Sea surface currents are of significant importance in various scientific and maritime applications. There are several measurement techniques available to study surface currents, however, they have limitations in spatial coverage and resolution. This study presents a proof-of-concept for a new measurement principle that relies on the difference between a ship's speed relative to water and land. The approach involves estimating the ship speed vector relative to water from optical satellite imagery of Kelvin wakes. This ship speed vector is subtracted from the ship speed over ground, which is determined from Automatic Identification System (AIS) data, to estimate the surface current. A case study in the Strait of Gibraltar was performed using two months of Sentinel-2 imagery, which yielded 81 visible Kelvin wakes over 25 images. Surface currents were estimated in directions parallel and perpendicular to the ship's sailing line for each Kelvin wake. The estimated currents were validated with respect to surface currents derived from High-Frequency Radars (HFRs) and modelled currents from the Copernicus Marine Environmental Monitoring Service (CMEMS). The uncertainty in the two surface current components was estimated using triple collocation. After removing 12 data points with large ship course variability, standard deviations of 0.14 and 0.16 m s⁻¹ were estimated for the surface currents along and across the sailing line, respectively. Despite limitations in measurement frequency due to satellite revisit times, cloud cover and Kelvin wake visibility, this new method can provide accurate estimates of sea surface currents in regions with high vessel density.

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On the 26th of January 2022 the new Sea Lock IJmuiden in the Netherlands was officially opened. Before the lock was put in use, two in-situ measurement campaigns have been carried out to verify the performance of the lock and after one year of operation a third measurement campaign was performed. The present paper provides an overview of these three monitoring campaigns conducted in the first two years of operation. The measurements verified that the lock performed within predetermined requirements and outcomes of the measurements were used to derive safe procedures for vessel handling during lockage. The findings were in good agreement with expectations from physical scale model research and numerical simulations performed earlier in the design process of the lock. For Sea lock IJmuiden, density currents play a major role in the lock operation. Better understanding of these processes led to a safer lock operation. A fundamental aspect for the success and usefulness of these measurement campaigns was the cooperation between all parties involved in the locking process.
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Propellers of ships generate high velocities adjacent to quay walls, jetties and locks. Generally, a bottom protection is installed in order to prevent instability due to scour. Although design guidance exist, propeller-induced loads are far from fully understood and have predominantly been derived on the basis of model tests. The validation of the existing design methods is lacking, especially for specific types of bow thrusters. In this research, field measurements of flow velocities induced by a 4-channel bow thruster system against a vertical quay wall have been performed. Test results showed a flow characterized by low mean velocities and large fluctuations, with the extent of reflected flow limited to few meters from the quay wall and inflow beneath the suction points playing a role.

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Accurate modelling of waves in harbours and the response of moored ships to that type of forcing is of prime importance to determine the safety and workability of ships moored at berths exposed to local wave conditions. This study investigates the combination of a non-hydrostatic wave-flow model (SWASH) and a 3D boundary-integral diffraction model (Harberth) to compute wave forces acting on moored ships. A series of systematic numerical tests has been performed to develop the proposed methodology and gain insight on its limits of application. The approach is validated using physical scale model test data of waves and forces acting on a restrained ship. Results indicate a good performance even for extremely energetic wave conditions, setting the investigated modelling approach as a potential alternative for future applications.

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Recent constructions of large sea locks in the Netherlands at IJmuiden and Terneuzen have been accompanied by extensive hydraulic research, including physical scale model tests which took into account the effects of density differences across the lock heads during leveling operations. The case study presented here compares the situations and results from the studies of the two locations, and shows the importance of density effects in an accurate assessment of the hydrodynamic forces on the vessels and subsequently the forces on the mooring lines. Supposedly small differences in the local boundary conditions at the two locations lead to very different results, owing primarily to the differences in propagation of the density currents. Numerical models do not as yet predict this with sufficient accuracy. This further underlines the importance of doing extensive preliminary hydraulic investigations when designing large new shipping locks.

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Floating breakwaters are moored structures that attenuate wave energy through a combination of reflection and dissipation. Studies into floating breakwaters have been generally restricted to optimising the attenuation performance. This study presents a novel floating breakwater type that was developed to have good attenuation performance while keeping wave drift loads as small as possible. The floating breakwater was designed as a submerged parabolic beach that enforces wave energy dissipation through breaking. The design was tested in a 3D shallow-water wave basin in captive and moored setups for regular and irregular wave conditions. Results are presented in terms of attenuation performance, motions, and (mooring) loads. The results show that the breaking of waves improves the attenuation performance of the floater in captive setup. However, in moored setup, the attenuation performance was dominated by diffraction and radiation of the wave field, with breaking being of secondary importance. This shows that breaking-enforcing floating breakwaters have potential, but require a high vertical hydrostatic and/or mooring stiffness in order to enforce intense breaking. Mean wave drift loads on the object showed significant difference between breaking and non-breaking waves in both setups, with breaking waves leading to lower normalized loads. This is attributed to breaking-induced set-up and set-down of the water level. As a result, the new breakwater design has a more favourable balance between wave attenuation and drift loads than common (i.e., box-, pontoon-, or mat-type) floating breakwater designs. Tests with varying surface roughness showed that floating breakwaters may benefit from dual-use functions that naturally increase the roughness (e.g., shellfish, vegetation), which have a marginal effect on the attenuation performance, but increase the added mass and hydrodynamic damping and as such, reduce mooring line loads.@en

Seaport operability is key to the economic viability of ports. Metocean conditions (e.g., wind, short waves, and infragravity waves) affect this operability when certain thresholds are exceeded. This paper describes a method for the global mapping of seaport operability risk indicators using open-source metocean data. This global-scale assessment provides a geographic overview of operability risks and first-order insights into the most relevant metocean risk indicators at each location. The results show that locations around the equator and inland seas have lower operability risk than locations farther away from the equator. “Hotspots” are mainly located along the southern capes (Cape of Good Hope, Leeuwin, Horn), around the ‘Roaring Forties’, and at exposed locations along the oceans. Of the metocean parameters considered, short waves are found to be the most critical risk indicator for port operability at most locations. Using (the insights of) this study, port authorities, operators, and designers can prepare for metocean risks at an early stage and effectively respond with mitigation measures and layout adjustments to improve port operability.

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This paper investigates the effect of density differences on the forces acting on a moored vessel during lock operations, focusing on the effect of the position of the moored vessel in the lock chamber in the presence of density currents. The extensive scale-model research performed for the new sea lock in IJmuiden, The Netherlands has shown that the combination of density differences and an asymmetric layout of the moored vessel in the lock chamber may lead to high forces on the vessel that can largely exceed the allowable force limit. In particular, as a result of the density currents, forces in the transverse direction build up, pushing the vessel away from the chamber wall, during leveling and after opening the lock gate, leading to higher loads on the mooring lines. The forces caused by the density difference are the dominant forces and the performance of the leveling system cannot be assessed without taking this into account. Based on the results of the performed tests, criteria for achievable leveling times and allowable hydrodynamic forces during leveling are determined for the new sea lock of IJmuiden. Furthermore, the obtained results can be used for calibration or validation of numerical models that are valuable tools for the design of future locks.

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Background and Objectives: To determine the value of erythropoietin in reducing allogeneic transfusions, it is important to assess the effects, safety and costs for individual indications. Previous studies neither compared the effects of erythropoietin between total hip and total knee arthroplasty, nor evaluated the safety or costs. We performed a meta-analysis to assess the effects of erythropoietin in total hip and knee arthroplasty separately. Safety and costs were evaluated as secondary outcomes. Materials and Methods: A systematic literature search was performed to identify randomized controlled trials evaluating the effect of erythropoietin in total hip and knee arthroplasty until April 2014. Study data were extracted using standardized forms and pooled using a random-effects model. Strength of the evidence was evaluated using Cochrane's Collaboration's tool for risk of bias assessment. Results: Seven studies were included (2439 patients). Erythropoietin significantly reduced exposure to allogeneic transfusion in both hip (RR 0·45; 95%CI 0·33–0·61) and knee (RR 0·38; 95%CI 0·27–0·53) arthroplasty, without differences between indications (P = 0·44). Mean number of transfused red blood cell units was significantly decreased in erythropoietin-treated patients (mean difference −0·57; 95%CI −0·86 to −0·29)(unable to split). No differences in thromboembolic or adverse events were found. Only one study evaluated costs, so that no pooled cost-effectiveness estimates could be given. Conclusion: Erythropoietin is effective in both hip and knee arthroplasty and can be considered as safe. However, the decision to use erythropoietin on a routine base should be balanced against its costs, which may be relatively high.@en