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Background Vaccine-induced immunity is at present the main strategy to stop the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Recent evidences suggested a protective effect of influenza vaccination against coronavirus disease 2019 (COVID-19) severity, while impact on the immune response to BNT162b2 messenger RNA (mRNA) vaccine is under investigation. Methods We aimed to evaluate this aspect in a cohort of 297 healthcare workers (108 males, 189 females) after seasonal influenza vaccination compared to no-flu-vaccination. VAX+ (165 individuals; 63 males and 102 females) had tetravalent influenza vaccine, and VAX- (132 individuals; 45 males and 87 females) had no flu vaccination. Anti-spike-receptor binding domain (RBD) level was tested 15 - 70 days after BNT162b2 second inoculum. Results Increased antibody response was observed in total VAX+ compared to VAX- (2,047.4 vs. 1,494.2 binding antibody unit (BAU)/mL, P = 0.0039), independently from gender and body mass index (BMI). Younger total individuals (< 35 years) showed significant increase of the level of binding antibodies (2,184.8 vs. 1,590.9 BAU/mL, P = 0.0038) compared to ≥ 35 years; young/old difference was lost restricting to VAX+ subgroup. Flu vaccinations appear associated to better antibody response in older individuals (P = 0.027, ≥ 35 years VAX+ vs. VAX-). A decreasing trend during time was observed for both VAX+ and VAX-, except for < 35 years VAX- individuals. Early response was higher in VAX+ compared to VAX-; however a more rapid waning was observed in VAX+ subjects. Conclusions Our data showed better antibody response to SARS-CoV-2 vaccine in subjects already vaccinated against seasonal influenza; this may represent one of the mechanisms underlying the cross-protective effects of influenza vaccination against heterologous infections reported in recent epidemiological studies.

COVID-19 pandemic led to a worldwide increase of hospitalizations for interstitial pneumonia with thrombosis complications, endothelial injury and multiorgan disease. Common CT findings include lung bilateral infiltrates, bilateral ground-glass opacities and/or consolidation whilst no current laboratory parameter consents rapidly evaluation of COVID-19 risk and disease severity. In the present work we investigated the association of sFLT-1 and CA 15.3 with endothelial damage and pulmonary fibrosis. Serum sFlt-1 has been associated with endothelial injury and sepsis severity, CA 15.3 seems an alternative marker for KL-6 for fibrotic lung diseases and pulmonary interstitial damage. We analysed 262 SARS-CoV-2 patients with differing levels of clinical severity; we found an association of serum sFlt-1 (ROC AUC 0.902, decision threshold > 90.3 pg/mL, p p 24.8 U/mL, p

Background: Sepsis is a life-threatening dysregulated host response to infection responsible of multiple organs dysfunction (Sepsis-3 International Consensus Definition), during which clinical outcome is a balance between inflammation and immune suppression. Monocytes and lymphocytes may play an important role in immune paralysis, and their impaired functional activity can decrease overall immune system efficiency. We evaluated sepsis-induced changes in monocytes human leukocyte antigen-DR isotype (HLA-DR) expression and T cell capacity of interferon (IFN)-gamma production in relation with patient’s clinical outcome. Methods: Analysis of HLA-DR expression on blood monocytes (mHLA-DR) was performed in 55 patients with high procalcitonin (hPCT, > 0.5 ng/mL,) and suspected/confirmed sepsis, and 20 controls. HLA-DR absolute quantification and IFN-gamma release assay were monitored in 16 septic patients for 4 weeks following sepsis confirmation. Results: Cytofluorimetric analysis revealed a significant decrease of mHLA-DR percentage in septic patients with adverse outcome compared to patients with better clinical outcome (88.4% vs. 98.6% with P < 0.05), in combination with a significant decrease of absolute number of HLA-DR molecules per monocyte (P < 0.05, starting at 1 week of follow-up). Lymphocytes stimulation with phytohemagglutinin (PHA), Staphylococcus aureus ( S. aureus ) and Candida albicans ( C. albicans ) showed a severe declining of IFN-gamma release related to fatal clinical outcome of patients. Conclusions: This immunologic anergy of innate and adaptative immunity showed an early immune paralysis during sepsis which appears correlated with the impairment of clinical outcome. J Clin Med Res. 2021;13(5):293-303 doi: https://doi.org/10.14740/jocmr4474

In the quest for a numerical method for surface waves and wave-induced effects applicable when linear or weakly nonlinear methods are insufficient, a three-dimensional numerical wave tank assuming fully-nonlinear potential-flow theory is proposed. When viscous-flow effects, breaking waves or other violent flow-phenomena are not of primary importance, potential-flow methods may have similar capability in capturing the involved physics as Navier-Stokes solvers while being potentially more accurate in handling wave-propagation mechanism and more computationally efficient. If made sufficiently accurate, efficient and numerically robust, fully-nonlinear potential flow models can therefore represent a powerful tool in the study of ocean waves and their interaction with marine structures, which is the main motivation behind the present work. The governing Laplace equation for the velocity potential is solved using the harmonic polynomial cell method, which is a field method giving high-order accuracy provided that the cells used to describe the water domain have no stretching or distortion. This can only be achieved in a grid with cubic cells, which leads to poor numerical efficiency unless measures are introduced to refine the grid locally. Here, to improve the efficiency using strictly cubic cells, an adaptive grid refinement technique is introduced. It is shown that this has the ability to improve the computational speed with a factor of up to 20 without sacrificing accuracy. Numerical results are shown to be in good agreement with highly accurate nonlinear reference solutions for regular and irregular waves of various steepness up to the limit of theoretical wave breaking. For long-crested irregular waves, significant discrepancies with a second-order theory for the crest-height distribution are identified, while the second-order theory appears to provide a better description of the crest height for the single short-crested irregular sea state simulated. Having demonstrated that the proposed numerical method accurately models nonlinear wave phenomena up to the limit of wave breaking, future work should seek to implement wave-body interaction capabilities. The adaptive grid refinement technique, which refines the grid dynamically depending on the position of boundaries of interest, is developed with this application in mind. Except from providing a robust way of dealing with wave-body intersection points, extending the method to account for wave-body interactions should therefore involve limited difficulty.

The present work deals with wave generation in fully nonlinear numerical wave tanks (NWT). As an alternative to modelling a moving (physical) wavemaker, a two-dimensional (2D) potential-flow NWT is coupled with an external spectral wave data (SWD) application programming interface (API). The NWT uses the harmonic polynomial cell (HPC) method to solve the governing Laplace equations for the velocity potential and its time derivative, and has previously been extensively validated and verified for numerous nonlinear wave-propagation problems using traditional wave-generation mechanisms. Periodic waves of different steepness generated with a stream-function theory as reference solution in the SWD API are first considered to investigate the method’s numerical accuracy. Thereafter, with a higher-order spectral method (HOSM) as the SWD API solution, irregular waves with different wave heights and water depths relevant for e.g. aquaculture and offshore structures are simulated. Differences between the HPC and HOSM solutions in and near steep crests are investigated. The study aims to demonstrate a robust method to generate and propagate general wave fields for further studies of nonlinear waves and wave-body interaction in both two and three dimensions.

Fishes are talented swimmers. Depending on the propulsion mechanisms many fishes can use flapping tails and/or fins to generate thrust, which seems to be connected to the formation of a reverse von Kármán wake. In the present work, the flow past a 2D flapping foil is simulated by solving the incompressible Navier-Stokes equations in the open-source OpenFOAM platform. A systematic study by varying the oscillating frequency, peak-to-peak amplitude and Reynolds number has been performed to analyze the transition of vorticity types in the wake as well as drag-thrust transition. The overset grid method is used herein to allow the pitching foil to move without restrictions. Spatial convergence tests have been carried out with respect to grid resolution and the size of overset mesh domain. Numerical results are compared with available experimental data and discussed. The results show that the adopted methodology can be well applied to simulate large amplitude motions of the flapping foil. The transitions in the types of wake are consistent with the benchmark experimental data, and the drag-thrust transition of the pitching foil does not coincide with von Kármán (vK)-reverse von Kármán (reverse-vK) wake transition and it is highly dependent on the Reynolds number.

An analytical model has been proposed for the response of beams and stiffened panels subjected to extreme flat or nearly flat water impacts in Part I of the two-part companion paper. The model aims to capture the significant hydro-plastic coupling between large plastic structural deformations and the hydrodynamic pressure. Governing non-dimensional parameters for the hydro-plastic slamming phenomenon were identified and discussed. This Part II paper verifies the analytical model proposed in Part I by comparison with the hydro-plastic slamming response of beams and stiffened panels using multi-material Arbitrary Lagrangian Eulerian (ALE) methods in LS-DYNA. Numerical modelling and settings with the ALE simulations are firstly validated by comparison against drop-test experiments of a rigid wedge and of an elastic plate. Then, water entry simulations of flat plates and stiffened panels are carried out, where structural deformations go into the plastic regime. The simulated scenarios cover different plate thicknesses/cross sectional dimensions of stiffened panels, and various initial water-entry velocities. The analytical model is discussed with respect to the fluid flow, structural deflections, the pressure history and the impulse. Validity of assumptions of the analytical model is also discussed. Potential applications and limitations are indicated. The proposed design curves are well suited to be utilized in rules and standards for designing against extreme water slamming.

Dynamic response of a well boat operating at a fish farm in current is investigated numerically. An objective is to determine the operational conditions of the well boat. In terms of the fish farm, a realistic set-up (with single cage) is considered, including a floating collar, an elastic sinker tube, a flexible-closed net cage and a complex mooring system. A time-domain solution is used to find the steady configuration and response. Transverse viscous current loads are estimated using the cross-flow principle. The drag coefficients are obtained empirically by considering cross-sectional details, free surface and three-dimensional (3D) flow effects. The drag force is experimentally validated. The effect of the ship wake on the net loading is also assessed. The most critical scenario with the well boat placed at the weather side of the fish farm is analyzed in detail. Critical response variables for operational limits are the maximum anchor-line tensions and floater stresses. Numerical results show that the anchor loads will increase more than 40% in small current velocities and up to 90% in high current velocities due to the viscous current loads on the boat. There is also a strong increase of the floating collar deformations and stresses when the well boat is in contact with the floating collar. A sensitivity analysis has been carried out to identify the physical parameters affecting the anchor loads and the maximum stress in the floating collar. From our studies, the anchor loads are more sensitive to current direction, bottom weight system, sinker tube depth and mooring line properties (pretension load, anchor chain weight, etc.) and less sensitive to other parameters such as floating collar stiffness and cross-sectional drag coefficients of the well boat. The shading effect of the well boat on the fish-farm inflow has been examined and appeared not negligible with 4% to 10% reduction of the anchor loads for the studied current conditions. The maximum stress in the floating collar is sensitive to well-boat loads related parameters (current direction, cross-sectional drag coefficient) and pretension load in the anchor line; not so sensitive to net loading related parameters such as sinker tube depth and sinker tube weight. Lastly, the operational conditions of the well boat at the fish farm were discussed. Numerical results show that the maximum stresses in the floating collar should be of major concern. The loads in the mooring lines are moderate compared with the corresponding breaking limits.

The emergence of coronavirus disease 2019 (COVID-19) is globally a major healthcare threat. There is little information regarding the mechanisms and roles of the humoral response in SARS-CoV-2 infection. The aim of this study was to analyze the antibody levels (IgM and IgG) by chemiluminescence immunoassay in 54 subjects positive to SARS-CoV-2 swab test in relation to their clinical status (whether asymptomatic, pauci-symptomatic or with mild, sever or critical symptoms), the time from the symptom onset, sex, age, and comorbidities. Overall, the presence of comorbidities and the age of subjects were associated with their clinical status. The IgG concentrations were significantly higher in patients who developed critical and severe symptoms and seemed to be independent from age, sex and comorbidities. IgG titers peaked around day 60, and then began gradually to drop, decreasing by approximately 50% on the 180th day, while the IgM titers progressively decreased as early as the tenth day, but they could be detected even at later time points. Despite the small number of individuals, some peculiar characteristics of the humoral response in COVID-19 emerged. We observed a high inter-individual variability, an ephemeral IgG half-life in several patients, and a persistence of IgM in others.

Deliverable della LA 1.2 del progetto RDS che ha come obiettivo quello di incrementare ulteriormente la complessità dei modelli per il calcolo delle forze idrodinamiche, che `e poi uno degli `obiettivi dell'intero progetto di ricerca. Viene proposto un modello matematico e numerico per la soluzione del problema di superficie libera completamente non lineare nell'ipotesi di flusso a potenziale. Tale modello, seppure utilizzato in questa fase limitatamente a domini bidimensionali, puo essere facilmente esteso al caso 3D.

Progettazione, realizzazione e studio di un modello in scala di isola solare galleggiante

In this paper, a new open-source implementation of the lower-order, 3-D Boundary Element Method (BEM) of solution to the deep-water, zero Froude-number wave-body interaction problem is described. A validation case for OMHyD, the new open-source package, is included, where the outputs are compared to results obtained using the widely used frequency-domain hydrodynamic analysis package ANSYS-AQWA. The theory behind the solution to the diffraction-radiation problem is re-visited using the Green function method. The Hess and Smith panel method is then extended to the case of a floating object using the image-source to impose the wall condition at the free-surface, and a wavy Green function component to account for presence of free-surface waves. An algorithm for computer implementation of the procedure is developed and subsequently implemented in PYTHON. The wavy part of the Green function is determined using a verified and published FORTRAN code by Teleste and Noblesse, wrapped for PYTHON using the Fortran to Python (F2PY) interface. Results are presented for the various stages of implementation viz. panelling, body in infinite fluid domain, effect of the free-surface, and effect of surface-waves. The hydrodynamic coefficients obtained from this preliminary frequency-domain analysis are shown to be in satisfactory agreement with ANSYS-AQWA results. Conclusions are drawn based on the performance of the code, followed by suggestions for further improvement by including the removal of irregular-frequencies, multi-body interactions, and bottom interference, which are not considered in the present implementation.

A fully nonlinear two-dimensional numerical method based on potential-flow theory for water waves and their interaction with surface-piercing rigid bodies is presented. The harmonic polynomial cell (HPC) method is used to solve the Laplace equation for the velocity potential and its time derivative. The HPC method, which is a high-order method using analytical expressions (harmonic polynomials) to represent the solution inside overlapping cells, has previously been shown accurate and efficient. Supplementary research has shown that, in order to maximally benefit from the method’s accuracy, it is a requirement that square or close-to-square cells are used. Here, we use an immersed boundary method to model non-stationary boundaries such as the free surface or the surface of a rigid body, and overlapping, body-fixed grids that are locally Cartesian to refine the solution near moving bodies. Combining these two modelling concepts with the HPC method represents the main novel contribution in the present work. With this combined method, denoted as an immersed-boundary overlapping grid method (IBOGM), the challenge of generating boundary-fitted grids for complex boundaries is avoided. Moreover, square cells can be used throughout the domain and the solution can be refined locally without increasing the number of unknowns unnecessarily. The method is systematically validated and verified against analytical, experimental and numerical reference results. The cases studied include propagation of steep waves, forced heave motions of a semi-submerged circular cylinder and a fixed and freely floating ship section in beam-sea waves. For the freely floating ship section, the present method is compared in detail with results from a dedicated study performed with a fully nonlinear boundary element method for cases with roll motions up to 30◦ . The present results are generally in good agreement with reference results, even for the most challenging wave–body interaction cases considered. Based on this, we later intend to use the method to examine in depth the importance of nonlinear effects in the interaction between waves and rigid bodies. © 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

OpenFOAM (OF) represents an attractive and widely used open-source environment for simulating complex hydrodynamic scenarios with several implemented numerical methods and wide variety of problems it can be applied to. For commercial and open-source solvers, though, expertise and experience are required to get physical and reliable results. Here, without pretending to be exhaustive, we aim to contribute in highlighting advantages and challenges of some key computational fluid dynamics (CFD)-simulation tools, with focus on the OF platform. We examine the effect of grid type, grid size and time-evolution scheme. Dynamic-mesh techniques and their influence on local and global numerical results are discussed, as well as the use of an overset grid versus a deforming mesh. Lastly, possible error sources in CFD simulations are discussed. These numerical studies are performed investigating two complex hydrodynamic problems: 1. a fully-immersed flapping hydrofoil aimed to generate thrust, 2. a damaged and an intact ship section fixed in beam-sea waves, in forced heave and roll motion in calm water. In the first case, vortex-shedding and wake features are crucial; in the second case, free-surface flow effects play the key role while the importance of vortex-shedding and viscous-flow effects depends on the scenario. The first problem is solved with OF and validated with results from benchmark experiments. The second problem is solved using (A) OF, (B) an in-house CFD solver and (C) a fully-nonlinear potential-flow code. A and B assume laminar-flow conditions and use, respectively, a volume-of-fluid and a level-set technique to handle the free-surface evolution. C is considered to examine importance of nonlinear versus viscous effects for the examined problems. The results are compared against in-house experiments. Copyright © 2020 by ASME. Locked until 18.6.2021 due to copyright restrictions.

The parametric resonance in roll motion (known shortly as parametric roll) was studied for a fishing vessel in regular waves. This is an instability and resonance phenomenon that can lead the roll to reach very high oscillation amplitudes at its natural frequency, depending on the damping level involved. In the worst cases it is responsible for vessel capsize. Here the problem was investigated numerically and experimentally, performing dedicated physical tests on a typical Norwegian fishing vessel with blunt hull and small length-to-beam ratio. Experimentally, a dedicated study was carried out on the SFH112 fishing vessel in scale 1:10 in regular head-sea waves with different wave frequencies and steepnesses. The tests were performed without and with forward speed, with corresponding Froude number Fn = 0.09 and 0.18. Numerically, a blended method was developed based on a 6-DOF 3D hybrid method where the radiation and diffraction potentials were computed for zero forward speed by WAMIT and used in the STF strip theory to obtain speed dependent loads. The convolution integrals were used to account for the effect of radiation free-surface memory effect. Nonlinearities in the Froude-Krylov and restoring loads were accounted for by integrating the corresponding pressure terms on the instantaneous wetted-hull surface defined by the incident waves and body motions. Use of the weak-scatterer hypothesis in radiation and diffraction loads has also been considered. The method was applied to reproduce and complement the experiments on the SFH112 fishing vessel. The numerical simulations showed good agreement with the experimental results. For the cases near the instability border of a 1-DOF Mathieu-type instability diagram, the physical and numerical predictions were different in terms of parametric roll occurrence. The instability borders for the experimental cases are also different from the instability borders of 1-DOF Mathieu-type instability diagram. The instability region for the experiments and 6DOF simulations cover a wider range of frequency ratio and the threshold value of metacentric height variation amplitude to have parametric roll seems to be lower than predicted by the 1-DOF Mathieu instability diagram. The results also show that the instability region for the cases with forward speed shifts to the lower frequency ratios(natural roll frequency to encounter frequency ratio) compared to the cases without forward speed. The effect of the weak-scatterer hypothesis on the results is also assessed and shown to be important for parametric roll. The results show that the simulations without this hypothesis tend to underestimate the occurrence and severity of parametric roll especially in longer and steeper waves. This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A comparative analysis between a closed cage (CC) and a semi-closed/open-bottom cage (OC) in regular, white-noise and irregular waves is presented. Both cages consist of a vertical circular free surface-piercing cylinder with an external toroidal floater. A main target is to examine experimentally and theoretically the similarities and differences of the hydrodynamic behavior between the two cages. Transfer functions obtained from regular and white-noise waves test show that the two cages have similar performance in surge motion, ovalizing deformations, interior wave elevation and mean drift loads in shorter waves (wavelength to cage diameter ratio ). This is not the case for heave, with OC experiencing much larger heave. A clear sinkage (minus average heave) is also observed for OC, which is almost proportional to the square of the incident wave amplitude. The linear potential flow solver WAMIT can provide a reasonable prediction of surge and pitch motions, and mean drift loads for OC in shorter waves (), but is unsatisfactory in longer waves and, in general, for heave motion. From the analysis of irregular wave tests, there is a small difference in the standard deviations of the surge motion (wave-frequency component) and interior waves for the semi-closed and closed cages. The slow-drift component is dominant in surge for both cages, with OC having a smaller value due to larger viscous damping associated with flow separation at the bottom. Theoretical evaluations of standard deviations based on transfer functions from a white-noise test and from WAMIT are performed, assuming that the linear superposition principle applies. Reasonable agreement against results from experiments in irregular waves is achieved except for response variables with strong nonlinear effects. Survival conditions for both cages are determined through systematic evaluations. The platform freeboard is identified as the most critical parameter. The minimum freeboard for the closed and semi-closed cage should be at least 1.05 and 1.3 m, respectively, to operate at moderate exposure sea states. The standard deviation of vertical acceleration due to rigid body motions and interior waves could reach 0.72 m/s2 for both cages at high exposure sea states, which might be of concern for fish inside.

Sepsis outcome is determined by a balance between inflammation and immune suppression. We aimed to evaluate monocytes polarization and reprogramming during these processes. We analyzed 93 patients with procalcitonin level >0.5 ng/mL (hPCT) and suspected/confirmed sepsis, and 84 controls by analysis of CD14, CD16 and HLA-DR expression on blood monocytes using fluorescent labeled monoclonal antibodies and BD FACS CANTO II. Complete blood cell count, procalcitonin and other biochemical markers were evaluated. Intermediate monocytes CD14++CD16+ increased in hPCT patients (including both positive and negative culture) compared to controls (13.6% ± 0.8 vs 6.2% ± 0.3, p

Background: Sepsis is currently defined as a life-threatening organ dysfunction caused by a deregulated host response to infection. There is increasing evidence that the endothelium plays a crucial and pathogenic role in sepsis. Profound alterations of the endothelium associated with sepsis include increased leucocytes adhesions, shift to a procoagulant state, vasodilatation, altered barrier function with more permeable capillaries and tissue edema. The vascular endothelial growth factor (VEGF) pathway is involved in the control of microvascular permeability and has been involved in the pathogenesis of conditions associated with endothelial barrier disruption such as sepsis. sFlt-1 is a soluble variant of the VEGF receptor (Fms-like tyrosine kinase-1, Flt-1 or VEGFR-1) able to down-regulate the effects of VEGF by decreasing its signaling. We investigated the possible involvement of sFlt-1 as biomarker of endothelial alteration during sepsis, organ dysfunction and death. Methods: Serum levels of s-Flt1 were measured in 170 hospitalized patients (77 with sepsis, confirmed by positive blood culture), and in 18 healthy volunteers. The sequential organ failure assessment (SOFA) score was determined by using biochemical and clinical parameters. In a small number of patients (9 individuals), s-Flt1 concentration was evaluated after negativization of the blood culture. Results: Serum level of s-Flt1 was significantly higher in septic patients than blood culture-negative patients (277.7 ± 52.7 and 133.4 ± 12.4 pg/mL, respectively, P = 0.0088), both groups of patients had significantly higher concentration of sFlt-1 than healthy individuals (78.9 ± 2.5 pg/mL). Among sepsis cases, 68% was caused by Gram-negative bacteria, 27% by Gram-positive bacteria and 8% by Candida species. Serum level of s-Flt1 showed a significant difference between Gram-negative (274.1 pg/mL) and Gram-positive (145.7 pg/mL) sepsis. SOFA score (evaluated in 20 patients with sFlt-1 >190 pg/mL) showed a positive trend of correlation with the increasing sFlt-1 level. After blood culture negativization, serum level of sFlt-1 decreased (37%). Conclusion: Our findings confirm, in a larger population of patients with sepsis, recent evidences that sFlt-1 levels are higher in patients with complicated-sepsis that evolve to septic shock and suggest that sFlt-1 could be a useful biomarker for sepsis severity. An anti-VEGF effect mediated by sFlt-1 could be hypothesized as salvage compensatory mechanism activated in response to sepsis. J Clin Med Res. 2018;10(9):700-706 doi: https://doi.org/10.14740/jocmr3505w

Wave-induced response of a closed floating fish cage consisting of a vertical circular cylinder with an external toroidal floater is studied theoretically and experimentally. A main purpose was to investigate how the internal sloshing would influence the global response of the cage, the interior wave elevation and also the mean drift loads. An ocean basin laboratory was used in order to minimize tank wall effects. An optical system involving eight markers was used to obtain experimental values for radial elastic deformations of the cylindrical part. The closer a coupled natural period between body motions and sloshing is to a corresponding natural sloshing period, the more nonlinear sloshing can be. In the examined case, the highest coupled natural period between surge, pitch and sloshing is 0.8 times the highest natural sloshing period. Linear potential flow theory can, in general, explain experimental transfer functions of rigid-body motions and sloshing due to rigid-body motions obtained by both regular wave and truncated white noise tests. Theoretical second order mean wave drift forces based on a rigid body and potential flow agree also well with experimental results. Resonant 3D sloshing was excited due to ovalizing hydroelastic structural modes in both regular waves and white-noise tests. The closeness between the corresponding structural and sloshing frequencies caused large response. A linear hydroelastic analysis based on WAMIT and LS-DYNA could partly explain the response. Parametric resonant pitch response occurred experimentally at large wave periods partially due to in and out of water motion of portions of the floater and was explained by treating the pitch as uncoupled motion modeled by the Mathieu equation. The pitch motion predicted by linear potential flow theory was, in general, unsatisfactory when the floater was partly out of the water occasionally.

A detailed and systematic analysis is performed on the local and global properties of the recently developed Harmonic Polynomial Cell (HPC) method, a very accurate and efficient field solver for problems governed by the Laplace equation. At the local cell level, a simple rule is identified for the proper choice of harmonic polynomials in the local representation of the velocity potential in cells with symmetry properties. The local solution error, its convergence rate, its dependence on the cell topology, its distribution inside the cell and its features across cells with different dimensions, are carefully examined with relevant findings for HPC numerical implementations. At the global level, the error convergence rate is analytically estimated in terms of error contributions from the boundary conditions and from inside the liquid domain. In most cases, the error associated with boundary conditions dominates the global error. In order to minimize it, Quadtree grid strategies or high-order local expressions of the velocity potential are proposed for cells near critical boundary portions. To model accurately the boundary conditions on rigid or deformable surfaces with generic geometries, three different grid strategies are proposed by adopting concepts of immersed boundary method and overlapping grids. They are comparatively studied for a circular rigid cylinder in infinite fluid and for the propagation of a free-surface wave. Then, an immersed boundary strategy, using numerical choices suggested in this paper, is successfully compared against a fully nonlinear Boundary Element Method for the case of a surface-piercing circular cylinder heaving in otherwise calm water. This is the pre-peer reviewed version of the following article: Local and Global Properties of the Harmonic Polynomial Cell Method: In-depth Analysis in Two Dimensions, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/nme.5631/epdf. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Several cases of nonlinear-wave propagation are studied numerically in two dimensions within the framework of potential flow. The Laplace equation is solved with the Harmonic Polynomial cell (HPC) method, which is a field method with high-order accuracy. In the HPC method, the computational domain is divided into overlapping cells. Within each cell, the velocity potential is represented by a sum of harmonic polynomials. Two different methods denoted as Immersed Boundary (IB) and Multi-grid (MG) are used to track the free surface. The former treats the free surface as an immersed boundary in a fixed, Cartesian background grid, while the latter uses a free-surface fitted grid that overlaps with a Cartesian background grid. The simulated cases include several nonlinear wave mechanisms, such as high steepness and shallow-water effects. For one of the cases, a numerical scheme to suppress local wave breaking is introduced. Such scheme can serve as a practical mean to ensure numerical stability in simulations where local breaking is not significant for the result. For all the considered cases, both the IB and MG method generally give satisfactory agreement with known reference results. Although the two free-surface tracking methods mostly have similar performance, some differences between them are pointed out. These include aspects related to modelling of particular physical problems as well as their computational efficiency when combined with the HPC method. This is the pre-peer reviewed version of the following article: Free-Surface Tracking in 2D with the Harmonic Polynomial Cell Method: Two Alternative Strategies, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/nme.5615/epdf. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

An integral version of the line-of-sight guidance method is shown to compensate for both kinematic and dynamic disturbances generated by wind, waves and sea currents. The guidance law is designed for path following tasks of underactuated marine vessels moving in the horizontal plane. Specifically, the control system consists of an integral line-of-sight heading reference generator in a cascaded configuration with an adaptive surge-yaw controller. The total drifting effect of the environmental disturbances is modeled as a combination of a constant and unknown kinematic drift, and a constant, unknown and heading-dependent dynamic pressure acting on the vessel. The closed loop stability analysis shows that path following is achieved with global k-exponential stability properties. The theoretical results are supported by simulations. © 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

The dynamic response of a coupled well boat–fish farm system in irregular long-crested waves and current is analyzed numerically in the time domain. The main purpose is to investigate the influence of the well boat on the fish farm and then to determine the operational conditions of the well boat. The numerical study of slow-drift sway motion of the well boat is performed at first. Hydrodynamic and statistical theories are briefly introduced. The cross-flow principle is assumed valid for evaluating the transverse viscous loads and the needed cross-sectional drag coefficients are estimated empirically and validated against available experiments. The mean value and standard deviation of the slow-drift motion from time domain agree well with those from frequency domain when equivalent linearized drag damping is incorporated. The coupled system with the well boat placed at the weather side of the fish farm is then analyzed in detail. Special attention is paid to two critical response variables, i.e., maximum anchor-line loads and maximum floating collar stresses. Numerical results show that the examined two variables will increase more than 300% due to the well boat in moderate exposure sea states. A sensitivity analysis is also carried out to identify the important parameters influencing these two response variables. Cross-sectional drag coefficients for the well boat and fish-farm related parameters (pretension load in the anchor lines and anchor-line stiffness) have moderate influence on the two variables. Simplifying the modeling of the coupled system, for instance neglecting the net cage and the first-order motion, has more effect on the maximum anchor load than on the maximum floating-collar stress and reduced sensitivity is observed in current, especially for the latter variable. Lastly, the operational conditions of the well boat are determined through systematic simulations. Numerical results show that the maximum loads in the mooring lines are moderate compared with the corresponding breaking limits even in high exposure sea states, while for the maximum stress in the floating collar can be close to the yield stress when operating in moderate exposure regions.

This work documents a detailed series of experiments performed in a wave flume on a thin walled prismatic hull form. The model consists of a rectangular opening located on the side. The length of the model is slightly smaller than the flume breadth to achieve two-dimensional (2D) behavior in the experiments. Forced oscillatory heave tests in calm water have been carried out by varying the model-motion parameters and examining both intact and damaged conditions. Video recordings, measurements of the wave elevation inside the damaged compartment and of the force on the model were performed in all the experiments. The effect of damage opening in the model on hydrodynamic loads is examined by comparing with an intact section. A theoretical analysis is used to explain the behavior of added mass and damping coefficients in heave for a 2D damaged section. The presented results demonstrate occurrence of sloshing and piston mode resonances in the tests and their influence on the hydrodynamics loads of a damaged ship. Detailed physical investigations are presented at these resonance frequencies for the damaged section. Effect of filling level in the damage compartment, damage-opening length and air compressibility in the airtight compartment is examined. Nonlinear effects are documented and appear dominant, especially, for lowest filling level where we have shallow-water depth conditions in the damaged compartment. Resonance phenomena that can lead to significant local loads are identified for the shallow water condition. Air compressibility in the airtight compartment and floodwater act as a coupled system and influence inflow/outflow of floodwater in the compartment. It has a significant effect on local floodwater behavior in the damaged compartment.

Water impact (slamming) is a strongly nonlinear phenomenon including significant fluid structure interactions. In the case of slamming with a small impact angle between the structure and water, the coupling between hydrodynamic pressure and the elastic responses of structures, known as hydroelasticity, matters. This has been studied extensively. However, when structures are subjected to violent water slamming in extreme sea states, large stresses may occur that exceed the material yield stress, causing large plastic flow and permanent damage. In such cases, the plastic responses of a structure will be strongly coupled with the hydrodynamic pressure, termed as hydro-plasticity. Hydro-plastic slamming has rarely been studied before. This is Part I of a two-part companion paper. The paper advances the state-of-the-art of hydro-plastic slamming by formulating, for the first time, an analytical model coupling the hydrodynamic forces and the plastic response of rectangular beams and one-way stiffened panels. The studied scenarios are flat or nearly flat water impacts, which are critical for hydro-plasticity excitation. The impact angle between the water free surface and the structure should preferably be no larger than 5°. Based on the proposed model, the governing non-dimensional parameters for hydro-plastic slamming are identified and discussed. Design curves for plate strips and stiffened panels against extreme slamming are developed. Part II-Numerical verification and analysis presents numerical verification and discussion of the analytical model by comparing with results from the multi-material Arbitrary Lagrangian Eulerian (ALE) simulations. The proposed analytical model does not require the challenging estimation of pressure history that is normally used in the design against slamming. Only the initial impact velocity is needed as the main input. The resulting non-dimensional curves may be utilized in rules and standards for the design of ships and offshore structures against extreme slamming loads.

Objective: Mutations in Mediator Complex Subunit 12 (MED12) gene are typical genomic aberrations, commonly detected in a high percentage of uterine leiomyomas (ULs). The aim of this investigation was to define the fibroid or non-tumor origin of uterine leiomyoma pseudocapsule (PC) surrounding fibroids and its possible therapeutic targets in uterine fibroid management. Research design and methods: A non-randomized observational study was performed on 36 women, not subjected to any previous drug treatment, undergoing laparoscopic intracapsular myomectomy. Specimens of myometrium (UM), ULs and corresponding PCs were sampled to analyze MED12 gene status, by direct sequencing of exon 2. Main outcome measures: Defining the status of MED12 gene in PCs associated to ULs harboring mutations. Results: PCs always showed a wild type MED12 gene status, even when associated to a UL harboring a specific MED12 aberration. Conclusion: The wild-type status of MED12 gene in the PCs indicates the non-tumoral origin of this structure: it appears as a protective structure for the healthy tissue that could enhance regenerative mechanisms. The limitations of this study, as the restrained number of patients, will be solved in the future extending the analysis to a larger cohort of women, as tester of such pharmacological treatments on PC.

This work presents a series of experiments performed with a prismatic hull form in a small wave flume. The model is a midship section with rectangular damage opening on the side. It is slightly smaller than the flume breadth to achieve predominantly two-dimensional behavior in the experiments. Freely-floating tests in regular beam-sea waves have been carried out on the model section in intact and damaged conditions. Free-roll decay tests were performed for intact and damaged sections to understand the effect of floodwater on roll natural period and roll damping of the model. Video recordings and measurements of wave elevation inside the damaged compartment were performed in all experiments. Linear response amplitude operators (RAOs) for water elevation inside the model and model motions are presented and discussed. Effect of wave steepness, wave period, initial loading condition, damage-compartment division about centerplane (symmetric/asymmetric flooding), damage-opening size and air compressibility in the damaged compartment are examined. The presented results demonstrate occurrence of sloshing and piston mode resonances and their influence on damaged ship motions in waves is highlighted. A linearized strip theory method based on viscous flow is implemented to cross-check and complement the experimental results. The latter method can estimate the damaged ship motions with reasonable accuracy. The initial loading condition determines the equilibrium flooding state and, therefore, the sloshing and piston mode resonance frequencies of the flooded water. The damage-opening size mainly affects the roll damping behavior of the section. Air compressibility in the airtight compartment acts as a coupled spring system with the floodwater and restricts the free-surface motion in the damaged compartment. Cases of transient flooding for a damaged section are also presented, where the freely floating model moves in beam-sea waves and subsequent flooding takes place. Effect of wave steepness, incident wave period and initial intact stability of the model is examined for this scenario. The present work is a continuation of a series of experiments conducted on the same damaged section for forced heave motions documented in [1]. Due to the complex and nonlinear behavior of floodwater inside a damaged ship section, as the previous analysis, the current work is aimed to contribute in the physical understanding of ship behavior in damaged conditions, as well as to serve as a database for the research community to be used for numerical validation. This article is available under the Creative Commons CC-BY-NC-ND license and permits non-commercial use of the work as published, without adaptation or alteration provided the work is fully attributed.

A realistic aquaculture fish farm system in both regular and irregular waves is investigated by numerical simulations and model tests. The main purpose is to develop a reliable numerical tool and in this respect to investigate the survival conditions of the system. The structural and hydrodynamic modelings of the system are briefly introduced. Numerical sensitivity analysis is performed to investigate which physical parameters are dominant when modeling the system.& para;& para;The considered fish farm comprises a floating collar with two concentric tubes, a flexible net cage including a cylindrical part and a conical part with a center point weight at the bottom, and a sinker tube attached directly to the net. The system is moored with a complex mooring system with bridle lines, frame lines and anchor lines, supported by buoys.& para;& para;The mooring loads in the front two anchor lines and bridle lines are investigated in detail. Numerical results are first validated by the experimental data. Both numerical and experimental results show that one of the bridle lines experiences larger load than the rest of the mooring lines, which is surprising. Then a sensitivity analysis is carried out. The mooring loads are not sensitive to the majority of the parameters. The flow reduction factor in the rear part of the net is the most important parameter for the anchor loads. Modeling the floating collar as a rigid body has a small effect on the anchor loads but not for the bridle lines as it will alter the force distribution between bridles. The mooring loads are not sensitive to the wave load model for the floating collar in both regular and irregular seas and modeling the floating collar as elastic with zero frequency hydrodynamic coefficients is enough to give reliable results.& para;& para;Finally, the survival conditions of the fish farms with different set-ups is studied. Numerical results indicate that the dominant limitation to move the conventional fish farms to more exposed sea regions is the large volume reduction of the net cage. The existing mooring system can be applied in offshore regions as long as the bridle lines are properly designed. The maximum stress in the floating collar is moderate compared with the yield stress. (C) 2018 Elsevier Ltd. All rights reserved.

The uterine myoma pseudocapsule is a neurovascular bundle surrounding fibroid, containing neuropeptides, probably involved in uterine scar healing. We studied neurotensin (NT), neuropeptide tyrosine (NPY), and protein gene product 9.5 (PGP 9.5) nerve fibres in the pseudocapsule neurovascular bundle of intramural uterine fibroids on 67 no pregnant women by intracapsular myomectomy sparing the neurovascular bundle, sampling full thickness specimens of the pseudocapsule of uterine fibroids (PUF) and normal myometrium (NM) obtained from the fundus uteri (FU) and the uterine body (UB). The samples were sent for histological and immunofluorescent analyses and compared by morphometrical quantification. The Conventional Unit (C.U.) difference of NT, NPY, and PGP 9.5 nerve fibres was statistically analyzed. Our results showed that NT, NPY, and PGP 9.5 neurofibers are almost equally present in PUF as in NM of a no pregnant uterus. As all of these neuropeptides are present in the uterine muscle and can affect muscle contractility, uterine peristalsis and muscular healing. A myomectomy respecting the pseudocapsule neurofibers should facilitate smooth muscle scarring and promote restoration of normal uterine peristalsis with a possible positive influence on fertility.

Parametric resonance (PR) in roll is of concern for fishing vessels, especially in head-sea waves. Here the effect of passive anti-roll free-surface tank is investigated experimentally and numerically on realistic fishing-vessel geometry at zero forward speed. On the numerical side, the onboard tank is simulated using an open source computational fluid dynamic (CFD) development platform, OpenFOAM (Open Field Operation and Manipulation). The internal flow solver is coupled with the seakeeping solver, which is based on the weakly nonlinear method proposed in [1]. Experimentally, two different relevant scenarios were examined: 1) a 2D rectangular tank with shallow-water filling depth was forced to oscillate in roll and the loads induced on the tank were measured; 2) a fishing vessel was tested in a towing tank, prescribing regular head-sea waves. The vessel was examined both without and with anti-roll tanks and a mooring-line system was designed so to control the horizontal motions with limited effect on the parametric occurrence. The experiments on the fishing vessel are considered to assess the seakeeping solver. Both model tests and numerical results confirmed the effectiveness of an on-board tank in avoiding PR. For the examined cases with tank, the parametric resonance did not occur without forcing an initial roll. Moreover, the initial roll amplitude and roll phase relative to the heave motion matter for triggering the instability.

A numerical wave tank (NWT) based on potential flow of incompressible liquid is developed to study nonlinear wave-body interactions in two dimensions. The NWT uses an efficient field method with high accuracy to solve the Laplace equation together with the concepts of immersed boundary method (IBM) and overlapping grids.

The present work extends the semi-integrated method proposed by Antuono and Brocchini [“Beyond Boussinesq-type equations: Semi-integrated models for coastal dynamics,” Phys. Fluids 25(1), 016603 (2013)], which comprises a subset of depth-averaged equations (similar to Boussinesq-like models) and a Poisson equation that accounts for vertical dynamics. Here, the subset of depth-averaged equations has been reshaped in a conservative-like form and both the Poisson equation formulations proposed by Antuono and Brocchini [“Beyond Boussinesq-type equations: Semi-integrated models for coastal dynamics,” Phys. Fluids 25(1), 016603 (2013)] are investigated: the former uses the vertical velocity component (formulation A) and the latter a specific depth semi-averaged variable, ϒ (formulation B). Our analyses reveal that formulation A is prone to instabilities as wave nonlinearity increases. On the contrary, formulation B allows an accurate, robust numerical implementation. Test cases derived from the scientific literature on Boussinesq-type models—i.e., solitary and Stokes wave analytical solutions for linear dispersion and nonlinear evolution and experimental data for shoaling properties—are used to assess the proposed solution strategy. It is found that the present method gives reliable predictions of wave propagation in shallow to intermediate waters, in terms of both semi-averaged variables and conservation properties. This is the authors' submitted pre-refereed manuscript to the article. The following article appeared in Physics of Fluids and may be found at http://aip.scitation.org/doi/10.1063/1.4984079

The recently developed Harmonic Polynomial Cell (HPC) method has been proved to be a promising choice for solving potential-flow Boundary Value Problem (BVP). In this paper, a flux method is proposed to consistently deal with the Neumann boundary condition of the original HPC method and enhance the accuracy. Moreover, fixed mesh algorithm with free surface immersed is developed to improve the computational efficiency. Finally, a two dimensional (2D) multi-block strategy coupling boundary-fitted mesh and fixed mesh is proposed. It limits the computational costs and preserves the accuracy. A fully nonlinear 2D numerical wave tank is developed using the improved HPC method as a verification. Copyright © 2017 Society of Naval Architects of Korea. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

SUMMARY The problem of a high-pressure gas cavity and its interaction with surrounding liquid and a close-by structure is examined numerically. Even though this is of interest in many practical applications, here, the focus is on an underwater explosion. A one-way DD strategy coupling a radial and a 3D solver for compressible multiphase flows is proposed, and the different components are successfully validated. This is a time-space DD, which assumes the explosion that occurs sufficiently far from boundaries. It means that the radial solution is used everywhere until radial symmetry is no more applicable. When acoustic waves reach a close structure, the radial solution initiates the 3D solution near the body and continues to be applied only far from the structure and to provide the boundary conditions for the 3D sub-domain. The advantage is to limit the computational costs and preserve reliability and accuracy. The radial solution could be applied to assess local damages during the initial acoustic phase; the time-space DD needs to be used to investigate both local and global consequences on the vessels. The structure is modeled both as a rigid wall and as an orthotropic plate, which provides a good representation of the bottom grillages of ships. Copyright © 2014 John Wiley & Sons, Ltd.

SUMMARY A 3D Domain-Decomposition (DD) strategy has been developed to deal with violent wave-ship interactions involving water-on-deck and slamming occurrence. It couples a linear potential flow seakeeping solver with a Navier–Stokes method. The latter is applied in an inner domain where slamming, water-on-deck, and free surface fragmentation may occur, involving important flow nonlinearities. The field solver combines an approximated projection method with a level set technique for the free surface evolution. A hybrid strategy, combining the Eulerian level set concept to Lagrangian markers, is used to enforce more accurately the body boundary condition in case of high local curvatures. Main features of the weak and the strong coupling algorithms are described with special focus on the boundary conditions for the inner solver. Two ways of estimating the nonlinear loads by the Navier–Stokes method are investigated, on the basis of an extrapolation technique and an interpolation marching cubes algorithm, respectively. The DD is applied for the case of a freely floating patrol ship in head sea regular waves and compared against water-on-deck experiments in terms of flow evolution, body motions, and pressure on the hull. Improvement of the solver efficiency and accuracy is suggested. Copyright © 2013 John Wiley & Sons, Ltd.

When ice floes collide against marine structures, pronounced hydrodynamic loads are induced by the water-ice-structure interaction. With today’s highly competitive structural design market, it is nearly impossible to ignore the advances that have been made in the computer analysis of fluid-structure interaction (FSI) problems. FSI methods can provide accurate representation of hydrodynamic effects. A number of commercial programs have been developed, and their applications in structural design increases rapidly. For instance, Arbitrary Lagrangian-Eulerian (ALE) formulations have been used to solve underwater explosions problems in ocean engineering, and soil-structure interaction problems in civil engineering. Application to fluid-ice-structure interaction problems is more recent and growing. This paper represents a contribution in assessing the capabilities of the ALE formulation for fluid-ice-structure collision problems. The ALE and coupling algorithms have been successfully validated through the comparison against model tests of an ice-structure collision. The work also examines the numerical convergence and the sensitivity of the results to the theoretical modelling used. From the sensitivity study it is concluded that the effect of viscosity and equation of state for the water model within the ALE formulation are insignificant, whereas the choice of the element size has a noticeable effect on the computed contact forces and the motions of the impacted structure.

A spar torus combination (STC) concept is an energy converter concept for both wind and wave. A torus shaped wave energy converter (WEC) is installed on a spar floating wind turbine to absorb wave power. Model tests were performed on the survivability of the concept with the focus on different survival modes, and water entry and exit phenomena of the WEC were observed for one survival mode during the tests under extreme sea conditions. A hybrid numerical solver is proposed to simulate the dynamic responses of the STC in extreme sea states conditions involving water entry and exit of the WEC, as well as water on deck phenomena. The method combines a weakly nonlinear potential-flow solution for the wave-body interactions, a local Wagner-type model for the bottom slamming phenomenon and a shallow water approximation for water on deck events. The viscous damping loads acting on the different component of the STC system are modelled using empirical formulas based on the involved damping mechanisms and the local Keulegan-Carpenter number. Comparisons between the numerical predictions and model test results in mild and steep regular waves are presented in this paper, and show reasonable agreement for the induced body motions and occurrence of water shipping and slamming events. The hybrid solver is then used to investigate the effects of green-water and slamming loads on the motions of the platform, showing important influence of the former.

Ship collisions and groundings are highly nonlinear and transient, coupled dynamic processes involving large structural deformations and fluid structure interactions. It has long been difficult to include all effects in one simulation. By taking advantage of the user-defined load subroutine and the user common variable, this article implements a model of hydrodynamic loads based on linear potential-flow theory into the nonlinear finite element code LS-DYNA, facilitating a fully coupled six degrees of freedom (6DOF) dynamic simulation of ship collision and grounding accidents. Potential-flow theory both with and without considering the forward speed effect is implemented for studying the speed influence. With the proposed model, transient effects of the fluid, global ship motions, impact forces, and structural damage can all be predicted with high accuracy. To the authors' knowledge, this is the first time the fully coupled 6DOF collision and grounding simulations are carried out with linear hydrodynamic loads for transient conditions but without simplification of collision forces. The proposed method is applied to calculations of an offshore supply vessel colliding with a rigid plate and with a submersible platform. The results are compared with a decoupled method and discussed with emphasis on the influence of different initial velocities. The proposed method is capable of predicting both the 6DOF ship motions and structural damage simultaneously with good efficiency and accuracy; hence, it will be a very promising tool in the application to ship collision and grounding analysis.

A synergic 3-D experimental and numerical investigation is conducted for wave-ship interactions involving the water-on-deck and slamming phenomena. The adopted solver has been developed in Greco and Lugni (in press) and combines (A) a weakly nonlinear external solution for the wave-vessel interactions with (B) a 2-D in-deck shallow-water approximation, which describes water shipping events, and (C) a local analytical analysis of the bottom-slamming phenomenon. This solver can handle regular and irregular sea states and vessels at rest or with limited speed. The experiments examine a patrol ship at rest or with forward speed that is free to oscillate in heave and pitch in regular and irregular waves. In this study, the head-sea regular-wave conditions are examined in terms of (1) response amplitude operators (RAOs) and relative motions, (2) occurrence, features and loads of water-on-deck, bottom-slamming and flare-slamming events and (3) added resistance in waves. A systematic and comprehensive analysis of the phenomena is made available in terms of the Froude number, incoming wavelength-to-ship length ratio and wave steepness for the examined ship geometry. The main parameters that affect the global and local quantities are identified and possible danger in terms of water-on-deck severity and structural consequences are determined. Different slamming behaviors were identified, depending on the spatial location of the impact on the vessel: single-peak, church-roof and double-peak behaviors. A bottom-slamming criterion, using the Ochi's (1964) velocity condition and the Greco and Lugni's (2012) pressure condition, is assessed. A statistical analysis of more than 100 events is needed for the bottom-slamming pressure peaks. The numerical solver is promising. The major discrepancies with the experiments are discussed, and the importance of viscous hull damping and flare impact for the most violent conditions is emphasized. Inclusion of these effects improved the numerical solution. © 2012 Elsevier Ltd.

A three-dimensional seakeeping numerical solver is developed to handle occurrence and effects of water-on-deck and bottom slamming. It couples (A) the rigid-ship motions with (B) the water flowing along the deck and (C) bottom slamming events. Problem A is studied with a 3-D weakly nonlinear potential flow solver based on the weak-scatterer hypothesis. Problem B, and so local and global induced green-water loads, are investigated by assuming shallow-water conditions onto the deck. Problem C is examined through a Wagner-type wedge-impact analysis. Within the coupling between A and B: the external seakeeping problem furnishes the initial and boundary conditions to the in-deck solver in terms of water level and velocity along the deck profile; in return the shallow-water problem makes available to the seakeeping solver the green-water loads to be introduced as additional loads into the rigid-motion equations. Within the coupling between A and C: the instantaneous ship configuration and its kinematic and dynamic conditions with respect to the incident waves will fix the parameters for the local impact problem; in return the slamming and water-entry pressures are integrated in the vessel region of interest and introduced as additional loads into the rigid-motion equations. The resulting numerical solver can study efficiently the ship interaction with regular and irregular sea states and the forward motion with limited speed of the vessel. This is crucial to perform reliable and feasible statistical investigations of vessel behavior. Main elements of the solver are described and validated against reference numerical solutions and model tests.

A numerical approach has been used to analyze the water shipping caused by head sea waves for a FPSO ship at rest. A 3D Domain-Decomposition (DD) strategy is used, where a linear potential-flow seakeeping analysis of the vessel is coupled with a local nonlinear rotational-flow investigation for the prediction of water-on-deck phenomena. The Navier-Stokes solver is applied in the region close to the ship bow. It combines a finite-difference spatial algorithm with a predictor-corrector time scheme. The sea and ship surfaces are tracked with a Level-Set (LS) technique and a hybrid Eulerian-Lagrangian algorithm. The inner solver receives the initial and boundary conditions in terms of velocity, pressure, sea-surface location and ship motions and provides the loads due to the nonlinear wave-ship interaction (including green-water loads) to the seakeeping method. Here the inner solver and its implementation within the DD are described in detail. Preliminary results in terms of water-on-deck occurrence are discussed and compared against 3D water-on-deck experiments.