TY - JOUR

T1 - Swash flows generated by a train of solitary waves on a planar slope

AU - Sou, In Mei

AU - Wu, Yun Ta

AU - Liu, Philip L.F.

N1 - Funding Information:
P.L.-F.L. would like to acknowledge the support from the National University of Singapore, Cornell University, and the Ministry of Education in Singapore through a research grant (MOE2018-T2-2-040). This research was also supported in part by the Yushan Program, Ministry of Education in Taiwan. Y.-T.W. would like to offer thanks for support from the Ministry of Science and Technology, Taiwan (MOST 108-2218-E-006-053-MY3) and, in part, by the Higher Education Sprout Project, Ministry of Education to the Headquarters of University Advancement at National Cheng Kung University.
Publisher Copyright:
© The Author(s), 2023. Published by Cambridge University Press.

PY - 2023/7/26

Y1 - 2023/7/26

N2 - Six consecutive solitary waves with identical wave height and separation time are generated to study the flow structures during the uprush-downwash interactions in the swash zone. Using particle image velocimetry, the cross-shore velocity fields are captured. Two different wave conditions are examined with different wave-height-to-water-depth ratios, i.e. and 0.22. The uprush-downwash interaction reaches quasi-steady state from the third solitary wave for both cases. For the former case, a weak non-stationary hydraulic jump appears during the downwash flow for all the six consecutive waves. The weak hydraulic jump evolves into a momentarily 'stationary' broken bore when the next wave arrives. For the latter case, the larger wave height generates stronger wave breaking. No non-stationary hydraulic jump is observed as the duration of downwash flow is relatively short. The flow reverses to the onshore direction before the downwash Froude number reaches the hydraulic jump condition. The temporal and spatial evolution of turbulence structure at the quasi-steady state is quantified using the spatial spectral analysis, the integral length scale and turbulence eddy viscosity. The results suggest that the large-scale energy generated during the uprush-downwash interaction modified the slope of the turbulence energy spatial spectrum in the inertial subrange from 5/3 to 1 in the larger length scale region, indicating the energy cascade depends not only on the dissipation rate, but also on the turbulent kinetic energy from the large-scale turbulence structure because of the large-scale energy injection in the inertial subrange.

AB - Six consecutive solitary waves with identical wave height and separation time are generated to study the flow structures during the uprush-downwash interactions in the swash zone. Using particle image velocimetry, the cross-shore velocity fields are captured. Two different wave conditions are examined with different wave-height-to-water-depth ratios, i.e. and 0.22. The uprush-downwash interaction reaches quasi-steady state from the third solitary wave for both cases. For the former case, a weak non-stationary hydraulic jump appears during the downwash flow for all the six consecutive waves. The weak hydraulic jump evolves into a momentarily 'stationary' broken bore when the next wave arrives. For the latter case, the larger wave height generates stronger wave breaking. No non-stationary hydraulic jump is observed as the duration of downwash flow is relatively short. The flow reverses to the onshore direction before the downwash Froude number reaches the hydraulic jump condition. The temporal and spatial evolution of turbulence structure at the quasi-steady state is quantified using the spatial spectral analysis, the integral length scale and turbulence eddy viscosity. The results suggest that the large-scale energy generated during the uprush-downwash interaction modified the slope of the turbulence energy spatial spectrum in the inertial subrange from 5/3 to 1 in the larger length scale region, indicating the energy cascade depends not only on the dissipation rate, but also on the turbulent kinetic energy from the large-scale turbulence structure because of the large-scale energy injection in the inertial subrange.

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U2 - 10.1017/jfm.2023.484

DO - 10.1017/jfm.2023.484

M3 - Article

AN - SCOPUS:85167662453

SN - 0022-1120

VL - 968

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

M1 - A1

ER -