Ship-generated Waves Research Articles

Investigation of ship-induced hydrodynamics and sediment resuspension in a restricted waterway

The movement of the ship-generated waves on restricted shallow waterways creates complex river dynamics. The irregular bathymetry increases the bed shear stress in the waterway, causing significant sediment resuspension. In order to investigate the impact of the ship-generated waves on the sediment resuspension, field measurements were performed at the Falta stretch of the Hooghly river, India (National Waterway 1). The present study applied the acoustic backscattering intensity of a horizontally-looking ADCP to quantify the sediment resuspension generated by ship waves. Based on the low-pass filter, the primary and secondary waves were separated. Based on the analysis, the low-frequency primary waves are less significant compared to the high-frequency secondary waves. The correlation study suggested that the ship-induced sediment resuspension is highly influenced by irregular bathymetry, river geometry, depth Froude number and ship speed. Finally, two new empirical models were proposed to estimate the sediment resuspension due to ship-generated waves by using correlation study and regression analysis.

Hydrodynamic Characteristics of an Ecological Revetment Cavity Structure under the Propagation of Ship-Generated Waves in a Restricted Channel

Hydrodynamic Characteristics of an Ecological Revetment Cavity Structure under the Propagation of Ship-Generated Waves in a Restricted Channel

A new method for predicting the maximum wave height of ship-generated onshore slopes in restricted channel

The ship-generated wave causes erosive damage to the slopes of inland waterways and confined waters such as the coastal zone. This critical issue is essentially associated with the navigational safety and sustainable development of coastlines, so it is vital to predicting the maximum wave height of the ship-generated wave (Hm) in the coastline of confined waters. The prediction equations of prior research works are mostly based on measured data and multiple regression analysis; however, this paper aims to propose a novel methodology to predict the maximum wave height of ship-generated waves in confined waters. The maximum wave height caused by a self-propelled ship under various conditions with confined water is measured by employing a water flume. Furthermore, the relationships of functions in the prediction model equation are appropriately derived by dimensional analysis, and the prediction equation model is then solved via the particle swarm optimization algorithm (PSOA). The experimental results reveal that the maximum wave height of the ship-generated wave is seriously affected by the water depth of the channel (hc), the navigation speed of the ship (Vc), and the distance from the forecast point to the navigation line of the ship (Sc). In addition, the maximum wave height grows and then lessens, which touches its peak point in the region close to Frh = 1. The dimensionless analysis indicates that the large wave height of the ship-generated wave can be expressed as a function of the channel depth (hc), ship speed (Vc), and the distance from the measurement point to the ship’s navigation line (Sc) as; HmSc=1Frh2f(gScVc 2). Subsequently, the specific prediction equation is determined by a regression model according to the measured data under various working conditions. By adopting the model expression equation, namely, HmFrh2Sc=k1(gScVc 2)k2, the coefficients k1 and k2 are evaluated via the PSOA, and the relationship between the water depth of the channel and the coefficients is suitably outlined to obtain the maximum wave height prediction model equations for ship-generated waves.

IMPACT OF THE SHIP WAVES AND TIDAL FORCES ON THE SEDIMENT RESUSPENSION IN INLAND WATERWAYS

Ship movement in narrow intertidal waterways generate complex hydrodynamics and sediment resuspension along with tides. In order to investigate the complex hydrodynamics and induced sediment concentration, field measurements were performed at the Falta stretch of the Hooghly river, India. The low frequency primary waves and high frequency secondary waves are dominant in this region as ships navigate in subcritical range due to complex river bathymetry. The time-frequency analysis is a useful tool to separate the ship-generated waves with the tides. The modest performance of the existing empirical models led to the development of the new empirical models for the prediction of ship-generated primary waves. The tides are the dominant factor for the sediment resuspension during the spring period whereas the ship-induced waves are dominant in neap period. The overall contribution of the ship waves on sediment resuspension during the tenure of field measurement was 24.66percent.

Numerical Simulation of Ship-Pack Ice-Water Interaction and Motion of Pack Ice Based on CFD-DEM Method

When a ship sails in pack ice area, it not only collides with the ice but also interacts with the water, generating ship-generated waves. The role and influence of ship-generated waves on the ship-ice-water interaction have not been thoroughly studied. In this study, a numerical model with ship-generated waves is established using a coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM), and an appropriate contact model is selected for numerical simulations. Meanwhile, a simplified numerical model without ship-generated waves is proposed. By comparing the simulation results under the same simulation conditions with and without ship-generated waves, the effects of ship-generated waves on the phenomena of ship-ice-water interaction, longitudinal and lateral contact forces between the ship and pack ice, and ice resistance are analysed, along with the underlying mechanisms. The results indicate that the ship-generated waves can mitigate and reduce the collision intensity and contact frequency between the ship and pack ice, resulting in a decrease in the contact forces and ultimately achieving a significant reduction in ice resistance. Furthermore, this mitigation effect becomes more pronounced with increasing ship speed.

A CFD investigation of the effects of passing ship on a small size ice floe

A RANS (Reynolds Averaged Navier-Stokes) CFD STAR-CCM+ model is used to investigate the hydrodynamic interactions between a ship and a circular ice floe. The overset mesh technique is employed to simulate the advancing movement of the passing ship. The ship has a hull of similar configuration to the KCS MOERI container ship. The ice floe has a diameter of 30% of the ship’s length and a thickness of 3 m. The paper primarily focuses on the motions of the ice floe and the hydrodynamic forces induced by the ship progressing in different speeds and calm water conditions. A parametric study on the influence of the ice floe surge and sway motions and associated hydrodynamic loads is presented. It is concluded that ship-generated waves can significantly affect the motions of the ice floe and the influence on sway is greater than that on surge. The ship speed is also found to have a distinct impact on ice floe motions.

Impact of Ship-Generated Waves on the Sediment Resuspension in Restricted Waterways

Impact of Ship-Generated Waves on the Sediment Resuspension in Restricted Waterways

A numerical study of passing ship effects on a moored ship in confined waterways with new benchmark cases

This study aims at a comprehensive investigation of passing ship effects on a moored ship in confined waterways with high blockage, referring to the new benchmark cases from the latest MASHCON conference. The whole process of a KCS container ship passing a moored Neo-Panamax container ship is simulated by combining the URANS method with the dynamic overset mesh technique. The hydrodynamic forces and moments, attitudes of the moored ship, and ship-generated waves are predicted. Firstly, the case with 10% UKC is simulated for validation. The results indicate that the numerical layout with a larger initial longitudinal distance between the two ships presents more accurate results agreeing well with the test data. Then, based on the validated method, the effects of tank width, water depth, lateral passing distance and passing ship speed are analyzed and are quantified by curve fittings in terms of the amplitudes of hydrodynamic quantities. It is found that these parameters have remarkable impacts on the moored ship, among which the passing speed is the most significant factor. In addition, the ship-generated drawdown dominates in the whole passing process, which causes prominent variations of the hydrodynamic quantities and induces pronounced pressure reductions on the moored ship.

Wash waves generated by ship moving across a depth change

Unsteady wash waves generated by a ship with constant speed moving across an uneven bottom topography is investigated by numerical simulations based on a Mixed Euler–Lagrange (MEL) method. The transition is accomplished by the ship traveling from the deep water into shallow water via a step bottom. A small tsunami would be created after this transition. However, the unsteady wave-making resistance induced by this new phenomenon has not been well documented by literature. Therefore, the main purpose of the present study is to quantify the effects of an uneven bottom on the unsteady wash waves and wave-making resistance acting on the ship. An upwind differential scheme is commonly used in the Euler method to deal with the convection terms on free-surface condition to prevent waves in upstream. Evidently, it cannot be applied to the present problem when the ship-generated waves could propagate upstream. A MEL method is therefore employed to investigate the upstream wave generated by the ship moving over the uneven bottom. The central differential scheme provides more accurate results, but it is not unconditionally stable. Simulation results show that the hydrodynamic interaction between the ship and the uneven bottom could initiate an upstream tsunami, as well as unsteady wave-making resistance on ships. The unsteady wave-making resistance oscillates periodically, and the amplitude and period of the oscillations are highly dependent on speed and water depth.

A Numerical Study on the Effects of Ship-Generated Waves on a Moored Ship in Restricted Waterways Considering Initial Acceleration Process

In order to develop a reliable numerical method to investigate the effects of ship-generated waves on a moored ship in restricted waterways, this paper takes the MASHCON2022 benchmark model test case as the study object and simulates the whole process of a ship passing a moored ship by using the unsteady Reynolds-Averaged Navier-Stokes (URANS) method coupled with the dynamic overset mesh technique. The initial acceleration process of the passing ship before approaching the moored ship is considered in the numerical simulations to reproduce the benchmark model tests more realistically. The numerical simulations with four acceleration modes are conducted. The comparisons among the numerical results and the test data verify that the prediction accuracy considering the acceleration process is obviously higher than that without the acceleration process, especially for the solitary wave system, and the results based on the linear acceleration agree with the test data best. The flow field results indicate that the impacts of the solitary wave system and the primary wave system on the moored ship are different: the solitary wave system induces significant positive pressures on the hull, while the primary wave system leads to remarkable negative pressures; both result in pronounced attitude variations of the moored ship, but the hydrodynamic forces and moments affected by the primary wave system are more pronounced.

Towards a full-scale CFD guideline for simulating a ship advancing in open water

ABSTRACT Computational Fluid Dynamics (CFD) simulations of a ship’s operations are generally conducted at model scale, but the reduced scale changes the fluid behaviour around the ship. Whilst ideally ship simulations should be run directly at full scale, a guide has not been published to advise on the suitable setups that can provide accurate results while minimizing the computational cost. To address this, the present work explores an optimal approach for full-scale ship simulations. Extensive sensitivity studies were conducted on relevant computational setups to investigate their influences on the prediction of ship resistance, ship-generated waves as well as the boundary-layer flow of the hull. A set of CFD setups for full-scale ship simulations in open water was recommended. It was demonstrated that the ideal Y+ and Courant numbers in full scale are evidently different from those given in current model-scale CFD guidelines, indicating the necessity to establish full-scale CFD guidelines separately.

Field measurement and analysis of ship generated waves in Hooghly river, India

Vessel movements in restricted waterways disturb the natural flow field and generate waves that create complex hydrodynamics. It is difficult to understand the general characteristics of ship-generated waves in restricted channels due to non-linearity and local bathymetry. A field study on the Hooghly river was conducted to assess and analyse the ship-generated primary and secondary waves. This paper investigated the wake signal from the field survey employing time-frequency analysis (short-term Fourier transform). The spectrogram study identified the primary and secondary waves from the wake signal. In comparison with the linear dispersion curve, the time-frequency study helps identify the divergent and transverse waves from the wave signal. The spectrogram study helps understand the influence of non-linearity from ship waves with increasing velocity. The energy content on the different components of the ship waves revealed the erosive potential of the waves. The measured primary and secondary waves were compared with the existing empirical relations, but satisfactory results were not obtained. Hence, a new empirical relationship between the primary and secondary waves has been obtained based on understanding the physical processes from the analysis of field data.

Waves in waterways generated by moving pressure field in Boussinesq equations using unstructured finite element model

A finite element model for depth integrated form of Boussinesq equations is presented. The equations are solved on an unstructured triangular mesh using standard Galerkin method with mixed interpolation scheme. The elemental integrals are calculated analytically and time-stepping is done using Runge–Kutta 4th order method. It is extended to simulate ship-generated waves using moving pressure fields. The unstructured formulation provides the flexibility of mesh refinement as needed, for capturing wave transformation or moving pressure field. The model is verified against experimental and numerical results for wave transformation over the Whalin shoal. The results for moving pressure field are compared against numerical results from FUNWAVE. Further, a simulation of ship navigating a curved path is presented. Finally, a real-life application and validation against field measurements is provided for waves generated by a fast ferry moving along a GPS tracked path in Tallinn Bay, Estonia.

Experiences of nature-based solutions for mitigating ship-induced erosion in confined coastal waters

Hydrodynamic forces from ships operating in sheltered, confined fairways can result in increased wave impact and sediment transport leading to loss of land and habitats. Nature-based solutions (NBS) offer the potential to mitigate ship-induced erosion and increase biodiversity and ecosystem services. The aim of this study is to evaluate the performance of NBS in a sheltered, confined fairway located in a cold, temperate region. The case study presents the results of a 2.5-year study of the morphologic response at two sites where NBS was implemented to mitigate bluff erosion and at one site where NBS was implemented to mitigate the retreat of a reed belt. Moreover, a qualitative assessment was made of the vegetation development at the sites. The results showed that fine sediments with planted vegetation could not withstand the hydrodynamic forces induced by the ships. However, by adding sills as stabilizing structures, the forces were sufficiently attenuated for the vegetation to establish. The vegetation, which reduced the ship-generated waves and currents, was especially important during high water-level events when the energy dissipation by the sill decreased. Moreover, a small-scale nourishment was successfully applied to mitigate bluff erosion without negatively affecting sediment supply to an adjacent sandy beach. This study demonstrates that NBS can be implemented to retain erodible sediment and favour vegetation growth in fairways experiencing primary and secondary waves produced by large, ocean-going ships.

Investigation on Resistance, Squat and Ship-Generated Waves of Inland Convoy Passing Bridge Piers in a Confined Waterway

The average and unsteady hydrodynamics of an inland convoy passing bridge piers in a confined waterway were investigated using both numerical and experimental approaches. The numerical simulations are realized by solving the RANS (Reynolds-averaged Navier–Stokes) equations accounting for the solid body motion using the sliding mesh technique, while the experiments were carried out in the towing tank. The advancing resistance, trim, sinkage and ship-generated waves were analyzed as functions of the water depth, distance between bridge piers, draught and velocity. The existence of the piers is found to only influence the transient hydrodynamics of the convoy, but not the averaged properties. The ship-generated waves, especially the wave profiles at a specific lateral position, were characterized. Two wave crests exist at the pier position because of the additional reflections, creating a very complex wave pattern in the confined waterway.

Speed limit determination of fishing boats in confined water based on ship generated waves

Ship generated waves (SGW) can cause bank erosion, disturbance to moored boats and bad impact on the environment especially in confined water. One of the important vessel parameters that will affect the SGW is the speed of the boat. The speed limit determination for fishing boats in confined water will be discussed which can be used as a reference to decide the maximum boat or ship speed. The confined water of Mersing River has been chosen for the current study. This river is a busy river located in Johor in the southeast area of Peninsular Malaysia. The limited speed is needed in this river because the river is restricted to many boat activities. The typical boat particulars in Mersing River are 14.05 m in length, 4.35 m in breadth and 1 m in draft. The field experiment has been conducted with several scenarios considering the speed and tidal conditions. The results of the experiment were used to determine the maximum energy of SGW in this area. By using trendline characteristics, the formula of maximum energy was generated by considering the speed of the boat. The Brisbane River Criteria in Australian River has been selected due to the same characteristic with Mersing River. Hence, the reference for allowable energy was defined in this study. By using this river criteria, the limit of the boat speed was provided for all tidal conditions (ebbing, slack and flooding), and it was found that the allowable speed as the speed limit in the Mersing River is 5 knots. This will reduce bank erosion, disturbance to moored boats, environmental impacts and energy consumption. Moreover, the generating process of the formula can be a reference to get the speed limit at particular area as the river in other areas.

Experimental and CFD investigation of the effects of a high-speed passing ship on a moored container ship

The effects of a high-speed frigate model passing close to a moored container model alongside a closed quay are experimentally and numerically investigated with a focus on ship-generated waves, transient ship motions, and hydrodynamic forces acting on the moored ship. Scaled model experiments are conducted to investigate the hydrodynamic interactions between the passing ship-generated waves and the moored ship. A RANS-based CFD method is applied to solve the hydrodynamic problem including the effect of the free surface. The overset mesh technique is adopted to simulate the relative movements between the two vessels. The numerical method is compared with experimental results for the ship-generated waves and total resistance in open water, then validated for the passing ship problem in restricted water. Numerical simulations are carried out to study the effect of different parameters on the passing ship effects. Results show that water depth, passing speed, and separation distance are important parameters that influence the transient interaction. The shape of hydrodynamic interaction forces and moments on the moored ship at relatively high speeds is different from the well-known behaviour at slow speeds. In practice, the most effective measure to reduce the effects of passing ship is to control the speed of the passing ship.

An Experimental Study on the Motion of the Floater Moored near Port in Waves Generated by a Ship

In the past, various research on the effects of waves generated by ships has been investigated. The most noticeable effect of the waves generated by a passing ship is the increase of the hydrodynamic forces and the unwanted large motion of the moored ship and high mooring forces that occur. Thus, it is crucial to investigate the effect of the waves generated by the passing ship near port on the motion of the moored ship and the tension of the mooring lines. A model test was performed with virtual ship-generated waves in a square tank at CWNU (Changwon National University). The IMU (Inertial Measurement Unit) and Optical-based system were used to measure the 6DOF (Six Degrees of Freedom) motion of the moored floater. Additionally the tension of mooring lines were measured by the tension gauges. The effects of the wave direction and wave height generated by the virtual ship-generated waves on the motion of the moored floater were analyzed.

Ship resistance when operating in floating ice floes: A combined CFD&DEM approach

Whilst climate change is transforming the Arctic into a navigable ocean where small ice floes are floating on the sea surface, the effect of such ice conditions on ship performance has yet to be understood. The present work combines a set of numerical methods to simulate the ship-wave-ice interaction in such ice conditions. Particularly, Computational Fluid Dynamics is applied to provide fluid solutions for the floes and it is incorporated with the Discrete Element Method to govern ice motions and account for ship-ice/ice-ice collisions, by which, the proposed approach innovatively includes ship-generated waves in the interaction. In addition, this work provides two algorithms that can implement computational models with natural ice-floe fields, which takes floe size distribution and randomness into consideration thus achieving high-fidelity modelling of the problem. Following validation against experiments, the model is shown accurate in predicting the ice-floe resistance of a ship, and then a series of simulations are performed to investigate how the resistance is influenced by ship speed, ice concentration, ice thickness and floe diameter. This paper presents a useful approach that can provide power estimates for Arctic shipping and has the potential to facilitate other polar engineering purposes.

Resistance and wave characterizations of inland vessels in the fully-confined waterway

The resistance and ship-generated waves of two inland vessels in the fully-confined waterway are investigated based on numerical simulations. The simulation results are validated using towing tank experiments. The influences of the channel dimension, water depth, ship draught and velocity are studied. Specially, the ship resistance is characterized as a function of the blockage ratio and the theory of the linear ship wakes is corrected using the ship draught. These results are expected to predict the ship hydrodynamics in the restricted waterway and reveal the acting mechanism of the confinement effect on a certain level.