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Flow Structures and Hydrodynamic Force During Sediment Entrainment: A Cause and Effect Analysis

Author(s): Ambuj Dwivedi; Bruce W. Melville; Asaad Y. Shamseldin

Linked Author(s): Bruce W. Melville

Keywords: Flow structure; Particle entrainment; Hydrodynamic forces; Drag; Lift; Protrusions

Abstract: An experimental investigation of the role of coherent structures and their effect on hydrodynamic forces responsible for inception of sediment motion has been carried out using a laboratory flume with PIV used to record the flow velocity along with simultaneous force measurement. The ratio of mean and entrainment velocity at 0.15D above the target particle is found to increases with increase in exposure and sweep events were found to be the dominant flow structures causing entrainment of both shielded and exposed particles. Short duration lift forces of magnitude greater than the submerged weight are thought to be responsible for partial lifting of the completely shielded particle. Quadrant analysis and pdf plots of the dominant hydrodynamic force reveals the higher probability of occurrence of high magnitude force induced by sweep (Q 4) events.


Year: 2010

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