@phdthesis{fdi:010096137,
  title = {{E}ffets des tourbillons de la zone de d{\'e}ferlement et du cisaillement vertical du courant de retour sur la dispersion des traceurs : approche de mod{\'e}lisation 3{D} {\`a} vagues r{\'e}solues},
  author = {{T}reillou, {S}imon},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he nearshore zone, encompassing the surf zone and the inner shelf, is a highly dynamic region where surfzone eddies and rip currents of varying scales coexist and interact. {T}his critical interface between land and sea determines the transport of various elements, including sediments, contaminants (such as heavy metals, microplastics, and pathogens), as well as biological tracers like plankton and larvae. {T}hese tracers are central to addressing key coastal challenges, such as beach erosion, coastal pollution, and ecosystemic services. {O}n longshore-uniform sandy beaches, one of the primary transport mechanisms is transient rip currents, driven by wave directional spread. {W}hile numerous studies have investigated passive tracer transport under these conditions, most have relied on depth-averaged wave-resolving models ({B}oussinesq models). {A}lthough these models offer valuable insights, they fail to capture the effect of vertical shear resulting from shoreward surface flow induced by breaking waves and seaward undertow. {T}hey typically underestimate mixing within the surf zone and overestimate offshore dispersion. {R}ecently, 3{D} wave-resolving models such as {CROCO} have provided researchers with the tools to conduct more comprehensive studies. {T}he objective of this thesis is to contribute to the ongoing improvement of these models and to assess the impact of undertow vertical shear on tracer dispersion. {T}he first step was to correct a coherent interference problem in the {CROCO} wavemaker, then to validate its ability to resolve transient nearshore dynamics using a recent wave basin experiment. {A}fter confirming the robustness of the model, the influence of vertical shear was examined through two dye release experiments, one in a wave basin and the other during a large-scale field experiment at {I}mperial {B}each, {C}alifornia. {C}omparisons of simulations with and without undertow vertical shear revealed two key findings: a reduction in offshore dispersion due to a weakening in the 2{D} inverse kinetic energy cascade, and enhanced mixing within the surf zone through a newly identified 3{D} process associated with "mini-rips", a type of intermediate-scale transient current recently discovered. {T}his research, which provides a more accurate representation of transport mechanisms in the nearshore zone, offers valuable feedback for improving parameterizations in coarser models.},
  keywords = {{ETATS} {UNIS} ; {PACIFIQUE} ; {CALIFORNIE} ; {IMPERIAL} {BEACH}},
  address = {{T}oulouse},
  publisher = {{U}niversit{\'e} {T}oulouse {III}  - {P}aul {S}abatier},
  pages = {204  multigr.},
  year = {2024},
  URL = {https://www.documentation.ird.fr/hor/fdi:010096137},
}