Numerical tests are performed to investigate wave transformations of nonlinear nonbreaking regular waves with normal incidence to the shore in decreasing and increasing water depth. The wave height transformation (shoaling) of nonlinear waves can, just as for linear waves, be described by conservation of the mechanical energy flux. The numerical tests show that the mechanical energy flux for nonlinear waves on sloping foreshores is well described by stream function wave theory for horizontal foreshore. Thus, this theory can be used to estimate the shoaled wave height. Furthermore, the amplitude and the celerity of the wave components of nonlinear waves on mildly sloping foreshores can also be predicted with the stream function wave theory. The tests also show that waves propagating to deeper water (de-shoaling) on a very gentle foreshore with a slope of cot(β) = 1200 can be described in the same way as shoaling waves. For de-shoaling on steeper foreshores, free waves are released leading to waves that are not of constant form and thus cannot be modelled by the proposed approach.
The design of large diameter monopiles (8–10 m) at intermediate to deep waters is largely driven by the fatigue limit state and mainly due to wave loads. The scope of the present paper is to assess the mitigation of wave loads on a monopile by perforation of the shell. The perforation design consists of elliptical holes in the vicinity of the splash zone. Wave loads are estimated for both regular and irregular waves through physical model tests in a wave flume. The test matrix includes waves with Keulegan–Carpenter (KC) numbers in the range 0.25 to 10 and covers both fatigue and ultimate limit states. Load reductions in the order of 6%–20% are found for KC numbers above 1.5. Significantly higher load reductions are found for KC numbers less than 1.5 and thus the potential to reduce fatigue wave loads has been demonstrated.
Maritime transport is the most energy-effective mode to move large amounts of goods around the world. Hauling cargo via waterway produces an enormous quantity of greenhouse gas emissions. Vessel fuel efficiency directly influences ship emissions by affecting the amount of burnt fuel. Optimizing ships operating in waves rather than in calm water conditions could decrease the fuel consumption of vessels. In particular, ship propellers are traditionally designed neglecting dynamic conditions such as time-varying wake distribution and propulsion factors, propeller speed fluctuations, ship motions, and speed loss. The effect of waves on the propeller performance can be evaluated using both a quasi-steady and a fully-unsteady approach. The former is a fast computational approximation method based on the assumption that the ratio of propeller angular frequency to wave encounter frequency is sufficiently large. The latter provides a complete representation of the propeller dynamics, but it is computationally expensive. The purpose of this paper is to compare the propeller performance in the presence of waves using the quasi-steady and the fully unsteady approach. This analysis is performed by observing the differences in unsteady propeller forces, cavitation volume, and hull pressure pulses between the two approaches. The full-scale KVLCC2 propeller is utilized for the investigation. Results show a good agreement between the quasi-steady and the fully-unsteady approach in the prediction of the temporal mean and the fluctuation amplitude of KT and KQ, the cavity volume variation, and the hull pressure pulses. Therefore, for the considered operating conditions, the quasi-steady approach can be used to compute the propeller performance in waves.
The regulation of private activities that take place overseas has received significant attention in the legal scholarship. The traditional discussion of the topic observes such regulation from the perspectives of public international law principles of jurisdiction or private international law conflict of laws rules. The present article contributes to the discussion from the perspective of private parties engaged in shipping activities, who face an increasing need of compliance with different regulatory acts of extraterritorial application. It argues that the proliferation of such acts incentivizes private parties to include regulatory interests in their business activities.
The article further suggests that extraterritorial regulation can serve as a trigger for transfer and intrinsic adoption of state’s regulatory interest by private parties. It observes the examples of such ‘privatization of extraterritoriality’ in corporate compliance policies and contractual CSR clauses used by shipping companies, noting their spillover effects over other parties. It further notes that the proliferation of extraterritorial regulation sometimes results in the universalization of responses from private parties, as acquisition of regulatory interest untied from its nation-state origins. The concluding section puts the observed phenomenon into a broader picture, discussing the contribution of extraterritorial regulation to the mechanisms of private governance.
This paper describes the challenges of the maritime supply chain compared to land transport and discusses the new digital initiatives to simplify the processes and enable a better plan for the entire supply chain. First, the background is outlined with an example of the extensive admin processes in maritime transport compared to road transport, followed by a case example presenting the processes of a booking. The case study concludes that the lack of integration is costly in terms of both admin resources, as well as lost capacity on some ships and missing capacity on others. Finally, the evolution of new digital initiatives are discussed, both in general and in terms of competing “alliances” as seen in the airline industry. The paper concludes that the information exchange in the maritime industry has moved drastically in the last 3 years and that one initiative, TradeLens, seems to have gained a position as maritime standard despite a problematic start with many competing initiatives.
In this study, a method for predicting the extreme value distribution of the Vertical Bending Moment (VBM) in a flexible ship under a given short-term sea state is presented. The First Order Reliability Method (FORM) is introduced to evaluate the Probability of Exceedances (PoEs) of extreme VBM levels. The Karhunen-Loeve (KL) representation of stochastic ocean wave is adopted in lieu of the normal wave representation using the trigonometric components, by introducing the Prolate Spheroidal Wave Functions (PSWFs) to formulate the wave elevations. By this means, reduction of the number of stochastic variables to reproduce ocean wave is expected, which in turn the number of computations required during FORM based prediction phases is significantly reduced. In this study, the Reduced Order Model (ROM), which was developed in our previous studies, is used to yield the time-domain VBMs along with the hydroelastic (whipping) component in a ship. Two different short-term sea states, moderate and severe ones, are assumed. The FORM based predictions using PSWF for normal wave-induced VBM are then validated by comparing with those using the normal trigonometric wave representation and Monte Carlo Simulations (MCSs). Through a series of numerical demonstrations, the computational efficiency of the FORM based prediction using PSWF is presented. Then, the validation is extended to the severe sea state where the whipping vibration contributes to the extreme VBM level to a large degree, and finally the conclusions are given.
Stowage planning is an NP-hard combinatorial problem concerned with loading a container vessel in a given port, such that a number of constraints regarding the physical layout of the vessel and its seaworthiness are satisfied, and a number of objectives with regard to the quality of the placement are optimized. State-of-the-art methods decompose the problem into phases, the latter of which, known as slot planning, involves loading the containers into slots of a bay. This article presents an efficient matheuristic for the slot planning problem. Matheuristics are algorithms using mathematical programming techniques within a heuristic framework. The method finds solutions for 96% of 236 instances based on real stowage plans, 90% of them optimally, with an average optimality gap of 4.34% given a limit of one second per instance. This is an improvement over the results provided by previous works.
Waiting times for trucks, trains, airplanes and ships in service represent apparent transport system inefficiencies, and measures to reduce these may have the potential to abate transport GHG emissions. In international shipping, transportation researchers have pointed out that reduced waiting time in association with port calls holds such promise. We explore the potential for GHG abatement through port call optimization, focusing on crews and their employers - the shipping companies. Adding new empirical evidence to the transportation literature, we confirm the existence of idle time during port calls, and go beyond this in describing the causes for it. We show how several port stakeholders, including government officials, limit the crews’ and shipping companies’ room for maneuver in relation to port calls. We also show why the process of reducing waiting time in shipping is more complex than that for onshore transport modes, where real-time traffic information guides drivers’ route choices, and reduces congestion and waiting time. Our findings have implications for both policy makers and transportation research.
The aim of this article is to examine the implications of environmental norms for fishing by analysing the South China Sea and Chagos Marine Protected Area cases. In so doing, the article considers the link between the regulation of fishing and the protection of marine biological diversity. Specifically, three issues are to be examined: (1) the implications of Articles 192 and 194(5) of the UN Convention on the Law of the Sea for the regulation of environmentally harmful fishing, (2) the implications of Article 194 of the Convention for the fishing rights of a state, and (3) balance between environmental considerations and the fishing rights of a state. In this connection, the article argues that environmentally harmful fishing can be regarded as a key concept when considering the regulation of fishing from the viewpoints of marine environmental protection.
In global liner shipping networks, a large share of transported cargo is transshipped at least once between container vessels, and the total transportation time of these containers depends on how well the corresponding services are synchronized. We propose a problem formulation that integrates service scheduling into the liner shipping network design problem. Furthermore, the model incorporates many industry-relevant modeling aspects: it allows for leg-based sailing speed optimization, it is not limited to simple or butterfly-type services, and it accounts for service-level requirements such as cargo transit time limits. The classic liner shipping network design problem is already a hard problem, and to solve the extended version, we propose a column-generation matheuristic that uses advanced linear programming techniques. The proposed method solves LINER-LIB instances of up to 114 ports and, if applied to the classic liner shipping network design problem, finds new best solutions to all instances, outperforming existing methods reported in the literature. Additionally, we analyze the relevance of scheduling for liner shipping network design. The results indicate that neglecting scheduling and approximating transshipments instead may result in the design of liner shipping networks that underestimate cargo transit times and their implications.