Measurements of near-surface longitudinal and vertical wind velocity c
omponents associated with particle reentrainment from a flat surface h
ave been examined in a wind tunnel. Sparsely covered particle beds wer
e used to assure that observed reentrainment events resulted primarily
from the action of fluid forces. Characteristic velocity patterns wer
e found to be associated with a majority of particle reentrainment eve
nts examined. These characteristics have been categorized and examined
as ensemble averages. The flow pattern most frequently observed durin
g particle reentrainment was termed Ejection-Sweep (E-S) and is very s
imilar to organized fluid motions previously observed in laboratory fl
ows and in the atmospheric-boundary layer. A simple two-tiered E-S pat
tern recognition scheme is described which strives to identify particl
e reentrainment events objectively based on flow characteristics alone
. The first step is to identify potential E-S patterns using criteria
which identify a characteristic longitudinal acceleration, and the sec
ond step is to use threshold values of pattern characteristics to acce
pt or reject these first-tier patterns. Pattern recognition results ar
e presented in terms of the ability to identify reentrainment events v
ersus false identifications, and show an exponential growth in false i
dentifications with an increasing number of reentrainment events ident
ified.