Dynamical loads are estimated on underwater vertical cylindrical parts of offshore platforms from the forcing of fully nonlinear internal wave motions generated by multicomponent barotropic tidal flow over topography along a vertical section for the conditions of the Sea of Okhotsk (Aniva Bay, near the south-eastern part of the Sakhalin Island shelf). The evolution of this process is analysed using numerical model of Euler equations for incompressible density-stratified fluid in a vertical plane. The intensity of pressure on lateral underwater surface and the rate inertia moment are expressed according to Morison’s formula for a cylindrical pile of 2.5 m diameter and 42 m height and computed as functions of time. They can reach values of 2.3∙10^{5} N and 4.8∙10^{6} N∙m, respectively, during the tidal cycle. The frequency of the appearance of large peak values in the internal wave velocity field and the probabilities of the corresponding high loads are also calculated.

In this paper, a brief review of theoretical and experimental studies on the effect of tsunami waves on elements of sloping structures is considered. Authors’ results of experimental and theoretical studies, which were used as the basis for guiding documents for the design of marine protective hydraulic structures and the Code of Rules “Buildings and Structures in tsunami-prone areas. Rules of Design”, published under the auspices of the Ministry of Construction and Housing and Communal Services of the Russian Federation in 2017. The influence of the roughness of structures on the magnitude of the solitary wave runup was investigated. The calculations were carried out using the long-wave model obtained by Professor Yu. Z. Aleshkov, realized by a difference scheme of the second order. In this paper, we consider protective structures in the form of a slope with a vertical wall and a slope with a berm and a vertical wall. Comparison of the calculated data with the experimental data for two relative wave heights is given. In the final part, new results obtained in the numerical modeling of tsunami based on the complete Euler equations are presented (the authors constructed a new, completely conservative second-order scheme for the numerical realization of these equations) and discusses the prospects for further study of the problem of tsunami interaction with protective structures.

]]>This work is dedicated to the studies of the soil structure changes near the marine hydrotechnical structures caused by the tsunami waves impact. The results of the experimental investigations are presented for two types of structures: for a marine ice-resistant stationary gravitational-type platform and for a bank reinforcement of the sloping type with a protective riprap layer. As the results of the experimental studies of the tsunami waves impact on the gravity-type offshore platform, the formed bed profiles were measured and their analysis was performed. The quantitative information was obtained on the degree of the soil loosening near the base of the platform. The obtained data testify to the possible independence of the soil loosening degree from the Euler number that characterizes the intensity of the wave impact on the soil. Experimental studies of the tsunami waves impact on the bank reinforcement structure of the sloping type shown that the filtration flows occurring inside the inclined facet of the structure as a result of the tsunami wave action lead to a change in the structure of the rock riprap. This increases the porosity of the soil that composes the structure. A qualitative similarity between the tsunami waves impact on the soil and on the embankment elements of the hydraulic engineering structure is noted.

]]>To reduce the wave loads on floating marine structures (like platforms, and pontoons), at present, protective barriers are used that are partially or completely impermeable. This work is dedicated to the study of the interaction between long sea waves with constructures formed by a protected structure and a protective barrier that are located above a shallow slope. The paper presents the results of experimental and numerical investigations of runup values and force impacts on a semi-submerged body over a wide range of incident wave heights for different barriers types, for different ratios between body draft and local depths, for the different distances between the barrier and the body and for other characterisitcs. Experimental studies were performed in a hydrowave laboratory in a flume with an installed vacuum wavemaker that creates tsunami-type waves. For numerical studies, we used the nonlinear model of incompressible fluid flows and a step-by-step computational algorithm using the moving grids that adapt to a mobile free boundary and condense near the structures under study. Wave generation was performed by a numerical wavemaker that simulates a real vacuum wavemaker of an experimental setup. The paper presents the values of design parameters, that allow the protective barrier to reduce the wave runup values and force impacts on the floating body.

]]>In this paper, the calculation method is described that makes it possible to determine the main characteristics of tsunami waves impact on marine hydrotechnical structures and objects located in the coastal zone. Taking into account the various forms of the objects makes the approach presented in the work useful for obtaining estimates for the solution of various applied problems including the calculating the criteria of safety of structures and objects during the planning of construction in tsunami-prone areas. The paper presents a mathematical model that is used for the quantitative describing of the process of tsunami waves interaction with marine structures and allows to determine the values of the pressure and force coefficients. Classification of offshore and coastal structures according to the degree of their permeability for the water flow is given. This classification makes it possible to identify different types of tsunami waves interaction with them. Formulas and relationships are given that allow to calculate the values of the wave loads on the structures and objects depending on their characteristics. Expressions for well-permeable objects are presented. Formulas are given for poorly permeable objects for the situation of the impact of the flow formed by the tsunami waves and for the stage of quasistationary flow around these objects.

]]>This paper presents the results of the studies of tsunami waveform characteristics obtained in laboratory conditions during propagation over a plane bed. The dependences of the rise rate of the leading wave front, the characteristics of the dispersive wave tail, the duration of the main wave impulse on its height for various water depths are investigated. Using the methods of the mathematical data processing, the mainly linear character of these dependences is shown. The paper presents a comparison of the waveform profile recorded during the experimental studies with the results of numerical calculations describing the process of wave generation by a laboratory wavemaker. These calculations were performed using mathematical models based on the potential theory of an ideal incompressible fluid (the method of boundary elements) and on the theory of a viscous incompressible two-component fluid (the method of finite differences). The obtained results can be used in engineering calculations of the characteristics of tsunami wave impacts on hydraulic structures, for approbation of numerical models that describe the generation and propagation of tsunami waves, including in the laboratory conditions. This paper continues the research of the authors’ team aimed at developing a mathematical model of the origin and propagation of solitary waves in a physical experiment.

]]>In theoretical and experimental researches of loads from a collapsed wave on marine and coastal structures from tsunami dynamic effect due to the flexibility of the structure and the foundation was not taken. The generalized dependence of the resultant pressure waves of the collapsed wave (bore) from time was established based on the analysis of modern publications. The reaction of structures to the effects of bore depends of loading and stiffness of the system «soil-construction». Numerical evaluation of dynamic effects for different values of the loading rate and the stiffness of the system, for example, of protective breakwater are made. Various ground bases corresponding to possible conditions of construction are examined. As the analyses scheme of the building there was considered an absolutely rigid body on an elastic base with two degrees of freedom — displacement in the horizontal direction and rotation in the plane perpendicular to the axis of the pier. Self-oscillations corresponding to the lower mode taking into account the inertial effects of water are considered. From the results of the article, researches have shown that, when defining loads from the bore on the protection structure should take into account their dynamic nature. For a conservative evaluation in approximate calculations it is allowed to take the value of the dynamic factor equal to two.

]]>Tsunami research is a very complex applied problem. Even a partial solution of this problem will significantly mitigate catastrophic destruction and reduce the number of human casualties after this natural phenomenon. In the process of tsunami studying physical modeling often provides the additional information for numerical simulation. First of all, this is the information about the interaction of tsunamis with the complex design constructions and possible destruction of these constructions. Such information is, in principle, can be obtained using a CFD simulation method. However, CFD model also requires verification by the laboratory data. There are many ways to conduct tsunami simulation and many methods of tsunami wave generation. The most widespread and studied way of wave generation is moving block method. The method of wave generation using special wave paddles or shields is also used. In recent times, a fundamentally new way of tsunami simulating was developed. New pneumatic tsunami generator consists of a tank with water and vacuum pump. Each of the methods has its advantages and disadvantages.

]]>Tsunamis in shallow water zones lead to sea water level rise and fall, strong currents, forces (drag, impact, uplift, etc.), morphological changes (erosion, deposition), dynamic water pressure, as well as resonant oscillations. As a result, ground materials under the tsunami motion move, and scour/erosion/deposition patterns can be observed in the region. Ports and harbors as enclosed basins are the main examples of coastal structures that usually encounter natural hazards with small or huge damaging scales. Morphological changes are one of the important phenomena in the basins under short and long wave attack. Tsunamis as long waves lead to sedimentation in the basins, and therefore, in this study, the relation to the current pattern is noticed to determine sedimentation modes. Accordingly, we present a methodology based on the computation of the instantaneous Rouse number to investigate the tsunami motion and to calculate the respective sedimentation. This study aims to investigate the effects of the incident wave period on an L-type harbor sedimentation with a flat bathymetry using a numerical tool, NAMI DANCE, which solves non-linear shallow water equations. The results showed that the corner points on the bending part of the basin are always the critical points where water surface elevation and current velocity amplify in the exterior and interior corners, respectively. This phenomenon is more obvious in wave amplification. Comparing the maximum current velocity results with the minimum Rouse number results, one can conclude that the pattern of sediment motion in the mentioned two critical corner points and in the whole basin depends on both the current pattern and magnitude. In large wave periods, the sediment motion in the exterior corner (Gauge 63) is often in the bed load form, while in the interior corner (Gauge 57) in the wash load form. This indicates that, in higher periods, the interior and exterior corners can be exposed to the sediment erosion and deposition, respectively. However, sediment motion in long wave conditions needs further analysis in closed basins, where it becomes a prominent problem for harbors and ports. Further studies on sediment motion seem necessary to determine the performance and validity of NLSWE when the volume of the transmitted sediments needs to be measured under the current behavior of the long waves. Furthermore, more investigations should be performed to analyze the behavior of L-type basins with varying depths and then applied to real harbors of this type.

]]>Tsunamis are high-impact, long-lasting disasters, which in most cases allow for only a few minutes of warning before impact. The amount of energy behind huge tsunami waves can cause severe destruction when it hits land and consequently causes massive loss of human life. The impact of tsunami can be considered in social, environmental, and economic dimensions. The social impact can be seen in destruction of life and property, health crisis and disease. Tsunamis may cause massive environmentally impact by devastating effects. In this paper, the impact of 2004 and 2011 tsunamis on coasts and constructions are evaluated from the engineeering perspective. Discussions with suggestions are presented.

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