A general framework for wave separation in the frequency domain

A general framework for wave separation in the frequency domain is presented and evaluated with successful results using theoretical examples of nonlinear waves. This framework consists of a qualitative and a quantitative analysis. The qualitative analysis is a novel approach that provides useful information about the existing wave trains within a wave field. This information includes an estimation of the number of wave trains, their direction of propagation (seaward or shoreward), their nature (free or bound) and their relative importance. The quantitative analysis consists in a revisited wave separation method applicable to separate free and bound wave trains travelling seaward and shoreward for both high and low frequencies propagating over uneven bathymetries. This versatility represents an improvement compared to existing methods. The presented separation method is low-sensitive to noise and its robustness is tested for a range of wave separation settings. The potential application of the separation method to random waves is discussed.Peer ReviewedPostprint (author's final draft

Long wave generation induced by differences in the wave-group structure

The propagation of bichromatic wave groups with differences in the wave-group structure and its influence in long-wave generation are investigated. The wave-group structure is controlled by the number of wave groups (Ng) within a repetition period. Consequently, an important energy content is measured at lower frequencies than the group frequency fg, in particular, at the repetition frequency fr. The cross-shore evolution of the energy at fr is partly explained by nonlinear energy transfers from the primary frequencies and partly by a breakpoint forcing. When Ng increases, the energy transfer to fr during wave group shoaling reduces. When Ng=3, the amplitude of fr suddenly grows at the breakpoint displaying a node-antinode pattern within the surf zone. In this case, the observed dominance of the breakpoint forcing over the energy transfers is justified by the combination of steep-slope regime and steep-wave conditions. The resultant cross-shore structure is in agreement with the Symonds et al. (1982, https://doi.org/10.1029/JC087iC01p00492) mechanism. A new methodology is proposed to identify the amplitude and phase cross-shore evolution of the radiated and reflected components. Due to energy dissipation of short waves and long waves at fg, the swash zone motion can be dominated by wave motions occurring at fr.Peer ReviewedPostprint (published version

Assessment and improvement of the wave generation accuracy using a wave separation method

Free-wave contamination is a non-desirable but frequent characteristic in many wave tank experiments. Higherorder wave generation is not widely implemented yet, whereas the effectiveness of active wave absorption systems is frequency-dependent, and usually unknown. The resulting free-wave contamination usually remains unnoticed, but may have important consequences especially at low frequencies. We present a Generation– Separation–Compensation (GSC) procedure to identify, quantify and attenuate the free-wave contamination. The resulting wave field behaves as expected from a higher-order wave generation with no re-reflections at the wave paddle. The attenuation ratio of the unwanted energy content is relatively high (between 60% to 90%). The GSC procedure uses the general framework for wave separation proposed by Padilla and Alsina (2020) with an array of in-line probes. The application of this technique over experimental data is presented with excellent results. The robustness of the qualitative analysis is guaranteed for experimental settings fulfilling a minimum distance between the first and the last probe and a maximum spacing between probes. The stability of the quantitative analysis is guaranteed when ¿ , number of probes forming the array, is above five, and ¿¿¿¿¿/¿, ratio between the spacing of the probes forming the array and the wavelength, is within the recommended range 0.1–0.45.Peer ReviewedPostprint (published version

LOCATE: prediction of plastic hotspots in coastal regions using numerical simulations in a coupled system

Los mecanismos de transporte de basura marina flotante en zonas costeras no se conocen bien, y su seguimiento con modelos numéricos es complejo debido a la geometría, procesos hidrodinámicos y la influencia de los procesos costeros, con estos últimos siendo especialmente complicados de incorporar. La herramienta LOCATE fue desarrollada para simular el movimiento y la acumulación de partículas de plástico en zonas costeras, usando mallas anidadas de diferentes resoluciones y escalas espaciales (2,5 km, 350 m y 70 m) para tener en cuenta los procesos costeros. La herramienta LOCATE acopla datos hidrodinámicos eulerianos con un modelo lagrangiano, requiriendo configuración y optimización para un funcionamiento adecuado. El modelo ha sido aplicado a la costa de Barcelona donde la geometría de costa y procesos costeros pueden actuar como acumuladores de basura y las concentraciones encontradas son comparables a otras zonas altamente contaminadas.Transport mechanisms of floating marine litter (FML) in coastal zones are poorly understood. Tracking FML dispersion with numerical models is complex due to the geometry, hydrodynamic processes and the influence of coastal processes, the latter being especially challenging to incorporate. The LOCATE tool was developed to simulate the motion and accumulation of plastic particles in coastal areas, using nested grids of varying spatial scales and resolutions (2.5 km, 350 m and 70 m) to account for coastal processes. LOCATE couples Eulerian hydrodynamic data with a Lagrangian particle solver, thus requiring configuration and optimization. As proof of concept, the model has been applied to the Barcelona coastline where the coastal geometry and processes can behave as marine litter traps and concentrations are comparable to some other heavily polluted areas

Suspended sediment transport and beach dynamics induced by monochromatic conditions, long waves and wave groups

This study presents the analysis of the water surface elevation, velocity and suspended sediment concentration measurements obtained at a large wave flume under mobile bed conditions. The wave reproduced erosive and accretive conditions, and included monochromatic, short waves perturbed with a free long wave, bichromatic and random conditions. Each tested condition started from a handmade 1/15 slope and lasted for an approximate time period of 2.4 h (6 runs of the selected wave condition), to compare the different beach profile developments and, in particular, the events that control sediment transport in the swash and surf zones. All erosive tested conditions produced a shoreline retreat and a bar at the breaking area whose development in time is directly correlated to the length of the breaking area. On the other hand, not all accretive conditions present a shoreward transport, and random conditions do not seem to alter the initial profile. The processed data show the suspended sediment event control produced by the existence or absence of wave–backwash interactions in the swash zone. The existence of these interactions, and their number within the wave group, will be a key parameter in controlling the sediment stirring, water velocity magnitudes and, therefore, the suspended sediment fluxes in the inner surf and outer swash.This work has been supported by the European Community's 6th Framework Programme through the grant to the budget of the Integrating Activity HYDRALAB III (Contract no. 022441). The first author also acknowledges the economical funding and support received from the MINECO and FEDER who founded the Plan-Wave project (Ref. CTM2013-45141-R), and the Secretaria d'Universitats i Recerca del Dpt. d'Economia i Coneixement de la Generalitat de Catalunya (Ref 2014SGR1253).Peer ReviewedPostprint (author's final draft

Aplicación de enzimas como auxiliares en tintura de lana

Il s’agit d’une étude comparée sur l’action de trois enzymes ajoutées au bain de teinture comme adjuvants. Nous avons déterminé les absorptions de colorant, les différences de couleur entre les laines teintées avec et sans enzymes et la bonne tenue de la couleur. L’action des trois enzymes augmente l’absorption de colorant et semble également améliorer sa diffusion à l’intérieur de la fibre. L’emploi d’enzymes dans la teinture de la laine permet de teindre à des températures plus basses.Este trabajo es un estudio comparativo de la acción de tres enzimas cuando se añaden al baño de tintura como auxiliares. Se han determinado las absorciones de colorante, las diferencias de color entre lana teñida con y sin presencia de enzimas y las solideces del color. La acción de los tres enzimas incrementa la absorción de colorante y parece que a la vez mejora la difusión hacia el interior de la fibra. El uso de enzimas en la tintura de lana ofrece la posibilidad de teñir a temperaturas más bajas.The action of three enzymes has been comparatively studied when used as auxiliary agents in dyebath. The absorption rate of the dye, the colour differences between wool dyed with and without enzymes and the colour fastness were determined. The action of enzymes consists of increasing dye absorption and also seems to produce a better diffusion of the dye into the fibre. The use of the enzymes in wool dyeing offers the possibility of dyeing under mild temperature conditions

Laboratory measurements of the wave-induced motion of plastic particles: influence of wave period, plastic size and plastic density

The transport of plastic particles from inland sources to the oceans garbage patches occurs trough coastal regions where the transport processes depend highly on wave-induced motions. In this study, experimental measurements of the plastic particles wave-induced Lagrangian drift in intermediate water depth are presented investigating the influence of the wave conditions, particle size and density on the motion of relatively large plastic particles. A large influence of the particle density is observed causing particles to float or sink for relative densities lower and larger than water respectively. The measured net drift of the floating particles correlates well with theoretical solutions for particle Stokes drift, where the net drift is proportional to the square of the wave steepness. Floating particles remain at the free water surface because of buoyancy and no evidence of any other influence of particle inertia on the net drift is observed. Nonfloating particles move close to the bed with lower velocity magnitudes than the floating particles’ motion at the free surface. The drift of nonfloating particles reduces with decreasing wave number, and therefore wave steepness.Peer ReviewedPostprint (published version

Influence of the initial beach profile on the sediment transport processes during post-storm onshore bar migration

Onshore bar migration is a characteristic bar behavior during post-storm beach recovery. The present large-scale experiments, feature bichromatic wave groups over an initially steep (1:15), fully-evolving beach. The same accretive wave condition is applied on two different post-storm beach profiles featuring outer and inner bars. They are characterized by a larger (smaller) shoreline erosion and a larger (smaller) outer breaker bar located farther away from (closer to) the shoreline depending on the larger (smaller) energy of the storm condition. After a considerable post-storm recovery time, similar equilibrium profiles are obtained, stressing the link between wave condition and equilibrium beach configuration. However, the evolution toward the equilibrium is different and depends on the initial morphological condition (post-storm beach profile). After the larger storm, the morphological evolution is termed accretive merging (AM) and characterized by merging of the two bars (outer bar dissipation). After the smaller storm, the morphological evolution denoted as accretive non-merging (AN) is characterized by onshore migration of the two bars with constant distance between them (bar maintenance). This study focuses on processes around the outer bar. During AN it features wave breaking, causing large suspended net offshore transport. AM, in contrast, mainly features bedload related to short wave asymmetries and low decomposed net transport rate magnitudes. High suspended net offshore transport occurs solely onshore of the outer bar trough. This causes filling of the bar trough and bar dissipation during migration. Additionally, processes around the outer bars are linked to accretion onshore of the bars and at the shoreline.We thank Dr. Tom Baldock and Dr. Marissa Yates for their valuable comments which helped to improve the manuscript. The experiments described in this work were funded by the European Community's Horizon 2020 Programme through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB+, Contract no. 654110, and were conducted as part of the transnational access project RESIST. FG acknowledges funding from the Agency for Management of University and Research Grants (AGAUR). DH acknowledges funding from the French DGA funded ANR ASTRID Maturation project MESURE (ANR-16-ASMA-0005-01). JA acknowledges funding from the Serra Húnter Programme (SHP). We wish to thank fellow RESIST researchers and the CIEM staff (Joaquim Sospedra, Oscar Galego, Dr. Andrea Marzeddu and Dr. Iván Cáceres) for their contributions to the experiments.Peer ReviewedPostprint (published version

The influence of wave groups and wave-swash interactions on sediment transport and bed evolution in the swash zone

Large scale laboratory measurements of sediment dynamics in the swash zone are presented. Two bichromatic wave group conditions were generated, having the same energy content but different wave group period (Tg = 15.0 s and 27.7s). For the shortest wave group, due to bore focusing, the shoreline fluctuates predominantly at the time scale, showing a large runup and the presence of wave–swash interactions with strong momentum exchange. In contrast, for the longer wave groups, the swash excursion is dominated by the individual waves. The uprush generally promotes onshore sediment advection with consequent erosion at the rundown location but accretion close to the runup. On the contrary, the backwash promotes seaward sediment advection and accretion at the rundown location. The presence of repeated wave–swash interactions modifies these patterns slightly. A wave overrunning a previous uprush promotes a reduction in onshore sediment advection while weak wave–backwash interactions reduce seaward advection. Consequently, the measured sediment dynamics shows stronger intra–swash cross–shore sediment advection for the swash events produced by the short wave groups. Measurements of the sheet flow layer near the shoreline show that for the shortest wave groups the vertical structure of the concentration is influenced by horizontal advection, leading to large sheet-flow layer thickness. However, for the longer wave groups, the local vertical exchange of sediment in the sheet–flow layer is dominant, with the presence of a pick–up and mirroring upper layer similar to oscillatory sheet–flow measurements. These results reaffirm the important effects of the wave group structure and the wave–swash interactions on the swash zone sediment dynamics and beach face evolution.Peer ReviewedPostprint (author's final draft

Study of atmospheric forcing influence on harbour water renewal

In this study, we use observations and numerical simulations to investigate the effect of meteorological parameters such as wind and atmospheric pressure on harbour water exchanges. The modelled information is obtained from the SAMOA (Sistema de Apoyo Meteorológico y Oceanográfico de la Autoridad Portuaria) forecasting system, which is a high-resolution numerical model for coastal and port-scale forecasting. Based on the observations, six events with high renewal times have been proposed for analysis using the SAMOA model. Therefore, the conclusions of this study have been possible due to the combination of observed data from the measurement campaigns and the information provided by the model. The results show that days with higher renewal times coincide with favourable wind-direction events or increases in atmospheric pressure. After analysing these events using model results, it was observed that during these episodes, water inflows were generated, and in some cases, there was a negative difference in levels between inside and outside the harbour produced by atmospheric pressure variations. The latter may be due to the fact that the water in the harbour (having a lower volume) descends faster and, therefore, generates a difference in level between the exterior and the interior and, consequently, inflow currents that imply an increase in the renewal time. These results are a demonstration of how meteorological information (normally available in ports) can be used to estimate currents and water exchanges between ports and their outer harbour area.This research received funding from the EuroSea project, under agreement with the European Social Fund (ESF) through a grant from FI AGAUR 2020 (Agency for the Management of University and Research Grants). This research has received funding from EuroSea project GA862626 funder H2020-EU.3.2.5.1 The authors want to acknowledge the ECO-BAYS research project (PID2020-115924RB-I00, financed by MCIN/AEI/10.13039/501100011033). The lead author has been financed by the Secretaria d’Universitats i Recerca de la Generalitat de Catalunya and the European Social Fund (ESF).Peer ReviewedPostprint (published version