# Coarse and fine sand transport processes in the ripple vortex regime under asymmetric nearshore waves

Noémie Fritsch, Guillaume Fromant, David Hurther, Iván Cáceres

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Noémie Fritsch, Guillaume Fromant, David Hurther, Iván Cáceres. Coarse and fine sand transport processes in the ripple vortex regime under asymmetric nearshore waves. THESIS-2022 Two-pHase modEling for Sediment dynamIcS - 5th symposium on particulate geophysical flows, University of Grenoble Alpes LEGI; INRAE/ETNA, Jun 2022, Les Houches, France. hal-04974881

HAL Id: hal-04974881

https://hal.science/hal-04974881v1

Submitted on 3 Mar 2025

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Coarse and fine sand transport processes in the ripple vortex regime under asymmetric nearshore
waves.

Noémie Fritsch ¹, Guillaume Fromant ², David Hurther ³, Ivan Cáceres ⁴.

1. Laboratoire de Géosciences Océan, Université de Bretagne Occidentale, Brest, France.

2. Laboratoire d'Informatique Signal et Image de la Côte d'Opale, Calais, France.

3. Laboratoire des Ecoulements Géophysiques et Industriels, Grenoble, France.

4. Universitat Politècnica de Catalunya, Barcelone, Espagne.

Precise sand transport modelling and process-based parametrization are needed for improved long-
term predictions of coastal morphology evolution in the context of increasing anthropic activity. In
particular, ripple vortex regime modelling still presents shortcomings, despite the fact that sand ripples
are common bedforms found all across the oceanic nearshore region. In particular, the agreement
between experimental data and model predictions of sand ripple dimensions is still considered as poor
from a quantitative point of view. In the present study, an ACVP (Acoustic Concentration and Velocity
Profiler) and other flow measurement tools were deployed in the CIEM wave flume of Barcelona
(HYDRALAB-RIPCOM) to collect high-resolution concentration and velocity profile data above coarse
sand ripples generated under regular asymmetric nearshore waves. Intrawave, intraripple and net
contributions of sand transport rates are discussed for both the bedload and suspended load
contributions. In particular, the detailed ripple vortex dynamics on either side of the ripple crest is
analyzed in relation to acceleration skewness. The obtained results are compared to the recent study
of Wang and Yuan (2020) conducted in acceleration skewed oscillatory flows for coarse sand ripples.
Moreover, the differences are highlighted in terms of ripple vortex dynamics, associated sand
entrainment, net bedload and suspended load sand fluxes compared to the well documented ripple
vortex regime under velocity skewed oscillatory flows (van der Werf et al. 2007, 2008, Salimi-Tarazouj
et al. 2021) and skewed shoaling waves (Hurther and Thorne 2011). Finally, differences seen between
coarse and fine sand experiments are discussed in terms of ripple vortex processes inside the Wave
boundary Layer. This work offers new perspectives for process-based parametrization of sand
transport models in the ripple vortex regime and highlights the need to collect high-resolution in situ
data, since field experiments under irregular waves are lacking.