ABSTRACT

Dong, C.; Zhao, P.; Yu, G., and Zhang, M., . Laboratory flume experiments on cohesive sediment erosion by oscillating wall jet.

Jet scour, a common method of dredging clay, must be accurately estimated. Cohesive sediment is aggregated by adhesion and is sensitive to erosion when the flow shear is appended with oscillation, as indicated by sediment rheology. On the basis of sediment rheology, this study experimentally investigates the timescale of the erosion of cohesive sediment under an oscillating wall jet in a laboratory flume. The oscillating wall jet is induced by a swinging oblique impingement jet. The erosion of the cohesive sediment was performed under an oscillating wall jet with a fixed flow rate but different oscillating intensities. The morphological properties, scouring depths, and rheological characteristics of the sediment were observed. The results show that when the oscillating frequency is zero or low, the sediment particles scatter similarly to aggregates, forming ridges at the intersection of the scouring slope and bed surface. However, these aggregates and ridges disappear when the oscillating frequency increases. Further, evaluations of the cohesive sediment under different oscillating frequencies indicate that the yield stress decreases with an increase in the scouring frequency. Submerged cohesive sediments tend to fluidize under oscillating shear, which indicates shear thinning behavior. Under the conditions of the oscillating wall jet, the scouring depth of the cohesive sediment increases exponentially with the oscillating intensity.

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