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1

Synchronization system for underwater acoustic communications using in shallow waters

Schmidt Jan H., Schmidt Aleksander M.

Vibrations in Physical Systems

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2023

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Vol. 34, nr 1

art. no. 2023102

EN

A reliable synchronization system of the transmitted data frame has a significant impact on the efficiency of the underwater communication system. This applies in particular to communication systems dedicated to work in shallow waters, where the phenomenon of multipath permanently occurs. To overcome these difficulties, the concept of a synchronization system consisting of two broadband signals of opposite monotonicity was presented. The method of receiving these signals has been described in detail. The stochastic channel model with Rician fading and the Watermark simulator was used to test the efficiency of the synchronization system in the underwater multipath channel.

2

Development and validation of an operational fast time ship manoeuvring solver to increase navigation efficiency in horizontally restricted waterways

Kazerooni M. F., Rahimian M., Tree M., Womersley T., Jensen B.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2023

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Vol. 17 No. 1

71--76

EN

Growth of demand for containerized cargo shipping has put more ports into pressure to accommodate larger vessels. Considering the limitations on dimensions of navigation channels, this is not feasible unless aiming for significant capital dredging or alternatively creating high precision predictions of vessel motions subjected to environmental forcing and interaction with shallow and restricted waterway. NCOS ONLINE (Nonlinear Channel Optimisation Simulator) is a state of the art navigation support tool which combines DHI’s high level forecast of environmental conditions with mathematical model of ship motions to add an extra level of accuracy in predicting the under-keel clearance and vessel swept path to boost the efficiency of navigation and pilotage within restricted channels. NCOS Manoeuvring Module utilizes an autopilot scheme based on PID (Proportional / Integral / Derivative) controller and Line of Sight Algorithm to FORCE Technology’s SimFlex4 manoeuvring solver for prediction of manoeuvring ship swept path and response, which will effectively bring the accuracy of real time full bridge simulator to fast time operation support tool. In this paper, the result of mathematical model is validated against fullscale measurements of containership transits through Port of Auckland Navigation channel by comparing pilot commands, leeway drift and swept path through output of portable pilotage unit. According to the results the model is found promising to predict the behaviour of human pilots with precision required in operational use. Finally, the swept path and manoeuvring performance of a sample transit is assessed on different environmental conditions and tide stages to evaluate the safe transit windows in operation.

3

2D Modeling of Wave Propagation in Shallow Water by the Method of Characteristics

Khalilabadi Mohammad Reza

Archives of Acoustics

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2022

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Vol. 47, No. 3

407--412

EN

In this paper, a 2D numerical modeling of sound wave propagation in a shallow water medium that acts as a waveguide, are presented. This modeling is based on the method of characteristic which is not constrained by the Courant–Friedrichs–Lewy (CFL) condition. Using this method, the Euler time-dependent equations have been solved under adiabatic conditions inside of a shallow water waveguide which is consists of one homogeneous environment of water over a rigid bed. In this work, the stability and precision of the method of characteristics (MOC) technique for sound wave propagation in a waveguide were illustrated when it was applied with the semi-Lagrange method. The results show a significant advantage of the method of characteristics over the finite difference time domain (FDTD) method.

4

Underwater acoustic communication system using broadband signal with hyperbolically modulated frequency

Schmidt Jan H., Schmidt Aleksander M.

Vibrations in Physical Systems

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2021

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Vol. 32, nr 1

art. no. 2021116

EN

The implementation of reliable acoustic underwater communication in shallow waters is a scientific and engineering challenge, mainly due to the permanent occurrence of the multipath phenomenon. The article presents the concept of a transmission system using a broadband signal with hyperbolically modulated frequency (HFM) to transmit data symbols and synchronize data frames. The simulation tests were carried out in channels with Rician fading, reflecting the short- and medium-range shallow water channels. The simulation also took into account the presence of additive Gaussian noise in the channel on the functioning of the receiver. The obtained results prove the high reliability of the underwater communication system based on broadband HFM signals.

5

Observation and Modelling on the Shipping Noise in Shallow Waters with Complex Islands and Reefs of the East China Sea

Peng Zilong, Zhou Fulin, Fan Jun, Wang Bin, Wen Huabing

Archives of Acoustics

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2021

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Vol. 46, No. 2

301--311

EN

The impact of the noise radiated from merchant ships on marine life has become an active area of research. In this paper, a methodology integrating observation at a single location and modelling the whole noise field in shallow waters is presented. Specifically, underwater radiated noise data of opportunistic merchant ships in the waters of Zhoushan Archipelago were collected at least one day in each month from January 2015 to November 2016. The noise data were analyzed and a modified empirical spectral source level (SSL) model of merchant ships was proposed inspired by the RANDI-3 model (Research Ambient Noise Directionality) methodology. Then combining the modified model with the realistic geoacoustic parameters and AIS data of observed merchant ships, the noise mappings in this area were performed with N × 2D of Normal Mode calculations, in which the SSL of each ship was estimated using the modified model. The sound propagation at different receiving positions is different due to the shielding effect of islands and bottom topography. The methodology proposed in this paper may provide a reference for modelling shipping noise in shallow waters with islands and reefs.

6

Presentation of the ship squat effect as a function

Zwolan Piotr, Kacprzak Paweł

Annual of Navigation

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2021

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No. 27

28--38

EN

In this article the authors propose a change in approach when providing information included in maneuvering documents on the squat effect of a ship. The development of ships which is aimed at increasing the loading capacity contributes to the increase of their draft and construction dimensions. This fact renders it necessary to develop ports and to interfere in the bathymetric layer of the basin, i.e. its deepening. However, the under keel clearance along the ship’s route and during the port towing maneuvers is often significantly limited. This makes it crucial to adapt the speed to the sailing conditions. Knowledge of the draft change with a low water level under the keel is important for the safety of navigation. Hence, the authors proposed expanding the maneuvering information contained in the ship's documentation with the additional curve of squat effect presented in the form of polynomial functions.

7

Numerical investigating the effect of water depth on ship resistance using RANS CFD method

Hoa Nguyen Thi Ngoc, Vu Bich Ngoc, Tran Ngoc Tu, Chien Nguyen Manh, Le Tat Hien

Polish Maritime Research

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2019

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nr 3

56--64

EN

On inland waterways the ship resistance and propulsive characteristics are strictly related to the depth of the waterway, thus it is important to have an understanding of the influence of water depth on ship hydrodynamic characteristics. Therefore, accurate predictions of hydrodynamic forces in restricted waterways are required and important. The aim of this paper is investigating the capability of the commercial unsteady Reynolds– Averaged Navier–Stokes (RANS) solver to predict the influence of water depth on ship resistance. The volume of fluid method (VOF) is applied to simulate the free surface flow around the ship. The hull resistance in shallow and deep water is compared. The obtained numerical results are validated against related experimental studies available in the literature.

8

Investigation of the underwater noise associated with remotely-operated vehicles

Buszman K., Mironiuk W.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2018

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nr 54 (126)

129--132

EN

There is increasing demand for various types of submersible and floating remotely-operated vehicles which have herein been studied with respect to the threats posed by these kinds of objects. Local physical field disorder analyses have demonstrated the possibility of detecting and classifying objects based on hydroacoustics. Hydroaocoustic analysis results are presented as narrowband and One-Third-Octave spectra of different types of remotely-operated vehicles. Investigations were performed using an underwater measuring system located in very shallow water in a coastal zone characterized by conditions considered as poor for sound propagation.

9

Some notes on safety measures when approaching port of Świnoujście

Szymoński M.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2018

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Vol. 12, no. 1

77--80

EN

The paper describes new directions in which the safety of navigation in Pomeranian Bay (Poland) became into a new era since the LNG Terminal in port of Świnoujście begun to attend to a large gas tankers at around 320 meters length, 50 meters breadth, and draught of 12.5 meters. For the safety of naviga-tion in Pomeranian Bay, the Maritime Administration has modified the traffic regulations, directing the ship's traffic to the zones outside the main approaching channel. For some of the ships navigating in to Świnoujście the new regulations mean the necessity of passing the shallow waters, with all consequences of that. The most important effect, being predominating in shallow waters, it is the squat effect. This effect is causing the ship's speed reduction and the increase of fuel consumption. It is very difficult to select the influence of the squat effect from others, like weather conditions, waves high and direction, and sea keeping qualities for ships of different type. This paper is giving the contribution to deep analysis of the above, and is presenting the test results done for passenger/cargo Ferries, travelling as per regular service to the port of Świnoujście: M/F "Gryf" and M/F "Wolin".

10

Analysis and Modelling on Radiated Noise of a Typical Fishing Boat Measured in Shallow Water Inspired by AQUO Project’s Model

Peng Z., Fan J., Wang B.

Archives of Acoustics

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2018

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Vol. 43, No. 2

263--273

EN

The shipping noise near channels and ports is an important contribution to the ambient noise level, and the depth of these sites is often less than 100 m. However less attention has been paid to the measurement in shallow water environments (Brooker, Humphrey, 2016). This paper presents extensive measurements made on the URN (underwater radiated noise) of a small fishing boat in the South China Sea with 87 m depth. The URN data showed that the noise below 30 Hz was dominated by the background noise. The transmission loss (TL) was modelled with FEM (finite element method) and ray tracing according to the realistic environmental parameters in situ. The discrepancy between the modelled results and the results using simple law demonstrates both sea surface and bottom have significant effect on TL for the shallow water, especially at low frequencies. Inspired by the modelling methodology in AQUO (Achieve QUieter Oceans) project (Audoly et al., 2015), a predicted model applied to a typical fishing boat was built, which showed that the URN at frequencies below and above 100 Hz was dominated by non-cavitation propeller noise and mechanical noise, respectively. The agreement between predicted results and measured results also demonstrates that this modelling methodology is effective to some extent.

11

Study on Manoeuvring Criteria for Safety Assessment in Shallow Water

Nakamura S.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2017

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Vol. 11, no. 3

401--407

EN

The necessity of verifying manoeuvring mathematical models in shallow water for studying the safety of ships using a ship-handling simulator is pointed out in this report. Several instances of verification of mathematical models in shallow water are introduced here based on measurements of motion conditions of full-scale ships and shallow water tank tests of models. Results of safety assessment tests of five manoeuvring phases are given using the verified manoeuvring mathematical models to discuss manoeuvring criteria in shallow water. Objective manoeuvring criteria for safety assessment in shallow water are proposed based on subjective judgement related to control margin assessed by more than 3,200 masters and pilots for over 325 simulation tests and by analysis of the study results of 15 full-scale ships.

12

Tracking of the broadband source of the underwater noise in the very shallow water conditions

Grelowska G., Kozaczka E.

Hydroacoustics

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2015

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Vol. 18

77--86

EN

The paper contains the results, both theoretical and experimental, connected with the tracking of the underwater noise source as small ships, pontoon, diver and so on. The problem of security in the shallow water area is the challenge for underwater acousticians. In this paper there is taken into account the detection of the sources that move on the surface of the sea or underwater in shallow and very shallow water. The main goal deals with characterization of the sound propagation at the shallow water channel. The next problem is formulation of the sound propagation inside of this acoustic duct including normal mode creations and dispersion of the acoustic energy. When we take into account the small ships noise the two main sources are analyzed. The first one is the vibration energy produced by the mechanisms located inside of the ship hull. The acoustical energy is transformed through structural elements of the hull to surrounding water. This energy propagates as broadband underwater noise. The next source is the ship propeller. The sources of the underwater noise give the some deposit to the total acoustical energy that means the ambient noise. The problem that should be solved is to discover these acoustical disturbances along with their classification, identification and tracking.

13

Matched-field Source Localization with a Mobile Short Horizontal Linear Array in Offshore Shallow Water

Zhao D., Huang Z., Su S., Li T.

Archives of Acoustics

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2013

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Vol. 38, No. 1

105--113

EN

Passive source localization in shallow water has always been an important and challenging problem. Implementing scientific research, surveying, and monitoring using a short, less than ten meter long, horizontal linear array has received considerable attention in the recent years. The short array can be conveniently placed on autonomous underwater vehicles and deployed for adaptive spatial sampling. However, it is usually difficult to obtain a sufficient spatial gain for localizing long-range sources due to its limited physical size. To address this problem, a localization approach is proposed which is based on matched-field processing of the likelihood of the passive source localization in shallow water, as well as inter-position processing for the improved localization performance and the enhanced stability of the estimation process. The ability of the proposed approach is examined through the two-dimensional synthetic test cases which involves ocean environmental mismatch and position errors of the short array. The presented results illustrate the localization performance for various source locations at different signal- to-noise ratios and demonstrate the build up over time of the positional parameters of the estimated source as the short array moves at a low speed along a straight line at a certain depth.

14

Ship seakeeping in UKC determination – a further study on wave force transfer functions

Artyszuk J.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2012

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nr 32 (104) z. 2

5-15

EN

Modeling of ship motions in waves concentrates in most applications on the response amplitude operator (RAO). This mathematically not demanding method of analysis is very attractive, but loses some essential information in certain situations. The objective of present contribution is to establish and investigate preliminary foundations for a seakeeping model as optimal for under keel clearance (UKC) estimation. A special attention was devoted to transients of motions, stationary harmonic motions, coupling between degrees of freedom, and the wave force transfer functions – all in the aspect of shallow water environment.

15

Metodika ocenki dvizenia sudov na melkovodnyh ucastkah

Arefyev I.

Zeszyty Naukowe / Akademia Morska w Szczecinie

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2012

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nr 31 (103)

19--23

EN

A method for assessing the impact of low water in the fairway on the movement of ships in the rivers and canals is shown in the work. The growth speed of the ship breaks down the river (channel), the territory of the area. It is important that when the motion is regular. This paper is an analysis of this problem.

16

Application of CFD Methods for the Assessment of Ship Manoeuvrability in Shallow Water

Górnicz T., Kulczyk J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2012

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Vol. 6, no. 1

57--62

EN

Safety in water transport plays a significant role. One way to increase safety in the waterways is to ensure that ships have proper manoeuvrability. Evaluation of manoeuvring properties performed at an early stage of design can detect problems that later would be difficult to solve. To make such an analysis the nu-merical methods can be used. In the paper the numerical method to evaluate the ship manoeuvrability on the shallow water is presented. Additionally author shows the procedure of determining hydrodynamic coeffi-cients on a basis of CFD calculation. The simulation results of inland ship was compared with experimental data.

17

ANAFIS and neural network for modeling and prediction of ship squat in shallow waters: a new approach

Zeraatgar H., Akbari Vakilabadi K., Salmalian K., Haghi A. K.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 1

211-231

EN

The reduction of the distance between ship floor and seabed, while the ship is moving forward, is called squat. In this research, squat is determined for vessels with Series-60 hull forms in various depths by experimental methods and then different numerical methods are employed for squat modeling. For this reason, a set of facilities for testing the ship movement in shallow waters is prepared. A series of models of the vessel is manufactured and many tests are carried out. The aim of the present study is to demonstrate the usefulness of an adaptive-network-based fuzzy inference system (ANFIS) for modeling and predicting the squat parameter for ships in shallow waters. It is also shown how dimensionless squat (S*) varies with the variation of important parameters, namely: block coefficient (CB), dimensionless distance between the seabed and ship floor […] and hydraulic Froude Number (Fnh). The results obtained through the ANFIS are also compared with those of a multiple linear regression and GMDH-type neural network with multi-layered feed forward back propagation algorithm. The results show that the ANFIS-based squat has higher predictability function than other numerical methods.

18

On the Description of Long Water Waves in Material Variables

Szmidt K., Hedzielski B.

Archives of Hydro-Engineering and Environmental Mechanics

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2009

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Vol. 56, nr 1-2

63-83

EN

Shallow water equations formulated in material variables are presented in this paper. In the model considered, a three-dimensional physical problem is substituted by a two-dimensional one describing a transformation of long waves in water of variable depth. The latter is obtained by means of the assumption that a vertical column of water particles remains vertical during the entire motion of the fluid. Under the assumption of small, continuous variation of the water depth, the equations for gravity waves are derived through Hamilton's principle formulated in terms of the material coordinates. This formulation ensures the conservation of mechanical energy. The approximation depends on the wave parameters as well as on the bed bathymetry. The latter may influence a solution of the model decisively; thus, one should be careful in applying the description to complicated geometries of fluid domains encountered in engineering practice.

19

Computation of flow around inland waterway vessel in shallow water

Tabaczek T.

Archives of Civil and Mechanical Engineering

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2008

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Vol. 8, no 1

99-107

EN

Flow around an inland waterway vessel in shallow water was computed in model scale using CFD software Fluent. Theoretical data were compared to the results of measurements in towing tank. The comparison comprises ship resistance, wave profile on hull surface, and distribution of velocity in tlow around bow and stern.

PL

Przy użyciu programu komputerowego Fluent obliczany był przepływ wokół kadłuba statku śródlądowego w skali modelu. Wyniki obliczeń zostały porównane z wynikami pomiarów w basenie holowniczym. Porównanie obejmuje opór kadłuba, profil fali na powierzchni kadłuba i rozkład prędkości przepływu w pobliżu dziobu i rufy.

20

Assessment of ship squat in shallow water using CFD

Jachowski J.

Archives of Civil and Mechanical Engineering

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2008

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Vol. 8, no 1

19-38

EN

In the recent years much research effort in ship hydromechanics is devoted to the practical navigation problems in getting larger ships safely into existing harbours or to the appropriate design of expansion of harbours for safe accommodation of larger ships. 80th these problems are directly related to the safety of navigation and therefore they receive high attention from ship designers. harbour designers. ship operators and maritime administration. The starting point of any navigational or design analysis lies in the accurate determination of the hydrodynamic forces generated on the ship hull moving in confined waters. The analysis of such ship motion should include the effects of shallow water, horizontal restrictions, asymmetric channels, muddy bottoms. ship squat. ship to ship interactions etc. It is natural to use advanced Computational Fluid Dynamics methods for this purpose. The paper includes a wide introduction into the problems of modelling of the restricted water effects on ship motion using CFD. This presentation is illustrated with the examples of calculations performed using the commercial system Fluent.

PL

W ostatnich latach przeprowadzone zostały liczne badania mające na celu identyfikacje sił hydrodynamicznych działających na manewrujący statek na akwenach portowych przystosowanych dla dużych statków. Problemy związane z bezpieczeństwem nawigacji na tych akwenach odgrywają ważną rolę w projektowaniu akwenów i są przedmiotem badań organizacji morskich. U podstaw jakiejkolwiek nawigacji i analizy projektów leży odpowiednie określenie sił hydrodynamicznych generowanych przez kadłub poruszający się na wodach ograniczonych. Analiza ta powinna zawierać przede wszystkim efekt osiadania, poziome ograniczenia kanałów, dna akwenów, oddziaływania kadłubów mijających się statków itp. Jest więc oczywiste, że do badań w tej dziedzinie stosuje się zaawansowane metody numerycznej mechaniki płynów. Artykuł zawiera wstęp do problemu modelowania efektów wody ograniczonej przy użyciu komercyjnego programu Fluent.