along with the production of Turbulent Kinetic Energy (TKE)
is analyzed. A relationship between $S_v$ and the local porosity and an inverse
relationship between the negative TKE production and the local porosity were
found, pointing to the idea that inertial effects caused by different pore
geometry in each ring contribute to the variation of the form constant with the
local porosity.
