Laboratory experiments on the role of hysteresis, defect dynamics and initial perturbation on wave-generated ripple development

Jin, Chuang; Coco, Giovanni; Tinoco, Rafael O.; Goldstein, Evan B.; Gong, Zheng

doi:10.1016/j.ecss.2019.05.003

Cited by 8 publications

(8 citation statements)

References 46 publications

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“…The neighboring structures are important when investigating the morphodynamics over ripple geometries. Although our study is based on fixed ripple geometries, our results strongly imply the potential migration of ripples neighboring defects, and further interactions between defects and neighboring crestlines, which are frequently observed in the field and laboratory experiments (e.g., Jin et al., 2019; Perron et al., 2018).…”

Section: Discussionsupporting

confidence: 60%

“…Ripple geometry readjusts toward the equilibrium through defect generation, interaction, and annihilation (Kocurek et al, 2010). The initial processes (Jin et al, 2019), with different types of defects highlighted. Bedform geometries used in the simulations, (b) Regular ripples (NER), (c) Ripples with a termination defect (NET), (d) Ripples with a bifurcation defect (NEB).…”

Section: Influence Of Defects On Hysteresismentioning

confidence: 99%

“…In a bedform sediment sorting model, Huntley et al (2008) reported a significant dependence of hysteresis on the defect density of the pre-existing bedforms. To test the influence of pre-existing bedform geometry, Jin et al (2019) conducted laboratory experiments that showed that pre-existing bedform geometry has an impact on final equilibrium ripple dimensions when the change in wave forcing is large. Overall, defects have been observed to affect transient bedform morphodynamics.…”

Section: Influence Of Defects On Hysteresismentioning

confidence: 99%

“…To test the influence of pre‐existing bedform geometry, Jin et al. (2019) conducted laboratory experiments that showed that pre‐existing bedform geometry has an impact on final equilibrium ripple dimensions when the change in wave forcing is large. Overall, defects have been observed to affect transient bedform morphodynamics.…”

Section: Introductionmentioning

confidence: 99%

“…There are clearly other factors controlling hysteresis that are still not well understood. For example, studies have shown that ripple hysteresis also depends on the presence and density of "defects" (e.g., Jin et al, 2019Jin et al, , 2020Myrow et al, 2018). The term defect refers to bedform irregularities (e.g., termination, bifurcation and secondary crest, Figure 1a), appearing over ripple crestlines.…”

mentioning

confidence: 99%

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High‐Resolution Large Eddy Simulations of Vortex Dynamics Over Ripple Defects Under Oscillatory Flow

et al. 2022

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We carried out high‐resolution Large Eddy Simulations to study the three‐dimensional hydrodynamic characteristics over regular and irregular wave‐generated ripples. Two types of irregularities in ripple crestlines are considered, namely ripples with a termination defect and with a bifurcation defect. Over regular ripples, the flow and vortex structures vary in the spanwise direction, displaying evident three‐dimensional vortex structures. Compared to regular ripples, the presence of a bifurcation or a termination defect implies local variations in ripple height and spacing. As a result, the maximum velocity, vortex strength and the position of the vortex center over ripples neighboring a defect are all affected by the presence of the defect. The maximum velocity at the ripple crest neighboring a defect is linearly related to the position of the vortex center. The presence of defects induces an asymmetric distribution of shear stress and sediment flux that will ultimately affect bedform evolution.

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Section: Discussionsupporting

confidence: 60%

Section: Influence Of Defects On Hysteresismentioning

confidence: 99%

Section: Influence Of Defects On Hysteresismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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High‐Resolution Large Eddy Simulations of Vortex Dynamics Over Ripple Defects Under Oscillatory Flow

et al. 2022

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Large Eddy Simulation of three‐dimensional flow structures over wave‐generated ripples

Jin

Coco

Tinoco

et al. 2021

Earth Surf Processes Landf

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We performed a three-dimensional high-resolution Large Eddy Simulation using a sinusoidal ripple-like bedform geometry with spacing and amplitude consistent with equilibrium conditions under the prescribed oscillatory forcing. The simulation results are validated qualitatively and quantitatively with previous laboratory experiments and numerical simulations. Our numerical simulations allow to analyze the presence of "ribs", strong flow rotational features in the spanwise direction developing perpendicular to the ripple crest. We show that ribs tend to appear on the upslope and crest of ripples and display a dominant spacing, ranging from 0.5λ to λ, during wave phases associated to flow acceleration. When the vortex is transported over the downstream ripple during the flow deceleration, ribs appear for the second time over the upslope of the downstream ripple, with the dominant spacing about 1/8 ripple wavelength. The presence of flow three-dimensionality corresponds to a large variability of the shear stress over ripples in the spanwise direction, which could ultimately favor the development of three-dimensional geometry. The threedimensional vortex dynamics are evaluated using the concept of vortex strength. Peak vortex strength is observed at the maximum free stream velocity, but the largest variation of the vortex strength and vortex size in the spanwise direction occurs prior to the flow reversal. The variability of the vortex structures might provide a favorable setting for the development of ribs and might relate to the spacing of ribs.

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Rhythmic Coastal Landforms

Coco¹,

Calvete²,

Bryan³

et al. 2022

Treatise on Geomorphology

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Laboratory experiments on the role of hysteresis, defect dynamics and initial perturbation on wave-generated ripple development

Cited by 8 publications

References 46 publications

High‐Resolution Large Eddy Simulations of Vortex Dynamics Over Ripple Defects Under Oscillatory Flow

High‐Resolution Large Eddy Simulations of Vortex Dynamics Over Ripple Defects Under Oscillatory Flow

Large Eddy Simulation of three‐dimensional flow structures over wave‐generated ripples

Rhythmic Coastal Landforms

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