title: The role of impulse on the initiation of particle movement under turbulent flow conditions.
abstract: Fundamental to our understanding of erosional and transport phenomena in earth-surface dynamics and engineering is knowledge of the conditions under which sediment motion will begin when subjected to turbulent flow. The onset criterion currently in use emphasizes the time-averaged boundary shear stress and therefore is incapable of accounting for the fluctuating forces encountered in turbulent flows. We have validated through laboratory experiments and analytical formulation of the problem a criterion based upon the impulse imparted to a sediment grain. We demonstrate that in addition to the magnitude of the instantaneous turbulent forces applied on a sediment grain, the duration of these turbulent forces is also important in determining the sediment grain's threshold of motion, and that their product, or impulse, is better suited for specifying such conditions.
authors.affiliation: Baker Environmental Hydraulics Laboratory, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061, USA. pdiplas@vt.edu
authors.forename: Panayiotis
authors.initials: P
authors.lastname: Diplas
authors.forename: Clint L
authors.initials: CL
authors.lastname: Dancey
authors.forename: Ahmet O
authors.initials: AO
authors.lastname: Celik
authors.forename: Manousos
authors.initials: M
authors.lastname: Valyrakis
authors.forename: Krista
authors.initials: K
authors.lastname: Greer
authors.forename: Tanju
authors.initials: T
authors.lastname: Akar