Waves In Seawater Research Articles

Dynamic response and performance assessment of subsea sandwich pipelines with different interlayer subjected to underwater explosion

The sandwich pipelines have been developed and applied in subsea due to their better resistance than single-layer pipelines. Explosive shock loads can cause fatal damage to subsea pipelines, thus the objective of this paper is to systematically evaluate the safety of subsea sandwich pipelines under explosion loading. The uniqueness of this study is to analyze the dynamic response of sandwich pipeline filled with different interlayer materials subjected to underwater explosion, especially considering the fluid-solid interaction (FSI) effect. Based on the Arbitrary Lagrangian-Eulerian (ALE) algorithm, the propagation of the blast shock wave in sea water and the FSI effect with the pipeline were investigated by using LS-DYNA code. The accuracy of the numerical method was verified, and then the evolution of the explosive pressure in sandwich pipes with different interlayer material was simulated. The energy absorbing capacity of each layer was analyzed. The structural dynamic response and deformation of the subsea sandwich pipelines was investigated by considering the influencing factors including the diameter-to-thickness ratio (λ) of the inner pipe and outer pipe, the interlayer material, and the explosive charge (Me). The results show that with the increase of λ and Me, the ovality of the pipe increase correspondingly. Moreover, the results demonstrate that with different material as the interlayer, each layer of the sandwich pipe shows different ability to absorb the internal energy caused by explosive shock wave, thus the deformation of the pipe differs significantly. This study can provide a reference for the optimized design of subsea sandwich pipelines to support the operational safety of deep-sea pipeline systems.

Rancang Bangun Instrumen Pengukur Tinggi Gelombang Permukaan Laut Menggunakan Sensor IMU GY955

Ocean waves are an up and down movement of sea water that occurs due to several factors such as wind, sun and moon gravity, volcanic eruptions or earthquakes at sea, moving ships, and so on. Information about the structure of sea water waves off the coast is very useful for human activities related to the sea such as fishing, shipping, and other activities. Based on this, it is necessary to have a tool that can monitor the height of the tides and low tides. The purpose of making this device is to determine the characteristics of sea water waves directly (real time) in order to determine the right time to sail off it was found that there is a difference in the maximum wave height reading of ±8 cm and an average difference of ±5 cm. While the difference in readings of wave crests has a maximum difference of ±7 cm and an average difference of ±4 cm.

The effect of square submerged breakwater on wave transmission in the coastal area

A transmission wave is a transmission wave that passes through an obstacle where its parameter can be expressed as the ratio of the transmitted wave height (Ht) to the incident wave height (Hi). Waves can occur due to wind, tides, artificial disturbances such as ship movements and earthquakes. To reduce wave energy coming from the high seas, a breakwater can be installed. The breakwater is a building that functions to break the waves of sea water, thereby reducing the energy in sea water waves. The aim of this research is to understand the wave transmission with an asymmetrical sinking structure with a square shape which is varied with respect to the length of the model. This research was conducted with a sinking square-shaped breakwater model. The results of this study indicate that the size of the transmission coefficient is influenced by the length of the model and the water depth of the sinking breakwater model. The longer the model arrangement installed, the greater the transmission coefficient, as if the water depth increases, the transmission coefficient will also increase.

PERBANDINGAN MODEL JARINGAN SYARAF TIRUAN DENGAN ALGORITMA LEVENBERG-MARQUADT DAN POWELL-BEALE CONJUGATE GRADIENTPADA KECEPATAN ANGIN RATA-RATA DI KOTA SEMARANG

Wind is one of the most important weather components. Wind is defined as the dynamics of horizontal air mass displacement measured in two parameters, namely speed and direction. Wind speed and direction depend on the air pressure conditions around the place. High wind speed intensity can cause high sea water waves. To estimate wind speed intensity required a study of wind speed prediction. One of method that can be used is Artificial Neural Network (ANN). In ANN there are several models, one of which is backpropagation. Thepurpose of this researchis to compare between backpropagation model with Levenberg-Marquadt and Powell-Beale Conjugate Gradient algorithms. The results of this researchshowing that Powell-Beale Conjugate Gradient better than Levenberg-Marquadtalgorithms. The best model architecture obtained is a network with two input layer neurons, six hidden layer neurons, and one output layer neuron. The activation function used are the logistic sigmoid in the hidden layer and linear in the output layer. MAPE value based on the chosen model is 0,0136% in training process and 0,0088% in testing process.

The Influence of Rock Resistance for Geomorphology of Krakatau Islands, South Lampung District, Lampung Province

Krakatoa Islands is one of the results of high activity volcanic islands located in the Sunda Strait, Indonesia. Volcanic activity of the research area is highly influential on the typical morphological conditions. Rocks produced from this volcano activity a role in the formation of geomorphology that is typical of areas with high volcanic activity. Rocks in the study area were the result of volcanic activity such as lava, pyroclastic alluvial. Geomorphology analysis was conducted by analyzing river flow pattern, slope criteria analysis and shoreline analysis since 1984. East Anak Krakatoa island which is dominated by lava, in contrast to the krakatoa west of which the rock formers are dominantly pyroclastic fall. Unconsolidated rocks form west Sertung island, east Panjang island and south Rakata island which the rock formers are dominantly pyroclastic flow. Evidence of 1883 catastrophic eruption is highly visible on the north Rakata island, east Sertung island and west Panjang island shown by vertical high cliff which is indicated as a caldera structure. The results of the geomorphological analysis are poured into geomorphological maps. Geomorphology unit in research area consist of 9 (nine) geomorphology units of Krakatoa Islands. Krakatoa Islands in this geomorphological case, is still controlled by climate change, erosional of sea water wave, 1883 catastrophic eruption which produces rock in the form of lava and pyroclastic and volcanic activity still continues to this day.

TIPOLOGI, DINAMIKA, DAN POTENSI BENCANA ALAM DI KAWASAN PESISIR KABUPATEN TULUNGAGUNG

This study aims to determine the typology, dynamics and potential of natural disasters in the coastal area of Tulungagung Regency, East Java Province. The results of this study indicate that the typology in the coastal area of Tuluagung Regency consists of structurally shaped coast, wave erosion coast, marine deposition coast, land erosion coast, sub aerial deposition coast and several forms of typology impact from human activities utilizing coastal resources. The form of dynamics that develop in the coastal area of Tulungagung Regency is generally influenced by environmental conditions, factors of sea water waves and human activities in meeting the needs of life as well as for meeting the means of tourism development. While the potential for disasters in the coastal areas of Tulungagung Regency such as tsunami, abrasion, and sea water intrusion.

Self-Organized Proactive Routing Protocol for Non-Uniformly Deployed Underwater Networks.

Electromagnetic (EM) waves cannot propagate more than few meters in sea water due to the high absorption rate. Acoustic waves are more suitable for underwater communication, but they travel very slowly compared to EM waves. The typical speed of acoustic waves in water is 1500 m/s, whereas speed of EM waves in air is approximately 3 × 108 m/s. Therefore, the terrestrial wireless sensor network (WSN) protocols assume that the propagation delay is negligible. Hence, reactive protocols are deemed acceptable for WSNs. Other important issues related to underwater wireless sensor networks (UWSNs) are determining the position of the underwater nodes and keeping a time synchronization among the nodes. Underwater nodes can neither determine their position nor synchronize using Global Navigation Satellite Systems (GNSS) because of the short penetration of EM waves in sea water. The limited mobility of UWSN nodes and variation in the propagation speed of acoustic waves make time synchronization a challenging task for underwater acoustic networks (UASNs). For all these reasons, WSN protocols cannot be readily used in UASNs. In this work, a protocol named SPRINT is designed to achieve high data throughput and low energy operation in the nodes. There is a tradeoff between the throughput and the energy consumption in the wireless networks. Longer links mean higher energy consumption. On the other hand, the number of relay nodes or hops between the source node and the final destination node is a key factor which affects the throughput. Each hop increases the delay in the packet forwarding and, as a result, decreases the throughput. Hence, energy consumption requires the nearest nodes to be chosen as forwarding nodes, whereas the throughput requires the farthest node to be selected to minimize the number of hops. SPRINT is a cross-layer, self-organized, proactive protocol which does not require positioning equipment to determine the location of the node. The routing path from the node to the gateway is formed based on the distance. The data sending node prefers to choose the neighbor node which is closest to it. The distance is measured by the signal strength between the two nodes.

Modeling and simulation of hydro-acoustic signal propagation in the Romanian Black Sea coast

Sound energy is the primary method of detecting and locating submarines and mines. The study of the propagation of sound waves in sea water is the most important issue in assessing sonar systems performances. The variation of the sound speed in the marine environment radically influences the propagation paths of the acoustic signals. This paper presents a modeling and simulation model of hydro-acoustic signal propagation for a specific sound speed profile from the Romanian Black Sea shore.

Numerical investigation of the stability of armour units in low-crested breakwaters using combined SPH–Polyhedral DEM method

Low-crested breakwaters have become more attractive because they do not hinder the beautiful coastal landscape and are more environmentally friendly comparing to traditional breakwaters. The available formulae for design of these types of structures mainly focus on wave transmission, reflection and dissipation aspects. However, stability of the armour blocks are not directly taken into account in the design process. In this study the Lagrangian meshfree method of SPH along with a discrete element method i.e. Polyhedral DEM are used to simulate the interaction between the sea water waves with different characteristics and low-crested breakwaters constructed using cubic armour blocks. SPH is used for computing the wave forces and moments applied to each armour unit subjected to sea wave action under various conditions. The fluid velocity and pressure time series near the armour units are calculated and based on those, the applied forces and moments are determined. Stability analysis for armour units are conducted by employing DEM which can determine whether the armour units can be displaced by wave action, a phenomenon that causes failure of the whole breakwater over time. Based on the results of a large number of numerical simulations, a practical non-dimensional relationship is proposed for calculating the required dimension of the cubic armour units that can be used for preliminary design of low-crested breakwaters. The newly proposed relationship can fill the gap that currently exists in the literature regarding using cubic armour units for this type of marine structures.

Sea Urchin (Echinoidea) Distribution and Abundance in the Intertidal Zone of Bengkayang Regency

Sea urchins is the member of Echinoidea. This species can be found in tropical marine water to the poles. The study aimed to know the types, the abundance and spread of sea urchins in Bengkayang Regency. The research, used the transect method. Each station consisted of 3 transects with a length of 50 meters from the shore into the sea with the distance of 10 meters among the transects. This research obtained five species consisting of three species of the Diadema (genus) and two species of the Echinotrix (genus) i.e. Diadema antillarium, D. savignyi, D. setosum, Echinotrix calamaris and E. deadema. The density of sea urchins in Lemukutan Island ranges from 273 – 453 ind/Ha. The Density of sea urchins on Penata Kecil island ranges from 167 - 347 ind / Ha and on Penata Besar Island has a range from 307 - 387 ind/Ha. The highest diversity of sea urchins was found in Penata Kecil Island of (1.2355). The distribution of sea urchins in Lemukutan and Penata Besar Island was categorized into clumped and evenly distributed, while the distribution of sea urchin on Penata Kecil Island is included in the clustered and random categories. Distribution of sea urchins on the island is influenced by several factors such as sea water waves and food contained in the environment.

ECONOMIC VALUATION OF MANGROVES FOREST RESOURCES IN REGENCY OF BANGGAI DAN BANGGAI ISLAND CENTRAL SULAWESI

This study aims to determine how big the value of the total economic benefits of mangrove forest by using the concept of economic valuation to calculate the value of the benefits of natural resources which exist in 9 District of Banggai Regency and Banggai Island Regency located in Peleng Strait Costal Area there are: District of Batui Selatan, Batui, Luwuk Timur, Lamala, Masama, Balantak, Bualemo (in Banggai Regency Area) and District of Buko and Buko Selatan (Banggai Island Regency). The research was conducted in August to November 2016, by conducting field observations and interviews directly to the community and local government. Based on the results obtained that indicate the area of mangrove forest ecosystems in Peleng Strait Costal Area with a broad ± 167 ha, have total value of economic benefits amounted Rp 26,591,841,888/year with the largest contributor to the value of benefits is from the value of indirect benefits that is the value of the benefits of mangrove forests as a buffer abrasion or sea water waves is about Rp 16.030.000.000. The total value of economic benefits can be used as a reference or basic comparison for the community and the government in determining the policy management and utilization of existing mangrove forests. Keywords: mangrove forest ecosystems, benefits value, economicvaluation

Erosion as a possible mechanism for the decrease of size of plastic pieces floating in oceans

A sea water wave tank fitted in an artificial UV light weathering chamber was built to study the behaviour of polypropylene (PP) injected pieces in close ocean-like conditions. In air, the same pieces sees a degradation in the bulk with a decrease of mechanical properties, a little change of crystal properties and nearly no change of surface chemistry. Weathering in the sea water wave tank shows only a surface changes, with no effect on crystals or mechanical properties with loss of small pieces of matter in the sub-micron range and a change of surface chemistry. This suggests an erosion dispersion mechanism. Such mechanism could explain why no particle smaller than about one millimeter is found when collecting plastic debris at sea: there are much smaller, eroded from plastic surfaces by a mechano-chemical process similar to the erosion mechanism found in the dispersion of agglomerate under flow.

Controlling the failure of marine structures attached to the bottom of the sea under dynamic loading

PurposeAnalysis of designing and controlling the failure of marine structures attached to the bottom of the sea under dynamic load obtained from the sea waves is one of the main engineering challenges in recent years. The circumstances of the onshore marine structures have their own complexity and the difficulty due to the effect of hydrodynamic factors and dynamic responses which are dominant in the marine environment. The paper aims to discuss these issues.Design/methodology/approachThe structure elements are composed of the metal pipe with a length of 5 m, outside diameter of 20 cm and thickness of 1.5 mm. the failure control with a safety factor of 2 indicates the absence of the above marine structure failure. It has been diagnosed to be trustworthy and reliable.FindingsIn this study, the control of marine steel structure failure with the height of 60 m under the dynamic load of the sea water waves having sinusoidal shape in the Caspian Sea has been studied and analyzed.Originality/valueIn this paper, the minimum and maximum internal force and movement in six directions of freedom were obtained for each element. To analyze and control the failure, the combination of stresses caused by static and dynamic loads has been used. According to the regulation of 10-360-AISC, the control was conducted.

PERHITUNGAN BEBAN RANCANGAN (DESIGN LOAD) KONSTRUKSI KAPAL BARANG UMUM 12.000 DWT BERBAHAN BAJA MENURUT REGULASI KELAS

The ship’s design load to be affected by some factors such as; the inside force of ship, the outside force of ship, the kind of ship, the ship’s length, the comparison of ship’s dimension, the sea water waves, and the corrosion of steel. The design load of ship’s weather deck area (PD), the design load of ship’s bottom area (PB), although the design load of ship’s side area (PS) becomes parameter factor to calculate the ship’s construction. The subject of design load calculation is the general cargo ships with main dimension as : Loa = 131,273 m, Lpp = 122, 360 m, B = 19,50 m, H = 11,138 m, T = 8,77 m, Cb = 0,74, dwt = 12.000 tons, displacement = 15.875 tons, speed = 13 knots, Cm = 0,98, Cw = 0,83, ME = 6.700 hp. The calculation of of ship’s design load had many results such as : the design load of weather deck (PD) likes; the mean of PD = 107,851 kN/m2, the PD of after peak area = 9,99 % more than the PD of middle area, because the super structures likes ; poop deck, bridge deck, navigation deck, and wheel house to be supported by the deck plate of after peak area. Also the PD of fore peak area = 64, 00 % more than the PD of middle area, because location of the deck plate of fore peak area to the fore castle deck although the windlass to be close to one another, of course the deck plate of fore peak area support both of them. The design load of ship’s bottom area (PB) likes ; the mean of PB = 126, 515 kN/m2, the PB of after peak area = 13, 93 % more than the PB of middle area, because location of the after peak bottom plate to the engine room, the propeller, although the rudder to be close to one another, of course the bottom plate of after peak area can absorb the main engine vibration, the propeller vibration, although the rudder vibration. The PB of fore peak area = 29,50 % more than the PB of middle area, because part of the bottom plate of fore peak area becomes the stem plate, and then the stem plate to be striked by the sea water waves when the ship voyage on the sea.The design load of ship’s side area (PS) likes ; the mean of PS = 98, 471 kN/m2, the PS of after peak area = 11, 53 % more than the PS of middle area, and the PS of fore peak area = 20, 80 % more than the PS of middle area. The reason of them to be same with PD although PB before. More over, the mean value of PB more than the value of PD althought PS, the deferences value to be affected by the factor of steel corrosion and the factor of sea water wave. Also the mean PS value less than the mean value of PB althought PD, the deferences value to be affected by distance of the ship’s side plate to the ship’s longitudinal netral axis to be close to one another.

FAKTOR-FAKTOR YANG MEMPENGARUHI BEBAN RANCANGAN (DESIGN LOAD) TERKAIT DENGAN PERHITUNGAN KONSTRUKSI KAPAL- KAPAL NIAGA BERBAHAN BAJA MENURUT REGULASI KLAS

The ships construction system must be hold against the inside force of ship although the outside force of ship. The inside force of ship come from the the force of ships lightweight components, and the force ships deadweight components. While the outside force of ship come from the sea water wave and the air flow against the ships hull when the ship is sailing. The influence factors of design load of ships construction calculation such as: the kind of ship, the load force against the ships hull, the length area of ship likes after peak, middle, and fore peak, the area of sea water, the comparison of ships dimension (length/depth), the kind of steel, and the corrosion of steel

Enhancement of Sea Wave Potential Energy with Under-Sea Periodic Structures: A Simulation and Laboratory Study

This paper is devoted to a theoretical investigation on the wave amplitude enhancement of surface sea water waves with under-sea periodic arrays of cylinders. A two-dimensional shallow water wave equation is derived and solved by using the plane-wave expansion method. The lattice types studied here include triangular, square and hexagonal lattices. These under-sea structures alter the sea bottom topography and induce constructive interference on the surface water waves. Given that the wave potential energy is dependent on the square of the wave amplitude, this mechanism can thus be used to increase the potential energy. It is shown that the enhancement factor depends on two geometric parameters and the maximum wave amplitude can be found by adjusting the two geometric parameters. Among the lattice types, the triangular and square lattice structures can induce more wave amplitude enhancement (and thus potential energy) than the hexagonal structures. Guided by numerical simulations, we have performed a reduced-scale water tank experiment to demonstrate the feasibility of the proposed idea. Preliminary experimental results show promising evidence of the predicted wave amplitude enhancement, suggesting perspective real-scale nearshore deployment and test.

Capacity Estimation of the Very Short-Range Electromagnetic Underwater Channel Based on Measurements

The significant attenuation experienced by electromagnetic waves in sea water is the main reason why acoustic waves are generally preferred in underwater communication. Nevertheless, acoustic waves have various drawbacks. For example, they are negatively affected by factors such as mechanical noise, slow propagation speed, and, particularly, low bandwidth, which leads to digital links at a lower bit rate. However, in short-range links, these problems can be overcome by reconsidering the use of electric current communications. For instance, data collected by remote-control vehicles in offshore oil and gas and renewable energy plants can be transmitted at distances of even 1 m or less. This study uses previous frequency response measurements taken in deep water to explore the capacity of a short-range electromagnetic underwater channel. Because of water movement, the nonstatic position of the vehicle when the transmission occurs means that the channel is regarded as randomly time-variant. A statistical model is proposed and the ergodic capacity is calculated for a 7 MHz bandwidth channel at distances ranging from 0.5 m to 5 m as well as for different values of transmitter power. The results of this study reflect capacity values of tens of kbps at distances of approximately 5 m to several Mbps at distances of less than 1.5 m.

옵티컬 플로우와 마스킹에 의한 실시간 인터렉티브 비디오 개발

최근의 기술발달은 개인용 컴퓨터를 이용하여 실시간 영상처리 및 특수효과 처리를 가능하게 하였다. 본 논문에서는 개인용 컴퓨터를 이용하여 제작하고 시연한 실시간 인터렉티브 비디오 시스템을 기술하고 분석한다. 본 작품의 동기는 해변에서 파도가 부서지는 시각적 모습으로 부터 파도소리를 대체하는 사운드를 생성하고 자연과 하나가 되어가는 경험을 제공하기 위한 것이다. 이를 위하여 해변의 모습을 촬영한 실사 영상을 컴퓨터 비젼 기법인 옵티컬 프로우(Optical Flow)에 의하여 처리함으로써 프레임간의 변화에 대한 정보를 얻어 이를 카메라에서 실시간으로 캡쳐 받은 관객의 실루엣 이미지와 마스킹(masking)에 의하여 결합하고 그 결과를 프로젝터를 통하여 보여준다. 결과 이미지의 특성을 반영하여 미디 피아노 사운드가 함께 생성된다. 이는 하나의 인터렉티브 비디오 작품으로써 의도된 개념을 반영하여 상호작용 공간을 창출한다. Recent advances in computer technologies support real-time image processing and special effects on personal computers. This paper presents and analyzes a real-time interactive video system. The motivation of this work is to realize an artistic concept that aims at transforming the timeline visual variations in a video of sea water waves into sound in order to provide an audience with an experience of overlapping themselves onto the nature. In practice, the video of sea water waves taken on a beach is processed using an optical flow algorithm in order to extract the information of visual variations between the video frames. This is then masked by the silhouette of an audience and the result is projected on a gallery space. The intensity information is extracted from the resulting video and translated into piano sounds accordingly. This work generates an interactive space realizing the intended concept.

Optimum inspection planning for minimizing fatigue damage detection delay of ship hull structures

Fatigue is one of the main factors which can produce cracks, and lead to failure of ships. For these structures, damage occurrence and propagation due to fatigue are affected by the action of sea water waves and the sea environment as well as operation, fabrication, and modeling of ship structures under uncertainties. In order to efficiently maintain the safety of ship structures, an optimum inspection plan should be made by considering these uncertainties using a probabilistic approach. In this paper, such an approach is presented and applied to ship hull structures subjected to fatigue. The resulting inspection plan is the solution of an optimization problem based on the minimization of expected fatigue damage detection delay. Damage detection delay will produce the maintenance delay which, in turn, is likely to endanger the serviceability and even the survival of the structure. The formulation of the expected damage detection delay includes uncertainties associated with damage occurrence, propagation, and detection. The effects of the quality and number of inspections on the optimum inspection planning are investigated. A well-balanced inspection planning is considered as a solution of an optimization problem with two conflicting criteria. This well-balanced inspection planning provides optimum inspection types and times. Furthermore, the cost-effective inspection plans are designed to provide the optimum strategy either by considering a single type or multiple types of inspections.

The effect of E-M wave's attenuation on sea surface reflectivity, emissivity and estimation of sea surface temperature

The imaginary component of the complex index of refraction denotes the attenuation of E-M waves in amplitude within the procedure of propagation in a medium. The attenuation of E-M waves in sea water is of great importance in microwave remote sensing, because the Snell's law of refraction in air–sea interface, sea surface reflectivity, sea surface emissivity and the estimation of sea surface temperature (SST) from microwave radiometer detections are all related to it. The well-known expressions of the reflectivity were derived in optics, but they cannot be applied directly to microwave remote sensing, since the E-M waves of microwave bands propagating in the sea water are greatly attenuated. In this study, a more appropriate formula of the reflectivity is proposed for the full range of E-M waves with considering the attenuation of E-M waves in the sea water. The proposed formula can be used to obtain the emissivity of sea surface, which is useful to estimate SST in microwave remote sensing. The error analysis indicates further that the proposed formula of the reflectivity is significant for improving ocean microwave remote sensing and increasing the retrieval accuracy of SST.