Ship Waves Research Articles

A numerical modeling‐based predictive methodology for the assessment of the impacts of ship waves on YOY fish

AbstractThe effects of inland navigation on the aquatic ecosystem are numerous. One of the most relevant impacts from the ecohydraulic point of view is ship‐induced waves, resulting in the local and temporary alteration of the hydrodynamic regime, especially in shallow water areas. In this paper, a novel hydrodynamic modeling‐based evaluation framework is presented and tested for the prediction of habitat use and drift risk of juvenile fish during wave events of different intensities. A vertically resolved numerical wave tank was built up using field measurements of a real vessel‐generated wave event from the Hungarian Danube. High‐frequency pressure time series were utilized to numerically reproduce the phase accurate wave trains, while acoustic Doppler velocity time series were exploited for the verification of the model. Results of the spatiotemporally resolved hydrodynamic model were combined with data from the literature to explore a case study of juvenile Nase (Chondrostoma nasus). Results highlighted the significant horizontal extension (10–15 m) of the area exposed to decreased habitat suitability and increased drift risk. Moreover, the model revealed significant vertical variabilities in the investigated near‐bank area as well, emphasizing the relevance of depth resolved hydrodynamic modeling in ecohydraulic investigations.

A Theoretical Model for Ship–Wave Impact Generated Sea Spray

AbstractSpray generated by ships traveling in cold oceans often leads to topside icing, which can be dangerous to vessels. Estimation of the spray flux is a first step in predicting icing accumulation. The amount of spray water, the duration of exposure to the spray, and the frequency at which the spray is generated are all important parameters in estimating the spray flux. Most existing spray flux formulae are based on field observations from small fishing vessels. They consider meteorological and oceanographic parameters but neglect the vessel behavior. Ship heave and pitch motions, together with ship speed, determine the frequency of spray events. Thus, the existing formulae are not generally applicable to different sizes and types of vessels. This paper develops simple methods to quantify spray properties in terms that can be applied to vessels of any size or type. Formulae to estimate water content and spray duration are derived based on principles of energy conservation and dimensional analysis. To estimate spray frequency considering ship motions, a theoretical model is proposed. The model inputs are restricted to ship’s principal particulars, operating conditions, and environmental conditions. Wave-induced motions are estimated using semi-empirical analytical expressions. A novel spray threshold is developed to separate deck wetness frequency from spray frequency. Spray flux estimates are validated against full-scale field measurements available in the open literature with reasonable agreement.

Numerical Simulation of Mountain Waves over the Southern Andes. Part I: Mountain Wave and Secondary Wave Character, Evolutions, and Breaking

AbstractThis paper addresses the compressible nonlinear dynamics accompanying increasing mountain wave (MW) forcing over the southern Andes and propagation into the mesosphere and lower thermosphere (MLT) under winter conditions. A stretched grid provides very high resolution of the MW dynamics in a large computational domain. A slow increase of cross-mountain winds enables MWs to initially break in the mesosphere and extend to lower and higher altitudes thereafter. MW structure and breaking is strongly modulated by static mean and semidiurnal tide fields exhibiting a critical level at ~114 km for zonal MW propagation. Varying vertical group velocities for different zonal wavelengthsλxyield initial breaking in the lee of the major Andes peaks forλx~ 50 km, and extending significantly upstream for largerλxapproaching the critical level at later times. The localized extent of the Andes terrain in latitude leads to “ship wave” responses above the individual peaks at earlier times, and a much larger ship-wave response at 100 km and above as the larger-scale MWs achieve large amplitudes. Other responses above regions of MW breaking include large-scale secondary gravity waves and acoustic waves that achieve very large amplitudes extending well into the thermosphere. MW breaking also causes momentum deposition that yields local decelerations initially, which merge and extend horizontally thereafter and persist throughout the event. Companion papers examine the associated momentum fluxes, mean-flow evolution, gravity wave–tidal interactions, and the MW instability dynamics and sources of secondary gravity waves and acoustic waves.

The Influence of Ship Waves on Sediment Resuspension in the Large Shallow Lake Taihu, China.

Sediment resuspension induces endogenous nutrient release in shallow lakes, which has been demonstrated to be associated with eutrophication. In addition to natural wind-driven resuspension, navigable shallow lakes (such as Lake Taihu, China) also experience resuspension from human activities, such as ship waves. Both processes determine the intensity, frequency, and duration of sediment resuspension, and may consequently affect the pattern of cyanobacteria blooms in the lake. In this study, acoustic Doppler Velocimeter (ADV), Optical Backscatter Sensor (OBS), and temperature wave tide gauge (instrument model :RBR duo TD|wave) were placed in an observation platform in the lake to obtain high-frequency flow velocities, suspended sediment concentration (SSC), and wave parameters before, during, and after a cargo ship passed by. We found that the ship wave disturbance intensity is greatly influenced by the draft depth. The movement generated by ship disturbance is primarily horizontal rather than vertical. Compared with the wind-induced wave, the disturbance caused by the ship waves has a high intensity, short duration, and narrow range of influence. The maximum total shear stress under ship disturbance can reach 9~90 times the critical shear stress under a natural state. Therefore, the effect of ship waves on sediment resuspension near the channel of Lake Taihu is much greater than that of wind-induced waves. These findings represent an important step towards understanding the quantitative relationship between ship wave disturbance and sediment resuspension, and lay the foundation for future research in order to understand and control the eutrophication of shallow lakes.

Measurements and Analysis of Primary Ship Waves in the Stockholm Archipelago, Sweden

Primary ship waves generated by conventional marine vessels were investigated in the Furusund fairway located in the Stockholm archipelago, Sweden. Continuous water level measurements at two locations in the fairway were analyzed. In total, 466 such events were extracted during two months of measurements. The collected data were used to evaluate 13 existing predictive equations for drawdown height or squat. However, none of the equations were able to satisfactorily predict the drawdown height. Instead, a new equation for drawdown height and period was derived based on simplified descriptions of the main physical processes together with field measurements, employing multiple regression analysis to derive coefficients in the equation. The proposed equation for drawdown height performed better than the existing equations with an R2 value of 0.65, whereas the equation for the drawdown period was R2 = 0.64. The main conclusion from this study is that an empirical equation can satisfactorily predict primary ship waves for a large data set.

A Flux Source Method for Ship Wave Generation in a Boussinesq-type Wave Model

A Flux Source Method for Ship Wave Generation in a Boussinesq-type Wave Model

Propagation characteristics of ship waves in navigation tunnel and its influence on continuous navigation safety of ship

In parallel to the construction of navigable tunnels which is gradually put on the agenda in China, more and more navigable tunnels are bound to be built. However, the relevant technical support is still extremely lacking. The existing engineering design and construction only refer to the construction experience of various traffic tunnels or the inland waterway navigation regulations, which in turn creating a limitation that the influence of navigable hydrodynamic environment is not considered. Therefore, to fill in the gaps in the research on key technologies of ship navigation safety in navigable tunnels, the open-source package FUNWAVE-TVD based on completely nonlinear Boussinesq equation has been used to establish a numerical model, demonstrating ship travelling wave motion in navigable tunnels in linear canals. The model can help to determine the ship model by pressure source terms. The model size and research conditions are determined according to the inland river navigation code and existing engineering examples. The accuracy of the model is evaluated using numerical verification, grid convergence analysis and ship travelling wave stability. The temporal and spatial distributions of height and velocity of the solitary wave induced by ships in navigable tunnels are analyzed. The safety impact of ship travelling wave in navigable tunnels on continuous navigation is discussed. The results show that the model has a great ability to capture the propagation and evolution process of ship travelling wave in navigable tunnels. It is pointed out that large fluctuations are easily formed on both sides of the quay wall of the navigation tunnel and in the middle part. The multiple nonlinear regression equation containing the maximum solitary wave height η max, ship draught P , Fr , water depth, width of navigation tunnel and ship type is obtained. The equation shows that the maximum solitary wave height gradually increases with the increase of ship draught and Fr , but vice-versa with the increase of water depth, width and section coefficient of navigation tunnel. It is found that the wave velocity of the front solitary wave surface is in good agreement with the theoretical solitary wave surface equation. Taking the theoretical wave velocity of the solitary wave as the propagation velocity, the safe sailing distance of the ship during the continuous navigation, especially under the conditions of large speed and draught in existing navigation tunnels, is obtained. The novelty of this paper is serving as a reference and basis for the design of navigation tunnels in single-line straight canals and playing a role as a theoretical foundation for the formulation of any key technical standards or specifications for navigation safety of ships in navigation tunnels.

ESTIMATION OF THE WAVE FORMATION FOR EXTRA-CAPACITY CATAMARAN WITH VARIOUS FORMS OF INNER SIDES

The research was carried out by numerical methods of wave formation and resistance for an extra-capacity displacement catamaran in the range of Froude numbers from 0.181 to 0.3 and the range of relative clearance from 0.3 to 0.55. Symmetrical hulls and hulls with an inner flat side, developed on the basic lines of M. Ya. Alferiev were used. The ship wave heights generated by the hulls of the catamarans and their resistance were compared with the corresponding simulation results for a large mono-hull vessel with a hull width equal to the total width of the catamaran. Numerical simulation was performed in the FineMarineTM software package. It was found that the resistance and wave heights from a mono-hull vessel and a catamaran with a flat inner side exceed the resistance and wave heights of a catamaran with symmetrical hulls.

Prediction of the Side Drift Force of Full Ships Advancing in Waves at Low Speeds

In this study, we analyze the experimental results of the mean sway (side drift) forces of six full type ships at low speeds in regular waves of various directions and compare them with numerical results of the in-house 3D panel code NEWDRIFT. It is noted that the mean sway force is most significant in relatively short waves, with the peak being observed at λ/LPP ≈ 0.5–0.6. For λ/LPP > 1.0, the corresponding value is rather small. We also observe a solid recurring pattern of the mean sway force acting on the analyzed full type ships. On this basis, we proceed to approximate the mean sway force with an empirical formula, in which only the main ship particulars and wave parameters are used. Preliminary validation results show that the developed empirical formula, which is readily applicable in practice, can accurately predict the mean sway force acting on a full ship, at both zero and non-zero speeds.

Анализ волновых полей свободной поверхности воды от движущейся пластины, пары последовательно расположенных стоек и обсуждение возможных составляющих их волнового сопротивления

The paper presents and compares photographs of wave patterns from a moving plate with pointed and full ends, from which, with the exception of a cylindrical insert, there develops a post with a teardrop-shaped cross-section, as in a pair of tandem posts. The plate length equals to the overall size of the specified pair of consecutive posts. The conclusion is made about the possibility of selecting a unified wave resistance component from the total resistance, which can be determined experimentally based on the results of the study of a combination of individual posts and/or other objects of the specified shape. Possible variants of wave resistance components are being discussed. Besides, a variant of modeling the ship's wave resistance by representing two pairs of such wave systems rather than two Kelvin wave systems on a free surface is proposed. Additional fore and aft Kelvin wave systems are proposed to be shifted against the course of motion by half the wavelength. These additional wave systems are intended to describe internal intermediate waves located between the main transverse waves. There have been presented the expressions for wave resistance that contain some proportionality coefficients, possible components of wave resistance from smoothing diverging waves within the smoothing zone of wave structures, starting from the bow extremity and other unaccounted components of wave resistance. The photos proposed were taken in the experimental pool of Siberian State University of Water Transport (Novosibirsk State Academy of Water Transport) in 2006

Cross-Sectional Stability of a Canal under the Action of Ship Waves Based on Minimum Energy Hypothesis

The ship-induced hydrodynamics in a canal result in different mechanism of the cross-sectional evolution. However, the ship-induced hydrodynamic factors are not induced in existing studies of cross-sectional stability of a canal. In this paper, the minimum rate of energy dissipation equations for a canal are derived based on the theory of thermodynamics, introducing the ship wave factors, and variational equation is adopted to establish the stable cross-sectional shape equations. Then, the measured results in Changzhou segment of the Grand Canal are used to evaluate the performance of the derived equations by comparing with other typical equations without considering ship wave factors. The results show that the derived equations give better prediction of the cross-sectional area, mean water depth, maximum water depth and the bottom width of the stable cross-section with the relative error less than 20%. At last, an application of the derived equations is given for Yan River to predict the stable cross-sectional shape.

Field Measurements in the Kiel Canal, Germany: Ship Waves, Drawdown, and Sediment Transport

Ship waves and ship-induced flows are the main hydrodynamic loads on waterway beds and embankments. However, the underlying physical processes are not yet understood fully. Recent field measurements, conducted in the Kiel Canal, Germany, allow a better understanding of these loads and the resulting (ship-induced) sediment transport. The measurements include high-resolution time series of pressure, three-dimensional flow velocities, and turbidity, collected using stationary as well as vessel-mounted sensors. The focus of this paper is on two aspects. First, existing drawdown estimation approaches are reviewed and validated against field measurements. Based on this, a new approach is derived to improve the general description of ship waves in confined waters. Second, a new approach to estimate the ship-induced sediment transport in the Kiel Canal is developed using turbidity and flow measurements and validated against dredging volumes. Our results show that about 10% of the total transported sediment volume in the Kiel Canal can be attributed to ship traffic, whereas the remaining volume is mainly transported during regular dewatering periods. This paper provides an empirical-based method to estimate ship-induced sediment transport in artificial waterways as basis for future canal management strategies.

Resistance reduction technology research of high speed ships based on a new type of bow appendage

A new type of bow appendage is proposed to reduce resistance of high-speed ship with a Froude Number of 0.4–0.5 in this paper. The ship bow appendage can restrain the bow waves of high-speed ships, thus enabling to decrease the principal wave-making resistance significantly. In this study, resistance experiments and numerical simulation calculations on a ship model were carried out. This new type of bow appendage was designed according to wave pattern of the ship model at the Froude Number of 0.45, aiming to restrain the peak of bow wave. Numerical calculation shows that the bow appendage can affect the wave-making state and reduce the resistance of ship model at high speed, and the effect of the bow appendage is sensitive to its installation position and the model speed. The ship model experiments were conducted to verify the effects of the bow appendage on reducing the resistance of ship model. Experiment results show that this bow appendage is able to restrain bow wave of the ship model and reduce the total resistance by more than 8% to the maximum extent. The water spray induced by the bow appendage can be improved by optimization of the shape.

Practical flow-representations for arbitrary singularity-distributions in ship and offshore hydrodynamics, with applications to steady ship waves and wave diffraction-radiation by offshore structures

Diffraction-radiation of regular waves by offshore structures and flows around ships advancing in calm water or in regular waves are commonly analyzed via potential-flow methods based on the Green functions that satisfy the corresponding free-surface boundary conditions. This realistic, practical, and widely-used approach requires evaluation of free-surface flows due to arbitrary (notably constant, linear or quadratic) distributions of singularities (sources and dipoles) over (flat or curved) panels of various shapes (notably rectangles and triangles). Indeed, reliable, efficient and practical methods to evaluate the flows due to arbitrary singularity-distributions over hull-surface panels is a crucial core-element of the Green-function method in ship and offshore hydrodynamics. This core-issue is the object of the study. Free-surface flows due to singularity-distributions over panels (and related ‘influence coefficients’) are ordinarily evaluated via a two-step procedure that involves evaluation of a Green function G and its gradient ∇G (a Fourier integration) and subsequent integration of G and ∇G over a panel (a space integration). This common approach involves notorious analytical and numerical complexities related to the complicated singularities of the Green functions in ship and offshore hydrodynamics. An alternative general approach, applicable to generic dispersion relations and arbitrary distributions of singularities, is expounded. This alternative approach is based on a Fourier–Kochin representation of free-surface effects, in which the space integration over hull-panels is performed first and the Fourier integration is performed subsequently. Thus, the Green function and its gradient are not evaluated in this approach. Indeed, this usual first step is bypassed, and the flow due to a singularity distribution is evaluated directly. A major advantage of the Fourier–Kochin method is that the panel-integration is a trivial task as it merely involves integration of an exponential–trigonometric function. A crucial element of the approach expounded in the study is a general analytical decomposition of free-surface effects into waves and a local flow. The waves in this fundamental flow decomposition are expressed as single integrals along the dispersion curves defined by the dispersion relation in the Fourier plane, and the local flow is given by a double Fourier integral that has a smooth integrand dominant within a compact region of the Fourier plane. This analytical flow representation does not involve approximations, i.e. is mathematically exact, as is verified via numerical applications for two main classes of flows in ship and offshore hydrodynamics: ships advancing in calm water, and diffraction-radiation of regular waves by offshore structures. These applications also demonstrate that the general approach expounded in the study provides a practical, remarkably simple, basis that is well suited for accurate and efficient evaluation of flows due to arbitrary singularity-distributions. Indeed, the approach yields a smooth wave and local-flow decomposition that avoids the complexities related to the evaluation and subsequent hull-panel integration of the singular wave and local-flow components in the classical Green functions of ship and offshore hydrodynamics. The general approach expounded in the study is applicable to other classes of flows, notably wave diffraction-radiation by ships advancing through waves in deep water and by offshore structures in finite water-depth, and these important particular applications will be considered in sequels to the study.

Numerical modeling of ship wave generation using Green’s functions based on linear dispersive wave theory

ABSTRACT In this study, an efficient numerical model for predicting ship waves was developed using Green’s functions. Avoiding detailed description of the complex boundary conditions around a ship, this model simply used an inversion technique for estimating the wave source induced by a ship as a function of the navigation route and adjacent measured water level fluctuations. The Green’s functions were determined as linear summations of the water level fluctuations generated from discrete points along the navigation route. At each point, a time-varying wave source was determined as a linear summation of Gaussian pulses introduced at segments along the longitudinal direction of the ship. The linear inversion was then applied for estimating the optimum combinations of the magnitudes of these Gaussian pulses. Linear dispersive wave theory was applied to compute the water level fluctuations generated by a single Gaussian pulse so that the model can reproduce the dispersive characteristics of ship waves. The developed model was tested against experimental data and showed satisfactorily predictive skills of water level fluctuations for cases not used in the inversion. The present model was also found to be robust in that the estimated best-fitted wave source was not sensitive to changes in the conditions of the measured data used for the inversion.

Tam Ölçekli Yanal Yükleme Testinin Sayısal Modellemesi

Ports are very important structures at the national and international sea transportation. These structures are also in a critical position on economy and commerce capacity by providing shipping and distribution services. It is very important to design a port structure, considering its stability and resistance along its service time. In the design of this type of structure, the lateral loads caused by during ship berthing, wind and wave loads etc. can be more important compared with vertical loads. The design and the performance of a port structure foundation should be investigated by full scale field tests considering the service loads. The aim of this study is to investigate the performance of the steel pipe pile under lateral load by full scale in-situ loading tests at Mersin International Port Construction area in the Mediterranean Sea. Full scale pile lateral loading test (PLLT) on a single offshore pile has been conducted at the project site and the test pile has been loaded up to 2 times the service load with 4 loading-unloading cycles. In addition, a numerical analysis has been performed to simulate the real lateral load-deflection behavior by using Plaxis 3D finite element software. It has been observed that, the analysis results obtained from the numerical model has been reflected the test pile lateral load-displacement behavior with good convergence.

The influence of ship wave on turbulent structures and sediment exchange in large shallow Lake Taihu, China

Turbulent burst plays a key role in momentum transfer and sediment movement in large shallow lakes. This study addresses the quantitative influence of ship wave on turbulent structures, momentum and sediment fluxes in Lake Taihu, a large, shallow eutrophic lake that experiences heavy shipping traffic. Acoustic Doppler Velocimeter (ADV) and Optical Backscatter Sensor (OBS) were used to obtain high-frequency flow velocities and suspended sediment concentration (SSC) data before and when a cargo ship passed by. We found that ship waves mainly propagate along the horizontal direction. The near-bed turbulent bursting events with ship disturbance increased by 8.42%. Consequently, the vertical momentum and sediment fluxes were increased by 3.4 times and 8 times, respectively. In terms of bursting processes, ejection and sweep possess much stronger capacity in carrying sediment and are largely controlled by the disturbance in the vertical direction, while inward and outward interactions are mainly affected by horizontal disturbance. These findings represent an important step towards understanding the mechanism and effect of turbulent bursting under ship disturbance, and pave the way to future research in order to manipulate turbulent dynamics.

Response of a direct-drive large marine two-stroke engine coupled to a selective catalytic reduction exhaust aftertreatment system when operating in waves

Large two-stroke marine diesel engines are used as the prime mover in the majority of ocean going commercial vessels and are currently facing new stringent NOx emission reductions. Selective catalytic reduction is an aftertreatment technology which is able to reduce emitted NOx at allowable levels. In most marine applications, the selective catalytic reduction system is placed on the high pressure side of the turbine, due to limitations at the exhaust gas temperature at the inlet of selective catalytic reduction system. In this article, the operation of a large two-stroke marine diesel with a selective catalytic reduction aftertreatment system, is investigated in heavy weather conditions. Operation of a vessel in heavy weather results in increased ship resistance, wave-induced ship motions, and a highly varying flow field in the propeller due to ship motions. This results in a fluctuation of propeller demanded torque and hence a fluctuation in engine load and exhaust gas temperature which may affect engine and selective catalytic reduction performance significantly. To investigate this phenomenon and taking into account the engine–propeller interaction, the entire propulsion system was modeled, namely the propulsion engine, the high pressure selective catalytic reduction system, the directly driven propeller, and the ship’s hull. A propeller model was employed to simulate the transient propeller torque demand and torque fluctuations due to ship motions. A three-dimensional six degrees of freedom panel code was used to calculate ship motions and wave added resistance in regular waves. The coupled model of the marine propulsion plant was validated against available measured data from a ship-board propulsion system on good weather conditions. The model was then used to simulate the behavior of the system during transient loading conditions in the presence of regular waves.

Графический анализ волновых полей свободной поверхности воды от движущейся пары последовательно расположенных стоек, связанных тонкой пластиной

The article presents photographic materials of wave pictures from two consecutive posts of teardrop cross-section and the same posts with a thin plate installed between them, which introduces into consideration not only separate sequentially moving sources, but also reunites them into a single object, interacting along its entire length with the system of waves from the first source. The regularities of the wave field of consecutive posts with a plate in-stalled between them by means of graphic processing are considered. The possibility of finding the front imaginary source of the Kelvin wave pattern forming the ship's wave system at the position of both one and two wave-lengths in front of the top of the bow retaining wave is estimated. A method is proposed for determining the position of the fictitious location of the aft Kelvin wave system of the ship's wave system based on the results of the analysis of the wave field at the characteristic speeds 
 of movement, leading to the most successfully fixed inter-location of the wave pattern from the bow and aft extremities. There are shown the pictures of moving forward a pair of posts with 
 a blunt end of a horizontal section at the same speed and photo fixation from a close angle, pictures of moving forward the posts with a plate between them with a blunt end of a teardrop-shaped cross section at a low speed, moving forward posts with a plate at the side with a sharp end of a teardrop-shaped cross section, etc. All presented photographs were taken in the experimental pool of the Siberian state University of water transport (Novosibirsk state Academy of water transport) in 2006.

Numerical Analysis of a Surface Ship in Waves

Abstract Ship's resistance and engine power to sustain ship's speed in seaways are augmented due to complex non-linear interactions between the ship and the ambient sea (waves). Ship designers, in early design stage, use an ad hoc "sea margin" to account for the effects of seaways in selecting propeller and engine. A numerical tool capable of accurately predicting added resistance and power of a ship cruising in waves would greatly help select its powering (margin) requirement and determine the optimal operating point that can maximize the energy efficiency. For seakeeping analysis, strip theory-based methods have long been used. More recently, nonlinear time-domain three-dimensional (3D) panel methods have started being used widely. A more physics-based avenue to seakeeping analysis is offered by coupled solutions of two-phase unsteady Reynolds-Averaged Navier-Stokes equations and six degrees-of-freedom rigid-body motion (RBM) equations. The URANS approach also avails itself of including the effects of propulsors, either explicitly or approximately. By accounting for all the nonlinear effects in hydrodynamic forces and moments and the resulting ship motions, and the effects of fluid viscosity and turbulence, the coupled URANS-RBM method is believed not only able to predict added resistance and speed loss more accurately, but also to provide valuable insights into the physical mechanisms underlying added resistance and power. The objectives of this study are: (1) to validate a coupled URANS-RBM solver developed for high-fidelity prediction of added resistance, speed loss and added power on ships cruising in regular head sea and irregular waves, and (2) to conduct a detailed analysis of the interactions among ship hull, propeller and waves for a 1/49 scaled model of the ONR Tumblehome (ONRT) (Model 5613) in order to shed light on the physical mechanisms leading to added resistance, speed loss and added power. Figure 1 depicts the ONRT self-propellers with two 4-bladed propellers in regular waves. The main flow features such as the free surface, the hub vortices and blade-tip vortices from the propeller, as well as vortices generated by the sonar dome, shafts, shaft brackets and bilge keels are captured.