TY - JOUR
T1 - Beach steepness effects on nonlinear infragravity-wave interactions
T2 - A numerical study
AU - De Bakker, A. T M
AU - Tissier, M. F S
AU - Ruessink, B. G.
PY - 2016/1/1
Y1 - 2016/1/1
N2 - The numerical model SWASH is used to investigate nonlinear energy transfers between waves for a diverse set of beach profiles and wave conditions, with a specific focus on infragravity waves. We use bispectral analysis to study the nonlinear triad interactions, and estimate energy transfers to determine energy flows within the spectra. The energy transfers are divided into four types of triad interactions, with triads including either one, two or three infragravity-frequency components, and triad interactions solely between sea-swell wave frequencies. The SWASH model is validated with a high-resolution laboratory data set on a gently sloping beach, which shows that SWASH is capable of modeling the detailed nonlinear interactions. From the simulations, we observe that especially the beach slope affects nonlinear infragravity-wave interactions. On a low-sloping beach, infragravity-wave energy dominates the water motion close to shore. Here infragravity-infragravity interactions dominate and generate higher harmonics that lead to the steepening of the infragravity wave and eventually breaking, causing large infragravity energy dissipation. On the contrary, on a steep-sloping beach, sea-swell wave energy dominates the water motion everywhere. Here infragravity frequencies interact with the spectral peak and spread energy to a wide range of higher frequencies, with relatively less infragravity energy dissipation. Although both beach types have different nonlinear interaction patterns during infragravity-wave dissipation, the amount of infragravity-wave reflection can be estimated by a single parameter, the normalized bed slope.
AB - The numerical model SWASH is used to investigate nonlinear energy transfers between waves for a diverse set of beach profiles and wave conditions, with a specific focus on infragravity waves. We use bispectral analysis to study the nonlinear triad interactions, and estimate energy transfers to determine energy flows within the spectra. The energy transfers are divided into four types of triad interactions, with triads including either one, two or three infragravity-frequency components, and triad interactions solely between sea-swell wave frequencies. The SWASH model is validated with a high-resolution laboratory data set on a gently sloping beach, which shows that SWASH is capable of modeling the detailed nonlinear interactions. From the simulations, we observe that especially the beach slope affects nonlinear infragravity-wave interactions. On a low-sloping beach, infragravity-wave energy dominates the water motion close to shore. Here infragravity-infragravity interactions dominate and generate higher harmonics that lead to the steepening of the infragravity wave and eventually breaking, causing large infragravity energy dissipation. On the contrary, on a steep-sloping beach, sea-swell wave energy dominates the water motion everywhere. Here infragravity frequencies interact with the spectral peak and spread energy to a wide range of higher frequencies, with relatively less infragravity energy dissipation. Although both beach types have different nonlinear interaction patterns during infragravity-wave dissipation, the amount of infragravity-wave reflection can be estimated by a single parameter, the normalized bed slope.
KW - dissipation
KW - infragravity waves
KW - nonlinear interactions
KW - numerical model
KW - sea-swell waves
UR - http://www.scopus.com/inward/record.url?scp=84959553488&partnerID=8YFLogxK
UR - http://resolver.tudelft.nl/uuid:45732889-a515-4ae1-9f4f-efcab351c5c7
U2 - 10.1002/2015JC011268
DO - 10.1002/2015JC011268
M3 - Article
SN - 2169-9275
VL - 121
SP - 554
EP - 570
JO - Journal Of Geophysical Research-Oceans
JF - Journal Of Geophysical Research-Oceans
IS - 1
ER -