Title page for ETD etd-09072006-083326

Type of Document Master's Thesis
Author Greer, Krista
URN etd-09072006-083326
Title The Role of Instantaneous Forces in Particle Movement
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dancey, Clinton L. Committee Co-Chair
Diplas, Panayiotis Committee Co-Chair
Little, John C. Committee Member
  • incipient motion
  • sediment transport
  • impulse
  • electromagnet
Date of Defense 2006-08-31
Availability unrestricted
Many methods and equations have been developed to predict bed load transport rates, most of which use some comparison between shear stress and critical shear stress. The critical shear stress is determined by the point of incipient motion. Researchers have attempted to predict bed load transport both deterministically with mean parameters and stochastically attempting to take into account the fluctuations of velocity at points near threshold. This work attempts to show that more than simple force balances are needed to determine the point at which a particle will move. Turbulent fluctuations in velocity seem to have an effect of particle entrainment. The fluctuations in velocity can be several times greater than their time averaged counterparts. These short durations of high velocity often result in particle movement even though the mean flow may be less than or very near critical conditions. Through experiments of a single spherical particle on a simple bed geometry in air without the effects of water, it is shown that time duration of force has an effect on entrainment. This shows that there may be a constant force-time combination, or impulse, required to entrain sediment.
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