Restricted Waterways Research Articles

Coupled computational fluid dynamics-discrete element method for simulating the interactions between ship-induced waves and riprap on restricted waterway banks

In inland waterways, waves generated by passing boats cause the movement of riprap used for bank protection and stabilization. Previous studies have mainly concerned the natural channel erosion problem caused by wind-generated waves and neglected the research and findings on shipping behavior. This work presents a coupling of the computational fluid dynamics model and the discrete element method. The aim is to first study the interactions between ship waves in the confined channel and the movements of the riprap of the banks and shorelines and second to analyze the stability of these armourstones under the actions of various ship velocities and draught depths. These varying conditions exert influence on the ship-induced waves, the crucial point being the drawdown amplitude, and consequently create more intense flow behavior in the near-shore region, which results in instability and destruction of the overall structure of the armor protection layer. The higher ship velocity and the larger draught depth lead to the aggravation of instability processes of the blocs composing the protective layer. There is a critical phenomenon in the influence mechanism of vessel velocity, whereas the variation process induced by draught depth is relatively linear. In addition, the stability of the blocs also depends on their shapes, sizes, and the initial positions within the protective layer. This study could contribute to the high-quality development of inland navigation.

Approach angle estimation method for ships based on deep learning

Accurately estimating the ship's approach angle is crucial during berthing, or passing through navigational structures. It forms the foundation for ship navigation decisions. This study introduces the LiDAR point cloud-based ship pose perception network (PP-Net), a novel deep learning-based method for acquiring ship approach angles. Addressing the challenge of manually annotating approach angles, the ship pose perception method based on point cloud feature distribution (FD) was proposed to obtain initial angle estimates. The max-pooling function was utilized to address the disorder of point clouds, and a multi-resolution feature extractor was employed to enhance the network's robustness in extracting features from inconsistently dense point clouds. By using iterative farthest point sampling (IFPS), datasets with varying numbers of point clouds were standardized to a fixed number of points, thereby normalizing input dimensions and improving computational efficiency. Additionally, a novel loss function was proposed to improve the model's predictive accuracy. Experimental validation conducted in the scenario of ships entering ship lifts demonstrates the effectiveness of the proposed method. The outcomes can support safe navigation for ships in restricted waterways.

Dynamic tugboat deployment and scheduling with stochastic and time-varying service demands

Container ports serve as crucial logistics hubs in global supply chains, but navigating ships within such ports is complex due to restricted waterways. Tugboats play a critical role in ensuring safety and efficiency by escorting and towing ships under these conditions. However, the tugboat deployment and scheduling problem has received little attention. To fill the research gap, we propose a new research problem - the dynamic tugboat deployment and scheduling problem, in which not all requests are confirmed initially but dynamically confirmed over time and future tugging demands need to be anticipated when managing the utilization of tugboats. To formulate the problem, we propose an extended Markov decision process (MDP) that incorporates both reactive task assignment decisions and proactive tugboat waiting decisions, creating a reactive and proactive MDP. To solve the advanced MDP model efficiently for real-time decisions, we develop an anticipatory approximate dynamic programming method that incorporates appropriate task assignment and waiting strategies for deploying and scheduling a heterogeneous tugboat fleet and embed the method into an improved rollout algorithm to anticipate future scenarios. The effectiveness, efficiency, and performance sensitivity of the developed modeling and solution methods are demonstrated via extensive numerical experiments for the Singapore container port.

Rans investigation on the hydrodynamic performance of a ship moving obliquely in shallow and narrow channel

ABSTRACT The ship traveling in restricted waterways often experiences larger hydrodynamic forces and moments, together with larger sinkage, trim and heel, compared with that in open water. The hydrodynamic performance of an oil tanker moving obliquely in a shallow and narrow channel is investigated by using a RANS (Reynolds-Averaged Navier-Stokes) method in this work. The effects of ship-bank distance, water depth, etc. on hydrodynamic performance are analysed. When the ship gets closer to the channel bank or the inclination of the channel bank becomes steeper, the blockage effects due to the channel become more considerable. The effects of shallow water and ship drift motion will augment bank effects. The captive model test for a ship moving obliquely in a shallow and narrow channel are numerically carried out in both Circulating Water Channel (CWC) and Towing Tank (TT). The bank effects showed by TT are more considerable than that by CWC.

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.

An Integrated Method for Ship Heading Control Using Motion Model Prediction and Fractional Order Proportion Integration Differentiation Controller

Due to the influence of the natural environment, it is very challenging to control the movement of ships to navigate safely and avoid potential risks induced by external environmental factors, especially for the development of autonomous ships in inland or restricted waterways. In this research, we propose an integrated approach for ship heading control that improves the timeliness and robustness of navigation. Recursive least squares and backward propagation neural networks are utilized to identify the ship motion model parameters under the influence of external factors and predict their development in real time. A particle swarm optimization-integrated Fractional Order Proportion Integration Differentiation (FOPID) controller is then designed based on the dynamically identified motion model to achieve accurate heading control for ships navigating in restricted waterways. A case study was conducted based on the Korea Venture Large Crude Carrier 2 (KVLCC2) model to verify the effectiveness, and a comparison between the conventional FOPID controller and the improved FOPID controller was also conducted. The results indicate that the proposed identification–prediction–optimization FOPID controller has faster speed on stabilization and has higher robustness against external influences, which could provide added value for the development of a motion controller for the autonomous ship for inland and restricted waterway navigation.

Autonomous Ship Collision Avoidance in Restricted Waterways Considering Maritime Navigation Rules

Autonomous Ship Collision Avoidance in Restricted Waterways Considering Maritime Navigation Rules

Path following control for large inland ships in a restricted waterway using the nonlinear terminal sliding mode method

In order to solve the problem of path following for large ships travelling in restricted waterways, an adaptive Line-Of-Sight (LOS) guidance with the Nonlinear Terminal Sliding Mode (NTSM) algorithm is proposed in this paper. Compared to classical Sliding Mode Controller (SMC) and Adaptive Sliding Mode Controller (ASMC), the proposed system enables large ships to track the desired path much faster, meanwhile, the course stability can also be achieved with the controller saturation and environmental disturbance. To solve the problems of high nonlinearity and uncertainty of ship motion in restricted waters, the mathematical model with Extended state observer (ESO) is proposed to linearize problem. A drift angle observer is established to observe the drift angle during the vessel's navigation, and the LOS guidance law is used to achieve accurate tracking of the desired trajectory. The simulation results show that the inland ships under the control of the proposed scheme can accurately track the desired trajectory in a restricted waterway. The proposed algorithm has good robustness under the effect of environmental disturbances.

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

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

Evaluation of car-following model for inland vessel-following behavior

Due to the unique role of inland waterway transport in reducing carbon emissions, the demand for inland vessel transportation has greatly increased recent years in China. More and more vessels in the inland waterway have gradually formed a non-free following queue, rather than the free traffic flow of the past. To provide a theoretical basis for organizing the vessel traffic under a crowded state, it is necessary to understand accurately the microscopic characteristics of inland waterway vessel traffic flow, such as vessel-following behavior. This research carried out three vessel-following experiments to obtain valuable microscopic data of vessel-following behavior in different inland restricted waterways in Yangtze Delta, China. Considering the uniformity of traffic flow, six typical car-following models were tried to verify their applicability to inland vessel-following behavior. The parameters of the car-following models were recalibrated based on the experimental data. The simulation results of different models were evaluated, and the improved General Motor (GM) model was proposed to avoid vessel collision during the simulation process in GM model. The results show that the improved GM model, Newell model, Intelligent Driver model (IDM) and Longitudinal Control model (LCM) were confirmed to be suitable to describe the vessel-following behavior in the inland restricted waterway. These models may help professionals understand deeply the inland vessel traffic characteristics.

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.

Open-loop Scrubbers and Restricted Waterways: A Case Study Investigation of Travemünde Port and Increased Sulphur Emissions Immediately After the Scrubbers are Turned Off

Open-loop Scrubbers and Restricted Waterways: A Case Study Investigation of Travemünde Port and Increased Sulphur Emissions Immediately After the Scrubbers are Turned Off

Hydrodynamic interaction forces on different ship types under various operating conditions in restricted waters

To accurately understand the behavior of ships sailing in restricted waterways, it is necessary to scientifically analyze the influence of the bank effect on the hydrodynamic force of a ship. In this study, the water depth to draft ratio, distance between the wall and ship, speed of the ship, and loading condition are classified as factors influencing the confined water effect. Numerical analyses were performed on two different very large vessels to investigate the effects of the factors on hydrodynamic interaction using CFD. The sway force was gradually decreased as the water became shallower. The sway force acted on the container ship as a repulsion force in the very shallow water. The roll and yaw moments acted as the greatest hydrodynamic forces in the very shallow water. For the tanker, the direction of the yaw moment changed to bow-in as the speed increased. The effect of hydrodynamic force on the vessel is different depending on the loading condition, navigation area, and speed of the vessel. Comprehensive considerations and countermeasures according to ship type must be prepared to ensure the safe navigation of ships.

Applicability of Current Statutory Rules for Stability Requirements of Bangladesh Inland Passenger Vessels

_ Applicability of current Bangladesh inland vessels stability rule has been investigated for the local passenger vessels. Bangladesh inland vessel’s stability rule is exactly the same as international stability code (2008), despite of the different environmental load in navigational routes. The restricted waterways limit the dimension of the vessels. It has been found that domestic passenger vessels have changed their dimensions considerably from the year 1974 to 2009. But analysis shows, still most of the domestic passenger vessels exceed the dimensional ratio range that is specified in both the righting lever-based criteria and weather criterion of international code. The part of the weather criterion, specifically estimation method for the angle of roll due to wind and wave action has been studied in details. Different nationals have adopted values of governing parameters for extended range of vessel dimensions, which can also successfully cover all the Bangladesh domestic passenger vessels. As per the code 2008, for ships with values outside of the addressed range, the angle of roll may be determined with model experiments of a subject ship as alternative weather criterion. Bangladesh is still lacking both in facility and infrastructure for carrying model tests. This study shows that computer simulation can be used in exchange of experimental setup where the simulation result can be validated by Parameter Identification Technique, which is described as an alternative approach in the interim guideline of International Maritime Organization (IMO). Introduction Passenger vessel accident is a persistent phenomenon in Bangladesh inland waterways. Thousands of people have passed away due to these catastrophic incidents. The major two modes of failure that are responsible for accidents in waterways are identified as structural failure and stability failure (Islam et al. 2015a). Structural failure like collision also leads to stability failure (Damage Stability). Iqbal et al. (2008a, 2008b) analyzed the Bangladesh inland passenger vessels accident data of 25 years and found that in 49% cases, the failure was due to lose of intact stability. Raiyan et al. (2017) have done event tree analysis of marine accidents in Bangladesh taking initial condition as overloading. Literature study (Awal 2006; Awal et al. 2007; Awal et al. 2014; Islam et al. 2015b; Rahman 2017) shows that researchers have proposed many general recommendations from different point of view to prevent the passenger vessel accidents. But still now, no attempt has been made to analyze the currently applicable statutory rules for ensuring the safety in inland waterways, which is mainly Bangladesh Inland Vessels Stability Rule including Weather Criterion (Zulfikar 2005). Stability rules of inland vessels are to be governed by standard localized condition of the subjected parameters. The socioeconomic condition, local environment, as well as infrastructural development like availability of model test facilities need to be considered for smooth and proper application of stability rules which then can only ensure the safety of local vessels. This implies that the individual efforts of concern country in research and analysis are of great importance for the development of practicable stability rules of inland vessels.

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.

Computational fluid dynamics predictions of draught and trim variations on ship resistance in confined waters

Adjusting a vessel's trim and draught to enhance resistance characteristics is a promising strategy to improve the energy efficiency of maritime transport. However, the vast majority of scientific effort has been directed at such gains in deep, unrestricted waters. Shallow and confined waters modify the flow and pressure distribution around a ship, altering considerably the resistance curve. This study aims to elucidate trim and draught increase effects on a ship's resistance while advancing through a restricted waterway using Computational Fluid Dynamics. The results show that increasing the draught of a benchmark hull magnifies the hydrodynamic resistance by approximately 10% to 15% depending on the ship speed. This added hydrodynamic resistance may be compensated by adjusting the vessels’ trim, but the ability to compensate the added hydrodynamic resistance is sensitive to ship's speed. At low speeds, the numerical model predicts the increase in resistance due to a 10% higher draught can be reduced by varying the trim angle leaving the total resistance 0.87% higher than at the design draught and zero trim angle condition. On the other hand, higher speeds offer a greater potential for resistance reduction through trim.

COLREGS-Compliant collision avoidance for physically coupled multi-vessel systems with distributed MPC

This paper proposes a distributed control scheme for autonomous tugboats to tow a ship in a restricted water traffic environment ensuring collision avoidance while being compliant with maritime regulation called COLREGS. The complex problem is cooperatively solved by addressing three sub-optimization problems. The first is to optimize the towing forces and angles for solving ship waypoint following and collision avoidance problems. The second is to optimize the tug thruster forces and moment for solving the tug online trajectory tracking and collision avoidance problems. The third is to optimize the Lagrange Multipliers for solving the consensus problem between the ship and tugs. The distributed control architecture follows the Model Predictive Control (MPC) strategy using the Altering Direction Method of Multipliers (ADMM). Simulation experiments indicate that the proposed control scheme can deal with static and dynamic obstacles in restricted waterways for a physically interconnected multi-vessel system executing the towing process, and the collision avoidance complies with COLREGS rules.

Scheduling of waterways with tide and passing box

AbstractDue to the increasing amount of goods transported by vessels and the resulting increased size of the vessels, waterway scheduling becomes a challenging task. Waterways can often only be expanded with enormous costs and environmental damage. Therefore, this paper investigates a scheduling problem on a restricted waterway. Wide vessels are only allowed to pass in a passing box and vessels with deep draught can only pass the waterway in a time window around high tide. We present a mixed‐integer program (MIP) for the problem setting and develop techniques which allow us to fix variables and reduce the number of variables and constraints of the model. The resulting model formulations are evaluated in a comprehensive computational study on a real‐world setting at the river Elbe next to Hamburg (Germany).

Efficient online one-way traffic scheduling for restricted waterways

In Yangtze River traffic management, to manage ship sequencing and scheduling effectively and efficiently in restricted waterways has long been a challenging issue. This paper proposes a Sliding Window based Online ship Sequencing and Scheduling algorithm (OSS-SW) to tackle this problem. The OSS algorithm is capable of generating a more efficient ship sequence by introducing the ‘position shift’ concept which takes advantages of ships’ sailing time differences in the restricted waterway. The sliding window mechanism on the other hand is introduced to handle the traffic uncertainties and to reduce the computational complexity. The impact of the restricted waterway congestion on the performance of OSS-SW is also investigated. Further, the parameter settings of the proposed OSS-SW are investigated in detail. Both simulation studies and the real data applications confirm that the proposed OSS-SW algorithm outperforms the existing widely adopted Traffic Signal Revealing System (TSRS) and the Expert System based algorithm (FAHP-ES) in solving the ship sequencing and scheduling problem.

A CFD Study of the Resistance Behavior of a Planing hull in Restricted Waterways

The demand for high-speed boats that operating near to shoreline is increasing nowadays. Understanding the behavior and attitude of high speed boats when moving in different waterways is very important for boat designer. This research uses a CFD (Computational Fluid Dynamics) analysisto investigate the shallow water effects on prismatic planing hull. The turbulence fl ow around the hull was described by Reynolds Navier Stokes equations RANSE using the k-ɛ turbulence model. The free surface was modelled by the volume of fl uid (VOF) method. The analysis is steady for all the ranges of speeds except those close to the critical speed range Fh=0.84 to 1.27 due to the propagation of the planing hull solitary waves at this range. In this study, the planing hull lift force, total resistance, and wave pattern for the range of subcritical speeds, critical speeds, and supercritical speeds have been calculated using CFD. The numerical results have been compared with experimental results. The dynamic pressure distribution on the planing hull and its wave pattern at critical speed in shallow water were compared with those in deep water. The numerical results give a good agreement with the experimental results whereas total average error equals 7% for numerical lift force, and 8% for numerical total resistance. The worst effect on the planing hull in shallow channels occurs at the critical speed range, where solitary wave formulates.