Search Results (35)

Coastal defenses under tsunami-like long waves are judged not only by wave attenuation but by their own stability and the hazard left landward, so a porous structure is assessed through several responses at once. OpenFOAM (porousWaveFoam) and FLOW-3D HYDRO are the two models most widely used for such problems, representing the open-source and the commercial approach, and each has an extensive record for solitary waves and for porous structures separately. Which to adopt for a given response is not established, since the two have not been compared where both occur together. Five hydraulic benchmarks were, therefore, reproduced with both, taken as configured in practice, since the differing elements cannot be exchanged by the user. Agreement was decomposed into error components and into the scalars that enter a design check, and each difference was weighed against a combined uncertainty. Neither model is superior across the responses. Across 57 signals, the more accurate one changes with the metric in 81% of cases, and six of thirteen governing comparisons exceed the uncertainty. Some of the largest errors are shared, so changing the model does not remove them, and the cost ordering reverses with the problem size. Model selection should, therefore, follow the target design response, together with a statement of whether the difference exceeds the uncertainty. These findings hold within the configurations tested; extension to random waves remains for future work. Full article

This study experimentally investigated the wave transmission and setup characteristics of biomimetic submerged structures as Nature-based Solutions (NbSs) for coastal protection. A non-porous monolithic pillar and a highly porous, multi-branched staghorn coral replica were tested in a 2D flume featuring a 1:20 foreshore slope representative of Kuta Beach, Bali. The results revealed a highly divergent, period-dependent hydrodynamic response. Under short-period waves ($T=0.8 \mathrm{s}$), attenuation was density dependent; the porous replica gradually dissipates energy through canopy micro-turbulence, yielding transmission coefficients ($K_t$) ranging from 0.25 to 1.18. Conversely, under long-period waves ($T=1.6 \mathrm{s}$), the attenuation mechanism shifted to density-independent, depth-induced breaking. This establishes a critical hydrodynamic trade-off: higher wave attenuation (lower $K_t$) inherently generates a higher coastal wave setup due to momentum transfer. Crucially, while both structures reduced transmission, the internal porosity of the multi-branched replica facilitated sub-surface return flow, effectively capping the maximum normalized wave setup at 0.09. This represents an 18% reduction in setup-induced coastal hazards compared to the monolithic baseline. To facilitate practical engineering design, new empirical equations ($R^2\approx 0.80$) for predicting $K_t$ were derived, integrating the frontal area index (${\lambda }_f$). Ultimately, these findings demonstrate that multi-branched biomimetic structures provide an optimal NbS design, balancing effective wave energy attenuation with the mitigation of secondary setup hazards for vulnerable coastal regions. Full article

Sandy coastal ecosystems are among the most widespread yet ecologically simplified marine habitats, particularly where anthropogenic pressures and the scarcity of structurally complex habitats limit biodiversity. This study evaluated the ecological effects of eco-engineered submerged reefs deployed in 2021 along the sandy coast of Lido degli Scacchi (northern Adriatic Sea, Italy). Twenty-one fully submerged eco-engineered Tecnoreef^® modules were installed within the gaps between existing detached breakwaters, introducing a highly porous and architecturally complex habitat into a shallow sedimentary environment. Benthic communities were monitored over two years through the assessment of soft-bottom infaunal and hard-substrate epifaunal assemblages. Community development on Tecnoreef modules was compared with that occurring on adjacent limestone breakwaters under both windward and leeward exposure conditions. Infaunal assemblages were primarily influenced by hydrodynamic exposure and showed limited differentiation between habitat types, although abundance and diversity increased around the submerged structures over time. In contrast, epifaunal communities exhibited marked temporal changes and developed compositions distinct from those observed on breakwaters. Among the taxa contributing most strongly to community differentiation was the reef-building polychaete Sabellaria spinulosa. The progressive establishment of this ecosystem-engineering species suggests that the eco-engineered modules provided favorable conditions for the early stages of secondary biogenic habitat development, although longer-term monitoring will be required to determine whether these developing habitats persist and evolve into stable ecological systems. Our results provide encouraging evidence that structurally complex submerged reefs can increase habitat heterogeneity and support the development of diverse benthic assemblages in highly modified sandy coastal environments. Although longer-term monitoring is required to assess habitat persistence and ecosystem-level effects, these findings highlight the potential of eco-engineered reefs as nature-based tools for supporting biodiversity enhancement and habitat development in tourism-dominated coastal landscapes. Full article

The fractional Whitham–Broer–Kaup model governs nonlinear wave propagation in memory-dependent media, including porous structures, viscoelastic fluids, and irregular seabeds, yet the full dynamical spectrum from quasi-periodicity to deterministic chaos, the role of stochastic forcing, and reliable identification from noisy data remains insufficiently explored, particularly how the fractional order $\beta$ influences these regimes. This study addresses these gaps through a comprehensive, multi-method dynamical analysis of a representative nonlinear oscillator embodying key FWBK features. Three-dimensional attractor visualizations, return maps, and surrogate data tests demonstrate a transition from quasi-periodic toroidal attractors to fully developed chaos via torus breakdown, confirming that observed complexity originates from deterministic nonlinearity. Poincaré sections reveal multistability and KAM-type structures, where coexisting attractors depend on initial conditions, while increasing noise progressively disrupts coherent dynamics. The OGY control method effectively stabilizes unstable periodic orbits across chaotic regimes with minimal perturbation, and Lyapunov analysis indicates that stochastic forcing attenuates chaos while enhancing dissipation. The Fokker–Planck framework shows that noise reshapes probability landscapes, driving transitions from unimodal to bimodal distributions. Comparative analysis of SINDy, JMAP and VBA highlights trade-offs in interpretability, computational efficiency, and uncertainty quantification, while an integrated Bayesian–PCE–Sobol approach quantifies parametric uncertainty and reveals time-dependent sensitivity variations. Additionally, the overlapping of soliton solutions extracted via the enhanced modified Sardar sub-equation method reveals structural relationships among soliton families and their stability under interaction. Soliton branches that maintain high overlap under noise correspond to stable regimes, while those losing coherence indicate the onset of chaos. Furthermore, while the reduced dynamics in $\eta$-space are independent of $\beta$, the fractional order controls spatial compression and temporal scaling in physical coordinates, directly influencing observable wave localization. These results imply that fractional effects can modify chaos transitions, support controllability through OGY, and influence noise–instability interactions depending on $\beta$. This framework provides a robust, transferable methodology for analyzing and controlling nonlinear oscillatory systems under deterministic and stochastic conditions, with direct applications to FWBK-based models in coastal engineering, fiber optics, and quantum interference systems. Full article

The spatiotemporal evolution of seepage fields and the associated hydrodynamic risk of subsequent internal erosion pose a critical threat to the structural integrity of marine and hydraulic infrastructure. To quantify these complex fluid–solid interactions, this study develops a high-fidelity numerical model—coupling the Navier–Stokes equations with the Darcy–Forchheimer resistance model and the Volume of Fluid (VOF) method—to investigate transient hydrodynamics within porous foundations under complex geometric and geological boundary conditions. Parametric analyses reveal that spatial porosity distribution fundamentally dictates the system’s seepage capacity; notably, relocating a highly permeable stratum to the shallow sub-surface eliminates upper hydraulic bottlenecks and significantly escalates total volumetric discharge. Furthermore, the study systematically evaluates the hydrodynamic efficacy of multi-dimensional seepage control structures. Results demonstrate that while increasing the vertical depth of a cutoff wall is highly efficient in restricting bulk volumetric flux, it inadvertently induces intense localized streamline convergence and flow acceleration at the structural tip. Conversely, lateral expansion of the wall base, though yielding only a moderate reduction in total seepage, successfully diffuses this concentrated flow and substantially attenuates peak pore fluid velocities. Ultimately, a combined design paradigm is proposed for practical coastal engineering applications: prioritizing vertical penetration to optimize bulk seepage reduction, concurrently integrated with moderate lateral base expansion to redistribute concentrated hydrodynamic shear stresses, thereby minimizing the hydrodynamic potential for localized piping and ensuring long-term stability against seepage-induced degradation. Full article

The atypical proliferation of Sargassum (Sargassum spp.) in the tropical Atlantic and the Caribbean Sea over the past decade has triggered an unprecedented environmental and socioeconomic crisis along the Mexican coastline. Continuous beaching events of this macroalga on the Riviera Maya have caused coastal ecosystem degradation, severe impacts on the tourism sector, toxic gas emissions during decomposition, and high cleanup costs. To address this challenge, the valorization of Sargassum as a raw material for synthesizing functional materials represents a sustainable management strategy. In this study, a superabsorbent hydrogel was developed from Sargassum biomass (collected in Cancún, Quintana Roo, in 2025) using an innovative process that bypasses the conventional cellulose isolation step. The biomass was subjected to high-energy milling (15 and 30 min) to prepare Sargassum powder, which was subsequently carboxymethylated using monochloroacetic acid. This modified biomass was then crosslinked with citric acid, a process evaluated at three different citric acid/carboxymethylated Sargassum mass ratios. The hydrogel synthesized with the lowest crosslinking agent ratio achieved a maximum water absorption capacity of 1160 wt%, a value that exceeds the typical absorption capacities of 700–900% for biopolymer hydrogels. Successful material formation was confirmed by Fourier transform infrared spectroscopy (FTIR), which revealed the characteristic functional groups of CMC and the ester bonds formed during crosslinking. Additionally, scanning electron microscopy (SEM) analysis showed a well-defined porous structure with pore sizes ranging from 8.5 to 19.5 µm, which is essential for its high absorption performance. This study demonstrates the feasibility of producing high performance hydrogels from Sargassum through a simplified, cost-effective, and environmentally friendly process. These findings open a promising avenue for the integrated management of this problematic biomass, transforming it into value-added materials with potential applications in agriculture, hygiene, and environmental remediation. Full article

Low-lying and riverine areas of Sabah and Sarawak in East Malaysia are increasingly exposed to compound flood hazards driven by intensified monsoon rainfall, sea-level rise, and land-use change. Recent projections indicate stronger extreme rainfall, fewer dry days, but more high-intensity events, and significant increases in annual rainfall and sea level, all of which elevate fluvial, pluvial, and coastal flood risk. In this study, climate-responsive vernacular architecture is investigated as a passive, low-carbon strategy for enhancing residential flood resilience in East Malaysia. Traditional stilted Malay kampung houses, Bornean longhouses, and coastal stilt settlements were explored since they have historically evolved to cope with seasonal inundation, high humidity, and tropical thermal loads. In this study, the following was conducted: (1) historical flood and climate analysis for key basins (Rajang, Sarawak, Kinabatangan); (2) morphological and typological analysis of vernacular dwellings; (3) parametric physical and hydrodynamic simulation of elevated and amphibious configurations; and (4) multi-criteria performance assessment based on structural robustness, flood safety, thermal comfort, cultural acceptability, and embodied carbon. Results from scenario-based simulations show that well-configured stilted typologies, with optimized floor elevation, breakaway panels, and porous undercroft zones, can reduce flood damage depth by 60–80% and expected annual loss by 30–55%. By translating these findings into a design guideline and decision matrix for climate-responsive housing in East Malaysia, contemporary reinterpretations of vernacular strategies were embedded into Malaysian building codes, state-level planning policies, and community-led upgrading programmes. Full article

The present work focuses on wave scattering generated by an inverse T-type compound breakwater in the presence of the ocean current. The boundary value problem (BVP) is investigated using two distinct strategies: an exact formulation derived from the eigenfunction expansion method (EEM) and a computational framework developed with the boundary element method (BEM). A comparison of outcomes from both techniques with established studies confirms the consistency and accuracy of the present formulations. Reflection and transmission coefficients, along with the time-domain simulations of the free surface, are evaluated under different wave conditions and structural configurations. In the long-wave region, the reflection coefficient exhibits strong dependence on the wavenumber, with higher values observed as the height and width of the porous section increase. Increasing the friction coefficient within the porous layer considerably reduces wave transmission to the leeside, demonstrating the important role of friction in energy dissipation. Furthermore, greater ocean current velocity leads to an increase in the reflection curve, highlighting the significant effect of hydrodynamic conditions on wave–structure interaction. The time-domain simulations of the free surface are also presented to provide a clear visualization of the wave behavior on the surface, both with and without the presence of an ocean current. The findings shed light on the combined influence of breakwaters and ocean currents, enabling the development of coastal protection measures that enhance resilience, sustainability, and safety from erosion and damage. Full article

This research evaluates the stabilization of a clay collected from the northern expansion zone of Cartagena de Indias, Colombia. Laboratory analyses, including particle size distribution, Atterberg limits, compaction, specific gravity, and XRF/XRD, classified the soil as a highly plastic clay (CH) with moderate dispersivity, as confirmed by pinhole and crumb tests. The soil was treated with 3–9% lime, with and without the addition of NaCl (0% and 2%), and tested for unconfined compressive strength (q_u), small-strain stiffness (G_o), and microstructural properties under curing periods of 14 and 28 days at two compaction densities. Results showed that lime significantly improved mechanical behavior, while the inclusion of NaCl further enhanced q_u (up to 185%) and G_o (up to 3-fold), particularly at higher lime contents and curing times. Regression models demonstrated that both q_u and G_o follow power-type relationships with the porosity-to-lime index, with consistent exponents (−4.75 and −5.23, respectively) and high coefficients of determination (R² > 0.79). Normalization of the data yielded master curves with R² values above 0.90, confirming the robustness of the porosity-to-lime framework as a predictive tool. The G_o/q_u ratio obtained (3737.4) falls within the range reported for cemented geomaterials, reinforcing its relevance for comparative analysis. SEM observations revealed the transition from a porous, weakly aggregated structure to a dense matrix filled with C–S–H and C–A–H gels, corroborating the macro–micro correlation. Overall, the combined use of lime and NaCl effectively converts dispersive clays into non-dispersive, mechanically improved geomaterials, providing a practical and sustainable approach for stabilizing problematic coastal soils in tropical environments. Full article

Composite breakwater is a commonly employed structure for coastal and harbor protection. However, strong hydrodynamic impact can lead to failure and instability of these protective structures. In this study, a two-dimensional fluid-porous-solid coupling model is developed to investigate the stability of composite breakwaters. The fluid-porous model is based on the Volume-Averaged Reynolds-Averaged Navier-Stokes equations, in which the nonlinear Forchheimer equations are added to describe the porous layer. The solid model employs the Nodal-based Discontinuous Deformation Analysis (NDDA) method to analyze the displacement of the caisson. NDDA is a nodal-based method that couples FEM and DDA to improve non-linear processes. This proposed coupled model permits the examination of the influence of the thickness and porosity of the porous layer on maximum impacting wave height (${\mathrm{IWH}}_{\max }$) and the turbulent kinetic energy (TKE) generation. The results show that high porosity values lead to the dissipation of TKE and reduce the ${\mathrm{IWH}}_{\max }$. However, the reduction in the ${\mathrm{IWH}}_{\max }$ is not monotonic with increasing porous layer thickness. We observed that ${\mathrm{IWH}}_{\max }$ reaches an optimum value as the porous layer thickness continues to increase. These results can contribute to improve the design of composite breakwaters. Full article

This study presents an analytical model to reduce the impact of wave-induced forces on a vertical seawall by introducing a floating elastic plate (EP) located at a specific distance from two bottom-standing porous structures (BSPs). The hydrodynamic interaction with the EP is described using thin plate theory, while the fluid flow through the porous medium is described by the model developed by Sollit and Cross. The resulting boundary value problem is addressed through linear potential theory combined with the eigenfunction expansion method (EEM), and model validation is achieved through consistency checks with recognized results from the literature. A comprehensive parametric analysis is performed to evaluate the influence of key system parameters such as the porosity and frictional coefficient of the BSPs, their height and width, the flexural rigidity of the EP, and the spacing between the EP and BSPs on vital hydrodynamic coefficients, including the wave force on the seawall, free surface elevation, wave reflection coefficient, and energy dissipation coefficient. The results indicate that higher frictional coefficients and higher BSP heights significantly enhance wave energy dissipation and reduce reflection, in accordance with the principle of energy conservation. Oscillatory trends observed with respect to wavenumbers in the reflection and dissipation coefficients highlight resonant interactions between the structures. Moreover, compared with a single BSP, the double BSP arrangement is more effective in minimizing the wave force on the seawall and free surface elevation in the region between the EP and the wall, even when the total volume of porous material remains unchanged. The inter-structural gap is found to play a crucial role in optimizing resonance conditions and supporting the formation of a tranquility zone. Overall, the proposed configuration demonstrates significant potential for coastal protection, offering a practical and effective solution for reducing wave loads on marine infrastructure. Full article

The rampant growth of Spartina alterniflora has been wreaking havoc on the coastal ecosystems, leading to a serious environmental challenge in recent years. One potential solution to this issue involves converting Spartina alterniflora into activated carbon, offering a potential remedy for pollution while creating value in energy storage applications. Herein, through a facile carbonization process with sodium hydroxide activation, we successfully transformed obsolete Spartina alterniflora into a porous carbon material (called SAC) and its nitrogen-doped derivative (denoted as SANC) by using melamine as the nitrogen source in a similar procedure. The amorphous structure of these materials was confirmed to enhance lithium-ion storage and electrolyte permeation, making them ideal for use as anodes in lithium-ion batteries. As a result, both SAC and SANC, derived from Spartina alterniflora, exhibited outstanding electrochemical performance including high capacity (456.7 and 780.8 mA h g⁻¹ for SAC and SANC, respectively, at the current density of 6 mA g⁻¹), excellent rate performance (from 6 to 600 mA g⁻¹) and long-term cycling stability. Notably, compared to SAC, its N-doped derivative SANC showed superior properties in the battery (retaining a reversible capacity of 412.9 mA h g⁻¹ at the current density of 6 mA g⁻¹ even after 600 repeated charge–discharge cycles), demonstrating the significantly positive impact of heteroatom doping. This work not only offers a strategy to mitigate environmental challenges but also demonstrates the potential for converting waste biomass into a valuable resource for energy storage applications. Full article

Wooden or bamboo fences, commonly used for coastal protection, have limited effectiveness in reducing wave height due to their porous structure, which provides only moderate wave damping. To address this issue, our study proposes a modification that retains these fences while strategically incorporating submerged rocks, similar to gabions, to exploit friction and achieve significant wave height reduction. We employed a mathematical model based on modified Shallow Water Equations to investigate the wave attenuation. A key measure, the wave transmission coefficient ($K_t$), for quantifying wave height reduction was determined using both analytical and numerical methods. The numerical $K_t$ obtained from simulations was $0.2831$, whereas the analytically computed $K_t$ value was $0.2622$, which indicates a reduction of over 70% in the initial wave amplitude due to the combined effect of submerged rocks and wooden fences. These results, which align closely with experimental data, validate the credibility of our approach. A detailed sensitivity analysis illustrates the effectiveness of both wooden fences and submerged rocks in attenuating wave height, which depends on structure dimensions and friction coefficients. Optimization studies present various optimal structures, underscoring the critical role of the structure’s friction coefficient in minimizing the wave transmission coefficient, and recommend the use of rough materials for optimal wave height reduction. In summary, our paper offers a robust exploration of an innovative coastal protection strategy that integrates wooden fences and rocks. The validated model, supported by analytical, numerical, and experimental evidence, has the potential to provide practical insights for coastal engineers seeking efficient wave attenuation solutions. Full article

The study area was Anin Beach, where a 1.48-km-long breakwater, consisting of a non-porous caisson, was constructed over 16 months. During this process, significant erosion occurred over a wide area behind the coast, with a maximum reduction in the beach width of 36 m observed in the central part of the coastline. As a countermeasure to prevent erosion, a submerged breakwater was installed that consisted of concrete blocks and had a length of 600 m. Following the implementation of this submerged breakwater, the beach behind it increased in width by 64 m, in proportion to the installation length, while erosion phenomena, such as the loss of coastal roads, were observed at both ends of the structure. In this study, the topographical changes caused by waves and currents were analyzed to identify their causes and establish countermeasures. Additionally, the planned measures, established before structure installation, were closely examined against the actual occurrences observed onsite through a coastline survey. Full article

The permeable breakwater is an innovative, eco-friendly coastal protection structure that reduces wave impact while minimizing “dead water” and environmental harm. This study introduces a perforated pipe breakwater design with an increasing pipe diameter from top to bottom, evaluated through physical model tests using transmission coefficient K_t and reflection coefficient K_r serving as the primary parameters. The results indicate that K_t decreases as the relative width (B/L), wave steepness (H/L), and relative water depth (h/L) increase, but rises with a steeper breakwater slope. When B/L exceeds 0.3, H/L surpasses 0.06, or the h/L ratio is greater than 0.3, K_t gradually declines until reaching a stable state, resulting in a more pronounced wave reduction. As B/L and H/L increase, the coefficient K_r initially drops, then rises. The slope ratio of 1:1.5 demonstrates the most effective wave energy dissipation, with primary dissipation occurring on the front slope. The mixed pipe diameter design shows superior wave absorption over a uniform diameter. Compared to a porous horizontal plate, the perforated pipe breakwater exhibits better wave absorption. These findings offer valuable guidance for designing eco-friendly coastal protection projects. Full article