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Abstract We report on a laboratory study of wave‐swash interactions, which occur in the very nearshore environment of a beach when the shallow swash flow of a breaking wave interacts with a subsequent wave. Wave‐swash interactions have been observed in the field, hypothesized to be important for nearshore transport processes, and categorized into different qualitative types, but quantitative descriptions of their dynamics have remained elusive. Using consecutive solitary waves with different wave heights and separations, we generate a wide variety of wave‐swash interactions with large flow velocities and vertical accelerations. We find that wave‐swash interactions can be quantitatively characterized in terms of two dimensionless parameters. The first of them corresponds to the wave height ratio for consecutive waves, and the second is a dimensionless measure of the time separation between consecutive wave crests. Using measurements of bed pressure and free‐surface displacement, we estimate the total vertical accelerations and focus on the peak upward‐directed acceleration. We find that wave‐swash interactions can generate vertical accelerations that can easily exceed gravity, despite occurring in very shallow water depths. The large vertical accelerations are upward‐directed and are quickly followed by onshore‐directed horizontal velocities. Together, our findings suggest that wave‐swash interactions are capable of inducing large material suspension events of sediment or solutes in sediment pores, and transporting them onshore. While the data are from a single location making it difficult to generalize the findings across the swash zone, the results clearly demonstrate the importance of large vertical accelerations in wave‐swash interactions.
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HYDRODYNAMICS OF SWASH INTERACTIONS
In this work, we conduct controlled experiments in a wave flume to represent different wave-wave interactions occurring in the swash zone. Using solitary waves as the forcing condition, we combined different wave amplitudes with separation times between the wave events. Experimental results show that interactions developing in the swash zone present three main stages: A jet slamming, an induced splash, and a region where the flow becomes fully 3D turbulent. We identified that the location where the interactions occur and the type of interaction depends on two main factors, the relationship between the wave amplitudes and the separation time between these wave events. Additionally, we were able to mimic the wave-wave interactions observed in real-case scenarios. Our goal is to relate these findings to the sediment transport processes in the swash zone, where interactions could develop a potential impact on the sediment transport mechanism and possible morphological changes.
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- Award ID(s):
- 2048676
- PAR ID:
- 10493133
- Publisher / Repository:
- WORLD SCIENTIFIC
- Date Published:
- Journal Name:
- Coastal Sediments 2023
- ISBN:
- 978-981-12-7989-8
- Page Range / eLocation ID:
- 356 to 363
- Format(s):
- Medium: X
- Location:
- New Orleans, LA, USA
- Sponsoring Org:
- National Science Foundation
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