Underwater Barriers Research Articles

Morphology of Brine‐Seawater Interface and Spatial Distribution of Submarine Groundwater Discharge Windows in the Muddy Coast

AbstractThe brine‐seawater interface (BSI) is a unique type of groundwater‐seawater interface (GSI) characterized by the higher density of underground brine compared to seawater. This study focuses on characterizing the bay‐scale BSI morphology and identifying submarine‐groundwater discharge windows using a comprehensive in‐situ geophysical detection on the south bank of Laizhou Bay. Our findings reveal that the BSI forms an extensive mixing zone (15–20 km) without distinct contours between waters of varying salinities. The discharge windows for underground brine are located in nearshore areas with fine sand distribution and offshore pockmark areas. Hydraulic and salinity gradients drive the underground brine discharge through these windows. The aquitard window is the primary area for shallow and deep brine exchange, likely evolved from paleochannels, ancient tidal creeks, or ancient underwater barriers. These findings provide crucial modeling support for analyzing environmental evolution mechanisms and theoretical basis for planning the underground brine mining in similar coastal regions.

Cause Analysis of Salinity Intrusion by Environmental Changes Considering Water Intake and Sand Mining on Seomjin River Estuary Using Model for Maintaining Corbicula Habitats

Anthropogenic development can strongly influence natural river processes, leading to environmental changes that negatively affect important habitats and biodiversity and consequently reduce economically important natural resources. This study investigated the effects of salinity intrusion on the habitat of the clam Corbicula japonica in the Seomjin River estuarine zone. We employed the Environmental Fluid Dynamics Code (EFDC) model, which incorporates topographic data and hydrological changes, to simulate salinity. Two salinity measurement facilities were installed in Seomjin River estuarine and operated to optimize the EFDC model. The results show that reduced flow rates due to intake have a negligible impact on the increased salinity. Maintaining optimal salinity (15–20 psu) during neap tides at the Seomjin River Bridge requires constant high flow rates, which poses significant challenges. Saltwater stratification is identified as the primary cause of pronounced salinity stratification, particularly during neap tides. Addressing this issue through river discharge and intake facility operation is challenging. Structural measures, including riverbed restoration and underwater barriers, are recommended to improve resistance to seawater intrusion. Future research should aim to develop scenarios to reduce salinity, quantify the reduction efficiency, and propose region-specific measures.

Numerical simulation of long wave passage over underwater barrier

One of the ways to protect population and coastal infrastructure against a tsunami attack is massive vertical walls built around portal area or across the harbors entrance. During major tsunamis, such walls rising above the water often be ruined and fail to perform their function [1]. Compared to such protective structures, the submarine vertical barrier is more stable, although it lesser suppresses the height of tsunami wave passing above it. On the basis of energy relations for a long wave, the internal boundary conditions are formulated that realize partial reflection of the tsunami from submerged vertical barriers during wave passage above them in a course of numerical modeling. The results of calculations are well correlated with measurements of the heights of waves passing over underwater barriers during laboratory modeling in a hydrophysical flume [2]. Such protective structures are able to stop up to 45% of the energy of the tsunami wave, while reducing the height of the tsunami by 25%. A series of calculations of the tsunami wave entry into the harbors of the northeastern Japan was carried out in the presence of a virtual underwater barrier there. For different underwater wall height (relative to depth), wave amplitude was found at different points of the harbor coastline. Comparison of the obtained wave heights with the results of modeling in the absence of a barrier shows the wave suppressing effect of a protective structure of this type. It should be noted that it is not at all necessary to achieve total reduction the tsunami height down to zero with the help of protective walls. It is enough to lower the amplitude of the wave near the shore by 20-30 percent to significantly reduce the damage from this natural disaster.

Numerical Simulation of the Interaction between Solitary Waves and Underwater Barriers Using a VPM–THINC/QQ-Coupled Model

The interaction between solitary waves and underwater barriers is investigated using our in-house code, entitled VPM (volume-average/point-value multi-moment)–THINC/QQ (THINC method with quadratic surface representation and Gaussian quadrature)-coupled model. The stability and accuracy of the proposed model are validated by comparing the numerical results with those of the well established two-phase flow solver interFoam. All the results indicate that the presented coupled model has the advantage of high fidelity in simulating solitary wave propagation. Subsequently, solitary waves passing over a single underwater barrier are simulated by the present model. Numerical results are compared with experimental results in terms of the free surface elevation, velocity profile, vorticity field, and wave forces. Great agreements are obtained. In the end, the interactions between solitary waves and double underwater barriers are investigated numerically. The results reveal that the reflection coefficient increases first, and then decreases, with the increasing space between the two barriers. For cases with different wave heights, the transmission coefficient decreases monotonically, and the dissipation coefficient is opposed to the transmission coefficient.

Моделирование взаимодействия конических ударников с подводными преградами при наличии у ударников угла атаки

In this paper, the effect of the angle of impact and the angle of attack on the interaction between truncated coneshaped impactors made of BHZh-95 alloy and underwater barriers made of aluminum alloy is studied using experimental and computational methods. When such an impactor enters water, a supercavern appears around the impactor and minimizes the fluid friction. During the motion, the impactor afterbody periodically experiences impermanent contact with the walls of the supercavern, which maintains the steady motion. Note that the center of mass of the impactor is located closer to its afterbody, which can induce the angle of attack appearance during the motion. The experimental study is conducted using a hydroballistic track with high-speed video recording. The speed range of 250-350 m/s is considered. Mathematical modeling is carried out using the EFES original software package. It is revealed that a positive angle of attack β ≤ 10° leads to the normalization of the impactor and a decrease in the effective thickness of the barrier with its perforation. In contrast, at a negative angle of attack, the impactor rebounds from the barrier.

Investigation of Tsunami Waves in a Wave Flume: Experiment, Theory, Numerical Modeling

To protect the coastal areas of the seas and oceans from the destructive force of tsunami waves, coastal and surface barriers are usually built. However, for high waves, these barriers turn into underwater barriers through which tsunami waves pass practically without losing their energy. In this paper, we study a new principle of suppression of the energy of tsunami waves by underwater barriers. The problems of experimental and numerical modeling of the processes of generation, propagation, and interaction of gravity wave of the tsunami type with underwater barriers are considered. It is shown that, under certain conditions near the underwater barriers, large-scale vortex structures occur that accumulate a significant part of the energy of the incident wave. Here, if the barriers parameter h/(H + A) = 0.84 ÷ 0.85 (h—height of the barriers, A—amplitude of incident wave on a barrier, H—depth of the reservoir), then the vortex structures accumulate up to 50% of the wave energy incident on the barrier. A theoretical model explaining the effect of anomalous vortex suppression of tsunami wave energy by underwater barriers has been developed. Theoretical calculations and results of numerical modeling based on the Navier–Stokes Equations are consistent with experimental studies in a hydrodynamic wave flume.

Mathematical Modeling of the Motion of Supercavitating Strikers at Underwater Start

The paper is devoted to the investigation of the high-velocity motion of supercavitating kinetic strikers in water with account of the intraballistic processes in the powder chamber and outside the channel cut of the ballistic installation, the supercavity dynamics, and also the interaction of the strikers with underwater barriers (obstacles). The process of supercavitating motion at underwater start is modeled on the basis of solving Reynolds-averaged Navier–Stokes equations with turbulence equations and cavitation equations for a multiphase medium. To investigate the stressstrain state and a possible destruction of solid bodies in interacting with underwater barriers of various types, mathematical modeling is conducted on the basis of an elastoplastic model of a medium. The range of investigated velocities is 50–850 m/s.

Waste water discharge from a large Ni-Zn open cast mine degrades benthic integrity of Lake Nuasjärvi (Finland)

The Talvivaara/Terrafame multi-metal mining company is Europe’s largest nickel open cast mine, it is also known for the largest wastewater leakage in the Finnish mining history and a series of other accidents. In this paleolimnological study, influences of a recently constructed treated waste water discharge pipeline into Lake Nuasjärvi were investigated by analyzing past (pre-disturbance) and present community compositions of key aquatic organism groups, including diatoms, Cladocera and Chironomidae, along spatial (distance, water depth) gradients. In addition to defining ecological changes and impacts of saline mine waters in the lake, chironomids were used to quantitatively reconstruct bottom water oxygen conditions before and after the pipe installation (in 2015). The diatom and cladoceran communities, which reflect more the open-water habitat, showed only relatively minor changes throughout the lake, but a general decrease in diversity was observed within both groups. Chironomids, which live on substrates, showed more significant changes, including complete faunal turnovers and deteriorated benthic quality, especially at the sites close to the pipe outlet, where also chironomid diversity was almost completely lost. Furthermore, the reconstructed hypolimnetic oxygen values indicated a major oxygen decline and even anoxia at the sites near the pipe outlet. The limnoecological influence of the pipe decreased at sites located counter-flow or behind underwater barriers suggesting that the waste waters currently have location-specific impacts. Our study clearly demonstrates that whereas the upper water layers appear to have generally maintained their previous state, the deep-water layers close to the pipe outlet have lost their ecological integrity. Furthermore, the current hypolimnetic anoxia close to the pipe indicates enhanced lake stratification caused by the salinated mine waters. This study clearly exhibits the need to investigate different water bodies at several trophic levels in a spatiotemporal context to be able to reliably assess limnoecological impacts of mining.

Vortex suppression of tsunami-like waves by underwater barriers

A study of the energy losses of tsunami-like waves due to the formation of large eddies near the underwater barriers has been gaining importance in recent years. However, the conditions of the birth of the large-scale vortex behind the barriers are not yet fully understood. The paper presents the results of theoretical, experimental and numerical studies of the interaction between the long gravitational tsunami-like waves and the impermeable underwater barrier. The proposed mathematical model is based on the approximation of two-dimensional incompressible Navier-Stokes equations. The OpenFOAM toolbox is used to perform the numerical simulation with the method of finite volumes. The air-water interface is identified by the volume of fluid method (VOF). The numerical simulation is tested via a comparison with test activities and experiments carried out in a hydrodynamic wave flume, at the Institute of Applied Mechanics Russian Academy of Sciences. The efficiency of the underwater barrier is assessed as the percentage of the energy loss to the incident wave energy. It is shown that the barrier effectiveness depends on its relative height and the incident wave parameters. New experimental and numerical results are consistent with the theoretical model proposed earlier and research results of other authors.

Transformation of Long Surface and Tsunami-Like Waves in the Ocean with a Variable Bathymetry

We consider a transformation of long linear waves in an ocean with a variable depth. We calculate the transformation coefficients (the coefficients of transmission and reflection) as the functions of frequency and the total depth drop for three typical models of bottom profile variation: (i) piecewise-linear, (ii) piecewise-quadratic, and (iii) hyperbolic tangent profiles. For all these cases, exact solutions are obtained, analysed and graphically illustrated. This allows us to derive the transformation coefficients in the analytic form for the subsequent comparison with the results of approximate, numerical, or experimental study. We show that the results obtained are in agreement with both the energy flux conservation and Lamb’s formulae in the limiting case of zero frequency. We also study wave transformation on the underwater barriers and trenches of different shapes and compare the results obtained.

Features of Vortical Suppression of Tsunami Waves by Underwater Barriers

The features of vortical suppression of tsunami waves by an impermeable underwater barrier have been studied. The height of the barrier is close to the optimum corresponding to the maximum effect of vortical suppression of the wave energy. It is shown that the energy of suppressing tsunami waves by such a barrier depends on the wave height and can vary from zero to 80% of the incident wave energy.

Features of High-Velocity Penetration and Motion of Supercavitating Kinetic Strikers in Water

Consideration is given to conditions ensuring stable high-velocity motion of supercavitating kinetic strikers in water. To investigate the stressed-strained state and a possible destruction of solid bodies during the motion in water and in interaction with underwater barriers of various types, the authors carry out mathematical modeling based on a unified methodological approach of the continuum mechanics. The range of the velocities under study is 500–1590 m/s. Results of the group start of supercavitating strikers are given.

Influence of underwater barriers on the distribution of tsunami waves

Solitary wave propagation over underwater shelves and bumps is examined using straightforward analytical methods. Explicit solutions for wave propagation are obtained. Using the nonlinear shallow-water equations, it was found that propagation of small amplitude long waves can be well described by a linear approximation. The effects of topographical variety and proportion of underwater barriers (steps, bumps, multiple bumps) on the incident wave are demonstrated using linear wave theory. At a step, the incident wave is shown to be more strongly reflected for increased barrier size. The incident wave also transmits an amplified wave with smaller wavelength onto the obstacle. After propagating off of a bump, the wave experiences an amplitude decay. The decay rate is shown to be exponential with a variable number of bumps. Accounting for the presence of the small parameter, which represents the wave amplitude/water depth ratio, the nonlinear shallow-water equations were solved by the method of asymptotic expansions. Using the method of renormalization, a uniformly valid solution was obtained accounting for nonlinear effects in the vicinity of the sharp depth change. Far-field comparisons of the constructed solutions with the associated Riemann waves show good accuracy of the obtained solutions. Over an infinitely long shelf, the amplified transmitted wave breaks.

Reduction of a Ship's Magnetic Field Signatures

Decreasing the magnetic field signature of a naval vessel will reduce its susceptibility to detonating naval influence mines and the probability of a submarine being detected by underwater barriers and maritime patrol aircraft. Both passive and active techniques for reducing the magnetic signatures produced by a vessel's ferromagnetism, roll-induced eddy currents, corrosion-related sources, and stray fields are presented. Mathematical models of simple hull shapes are used to predict the levels of signature reduction that might be achieved through the use of alternate construction materials. Also, the process of demagnetizing a steel-hulled ship is presented, along with the operation of shaft-grounding systems, paints, and alternate configurations for power distribution cables. In addition, active signature reduction technologies are described, such as degaussing and deamping, which attempt to cancel the fields surrounding a surface ship or submarine rather than eliminate its source. Table of Contents: Introduction / Passive Magnetic Silencing Techniques / Active Signature Compensation / Summary

Numerical Simulation of the Propagation of a Solitary Wave over Underwater Barriers

The problem on the behavior of a solitary wave passing over different types of underwater barriers is considered. The problem has been solved numerically using the method of the correction of flows. The parameters of the method of solution have been selected. The results are compared with the Korteweg–de Vries theory. The interaction of two solitary waves is simulated and it is shown that they possess the properties of solitons. After the interaction, their shape and velocity remain constant; it is only the phase that undergoes a change. The case of disintegration of the initial perturbation in a cylindrically symmetric problem is considered.

WAVE DAMPING EFFECT OF SUBMERGED DIKE

Up to present, submerged dikes were mainly used as detatched breakwaters for artificial nourishment of beach or a front dikes to protect a rear main dike. However, the application of submerged dike to artificial creation of a fishing-ground has been recently taken into consideration with great interest. The following four points are considered as the characteristics of a submerged dike. (1) Wave pressure and wave force acting on a submerged dike is smaller than those on other type breakwater because its crown is below the still water level. (2) Submerged dikes damp comparatively great waves, while comparatively small waves freely pass over submerged dikes. This is the most suitable condition for the fishing-ground. Namely, slightly wavy surface of water in the fishing-groud is rather desirable from a view-point of fish ecology. (3) Submerged dikes are usually constructed at comparativel low cost because their heights are lower and wave pressure operating on them is smaller in comparison with other type breakwater. (4) Since the water depth on the crown of submerged dikes is the most important facter that determines the effect of submerged dikes against wave action, the wave damping effect of submerged dike varies according to chang of tidal level. As for study on submerged dikes, many researchers have already published the results of their investigations, such as the theoretical studies by Lamb, Jeffreys, Dean, Johnson and Fuchs, the investigation of trapezoidal and triangular underwater barriers by the B.E.B. (U.S.A.), that of rectangular barriers by Morison, that of horizontal barrier by Hein and that of submerged cylinder by Ursell. Moreover, Johnson has recently reexamined a submerged dike, and in Japan the report by Hosoi and Tominaga was already published. The causes of wave damping due to a submerged dike can be considered that it absorbs some of the incident wave energy by causing the waves to break. Some of the remaining energy is dissipated by reflection and friction on the crown of the submerged dike and some transmitted shoreward. In the published reports as previously mentioned, the transmission coefficient has been obtained mainly by the investigations of wave reflection due to the submerged dike. The theoretical analysis of breaking phenomena is very difficult because of its complication. However, the wave damping effect due to submerged dike is made remarkable by causing the wave to break on the submerged dike. From this point of view, this report mainly deals with the wave damping effect due to breaking on tbe submerged dike and offers the experimental data for the practical use.