The Role of Impulse on the Initiation of Particle Movement Under Turbulent Flow Conditions
Panayiotis Diplas,1*
Clint L. Dancey,2
Ahmet O. Celik,1
Manousos Valyrakis,1
Krista Greer,1
Tanju Akar1
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.
2 Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
Present address: Rummel, Klepper and Kahl, LLP Consulting Engineers, Baltimore, MD 21217, USA.
Present address: Civil Engineering Department, Akdeniz University, Antalya 07058, Turkey.
* To whom correspondence should be addressed. E-mail: pdiplas{at}vt.edu
