Wave Attack Research Articles

Niepoliczone i niepoliczalne (?) ofiary broni chemicznej, maj 1915 r.

The subject of this discussion are the almost forgotten victims of chemical weapons on the Eastern Front of World War I. Source data related to military operations, in particular to the German gas attacks in the region of the Bzura and Rawka rivers, are the basis for presenting problems related to the estimation of the number of victims of poisonous chlorine gas in the period between May and July 1915. Using the example of selected data relating to the wave attack of May 31, 1915, I show the specificity and complexity of the source documents closely related to the problem under consideration, that is the issue of the countability of victims of chemical weapons. Indirectly, I show the need and legitimacy of systematizing and interpreting all available information on what resulted from the historical use of chemical weapons. This would be conducive to deepening our knowledge about the fallen soldiers and their resting places. It would be helpful to initiate work on a digital repository of knowledge on the use of chemical weapons in the past, taking into account the very diverse descriptions of events and victims of chemical weapons from the Eastern Front of the Great War. Such a digitized resource could contribute to the systematization of highly dispersed source data, their further interpretation and reinterpretation, and their social activation, for the benefit of deepening knowledge about history and historical awareness and preventing the threat of again turning to the use of such weapons of mass destruction.

Experimental study of wave overtopping at rubble mound seawalls

Seawalls play a significant role in protecting coastal areas against wave attack and flooding. The accurate estimation of wave overtopping at seawalls is therefore crucial to adequately protect people and infrastructure in these regions. In this study, the mean wave overtopping rate at rubble mound seawalls was investigated through 140 small-scale physical model tests which adds to the limited existing data for this structure type in the extended CLASH database called EurOtop (2018). The combined dataset is used to evaluate the prediction skill of existing empirical formulae and to identify their limitations. The role of wave steepness on the mean overtopping rate is closely examined as it has not yet been considered properly in the EurOtop (2018) formulation. A new formula was derived using dimensional analysis and physical justifications of the overtopping phenomenon. The formula was found to provide a 40% decrease in RMSE in comparison to that of the EurOtop (2018). In addition, the new formula yields a BIAS ≈0, a significant improvement compared to −0.38 (non-dimensional discharge) of the EurOtop (2018) formula. The proposed formula has a simple form where non-dimensional overtopping discharge depends only on the relative crest freeboard and wave steepness, which were found to be the most important variables based on a sensitivity analysis.

Tsunami wave impact assessment for residences in Pattinapakkam, Chennai coast using DualSPHysics

The method of Smoothed Particle Hydrodynamics (SPH) is getting main-stream starting late to model non-linear problems of coastal engineering applications. This work has been conveyed to investigate the appropriateness of DualSPHysics to model Tsunami in disaster management program in predicting the wave pressure, velocity and wave height. A numerical model has been set up for assessing the wave loads on structures on the Pattinapakkam area along Chennai coast. The region selected for the study is located at a distance of 42 m from the shoreline which is more inclined to wave attack during Tsunami. For simplification, the area of the region considered in the model is 917 m2. The digital elevation model (DEM) output of Pattinapakkam has been used to reproduce the real coastal profile of the region. The tsunami waves considered in the SPH method is the solitary waves. The weakly compressible SPH approach has been used in this simulation because, in light of the fact that, the fluids are weakly compressible in nature. The results including the wave pressure, velocity and wave height parameters are presented and wave pressure acting on few structures are moreover given. ABAQUS model simulation has additionally been used to study the pattern of deformation of the structures in the domain. The study determined that DualSPHysics was able to model highly non-linear problems with practically no deformations. The main disadvantage is that it requires computationally efficient machine in modeling real time problems as the real model includes couple of million particles in simulation. It recommends that DualSPHysics goes about as a prevalent tool in the disaster management program.

Impact Of Seawall Development To The Sulawesi Fishermen Community In Pambusuang Village

A coastal protection structure mostly built to protect human from the detructive wind and wave energy. The various option of type and design has been invented in the development. This study investigates the impact of seawall development in Pambusuang Village, West Sulawesi. This study will examine the fishery activity change after the development of seawall. The benefit and disadvantages of the seawall structure to the community also as well as the community response to address the impact of seawall development will be explored in this study. A mix quantitave and qualitative approach is used in this study. A set of questionnare has been distributed and structured interview to selected infromant were also conducted. The study found that fishermen has changed their docking behavior due to the limited area to docking. Moreover, the respondent believes that seawall has properly function to halt erosion, protect their house and other infrastructure from the wave attack. The other issues is the disharmony between pro and contra seawall development, inundated river flow and damage of natural habitat. The response of the community to addressing some impact of the seawall development such as their adaptation to the sloping gate between the seawall, the use of traditional anti fouling painting and their suggestion to construct breakwater disattached from the shoreline. The findings above has been formed the basis of recommendations to have a participatory development approach and experience sharing between the parties in the community to adapt with the impact of seawall development.

Seismic dynamics of a pipeline shallowly buried in loosely deposited seabed foundation

It is widely known that submarine pipelines constructed in high seismic intensity zones are vulnerable due to soil liquefaction under the attack of seismic waves. It is meaningful for engineers to get insight into the seismic dynamic response mechanism of submarine pipelines, which mostly are buried in loosely deposited seabed floors in practical engineering. In this study, taking the integrated numerical model FSSI-CAS 2D as the platform, the seismic dynamic response of a shallowly buried submarine pipeline in a loosely deposited seabed floor is investigated. It is indicated by the numerical results that a shallowly buried submarine pipeline in loose seabed floor intensively responds to input seismic wave. Considerable vibration in horizontal and floatation in vertical occur for the pipeline due to the soil softening in the surrounding soil, as well as the soil liquefaction in the zone away from the pipeline. The buoyancy applied on the outer wall of the pipeline caused by the pore pressure accumulation makes a significant contribution to the upward floatation of the pipeline. It is found that the seismic wave-induced residual liquefaction firstly initiates in the medium depth of seabed floor due to the relatively great permeability of the loose seabed soil, and then develops toward to the upper and lower seabed synchronously. Because of the intensive interaction between the pipeline and its surrounding seabed soil, liquefaction has not occurred in the zone at the right and left-hand side of, as well as over the pipeline. Based on comparative analysis, it is found the magnitude of pipeline floatation if natural gas is transported is much greater than that if crude oil is transported. Finally, it is observed that considerable subsidence at the magnitude order of 1 m occurs for the pipeline in the post-reconsolidation process after seismic wave attacking. It is indicated by the analysis presented in this study that the integrated model FSSI-CAS 2D would be a trustworthy platform to study the seismic dynamic response of marine structures.

Mangroves As Coastal Bio-Shield: A Review of Mangroves Performance in Wave Attenuation

Mangroves have been recognized as soft structures that provide coastline protection. The capability of dampening waves helps minimize destruction from catastrophic events including erosive wave attacks, torrential storms, and tsunamis. Mangroves act as the first line of coastal defense in natural tragedies such as during the Super Typhoon Haiyan 2013 and Indian Ocean Tsunami 2004, whereby the leeward mangrove area encountered less damage than the unprotected area. This has further brought the attention of researchers to study the attenuation performance of these coastal vegetations. Based on an extensive literature review, this paper discusses the attenuation mechanism of mangroves, the factors influencing the dissipation performance, studies on mangrove dissipation via different approaches, the dissipation efficiency, mangrove conservation and rehabilitation efforts in Malaysia and implementation of mangrove as coastal bio-shield in other countries. The study highlights that mangrove parameters (such as species, width, density etc.) and wave parameters (such as wave period and incident wave height) are among the contributing factors in mangroves-induced wave attenuation, with different efficiency rates performed by different mangroves and waves parameters. Towards that end, several improvements are proposed for future research such as to incorporate all influencing dissipation factors with specific analysis for each species of mangroves, to perform validation on the studied mangroves attenuation capacity in different settings and circumstances, as well as to address the extent of protection by the rehabilitated mangroves. A systematic and effective management strategy incorporating ecological, forestry, and coastal engineering knowledge should be considered to ensure a sustainable mangroves ecosystem and promising coastline protection by mangroves. Doi: 10.28991/cej-2021-03091772 Full Text: PDF

Monitoring of Recovery Process at Yeongildae Beach, South Korea, Using a Video System

Once a beach is eroded by storm waves, it is generally recovered under milder wave conditions. To prevent or reduce damage, it is therefore important to understand the characteristics of the site-specific recovery process. Here, we present the results, based on a data set from a video monitoring system and wave measurements, of the recovery process in a pocketed beach located inside a bay where the shoreline retreated harshly (~12 m, on average, of beach width) during Typhoon TAPAH (T1917) in September 2019. It took about 1.5 years for the beach to be recovered to the level before the typhoon. During this period, the erosion and accretion were repeated, with the pattern highly related to the wave power (Pw); most of the erosion occurred when Pw became greater than 30 kWatt/m, whereas the accretion prevailed when Pw was no greater than 10 kWatt/m. The recovery pattern showed discrepancies between different parts of the beach. The erosion during storm events was most severe in the southern part, whereas the northern shoreline did not significantly change even during TAPAH (T1917). In contrast, the recovery process occurred almost equally at all locations. This discrepancy in the erosion/accretion process was likely due to human intervention, as a shadow zone was formed in the northern end due to the breakwaters, causing disequilibrium in the sediment transport gradient along the shore. The results in this study could be applied in designing the protection plans from severe wave attacks by effectively estimating the size of coastal structures and by correctly arranging the horizontal placement of such interventions or beach nourishment. Although the application of these results should be confined to this specific site, the method using wave energy parameters as criteria can be considered in other areas with similar environments, for future planning of beach protection.

An experimental study on the motion of solid spheres under solitary wave attack

In the present study, the motion of a single and the motion and collision of two spheres on a horizontal area under solitary wave attack are investigated, constituting a unique and integrated dataset. Sixteen experimental cases are considered on four experimental configurations changing the number of spheres, the porosity of the bottom, water levels, and the breaking condition of the solitary waves (non-breaking or breaking). The motion of the spheres is tracked using a color-detection-based image-processing algorithm. The experiments reveal four significant results: (i) The rate of damping on the porous bottom is 1.65 times of impermeable bottom on average. (ii) The water level changes the characteristics of the motion of the spheres significantly due to the friction forces and vortex structures created by the interaction of waves with moving spheres. (iii) The dimensionless terminal velocities of the spheres in the non-breaking cases are 1.38 times of breaking solitary wave cases on average. (iv) The type of solitary wave and the water level significantly affect the collision behavior; however, the bottom condition does not have an apparent contribution to the collision behavior.

Challenges of Teaching Control Engineering to Seafarers According to IMO – STCW 2010 Convention During the Mutated Corona Virus (COVID – 19) Pandemic

Mutated corona virus (COVID – 19) pandemic waves attack has significant impact in the maritime sector, and disrupted the smooth functioning of various teaching activities. Following precautionary extra – ordinary measures to limit the spread of infections, on – line implementation to the IMO- STCW 2010 convention was achieved to convey knowledge and proficiency regardless of lecturer’s, candidate’s, and instructor’s capabilities and experience in technological competencies as regard to readiness, accessibility, and platform. The present work is practically based, that is containing enough theories to present adequate understanding of the conceptual relations and cognitive processes. The curricula is complaint with the mandatory minimum requirement for certification for electrical, electronic, and control engineering at the operational and management levels for both principles and practical knowledge for targeted engineering cadets. Barriers in implementing the complete requirements of the IMO- STCW 2010 online encompass: evaluating and assessment lecturer’s and cadet’s satisfaction level, insufficient teaching hours allocated, evaluating teaching syllabus and lecturer’s confidence, reaction and participation, poor or even limited direct communication between lecturers and cadets, difficulty adjusting learning style, technical difficulties faced by lecturers in online teaching and assessments

Theoretical Hydrodynamic Analysis of a Surface-Piercing Porous Cylindrical Body

In the present study, the diffraction and the radiation problems of water waves by a surface-piercing porous cylindrical body are considered. The idea conceived is based on the capability of porous structures to dissipate the wave energy and to minimize the environmental impact, developing wave attenuation and protection. In the context of linear wave theory, a three-dimensional solution based on the eigenfunction expansion method is developed for the determination of the velocity potential of the flow field around the cylindrical body. Numerical results are presented and discussed concerning the wave elevation and the hydrodynamic forces on the examined body for various values of porosity coefficients. The results revealed that porosity plays a key role in reducing/controlling the wave loads on the structure and the wave run-up, hence porous barriers can be set up to protect a marine structure against wave attack.

Hydrological control shift from river level to rainfall in the reactivated Guobu slope besides the Laxiwa hydropower station in China

Landslides are common geohazards associated with natural drivers such as precipitation, land degradation, toe erosion by rivers and wave attack, and ground shaking. On the other hand, human alterations such as inundation by water impoundment or rapid drawdown may also destabilize the surrounding slopes. The Guobu slope is an ancient rockslide on the banks of the Laxiwa hydropower station reservoir (China), which reactivated during the reservoir impoundment in 2009. We extracted three-dimensional surface displacements with azimuth and range radar interferometry using European Space Agency's Copernicus Sentinel-1 and German Aerospace Center's TerraSAR-X data during 20152019. The upper part of the Guobu rockslide is characterized by toppling and is mostly subsiding with maximum rates over 0.4 m/yr and 0.7 m/yr in the vertical and horizontal directions, respectively. During filling of the reservoir prior to 2014, there was a long-wavelength in-phase response between rising reservoir level and GPS-observed increased slope movements. After the reservoir water level stabilized from 2015 to 2019, the slide movement became seasonal and we see a correlation between rainfall and landslide movement. These observations suggest that the slide motion is now primarily controlled by rainfall. The spatiotemporal landslide displacements allow us to estimate the hydraulic diffusivity of the rock mass, to be on the order (~1.05 × 10‐7 m2/s) and the thickness of the moving rock mass (~200 m). Our results demonstrate that InSAR is a useful tool for monitoring the rockslide movement as a function of seasonal precipitation.

Armor Damage of Overtopped Mound Breakwaters in Depth-Limited Breaking Wave Conditions

Armor damage due to wave attack is the principal failure mode to be considered when designing conventional mound breakwaters. Armor layers of mound breakwaters are typically designed using formulas in the literature for non-overtopped mound breakwaters in non-breaking wave conditions, although overtopped mound breakwaters in the depth-induced breaking wave zone are common design conditions. In this study, 2D physical tests with an armor slope H/V = 3/2 are analyzed in order to better describe the hydraulic stability of overtopped mound breakwaters with double-layer rock, double-layer randomly-place cube and single-layer Cubipod® armors in depth-limited breaking wave conditions. Hydraulic stability formulas are derived for each armor section (front slope, crest and rear slope) and each armor layer. The front slope of overtopped double-layer rock structures is more stable than the front slope of non-overtopped mound breakwaters in breaking wave conditions. When wave attack increases, armor damage appears first on the front slope, later on the crest and, finally, on the rear side. However, once the damage begins on the crest and rear side, the progression is much faster than on the front slope, because more wave energy is dissipated through the armored crest and rear side.

Reliability Analysis of Revetments near Canti Pier, South Lampung

Canti pier is located in Southern Lampung and faces the Sunda strait water areas. Locals use this pier sailing to Sebesi island, and tourists need it as the closest starting point from the mainland to explore Krakatoa’s natural reserve. As a volcano tsunami occurred last December of 2018, Canti was one of the affected locations. Previous study shows measured wave height of 3-7 m in Way Muli and Kahai beach, located around 10 km from Canti. Field observation clearly shows the damaged concrete structure of the T-shaped Canti pier’s end tip due to the tsunami. This research focuses on analyzing the reliability of the north and south revetments of the Canti pier that still exists using statistic and probability methods. Van der Meer’s rock stability formula is adopted as the basis of determining the Limit State Function (LSF). For the reliability method, the FORM (First Order Reliability Method) is applied and produces the probability of failure of the revetment’s system during particular designed service times. The result shows that the northern revetment is relatively more robust than the southern revetment as its probability of failure is slightly lower. The expected failure probabilities are acceptable during regular operation for both revetments (less than 15%). If there is a stormy condition, the chance of collapse south revetment is relatively higher. One could also foresee the total collapse of revetments if tsunami waves attack. This condition also describes the 2018 tsunami wave height in Canti is much lower than in Way Muli since this area is sheltered by some islands, such as Sebuku and Sebesi. To conclude, considering the normal wave condition, the revetment’s structures are still reliable. However, if extreme waves occur, the revetments’ reliability is noticeably low or even unreliable (tsunami waves).

The failure of NSW coastal management reform

In New South Wales (NSW), Australia, awareness of coastal erosion and shoreline recession had its genesis in the late 1920s when storms damaged houses at Collaroy one of Sydney’s northern beaches (Figure 1). At about the same time the Coogee “Fun” Pier, located on a southern Sydney beach and built between 1924 and 1928, was so damaged by wave attack that the remains had to be removed in 1934. Again in 1945 a new seawall at Cronulla, another southern Sydney beach, was damaged beyond repair and at the same time more houses were lost at Collaroy. This was followed in 1967, 1974, and 1978 by major erosion events that threatened both houses and high-rise buildings at Collaroy, resulted in the loss of houses at Bilgola, a northern Sydney beach and in 1978 the loss of houses at Wamberal, 46 km north of Sydney Harbour (Table 1). Unlike the United States of America (USA) where coastal management comes under both federal and state jurisdictions, in Australia it is the province of the governments of each of the states. The federal government does provide some aspirational guidance, but not significant legislative or financial support. There is also no equivalent to the U.S. Army Corps of Engineers to provide project delivery services. In Australia, the states devolve delivery down to local councils through Acts of Parliament and formal policies that can also have legislative force. However, the failure of the State of NSW to provide all the legislative tools necessary to effectively manage coastal matters at a local council level results in coastal management being abdicated rather than delegated by the state, particularly in relation to private development.

Nature-Based Coastal Protection by Large Woody Debris as Compared to Seawalls: A Physical Model Study of Beach Morphology and Wave Reflection

Anchored Large Woody Debris (LWD) is increasingly being used as one of several nature-based coastal protection strategies along the north-western coasts of Canada and the US. As an alternative to conventional hard armoring (e.g., seawalls), its usage is widely considered to be less harmful to the coastal ecosystem while maintaining the ability to protect the beaches against wave attack and erosion. The effects of seawalls on beaches have been extensively studied; however, the performance and efficacy of LWD and its potential as a suitable alternative to seawalls (and other shoreline protection structures) are still understudied in current research. This paper presents and compares the effects of a conventional vertical seawall with two different LWD structures on beach morphology and wave reflection through large-scale physical modeling in a wave flume at a 1:5 scale. An assessment of techniques used to measure beach morphology and an assessment of model effects were included in the study. It was found that the wave reflection could be reduced by using a single log instead of a wall structure, while changes in the beach morphology response largely depended on the type of the LWD structure. A stacked log wall showed near-identical behavior as a conventional seawall. Visible model effects from the experiments, including the effect of the flume sidewalls on the beach morphology, were quantified and analyzed to inform future research.

Hydrodynamic characteristics of vertical and quadrant face pile supported breakwater under oblique waves

This paper presents the results from a comprehensive experimental study on the Quadrant Face Pile Supported Breakwater (QPSB) in two different water depths exposed to three different oblique wave attacks. The results are compared with that for a Vertical face Pile Supported Breakwater (VPSB) for identical test conditions. The paper compares the reflection coefficient, transmission coefficient, energy loss coefficient, non-dimensional pressure, and non-dimensional run-up as a function of the relative water depth and scattering parameter. The results obtained for QPSB are validated with existing results. The salient observations show that QPSB experiences better hydrodynamic performance characteristics than the VPSB under oblique waves.

Study of the Failure Mode of a Jointed Rock Mass due to a Stress Wave

The mechanical response and failure process of a jointed rock mass subjected to dynamic loading is very important for the safety and stability of rock engineering projects. In this study, we use RFPA2D-Dynamic, a rock dynamic failure process analysis platform, to establish a two-dimensional impact model of a jointed rock mass to analyze the mechanism of crack propagation in a jointed rock mass with preexisting cracks under dynamic loading. We discuss the influence of the stress wavelength and precrack inclination on the dynamic failure process and mode of the rock mass and compare this failure process with the failure model under static loading. The results show that the dynamic failure process and crack initiation type of a jointed rock mass are closely related to the stress wavelength. For a given peak, as the stress wavelength increases, the failure mode changes from local cracking that occurs above the precracks to a global instability caused by wing cracks. Meanwhile, as the wavelength increases, the shear cracks and mixed tensile-shear cracks generated at the two ends of the precracks are replaced by tensile cracks. The precrack inclination on a jointed rock mass mainly affects the strength of the jointed rock mass and the final failure mode. Specifically, when the joint inclination is small, the rock mass is severely damaged in the region above the precracks because the stress wave forms a region of cracks with a concentrated distribution. As the joint inclination increases, the damaged region becomes larger while the rock mass is less prone to failure; the strength of the rock mass gradually increases, and the wing cracks produced at the two ends of precracks propagate toward the upper and lower ends of the rock mass. However, when the stress wavelength is small, the precracks of different inclinations form cracks in the region above the precracks with a length similar to the precracks. For this condition, the propagation of the cracks is mainly controlled by the stress wavelength, while the influence of the inclination of the precracks is not significant. There is a significant difference between the failure modes of a rock specimen under dynamic loading or static loading because the stress wave produces a reflected tension wave in the direction parallel to the wave attack of the joint plane, which leads to spalling, while the wing cracks are more likely to occur under static loading.

WHY MUCORMYCOSIS(BLACK FUNGUS) CAN NOT BE DECLARED AS EPIDEMIC IN INDIA

WHY MUCORMYCOSIS(BLACK FUNGUS) CAN NOT BE DECLARED AS EPIDEMIC IN INDIA

Calibration and preparation of field measurements of oblique wave run-up and overtopping on dikes using laser scanners

Wave overtopping is typically measured in the field using overtopping tanks. In this paper, an alternative system is developed that uses two laser scanners. The system also measures wave run-up, as well as run-up depths and velocities, both during perpendicular and oblique waves on a dike in the field. The paper considers the first calibration tests with the system in the field, with perpendicular and oblique waves generated by the wave run-up simulator on a grass dike slope. Furthermore, simulations are performed with the numerical wave model SWASH, to gain more insight in the potential performance of the system during actual oblique wave attack during a storm. The run-up is determined from the measured elevation and reflection intensity, which agrees well with the visually observed run-up. Run-up depths and front velocities can be determined accurately as well. The (virtual) wave overtopping discharge can be calculated from the data, which agrees well with the most commonly used overtopping equations for perpendicularly incident waves. Finally, from the simulated run-up data of obliquely incident waves, it is concluded that an estimate can be obtained of the incident wave period and wave angle of incidence at the toe of the structure.

Behaviour and performance of a dynamic cobble berm revetment during a spring tidal cycle in North Cove, Washington State, USA

In many places, sandy coastlines and their associated assets are at high risk of erosion and flooding, with this risk increasing under climate change and sea level rise. In this context, dynamic cobble berm revetments represent a potentially sustainable protection technique to armour sandy beaches, reduce wave runup and protect the hinterland against wave attack. However, the behaviour and performance of such structures is not well understood. The dynamic cobble berm revetment located in North Cove, WA, USA, was monitored over a spring tidal cycle in January 2019. A representative 60 m alongshore section was monitored over 10 days using 2D laser scanner (lidar) measurements, GPS ground elevation surveys, Radio Frequency Identification of individual cobbles and revetment thickness measurements. These data were used together to assess the dynamic behaviour and functionality of the revetment throughout the experiment. Over the course of the experiment, the surface elevation changed by up to ±0.5 m, and the revetment volume reduced by an average 0.67 m3/m. These changes were found to be caused by relatively large significant wave height and high water levels. The revetment demonstrated a dynamic stability and the capacity to quickly reshape under changing hydrodynamic conditions. The instrumented cobbles were transported along and cross-shore and accumulated at the toe of the revetment, but were never transported seaward of the toe. The revetment also managed to recover some of the lost volume under moderate wave conditions. The revetment behaviour was found to be influenced by variation in the cobble-sand matrix. The underlying sand dynamics – i.e., accumulation or removal of sand within the cobbles – were found to govern the overall volume changes and were important to the overall stability of the revetment. Seven possible transport regimes were identified, and a model of the internal sand dynamics was developed. During the spring tidal cycle measured here, the revetment protected the sand scarp immediately landward and prevented flooding of the hinterland, while armouring the underlying sand. Over time, renourishment will likely be required due to longshore sediment transport, and preliminary guidelines for this and other aspects of design are suggested.