Investigation of Thermal Effects in low-Re sedimentation at anomalously large Pe*

A recent metanalysis of hindered settling speeds reported in the literature showed that the data fall on two distinct branches, both of which are well-described by a hindered settling function of the Richardson-Zaki form H(φ)=(1-φ)ⁿ, where φ is the particle volume fraction, but with different exponents: n≈5.5 for Brownian systems with a small Peclet number, and n≈4.5 for non-Brownian systems with large Peclet number.  The critical Peclet number is Pe≈10⁸, which is surprisingly large. We present preliminary progress in determining the grain-scale, mechanistic origins of this result using a combination of light-scattering and image analysis techniques.