Javier L. Lara

Large-scale experiments on wave propagation over Posidonia oceanica

Posidonia oceanica, the most abundant seagrass species in the Mediterranean, supports a highly bio-diverse habitat and is crucial in protecting against coastal erosion. In this work, experiments in a large-scale facility have been performed, for the measurement of wave attenuation, transmission and energy dissipation over artificial Posidonia oceanica. The effects of submergence ratio corresponding to the seagrass height divided by water depth, and seagrass density as the number of stems per square metre on the above characteristics are investigated. Measurements of wave height at different locations along the vegetation meadow indicate the wave attenuation along the Posidonia oceanica for three different submergence ratios and two seagrass densities. Results are also analysed with regard to the wave-induced flow within the meadow, and the effects of the submergence ratio and the seagrass density on the mean flow characteristics, based on data of mean velocities taken at three locations within the seagrass.

Reynolds averaged Navier-Stokes modelling of long waves induced by a transient wave group on a beach

This paper presents the numerical modelling of the cross shore propagation of infragravity waves induced by a transient focused short wave group over a sloping bottom. A dataset obtained through new laboratory experiments in the wave flume of the University of Cantabria is used to validate the Reynolds averaged Navier–Stokes type model IH-2VOF. A new boundary condition based on the wave maker movement used in the experiments is implemented in the model. Shoaling and breaking of short waves as well as the enhancement of long waves and the energy transfer to low-frequency motion are well addressed by the model, proving the high accuracy in the reproduction of surf zone hydrodynamics. Under the steep slope regime, a long wave trough is radiated offshore from the breakpoint. Numerical simulations conducted for different bottom slopes and short wave steepness suggest that this low-frequency breakpoint generated wave is controlled by both the bed slope parameter and the Iribarren number. Moreover, the numerical model is used to investigate the influence that a large flat bottom induces on the propagation pattern of long waves.

Long-wave-induced flows in an unsaturated permeable seabed

We present both analytical and numerical solutions describing seepage flows in an unsaturated permeable seabed induced by transient long waves. The effects of compressibility of pore water in the seabed due to a small degree of unsaturation are considered in the investigation. To make the problem tractable analytically, we first focus our attention on situations where the horizontal scale of the seepage flow is much larger than the vertical scale. With this simplification the pore-water pressure in the soil column is governed by a one-dimensional diffusion equation with a specified pressure at the water-seabed interface and the no-flux condition at the bottom of the seabed. Analytical solutions for pore-water pressure and velocity are obtained for arbitrary transient waves. Special cases are studied for periodic waves, cnoidal waves, solitary waves and bores. Numerical solutions are also obtained by simultaneously solving the Navier-Stokes equations for water wave motions and the exact two-dimensional diffusion equation for seepage flows in the seabed. The analytical solutions are used to check the accuracy of the numerical methods. On the other hand, numerical solutions extend the applicability of the analytical solutions. The liquefaction potential in a permeable bed as well as the energy dissipation under various wave conditions are then discussed.

2-D Experimental and Numerical Analysis of Wave Interaction with Low-Crested Breakwaters Including Breaking and Flow Recirculation

An analysis of the near-field flow at porous low-crested structures under breaking conditions is conducted, using a VOF-type numerical model based on the Reynolds-Averaged Navier Stokes (RANS) equations and including a k-E model. Results of numerical simulations of small-scale laboratory experiments on rubble-mound submerged breakwaters are presented with emphasis on the influence of the crest width on the flow conditions. Both experimental and numerical wave flumes include a system of flow recirculation aimed to prevent the usual excessive set-up leeward of overtopped structures in 2DV configurations. The numerical model is proven to reproduce with a high degree of agreement the different phenomena of wave interaction with low-crested structures and can be used as a valuable tool for functional and structural design.

Modeling the Interaction of Water Waves with Porous Coastal Structures

AbstractThe mathematical modeling of the interaction of water waves with porous coastal structures has continuously been among the most relevant challenges in coastal engineering research and practice. Finding a tool to better predict essential processes, relevant to the functionality and stability of breakwaters and jetties, and how they are affected by permeability, has been hampered by computational limitations that are being overcome. Over the last 60 years, the Journal of Waterway, Port, Coast, and Ocean Engineering has witnessed gradual developments leading from linearized solutions based on wave theories and constant friction coefficients to very sophisticated Eulerian or Lagrangian solvers of the Navier-Stokes (NS) equations, including turbulence within porous media. Today, although not without difficulty, the first steps are being made toward addressing the simulation of a fully three-dimensional interaction of complete sea states with porous structures at prototype scale. In this paper, after po...

Analysis of Wave Reflection from Structures with Berms Through an Extensive Database and 2DV Numerical Modelling

This paper analyses wave reflection from permeable structures with a berm, including reshaping cases. Data are obtained from recent wave flume experiments and from 2DV numerical simulations performed with the COBRAS-UC code. The objectives of this research were to identify the proper representation of the average structure slope to be included in the breaker parameter and to check the performance of the formula for the reflection coefficient developed for straight slopes by the Authors. Based on the observation that for reflection, differently from what happens for overtopping and run-up, the whole slope below sea water level (SWL) is important, the slope to appear in the breaker parameter is evaluated as a weighted average of the structure slope below the berm level and the average slope in the run-up/run-down area. The inclusion of this slope in the proposed formula allows to extend its prediction capacity to structures with a berm and a fair agreement with both experiments and simulations is obtained.

Wave Interaction With Piled Structures: Application With IH-FOAM

This paper presents a numerical analysis of the interaction of waves with piles. A model called IH-FOAM, based on OpenFOAM®, is used. IH-FOAM is able to simulate and to absorb waves in three-dimensional domains, reducing the computational cost and extending the range of applicability of the CFD modelling to the study of offshore and coastal structures. In this work, a detailed analysis of mono and multi-piled structures is carried out. Several piles layouts are studied Wave run-up and forces have been studied for the multi-piled structures. Those magnitudes have been compared with the single piled structure pointing out the difference in the wave induced hydrodynamics and the non-linear interaction between the waves and the structures. The work contained in this paper presents a first step which will be extended in the future to analyse more complex layouts and the effects of broken waves.Copyright

Introducing marine climate variability into life cycle management of coastal and offshore structures

Coastal and offshore structures are subject to a life cycle process including several different phases. From the planning and design phase to the re-use or demolition phase marine climate information is extremely important to achieve cost effective functionality and technical quality. The complete life cycle may span over several decades what requires site-specific marine climate information at different time scales and including its natural variability. We present an integrated methodology to generate marine climate information relevant for life cycle management of coastal and offshore structures including short-term, seasonal, long-terms and very longterm information. An application of the methodology to a harbour is presented.

AN EXPERIMENTAL EVALUATION OF WAVE ENERGY DISSIPATION DUE TO SUBMERGED STRUCTURES

An experimental work regarding a group of submerged structures constructed of different materials is presented. The efficiency of each structure related to energy dissipation and the response of a beach profile is analyzed. Among the results, a strong dependency in porosity has been found. The deformation of the sheltered beach and the distribution of the sediment along the profile are used to rank the tested materials. and Javier L. Lara 3

Innovative Engineering Solutions and Best Practices to Mitigate Coastal Risk

Engineering solutions are widely used for the mitigation of flood and erosion risks and have new challenges because of the expected effects induced by climate change in particular sea level rise and increase of storminess. This chapter describes both active methods of mitigation based on the reduction of the incident wave energy, such as the use of wave energy converters, floating breakwaters and artificial reefs, and passive methods, consisting of increase in overtopping resistance of dikes, improvement of resilience of breakwaters against failures, and the use of beach nourishment as well as tailored dredging operations.Existing coastal management and defense approaches are not well suited to meet the challenges of climate change and related uncertanities. Professionals in this field need a more dynamic, systematic and multidisciplinary approach. Written by an international group of experts, Coastal Risk Management in a Changing Climate provides innovative, multidisciplinary best practices for mitigating the effects of climate change on coastal structures. Based on the Theseus program, the book includes eight study sites across Europe, with specific attention to the most vulnerable coastal environments such as deltas, estuaries and wetlands, where many large cities and industrial areas are located. * Integrated risk assessment tools for considering the effects of climate change and related uncertainties* Presents latest insights on coastal engineering defenses* Provides integrated guidelines for setting up optimal mitigation measures* Provides directly applicable tools for the design of mitigation measures* Highlights socio-economic perspectives in coastal mitigation