The issue of formulating an Ergun-like equation that applies to dynamic beds previously considered in Tupper et al. (2013) is revisited. Using new high quality positron emission particle tracking data, the volume and time averaged kinematic distributions of the granular (glass beads) and slurry (silica sand and water) mixture are computed. Incorporating these measured ingredients into the model then reveals that turbulence is not described by the usual effective viscosity, but nonetheless is negligible such that the new Inertial Cell Equation is first order in spatial derivatives. (c) 2015 American Institute of Chemical Engineers AIChE J, 62: 939-946, 2016