Underwater Barrier Research Articles

Neptunus and To Løver: An Archaeological, Archival, and Dendrochronological Survey of Two Danish Prize Ships, Scuttled in the Stockholm Archipelago in 1659

Abstract We report the archaeological survey, dendrochronological analysis, and archival research concerning two shipwrecks located in shallow waters outside Vaxholm in the Stockholm Archipelago, Baltic Sea. According to oral tradition, the two wrecks are the remains of Neptunus and To Løver, two former Danish warships that were taken as prizes at the battle of Fehmarn in 1644. The Swedish navy then used the two ships until 1659, when they were reportedly scuttled as a blockage along the sea route towards Stockholm. Before being intentionally scuttled, the two ships drifted away and sank. The work presented in this article confirms the substance of the tradition and reports that substantial portions of the two ships are preserved. Moreover, the two wrecks shed light on the scuttling process and the construction of an underwater barrier.

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.

Underwater barrier deformation and destruction in the high-explosive and shaped charges blast

Underwater barrier deformation and destruction in the high-explosive and shaped charges blast

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.

Two ships under rocks: a glimpse into rural shipbuilding in western Pomerania

The wrecks of two clinker-built vessels were excavated and lifted off the coast of Mecklenburg-Western Pomerania in northern Germany as part of the archaeological mitigation procedures for the Nord Stream 2 gas pipeline project.The ships formed part of an underwater barrier created by Swedish forces during the Great Northern War in 1715. As a result of the excavation carried out by the state authority for culture and monu­ments in Mecklenburg-Western Pomerania, both wrecks were documented underwater, disassembled, lifted and studied on the surface. All ship timbers were recorded in detail using a structured-­light scanner and photogrammetry before the wrecks were moved into temporary wet storage. After completion of the marine construction project, the wrecks will be re-deposited near their original locations.

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.

Features of vortical suppression of tsunami waves 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 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.

Evolution of Underwater DBD Plasma Jet

The evolution of an underwater dielectric barrier discharge from microdischarge to plasma jet has been investigated. Images of the discharge evolution with voltage are discussed.

Morphological, bathymetric and sedimentological surveys used to assess the coastline defensive measures

This paper outlines the results of a study recently carried out on the western coast of the Sestri Levante peninsula (Eastern Liguria-Italy), aiming to assess the effects of newly accomplished defensive measures against coastal erosion: the accretion of the beach with natural sand and its protection with artificial structures orthogonal and parallel to the shoreline. Through conventional and more innovative methodologies (respectively single beam echo sounders and global positioning system) the research work has resulted in a new evaluation of the morphological, bathymetric and sedimentological features that make up this shoreline and its volumetrical change over the century. The survey and the research carried out on the studied area have enabled us to give a more detailed picture of the evolution of the littoral, to assess the possible use of “non-traditional” techniques of beach development monitoring, to evaluate the volumetric variations of the emerged and submerged beaches, to establish the sedimentological activity of the beach after the latest nourishment measures, and finally, to verify the effectiveness of the protection measures implemented on this coastline. The acquired data have been stored in the database and a geographic information system has been used to process, analyze, and evaluate the results. The main findings show that the latest intervention has brought about a new phase in the evolution of the coastline, giving rise to a new pseudo-balanced condition. The re-distribution of materials used for the beach nourishment, leads us to believe that the defence underwater barrier has only partially worked. The main conclusion for a correct coastal zone management underline the necessity to plan local and more wide monitoring during at least 8–10 consecutive years.

Evaluation of a Bypass System for Spent American Shad at Holyoke Dam, Massachusetts

Abstract A bypass system for postspawned American shad Alosa sapidissima began operation in 1980 on the Connecticut River canal system at Holyoke Dam. The purpose of the bypass was to enable downstream migrants that enter the canal to exit and avoid death due to delay or passage through hydroelectric turbines at water use facilities. The bypass system had the following elements: (1) an underwater AC electrical or acoustic barrier to prevent American shad from leaving the bypass area, (2) an underwater DC electrical field to immobilize fish for collection, and (3) a collection box with transfer pipe to carry fish to the river below the dam. During studies of the bypass system from 1979 to 1983, we found that the fish barriers were ineffective, the collection system was partially effective for American shad but not for anadromous species that passed through trashracks, and American shad could be immobilized and transported at high velocity through a pipe and have only low mortality (4–9%). Radio-tagged Amer...

Propagation of oblique incident waves past rigid vertical thin barriers

The linear theory for waves impinging obliquely on a vertical thin barrier is examined. Three types of structures are analysed: a barrier descending from the water surface to a distance, d, an underwater barrier, and a barrier with a submerged horizontal slit. Theoretical solutions are obtained by an eigenfunction expansion method for the transmission and reflection coefficients. The plane wave approximation is further examined and compared to the full solution. The distribution of the pressure along the barrier is also calculated and the maximum horizontal force is compared to the case of a vertical wall.