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The original goal of the present research is to investigate the influence of surge on green water and slamming. Long-running experiments with forward velocity and irregular waves were repeated with and without surge. Surge is found to increase the probability of green water events, but the impact pressures on deck and the probability of a green water event reaching the deck box decreases when the ship is free to surge. Green water and slamming events turned out to not occur independently as both event types cluster for large probabilities of occurrence. Clusters are caused by large pitch motions. Larger pressures on deck are found for clustered events. [ABSTRACT FROM AUTHOR]

Since the slamming load could cause severe damage of wet deck of ship hull girder, the interaction between the structural response and hydrodynamic loading should be considered. A large scaled model of trimaran was designed, which could consider the structural elastic for studying the structural response of trimaran hull girder. The testing model was vertically dropped into still water in the tank to simulate typical hydroelastic slamming load, in which various impact velocities were considered. Each load condition was conducted several times to verify the repeatability and reproducibility of the experimental data. The slamming pressure and strain distributions are presented and discussed. The ranges of maximum slamming pressure and the danger area are identified for design of this type of trimaran. [ABSTRACT FROM AUTHOR]

ObjectivesWhen a large-bow naval ship encounters adverse sea conditions, bow flare slamming causes a hull girder whipping response which threatens the security of global longitudinal strength. The whipping bending moment resulting from slamming is related to the level of hull stiffness and bow flare shape. However, there are great differences in the structural arrangement and profile of different ship types, so it is necessary to carry out whipping response analysis.MethodsFirst, the COMPASS-WALCS-NE nonlinear time-domain hydro-elastic method is used to predict the hull girder response, and the results are compared and verified through a self-running subsection model test. Next, based on the obtained time histories of the resultant bow impact force, ship motion posture at typical moments and global load response of hull girders, the phase difference of high-and low-frequency components in the waveloads is analyzed, and the correlation between the midship's slamming moment and resultant bow flare slamming force is studied. Finally, the sensitivity analysis of the main design parameters affecting vertical bending moment is carried out.ResultsIn the designed sea conditions, the resultant slamming force has two peaks during bow water entry which correspond to the processes of bottom impact and bow flare impact respectively. The whipping bending moment is mainly caused by bow flare impact, but as the impact area is large and the resultant force far away from the midship, the slamming moment is at the same level as the wave bending moment. The slamming moment is very sensitive to changes in wave height.Conclusions The results of this study indicate that the effect of whipping impact resulting from slamming should be considered in the global longitudinal strength evaluation of large-bow naval ships; among them, the sagging vertical bending moment needs to be directly superimposed on the still water bending moment component and low-frequency wave load component, while the hogging vertical bending moment should be reduced to a certain extent and then superimposed considering dam-ping dissipation.

In this paper, the ditching performance of a seaplane model on calm water and a uniform water current coupled with wind was numerically investigated. The overset grid technique was applied to treat the large amplitude of the body motions of the seaplane without leading to mesh distortion. The effects of the initial velocity and the initial pitch angle on the slamming loads and motion responses were investigated for the seaplane's ditching on calm water. A good agreement with the experimental data on the velocity and angle was obtained. Besides ditching on calm water without the water current and wind, three more-complicated conditions were adopted, including the seaplane's ditching on calm water with wind, a water current without wind, and a water current coupled with wind. The accelerations and impact pressures of the seaplane can be influenced by the wind or current. Water splashing and overwashing could be observed during the water entry process, with water overtopping the seaplane head or nose and flowing over the body surface. It can be concluded that the relative motion between the water and the seaplane model should be carefully controlled to avoid possible damages caused by the occurrence of overwashing. [ABSTRACT FROM AUTHOR]

In this paper, the slamming loads and structural response of an aluminium flat stiffened-plate structure during calm water entry considering the hydroelasticity effects are studied by a partitioned CFD-FEM two-way coupled method. The target structure is simplified as one segment of an idealized ship grillage structure, comprising flat plate and stiffeners. The typical numerical results are analyzed such as vertical displacement, velocity, acceleration, impact loads, and structural stress of the flexible flat bottom grillage structure considering the hydroelasticity effect and air cushion effect in different free fall height conditions. Drop test results of the same structure and other existing numerical simulation data by both coupled and uncoupled solutions in the literature are used for comparison with the present numerical simulation results. This study provides a practical means to simulate the slamming behaviour and structural response of ship structures, which is useful for predicting ship hull stiffened panel loads and related structural design. [ABSTRACT FROM AUTHOR]

The interaction between the structural response and hydrodynamic loading (hydroelasticity) must be considered for design and operation purposes of high-speed planing craft made of composites that are prone to frequent water impact (slamming). A computational approach was proposed to study the hydroelastic slamming of a flexible wedge. The computational approach is a loose two-way coupling between a Wagnerbased hydrodynamic solution and a linear finite element plate model. Verification and validation (V&V) was performed on this coupled model. It was found that the model overpredicts rigid-body/spray root kinematics by <15% and hydrodynamic loading/ structural response by <26%. [ABSTRACT FROM AUTHOR]

Wave-piercing catamarans have center-bow to diminish slamming pressure and acceleration in sea waves. Bow section modification of marine craft towards low slamming loads is an on-going research topic. This study suggests insertion of a flat-bar, called spray rail, to center-bow to reduce both slamming pressure and acceleration. A section which is called J1-section from previous research is adopted for further modification. Modification is made via appending the spray rail to its center-bow, and the new section is called J1-section with spray rail. Evaluation of the slamming pressure and acceleration of both sections are experimentally accomplished using the water entry test facilities of Amirkabir Laboratory of Hydrodynamics. J1-section with spray rail in comparison with J1-section has shown peak acceleration and pressure drop of about 60% and 70%, respectively. This study suggests that the insertion of appendages to the catamaran sections is a superior solution for the slamming impact load reduction. [ABSTRACT FROM AUTHOR]

The inelastic deformation of a 30 m high-speed craft (HSC) subjected to slamming pressure is the main topic of this research. In this work, the commercial software package ABAQUS FEA is used to predict the structural behavior, especially in the hull area under the chine. Dynamic explicit solver simulations are done to predict plastic deformation. Before the principal analysis of the actual size of the ship hull structure model, the numerical studies were validated against relevant experimental data from the previous open literature. A reassessment of the design guidelines was also done to forecast the slamming load on the HSC structure. Then, with the slamming load pressure increased to the design limit, a parametric analysis was also conducted with two different idealizations of the pressure type: rectangular and triangular. Finally, this study identifies the variables that must be considered when calculating the degree of structural deformation brought on by slamming loads.

High-speed watercraft and ships undergo coupled motions which make the front portion of the hull exit and violently re-enter water. This induces short-term slamming loads that may compromise the structural integrity of the hull. The slamming of the bow can be modeled as straight wedges of different deadrise angles (DRAs) falling into water from different heights. The advent of computational fluid dynamics has allowed the problem of wedge-slamming to be simulated using the full Navier-Stokes equations thus complementing the pioneering studies based on experiments. Recently, most researchers are opting to use commercial software to simulate the wedge-impact problem as it allows access to overset meshing algorithms which are robust in modeling the wedge as a moving body. Embedded boundary methods (EBMs) offer some advantages over overset meshing in that the mesh only needs to be generated once and Cartesian mesh-based solvers can be implemented. However, the application of EBMs to wedge-impact has been limited in the literature and merits further development. In this context, we investigate the applicability of the fast-fictitious-domain (FFD) based embedded boundary treatment to simulate the violent water-entry of wedges. We extend our in-house Navier-Stokes model IITM-RANS3D to handle floating bodies through integration of a rigid-body dynamics solver and an algorithm to embed three-dimensional stereolithography (STL) geometries as solids over a Cartesian mesh. The proposed algorithm is extensively benchmarked against variable DRA wedge-slamming experiments reported in the literature as well as constant DRA wedge-slamming experiments performed in-house. Very good agreement is reported in terms of the time-history of hydrodynamic impact pressures measured at various locations on the hull as well as the wedge motion responses thus demonstrating the suitability of FFD for simulating the coupled hydrodynamics of slamming for simplified hull geometries. [ABSTRACT FROM AUTHOR]

Choosing the right hull shape is important in designing a ship, for example, a U-section or V-section of the hull. The hull shape will affect various aspects, such as design, resistance, seakeeping, structure and production. The ship hull must be properly designed so that it can operate according to the ship’s mission. From the seakeeping aspect of the ship's motion at sea, the difference in the hull shape will result in different motions and dynamic effects such as the slamming phenomenon. Based on the difference in the hull shape cases, this study analyzed the difference in the probability of slamming between the U and V hulls. Both hulls were made based on Formdata and almost all parameters were made the same. Parameters that cannot be forced to be the same are WSA (wetted surface area), (coefficient of waterplane area), and (distance of keel to buoyancy), where those parameters determine the difference in the results. The calculation of RAO (operator amplitude response) was obtained using the strip theory method which assisted by Maxsurf Motion software. The results became the input for the calculation of the slamming probability. The study results show that the U hull has a higher probability of slamming occurrence than that of the V hull, with the difference in values ranging from 20% to 35%. Therefore, the U hull will get more frequent slamming loads, so it has the potential to have a higher structural failure (fatigue) than that of the V hull.

Semi-submersible offshore platforms play a vital role in deep-sea energy exploitation. However, the vast waves threaten the platform's operation, usually leading to severe consequences. It is essential to study the wave-slamming mechanism of offshore platforms under extreme wave conditions. Existing research usually simplifies the offshore platform slamming problem. This paper establishes a model of a semi-submersible platform and a flexible mooring system in a numerical pool by means of the computational fluid dynamics (CFD) method. The distribution and the sensitivity of the slamming load on columns and deck in waves were investigated, and the model was verified through the basin test. Firstly, based on the Reynolds-averaged Navier–Stokes model, this study considers the volume-of-fluid method to track the free liquid level. After the column and floating body grid are locally refined, the slamming load under extreme regular wave impact is measured by measuring points on the column and deck. Then, the slamming experiment of the semi-submersible was carried out in the basin. The experiment model with a scale ratio of 1:100 was established to investigate the platform's motion and slamming loads under extreme regular and irregular waves. The findings indicate that the slamming load at the junction of the column and deck significantly increased, exhibiting a 'double-peak' phenomenon at the middle of the column. The maximum pressure of slamming at the top of the column demonstrated an inverted U-shaped distribution, with negative pressure occurring after the peak value, indicating a pronounced oscillation effect. [ABSTRACT FROM AUTHOR]

In this paper, the ditching performance of a seaplane model on calm water and a uniform water current coupled with wind was numerically investigated. The overset grid technique was applied to treat the large amplitude of the body motions of the seaplane without leading to mesh distortion. The effects of the initial velocity and the initial pitch angle on the slamming loads and motion responses were investigated for the seaplane’s ditching on calm water. A good agreement with the experimental data on the velocity and angle was obtained. Besides ditching on calm water without the water current and wind, three more-complicated conditions were adopted, including the seaplane’s ditching on calm water with wind, a water current without wind, and a water current coupled with wind. The accelerations and impact pressures of the seaplane can be influenced by the wind or current. Water splashing and overwashing could be observed during the water entry process, with water overtopping the seaplane head or nose and flowing over the body surface. It can be concluded that the relative motion between the water and the seaplane model should be carefully controlled to avoid possible damages caused by the occurrence of overwashing.

The design principle of the hull structure is to ensure sufficient strength and avoid excessive waste of materials. The equivalent dynamic coefficients (EDC) possess the advantages of both static analysis and dynamic analysis in engineering. However, there is still no clear method for determining the EDC of a trimaran. In this work, the EDC of the cross-decks are chosen as the research objects. The EDC of the plate, longitudinal girders, and transverse frame of the cross-decks are calculated respectively. A method considering material nonlinearity and a method considering transverse bending moment (TBM) are proposed, and the effect of elastic-plastic material and TBM on EDC is presented. Results show that it is feasible to use the EDC to analyze the trimaran under slamming loads. Besides, the EDC of different parts of the trimaran is different, hence it is not recommended to use the fixed value given by the ABS rules. [ABSTRACT FROM AUTHOR]

As part of the environmentally friendly policy of ships, active research is being conducted on energy storage systems (ESS) for ships. This ESS has a major influence on determining the propulsion and operation system of the ship in the future. A separate space must be provided for the ESS, but small and medium-sized ships often require it to be located at the bottom of the ship to make use of the available space. If the ESS is located at the bottom of the ship, the slamming impact load should be considered, and a study of the vibrations generated during the slamming impact is required. Ships are subjected to various environmental effects while sailing. Among them, the risk factor caused by waves is one of the direct risk factors for the operation of the ship. This slamming phenomenon affects not only ships but also offshore structures, and is a risk factor that can cause structural damage as well as damage to human life. Therefore, it is necessary to study the slamming load, and a method is needed to address it with a dynamic load instead of a static load. In order to reflect the slamming load in the design as a dynamic load rather than the equivalent hydrostatic pressure, which is a static load, it is necessary to study the elastic effect of the structure. The plate thickness is calculated by considering the equivalent design pressure based on the measured slamming pressure peak, and several experimental and theoretical studies have been conducted to estimate the exact value of the peak pressure. However, according to recent studies, structural damage is affected not only by the peak pressure but also by the peak width in the time interval of the peak pressure. Research on slamming has been ongoing for a long time, but structural damage due to slamming is still being reported steadily. In order to understand the slamming phenomenon and reflect it in the structural design formula, high-quality experimental results are required. The slamming phenomenon occurs in a very short time. In order to obtain high-quality experimental results for this slamming phenomenon, numerous experimental variables such as experimental equipment setting, appropriate sensor selection, and data measurement and storage capability must be carefully considered. Normally the slamming load can be expressed in terms of peak pressure, peak width, and duration of the pressure, and the maximum pressure and the idealized pressure value (impulse) are applied to the structure. This slamming pressure is affected by the shape and natural period of the structure and shows the largest pressure value when the dead-rise angle is 3° to 10°. In this study, the test was performed by repeatedly dropping into the water using structural bottom angles of 0°, 3°, 10°, and 20° to the free surface of the water. The peak pressure, peak width, impulse, pressure coefficient, and traveling velocity of peak pressure obtained from the repeated tests are estimated with mean and coefficient of variation. [ABSTRACT FROM AUTHOR]

A deeper comprehension of hydrodynamic slamming can be achieved by revisiting the wedge water entry problem using flexible structures. In this work, two wedge models that are identical, with the exception of different bottom thicknesses, are vertically dropped into calm water. Pressure, full-field out-of-plane deflection, strain, vertical acceleration, and vertical position are measured. Full-field deflections and strains are measured using stereoscopic-digital image correlation (S-DIC) and strain gauges. A non-dimensional number, R, quantifying the relative stiffness of the structure with respect to the fluid load is revisited. An experimental parametric study on the effect of R on the nondimensional hydrodynamic pressure and the maximum strain is presented. It was found there is a sharp change in the trend of pressure and strain when R passes through a critical value. It was also discovered that the structural deformation causes a delay in the peak pressure arrival time and a reduction in the peak pressure magnitude during the wedge water entry. [ABSTRACT FROM AUTHOR]

In order to further understanding and explore the structural responses induced by slamming pressures during high velocity water impacts, this paper conducts a series of experiments to study the response characteristics of elastic wedges with different deadrise angles. Initially, verification experiments, including static loading and hydrostatic immersion, are performed to establish the rigidly fixed boundary conditions of the test plate. The results indicate that the data are repeatable, with a maximum relative standard deviation of −6.8%. The discrepancy between the experimentally obtained results and the theoretical velocity values was less than 5%. Subsequent investigations focus on temporal and spatial evolution of stress, the propagation speed of stress peak, and hydroelastic effects. The findings indicated the average propagation speed of the stress peak exceeds that of the pressure peak, with the disparity increasing as the deadrise angle decreases. The stress contributions from the 1st and 2nd-order vibrations ranged from 0.18% to 2.6% and from 0.08% to 1.04%, respectively. • Structural responses of elastic stiffened wedges during high-velocity water impact are studied. • The boundary conditions of the test plate are verified by experimental techniques. • Temporal and spatial evolution, and average propagation speed of stress are studied in detail. • In elastic solid media, the propagation speed of stress outpaces that of pressure. [ABSTRACT FROM AUTHOR]

Background: This paper describes an online survey of men who have sex with men (MSM) and use drugs before or during sex ('chemsex') via injection ('slamming' or 'practising slamsex'). Approximately 15–30% of the MSM population in The Netherlands have practiced chemsex at some point, and 0.5–3.1% of them ever had 'slamsex'. This study investigates which substances are used in The Netherlands during slamsex, the motives for slamming and the health risks involved. Method: In total, 175 MSM from The Netherlands, who had used substances before or during sex via injection completed an ad hoc online questionnaire designed for this study. Results: Mean age of respondents was 47.8 years. During chemsex, almost every substance was used; the most common substances that were injected (slammed) were 3-methylmethcathinone (3-MMC), methamphetamine, ketamine, 4-methylethcathinone (4-MEC) and mephedrone (4-MMC). Reasons for slamming were mainly to experience a more intense rush and longer sex. Virtually none of the respondents used a condom during slamsex, but needles were almost never shared or used only once. Slammers reported health problems associated with injecting drugs (skin problems, collapsed veins and infections). Of most concern were the psychological symptoms reported by about three-quarters of respondents (e.g. insomnia, sadness, depressed mood, anxiety, suicidal tendencies). About half of respondents reported some degree of loss of control or concerns about their slamming behaviour. Conclusion: Results show that slamsex is associated with consciously chosen sexual risk behaviours and risk-avoidance slam behaviours. This study may contribute to the reinforcement of accessible, non-judgmental and well informed prevention and harm reduction activities to support MSM practising slamsex. About 0.5–3.1% of men who have sex with men (MSM) self inject drugs before or during sex ('slamming'). Our survey among 175 Dutch MSM, who had practised slamsex, reported various adverse health effects associated with slamsex (skin problems, collapsed veins, infections, and psychological symptoms, like insomnia, sadness, depressed mood, anxiety, suicidal tendencies and loss of control). The current information of slamsex by MSM may contribute to the reinforcement of accessible, non-judgmental and well informed prevention and harm reduction activities. [ABSTRACT FROM AUTHOR]

One of the most common applications of glass fiber composite materials (GFRP) is the manufacturing of the hulls of high-speed boats. During navigation, the hull of these boats is subjected to repetitive impacts against the free surface of the water (slamming effect), which can cause severe damage to the material. To better understand the behavior of the composite material under this effect, in the present work, an experimental test has been carried out to reproduce the slamming phenomenon in GFRP panels by means of a novel device that allows this cyclic impact to be obtained while the panels are always in contact with water. By means of non-destructive ultrasound inspection in immersion, it has been possible to establish the evolution of the damage according to the number of impacts received by each panel. Destructive tests in the affected zone, specifically shear tests (Iosipescu test), allow determination of the loss of mechanical properties experienced by the material after receiving a high number of impacts in the presence of water (up to 900,000 impact cycles in some panels). The behavior of the material was found to be very different in wet and dry conditions. Under dry conditions, the material loses stiffness as the damage density increases and its shear strength also decreases, as does displacement at maximum load. For wet conditions, the material shows higher displacements at maximum load, while the shear strength decreases with increasing stiffness. [ABSTRACT FROM AUTHOR]

ObjectivesThe hull plate of a trimaran cross-deck bottom is often subjected to slamming loads under high-level sea conditions, potentially causing severe structural damage. The objective of this study is to analyze the influence of the air cushion effect on the impact load of a trimaran cross-deck plate and propose a new type of hull plate for the cross-deck bottom in order to reduce the slamming load.MethodsThe two-phase flow problem of a trimaran ship section is simulated using the computational fluid dynamics (CFD) method. First, the accuracy of the numerical model is verified by comparing the predicted results with the experimental measurements. The influence of the air cushion on the slamming load of the trimaran cross-deck structure is then obtained by analyzing the evolution of the flow field. Finally, the influence of the air cushion is analyzed and the effects of different shapes and sizes of the proposed hull plate are evaluated.ResultsThe numerical results show two slamming peaks that appear during the process of a trimaran entering the water. The rectangular shaped plate reduces the slamming load by around 20% compared with the flat plate bottom.ConclusionsThe air cushion has a significant effect on the slamming load. A rectangular shaped hull plate can be used to cover the trimaran cross-deck bottom.

A bulbous bow is a typical ship structure. Due to the influence of the bulbous bow, complex flow separation and gas capture phenomena may appear during the water entry of ship-like sections. In this paper, experimental and numerical studies on the water entry of a ship-like section with an obvious bulbous bow are carried out. Two thin plates are installed at both ends of the test model to ensure that the flow field during the impact process is approximately two-dimensional. The free-fall drop test is carried out in the test rig equipped with guide rails. By changing drop heights, impact pressure on the model surface with different initial impact velocities is measured. A numerical model for simulating the water entry of the ship-like section is established by using the Computational Fluid Dynamics (CFD) method, based on the Navier-Stokes equations. Reasonable time steps and mesh size are determined by convergence analysis. Four different flow models are used in the numerical analysis. It is found that the K-Epsilon turbulence model can present the most reasonable numerical prediction by comparing numerical results with the experimental data. Furthermore, the influence of the bulbous bow on the impact loads is numerically studied by using the validated numerical model. It suggests that the bulbous bow has little effect on the impact force acting on the bow-flared area but, in the position near the bulbous bow, the pressure will be affected by the second slamming and the air cushion.

Three-dimensional effects on slamming load predictions of a ship section are investigated numerically using the unsteady incompressible Reynolds-averaged Navier-Stokes (RANS) equations and volume of fluid (VOF) method, which are implemented in interDyMFoam solver in open-source library OpenFOAM. A convergence and uncertainty study is performed considering different resolutions and constant Courant (CFL) number following updated ITTC guidelines. The numerical solutions are validated through comparisons of slamming loads and motions between the computational fluid dynamics (CFD) simulations and the available experimental values. The slamming force and slamming pressures on a 2D ship section and the 3D model are compared and discussed. Three-dimensional effects on the sectional force and the pressures are quantified both in transverse and longitudinal directions of the body considering various entry velocities. Comparing with 2D simulations, the 3D models provide lower predictions on slamming loads. The results show that the three-dimensional effects on the maximum slamming force coefficient are about 25%, while the effects on pressures differ from locations and entry velocities, ranging from 11% to 29%. [ABSTRACT FROM AUTHOR]

Ships and offshore structures are subjected to impact loads, such as slamming and sloshing. High impact pressures can cause permanent hull deformation by a single impact event. In addition, significant fatigue damage can be accumulated via repeated impact pressures. In this study, the plastic deformation behavior of flat plates under slamming impact is numerically investigated using a coupled Eulerian–Lagrangian method. The dynamic impact pressure of the flat plates by weight and drop height is investigated under the assumption of viscous and compressible fluids. To evaluate the plastic deformation of the plate, contact between water and the plate is removed after a certain duration after dropping, and then the remaining deformation is measured. Optimized finite element models for drop simulations are selected via a mesh sensitivity study, and the simulation results are calibrated and compared with experimental data. Results of the simulation and the experiment show good agreement in general in terms of deflection range. However, because the initial condition of the plate is not reflected in the simulation, some discrepancy is observed in maximum deflections. Finally, a discussion is presented for a more accurate fluid impact analysis model based on the comparison results with the experimental data. [ABSTRACT FROM AUTHOR]

Water entry of marine structures has long been an important problem in ocean engineering. Among the different techniques to predict fluid-structure interactions during water entry, smoothed particle hydrodynamics (SPH) method gradually becomes a promising method that is able to solve the impact pressure and the splashing fluid jets simultaneously. However, for three-dimensional (3D) problems, SPH method is computationally expensive due to the huge number of particles that are needed to resolve the local impact pressure accurately. Therefore, in this work an axisymmetric SPH model is applied to solve different water entry problems with axisymmetric structures including spheres and cones with different deadrise angles. Importantly, the Volume Adaptive Scheme (VAS) is added to guarantee the homogeneousness of particle volumes during the simulation. The axisymmetric SPH model with VAS scheme will be introduced in detail and the numerical results will be sufficiently validated with experimental data to demonstrate the high robustness and accuracy of the SPH model for solving 3D axisymmetric water entry problems in an efficient way. [ABSTRACT FROM AUTHOR]

Abstract Background We estimate the prevalence of drug injection, the variables associated with having ever injected and the proportion of ever injectors whose first drug injection was for having sex; we describe the first drug injection episode, analyze the drugs most frequently injected and estimate the prevalence of risky injecting behaviors. Methods The participants were 3387 MSM without a previous HIV diagnosis attending four HIV/STI diagnosis services in Madrid and Barcelona. Lifetime prevalence and prevalence ratios (PRs) by different factors were calculated using Poisson regression models with robust variance. We compared the characteristics of first drug injection episode, lifetime injection and risky injecting behaviors of those whose first injection was for sex (FIS) with those whose was not (non-FIS). Results Lifetime prevalence of injection was 2.1% (CI 1.7–2.7). In the multivariate analysis, it was strongly associated with having been penetrated by more than five men in the last 12 months (aPR = 10.4; CI 2.5–43.4) and having met most of their partners at private parties (aPR = 7.5; CI 4.5–12.3), and less strongly with other factors. Of those who had ever injected drugs, 81.9% injected for sex the first time they injected drugs (FIS). At first injection, FIS participants had a mean age of 31 years, 62.7% used mephedrone and 32.2% methamphetamine on that occasion. Of this FIS group 39.0% had ever shared drugs or equipment and 82.6% had always shared for sex. Some 30.8% of non-FIS reported having also injected drugs for sex later on. Conclusions Only two out of a hundred had ever injected, most to have sex and with frequent drug or injecting equipment sharing. Injecting for sex is the most common first episode of drug injection and is the most efficient risky behavior for the transmission of HIV, hepatitis B or C and other blood-borne infections. MSM participating in private parties should be considered a priority group for prevention policies.

Today, determination of slam-induced pressure is one of the interested issue of the researchers. Water entry of bow section of a ship is experimentally examined, in order to investigation of slamming pressure. This experimental study is distinguished because of the effect of longitudinal curvature in the ship shape body. A generalized Wagner theory is used to compare of experimental results. The predicted slamming pressure of experimental results is approximately 25 percent lower than Wagner theory because of differences in the assumption of theories. Longitudinal curvature of ships is ignored in the analytical method which is change of flow regime and produce of flow separation and air cavity. Thus, analytical method based on ignoring of longitudinal curvature cannot precinct predication of slamming pressure and a water entry test or 3D numerical method must be performed.

Water impacts form the critical load case for high-performance carbon fibre reinforced polymer (CFRP) racing craft. Such events produce a peaked, non-uniform pressure distribution that travels along a hull panel as it is immersed. Current design standards are based on static, uniform pressure loads that do not account for the directional nature of water impacts. With recent trends towards the use of directionally stiffened hull structures in the form of stringer stiffened composite panels (SSCPs), such simplifications of the load case may no longer be valid. In this study, a marine-based SSCP was tested experimentally and numerically to investigate the effects of flow-front orientation on high-performance hull panels. Parallel and perpendicular impacts at constant velocity were carried out using the novel Servo-hydraulic Slam Testing System (SSTS) and the results were used to validate a one-way coupled computational fluid dynamics — finite element analysis (CFD-FEA) Fluent/Abaqus solution. The highest strains in the monolithic skin and stringer were observed for perpendicular impacts. A parameter sweep across a range of impact orientations between parallel and perpendicular impacts was carried out. An approximately linear relationship between flow orientation angle and key structural strains was observed, with the highest strains reported at 70–90°. Results indicate that the critical load case for SSCPs occurs at 75°orientation angles, where strains in the stringer capping are maximum. • The location of pressure pulse has a significant effect on local loading. • Maximum strains occur in the monolithic skin or longitudinal capping laminate. • An approximately linear relationship exists between orientation angle and strains. • The most extreme load case occurs at 75°orientation impact angles. [ABSTRACT FROM AUTHOR]

For the design of vessels built by GFRP laminates, an insert with a memory foam layer is proposed to reduce the spread of damage produced by the vertical impact of the ship's bottom with the sea or slamming phenomenon. Using vertical drops-weight impact machine that reproduces the energy inferred to the panel during navigation, the propagation of the damage of OoA cured prepreg panels is studied by comparing it with modified panels with insertion of viscoelastic layer. The use of acceleration data reading allows the benefits of viscoelastic modification during impact to be quantified through the developed formulation. The force, displacement, and energy returned by the panel after impact have also been quantified, which does not become intralaminar and interlaminar damage. [ABSTRACT FROM AUTHOR]

In the scientific community, water entry impact study has been remained focus by various authors across the globe in past decades. This paper reviews different analytical, experimental and numerical techniques for water entry impact problem. In this article, water entry problems have been broadly categorised into two main groups i.e. water entry of wedges (focusing on hull slamming loads only) and water entry of projectiles (focusing on impact loads, trajectory calculations and cavity dynamics). The first part of the review commences with theoretical studies in the realm of water entry of wedges then overviews key accomplishments in experimental and numerical techniques. The later section discusses the theoretical, experimental and numerical work carried out on water impact of projectiles starting from background then reviews some major research studies from 2000 to most recent advances. In the end, review is summarised and some recommendations are presented for future work. [ABSTRACT FROM AUTHOR]

In this paper, a method to predict slamming pressures and pressure distribution at the time of water entry for 2D sections is presented. The mathematical model is based on the Schwarz-Christoffel conformal mapping method. This conformal mapping technique has been used to calculate slamming loads during water entry. The pile-up of water during motion is also considered and an alternative pile-up coefficient is assumed against Wagner’s generalized method. A simplified and accurate method is presented, which does not include non-linear terms and jet flow in the calculated pressure distribution on monotonically increasing 2D sections like wedge shapes. Comparison with real ship sections has been done to show accuracy of the results. Finally, a simple yet powerful method is obtained to aid the initial design stage of ships. [ABSTRACT FROM AUTHOR]

Un análisis estructural por medio del método de elementos finitos es realizado a una embarcación tipo CPV (Coastal Patrol Vessel) que es sometida a una carga de slamming. Se realizó el diseño estructural siguiendo el Reglamento High Speed Craft de Germanicher Lloyd (GL), así mismo las cargas de slamming fueron aplicadas de acuerdo a lo que contempla este reglamento a lo largo de la longitud de la embarcación. El modelamiento de la geometría fue hecho utilizando un software CAD, posteriormente mediante el uso de un paquete de simulación comercial de elementos finitos (ANSYS) se realizó el análisis respectivo, para ello se define previamente una condición de frontera apropiada, se obtiene las distribuciones de esfuerzos y deformaciones en toda la estructura. Finalmente se comparó estos resultados con los criterios de aceptación de la Casa Clasificadora GL. Palabras clave: Slamming, método de elementos finitos, esfuerzos, deformaciones, criterio de aceptación, CPV, análisis

As part of the environmentally friendly policy of ships, active research is being conducted on energy storage systems (ESS) for ships. This ESS has a major influence on determining the propulsion and operation system of the ship in the future. A separate space must be provided for the ESS, but small and medium-sized ships often require it to be located at the bottom of the ship to make use of the available space. If the ESS is located at the bottom of the ship, the slamming impact load should be considered, and a study of the vibrations generated during the slamming impact is required. Ships are subjected to various environmental effects while sailing. Among them, the risk factor caused by waves is one of the direct risk factors for the operation of the ship. This slamming phenomenon affects not only ships but also offshore structures, and is a risk factor that can cause structural damage as well as damage to human life. Therefore, it is necessary to study the slamming load, and a method is needed to address it with a dynamic load instead of a static load. In order to reflect the slamming load in the design as a dynamic load rather than the equivalent hydrostatic pressure, which is a static load, it is necessary to study the elastic effect of the structure. The plate thickness is calculated by considering the equivalent design pressure based on the measured slamming pressure peak, and several experimental and theoretical studies have been conducted to estimate the exact value of the peak pressure. However, according to recent studies, structural damage is affected not only by the peak pressure but also by the peak width in the time interval of the peak pressure. Research on slamming has been ongoing for a long time, but structural damage due to slamming is still being reported steadily. In order to understand the slamming phenomenon and reflect it in the structural design formula, high-quality experimental results are required. The slamming phenomenon occurs in a very short time. In order to obtain high-quality experimental results for this slamming phenomenon, numerous experimental variables such as experimental equipment setting, appropriate sensor selection, and data measurement and storage capability must be carefully considered. Normally the slamming load can be expressed in terms of peak pressure, peak width, and duration of the pressure, and the maximum pressure and the idealized pressure value (impulse) are applied to the structure. This slamming pressure is affected by the shape and natural period of the structure and shows the largest pressure value when the dead-rise angle is 3° to 10°. In this study, the test was performed by repeatedly dropping into the water using structural bottom angles of 0°, 3°, 10°, and 20° to the free surface of the water. The peak pressure, peak width, impulse, pressure coefficient, and traveling velocity of peak pressure obtained from the repeated tests are estimated with mean and coefficient of variation.

A higher-order moving particle semi-implicit (MPS) method was further developed to solve 2-D water entry problems. To overcome the inconsistency in the original MPS methods, a pressure gradient correction was implemented to guarantee the first-order consistency of the gradient. The corrective matrix was modified by using the derivative of the kernel function. A particle shifting technique was also applied to improve the numerical stability. Validation studies were carried out for water entry of a rigid wedge with the tilting angles of 0°, 10°, and 20°, and two rigid ship sections. Convergence studies were conducted on domain size, particle spacing, and time step. A particle convergence index method was proposed to evaluate numerical uncertainties in the improved MPS method. Uncertainties in numerical solutions due to spatial discretization were calculated. The predicted impact pressures and forces by the present method are in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

One of the most common applications of glass fiber composite materials (GFRP) is the manufacturing of the hulls of high-speed boats. During navigation, the hull of these boats is subjected to repetitive impacts against the free surface of the water (slamming effect), which can cause severe damage to the material. To better understand the behavior of the composite material under this effect, in the present work, an experimental test has been carried out to reproduce the slamming phenomenon in GFRP panels by means of a novel device that allows this cyclic impact to be obtained while the panels are always in contact with water. By means of non-destructive ultrasound inspection in immersion, it has been possible to establish the evolution of the damage according to the number of impacts received by each panel. Destructive tests in the affected zone, specifically shear tests (Iosipescu test), allow determination of the loss of mechanical properties experienced by the material after receiving a high number of impacts in the presence of water (up to 900,000 impact cycles in some panels). The behavior of the material was found to be very different in wet and dry conditions. Under dry conditions, the material loses stiffness as the damage density increases and its shear strength also decreases, as does displacement at maximum load. For wet conditions, the material shows higher displacements at maximum load, while the shear strength decreases with increasing stiffness.

Background: We estimate the prevalence of drug injection, the variables associated with having ever injected and the proportion of ever injectors whose first drug injection was for having sex; we describe the first drug injection episode, analyze the drugs most frequently injected and estimate the prevalence of risky injecting behaviors. Methods: The participants were 3387 MSM without a previous HIV diagnosis attending four HIV/STI diagnosis services in Madrid and Barcelona. Lifetime prevalence and prevalence ratios (PRs) by different factors were calculated using Poisson regression models with robust variance. We compared the characteristics of first drug injection episode, lifetime injection and risky injecting behaviors of those whose first injection was for sex (FIS) with those whose was not (non-FIS). Results: Lifetime prevalence of injection was 2.1% (CI 1.7–2.7). In the multivariate analysis, it was strongly associated with having been penetrated by more than five men in the last 12 months (aPR = 10.4; CI 2.5–43.4) and having met most of their partners at private parties (aPR = 7.5; CI 4.5–12.3), and less strongly with other factors. Of those who had ever injected drugs, 81.9% injected for sex the first time they injected drugs (FIS). At first injection, FIS participants had a mean age of 31 years, 62.7% used mephedrone and 32.2% methamphetamine on that occasion. Of this FIS group 39.0% had ever shared drugs or equipment and 82.6% had always shared for sex. Some 30.8% of non-FIS reported having also injected drugs for sex later on. Conclusions: Only two out of a hundred had ever injected, most to have sex and with frequent drug or injecting equipment sharing. Injecting for sex is the most common first episode of drug injection and is the most efficient risky behavior for the transmission of HIV, hepatitis B or C and other blood-borne infections. MSM participating in private parties should be considered a priority group for prevention policies. [ABSTRACT FROM AUTHOR]

Typically, the dominant load for the design of planing hulls is slamming, while sailing fast at head seas. Slamming is a violent fluid-structure interaction, where dynamics, hydro-elasticity, and nonlinearity are important. Considering these effects in a rational design may reduce the scantlings as compare to design by rules. This research verifies our rational design method, published recently. For this verification, we designed a special research boat, which has one rules-designed side and one rational-design side, with 20% thinner plates and double stiffeners spacing, which make hydro-elasticity significant. Comparison of critical stresses between rules-design, our rational-design, and measurements shows: For the heavy side (rules-design) rules, rational, and trials show similar stresses, so both rules and rational are applicable; however for the light side (rational-design), rules dramatically over assess the stresses, while rational and trials are similar. We therefore expect this study to advance the design of more efficient boats. [ABSTRACT FROM AUTHOR]