A unified criterion for initiation of sediment motion and inception of sheet flow under water waves |
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| Authors: | ZAI-JIN YOU † BAOSHU YIN† |
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| Institution: | Coastal Unit, NSW Department of Natural Resources, PO Box 2185, Dangar, NSW 2309, Australia (E-mail: ); Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Rd, Qingdao 266071, China |
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| Abstract: | A unified criterion is developed for initiation of non‐cohesive sediment motion and inception of sheet flow under water waves over a horizontal bed of sediment based on presently available experimental data. The unified threshold criterion is of the single form, Uo = 2πC1 + 5(TR/T)2]?1/4, where Uo is the onset velocity of sediment motion or sheet flow, T is wave period, and C and TR are the coefficients. It is found that for a given sediment, Uo initially increases sharply with wave period, then gradually approaches the maximum onset velocity Uo = 2πC and becomes independent of T when T is larger. The unified criterion can also be extended to define sediment initial motion and sheet flow under irregular waves provided the significant wave orbital velocity and period of irregular waves are introduced in this unified criterion. |
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| Keywords: | Initial motion irregular wave onset velocity sheet flow threshold criterion |
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