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Contains fulltext : 292919.pdf (Publisher’s version ) (Open Access) BACKGROUND: High myopia (HM), defined as a spherical equivalent refractive error (SER) ≤ -6.00 diopters (D), is a leading cause of sight impairment, through myopic macular degeneration (MMD). We aimed to derive an improved polygenic score (PGS) for predicting children at risk of HM and to test if a PGS is predictive of MMD after accounting for SER. METHODS: The PGS was derived from genome-wide association studies in participants of UK Biobank, CREAM Consortium, and Genetic Epidemiology Research on Adult Health and Aging. MMD severity was quantified by a deep learning algorithm. Prediction of HM was quantified as the area under the receiver operating curve (AUROC). Prediction of severe MMD was assessed by logistic regression. FINDINGS: In independent samples of European, African, South Asian and East Asian ancestry, the PGS explained 19% (95% confidence interval 17-21%), 2% (1-3%), 8% (7-10%) and 6% (3-9%) of the variation in SER, respectively. The AUROC for HM in these samples was 0.78 (0.75-0.81), 0.58 (0.53-0.64), 0.71 (0.69-0.74) and 0.67 (0.62-0.72), respectively. The PGS was not associated with the risk of MMD after accounting for SER: OR = 1.07 (0.92-1.24). INTERPRETATION: Performance of the PGS approached the level required for clinical utility in Europeans but not in other ancestries. A PGS for refractive error was not predictive of MMD risk once SER was accounted for. FUNDING: Supported by the Welsh Government and Fight for Sight (24WG201).

Cystic fibrosis (CF) is an autosomal recessive disease caused by dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) protein, and is marked by an accumulation of mucus in affected airways resulting in persistent infection and chronic inflammation. Quantitative differences in inflammatory markers have been observed in CF patient serum, tracheal cells, and bronchoalveolar lavage fluid, in the absence of detectable infection, implying that absent CFTR function alone may result in dysregulated immune responses. To examine the relationship between absent CFTR and systemic inflammation, 22 analytes were measured in CF mice (F508del/F508del) sera using the MSD multiplex platform. Pro-inflammatory cytokines IL-2, TNF-α, IL-17α, IFN-γ, IL-1β, and MIP-3α are significantly elevated in infection-naïve CF mice (p p = 0.00003, p = 0.004). Additionally, six general markers of inflammation are significantly different from non-CF controls (p Bordetella pseudohinzii infections. There are no statistical differences in nearly all inflammatory markers when compared to their infection-naïve CF counterparts, except in the Th2-derived IL-4 and IL-5 which demonstrate significant decreases following exposure (p = 0.046, p = 0.045). Lastly, following acute infection, CF mice demonstrate elevations in nearly all inflammatory markers, but exhibit a shortened return to uninfected levels over time, and suppression of Th1-derived IL-2 and IL-5 (p = 0.043, p = 0.011). These results imply that CF mice have a persistent inflammatory profile often indistinguishable from chronic infection, and a dysregulated humoral response during and following active infection.

Purpose: Serum lipids are modifiable, routinely collected blood test features associated with cardiovascular health. We examined the association of commonly collected serum lipid measures (total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], and triglycerides) with intraocular pressure (IOP). Design: Cross-sectional study in the UK Biobank and European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk cohorts. Participants: We included 94 323 participants from the UK Biobank (mean age, 57 years) and 6230 participants from the EPIC-Norfolk (mean age, 68 years) cohorts with data on TC, HDL-C, LDL-C, and triglycerides collected between 2006 and 2009. Methods: Multivariate linear regression adjusting for demographic, lifestyle, anthropometric, medical, and ophthalmic covariables was used to examine the associations of serum lipids with corneal-compensated IOP (IOPcc). Main Outcome Measures: Corneal-compensated IOP. Results: Higher levels of TC, HDL-C, and LDL-C were associated independently with higher IOPcc in both cohorts after adjustment for key demographic, medical, and lifestyle factors. For each 1-standard deviation increase in TC, HDL-C, and LDL-C, IOPcc was higher by 0.09 mmHg (95% confidence interval [CI], 0.06–0.11 mmHg; P < 0.001), 0.11 mmHg (95% CI, 0.08–0.13 mmHg; P < 0.001), and 0.07 mmHg (95% CI, 0.05–0.09 mmHg; P < 0.001), respectively, in the UK Biobank cohort. In the EPIC-Norfolk cohort, each 1-standard deviation increase in TC, HDL-C, and LDL-C was associated with a higher IOPcc by 0.19 mmHg (95% CI, 0.07–0.31 mmHg; P = 0.001), 0.14 mmHg (95% CI, 0.03–0.25 mmHg; P = 0.016), and 0.17 mmHg (95% CI, 0.06–0.29 mmHg; P = 0.003). An inverse association between triglyceride levels and IOP in the UK Biobank (–0.05 mmHg; 95% CI, –0.08 to –0.03; P < 0.001) was not replicated in the EPIC-Norfolk cohort (P = 0.30). Conclusions: Our findings suggest that serum TC, HDL-C, and LDL-C are associated positively with IOP in 2 United Kingdom cohorts and that triglyceride levels may be associated negatively. Future research is required to assess whether these associations are causal in nature.

Extensive research has documented associations between childhood abuse and neglect and adolescent mental health. This exploratory study adds the examination of differences in types of adverse childhood experiences (ACEs), including abuse, neglect, and household dysfunction, with a little studied population, those in therapeutic residential care. Also documented were the differences between types of treatment categories per the Youth Comprehensive Risk Assessment (YCRA) and adverse experiences, as well as the adolescent strengths of empowerment and social competence related to adverse childhood experiences in therapeutic residential care. Data was generated from 139 youth in two adolescent therapeutic residential care centers. The most commonly reported adverse experiences were emotional abuse (79.9%) and physical neglect (76.3%). Those with lower empowerment and social competence had significantly higher ACEs in the areas of abuse, neglect, and total ACEs. Youth categorized as high risk to others but not to self, had significantly fewer adverse childhood experiences than others. Study findings support broadening the current discourse on types of adverse events and challenges when considering pathways toward strength building and treatment type, especially related to social competence.

Purpose To describe and compare associations with macular retinal nerve fiber layer (mRNFL), ganglion cell complex (GCC), and ganglion cell–inner plexiform layer (GCIPL) thicknesses in a large cohort. Design Cross-sectional study. Participants We included 42 044 participants in the UK Biobank. The mean age was 56 years. Methods Spectral-domain OCT macular images were segmented and analyzed. Corneal-compensated intraocular pressure (IOPcc) was measured with the Ocular Response Analyzer (Reichert, Corp., Buffalo, NY). Multivariable linear regression was used to examine associations with mean mRNFL, GCC, and GCIPL thicknesses. Factors examined were age, sex, ethnicity, height, body mass index (BMI), smoking status, alcohol intake, Townsend deprivation index, education level, diabetes status, spherical equivalent, and IOPcc. Main Outcome Measures Thicknesses of mRNFL, GCC, and GCIPL. Results We identified several novel independent associations with thinner inner retinal thickness. Thinner inner retina was associated with alcohol intake (most significant for GCIPL: –0.46 μm for daily or almost daily intake compared with special occasion only or never [95% confidence interval (CI), 0.61–0.30]; P = 1.1×10–8), greater social deprivation (most significant for GCIPL: –0.28 μm for most deprived quartile compared with least deprived quartile [95% CI, –0.42 to –0.14]; P = 6.6×10–5), lower educational attainment (most significant for mRNFL: –0.36 μm for less than O level compared with degree level [95% CI, –0.45 to 0.26]; P = 2.3×10–14), and nonwhite ethnicity (most significant for mRNFL comparing blacks with whites: –1.65 μm [95% CI, –1.86 to –1.43]; P = 2.4×10–50). Corneal-compensated intraocular pressure was associated most significantly with GCIPL (–0.04 μm/mmHg [95% CI, –0.05 to –0.03]; P = 4.0×10–10) and was not associated significantly with mRNFL (0.00 μm/mmHg [95% CI, –0.01 to 0.01]; P = 0.77). The variables examined explained a greater proportion of the variance of GCIPL (11%) than GCC (6%) or mRNFL (7%). Conclusions The novel associations we identified may be important to consider when using inner retinal parameters as a diagnostic tool. Associations generally were strongest with GCIPL, particularly for IOP. This suggests that GCIPL may be the superior inner retinal biomarker for macular pathophysiologic processes and especially for glaucoma.

Abstract: This study examines the hydrodynamic performance of a high performance skiff hull using three different physical testing techniques which may be used in early stage design for assessment of the upright resistance of sailing vessels. The hull chosen as a benchmark form is a high-speed hard-chine sailing dinghy, typical of modern trends in skiff design, and is broadly similar to some high performance yacht hulls. The 4.55 m hull was tested at full scale in a moderate size towing tank, at 1:2.5 scale in the same tank, and at full-scale by towing on open water. The work presented here builds on the study of Day & Cameron (2017), with the model tests repeated and re-analyzed in the present study and additional results presented. The challenges of full-scale open-water testing are discussed and several potential improvements in practice are identified for future work. Results show that the open water testing broadly matches well with model-scale tank testing, with the mean discrepancy in the measured resistance between the two around 4% over the speed range tested after correction for the presence of the rudder. Agreement is initially less good for the full-scale hull in the tank for higher speeds, both for resistance and trim. ITTC guidelines suggest that blockage may be an issue for the full-scale boat in this size of tank; comparison of the results suggests that blockage, and/or finite depth effects for the full-scale hull in the tank present a substantial problem at the higher speeds. A correction approach for the wave resistance of the full scale results using a calculation based on a linear thin ship theory is effective in this case, and results show that the full scale and model scale tests agree satisfactorily for the majority of the speed range after this correction. In addition to upright resistance in calm water, results are presented for the impact of small waves, the addition of the rudder, and variations in displacement and trim on resistance for a skiff hull. Finally, the results are compared with predictions from the well-known Delft series regression equations, Savitsky's methods, and a thin ship calculation. The thin ship approach gives good agreement for the case in which the hull is trimmed bow-down and the transom is not immersed, while the Savitsky pre-planing approach gives good agreement for the level trim case. The Delft series and Savitsky planing hull approaches do not give good agreement with physical measurements.

Background Remission of Type 2 diabetes is achievable through dietary change and weight loss. In the UK, lifestyle advice and referrals to weight loss programmes predominantly occur in primary care where most Type 2 diabetes is managed. Objective To quantify the association between primary care experience and remission of Type 2 diabetes over 5-year follow-up. Methods A prospective cohort study of adults with Type 2 diabetes registered to 49 general practices in the East of England, UK. Participants were followed-up for 5 years and completed the Consultation and Relational Empathy measure (CARE) on diabetes-specific primary care experiences over the first year after diagnosis of the disease. Remission at 5-year follow-up was measured with HbA1c levels. Univariable and multivariable logistic regression models were constructed to quantify the association between primary care experience and remission of diabetes. Results Of 867 participants, 30% (257) achieved remission of Type 2 diabetes at 5 years. Six hundred twenty-eight had complete data at follow-up and were included in the analysis. Participants who reported higher CARE scores in the 12 months following diagnosis were more likely to achieve remission at 5 years in multivariable models; odds ratio = 1.03 (95% confidence interval = 1.01–1.05, P = 0.01). Conclusion Primary care practitioners should pay greater attention to delivering optimal patient experiences alongside clinical management of the disease as this may contribute towards remission of Type 2 diabetes. Further work is needed to examine which aspects of the primary care experience might be optimized and how these could be operationalized.

The tripartite protein complex produced by anthrax bacteria (Bacillus anthracis) is a member of the AB family of β-barrel pore-forming toxins. The protective antigen (PA) component forms an oligomeric prepore that assembles on the host cell surface and serves as a scaffold for binding of lethal and edema factors. Following endocytosis, the acidic environment of the late endosome triggers a pH-induced conformational rearrangement to promote maturation of the PA prepore to a functional, membrane spanning pore that facilitates delivery of lethal and edema factors to the cytosol of the infected host. Here, we show that the dominant-negative D425A mutant of PA stalls anthrax pore maturation in an intermediate state at acidic pH. Our 2.7 Å cryo-EM structure of the intermediate state reveals structural rearrangements that involve constriction of the oligomeric pore combined with an intramolecular dissociation of the pore-forming module. In addition to defining the early stages of anthrax pore maturation, the structure identifies asymmetric conformational changes in the oligomeric pore that are influenced by the precise configuration of adjacent protomers.

This article highlights one child and youth services agency's journey to develop and pilot a system for tracking training effectiveness for staff. Given the importance of intentional and strong staff training to the success of an agency, the purpose of this study was to report training outcomes across four-time intervals (i.e., immediately after training considered here as baseline, 6 months, 12 months, and 18 months) using a tracking system based on best practices in staff development. Results indicated that the tracking system allowed this agency to measure and describe post-training outcomes for staff across the four-time intervals. It can be inferred that such training positively influenced youth outcomes. Specifically, the training and follow-up expanded staff's ability to effectively internalize concepts and be more intentional with their time for the benefit of youth care.

This paper considers wave loads on bottom mounted vertical cylinders in the regime relevant to offshore wind turbine monopiles, examining the higher harmonics of the loading from non-breaking waves which are important in engineering design. Although we consider measurements of total force, our focus is on the moments applied about the seabed which have received much less attention in the literature. We consider an empirical ‘Stokes-like’ model whereby the magnitude of the higher harmonics of force or moment are dependent on the linear force or moment time-series raised to an appropriate power and a fixed coefficient. We compare this representation to high quality wave flume measurements and fully non-linear potential flow simulations. In general we find good agreement for all of the harmonic structure except for the triple frequency component where there are significant discrepancies. We also extend the Stokes-like model and show that harmonics of moments can be robustly predicted from the force harmonic and an appropriate constant moment arm for each harmonic, so a more elaborate calculation is generally not necessary.

Anthrax is a severe bacterial infection caused by Bacillus anthracis, which produces a tripartite toxin that includes protective antigen (PA), lethal factor (LF) and edema factor (EF). A series of dominant-negative mutations have been previously identified that prevent the heptameric PA prepore from forming the pH-induced, membrane spanning beta-barrel pore that is required for translocation of EF and LF to the cytoplasm of the infected cell. Here we show that the dominant negative D425A mutation stalls the formation of the pore at a reversible intermediate maturation state, which exhibits many of the structural aspects of the pore but fails to form the phi(ϕ)-clamp and beta-barrel structure needed for full pore maturation. Overall, this structure reveals that ϕ-clamp and beta-barrel pore formation are later steps in the pathway to pore formation, thereby providing a regulatory mechanism to prevent premature translocation of EF and LF.

This paper documents large laboratory-scale measurements of hydrodynamic force time histories on a realistic 1:80 scale space-frame jacket structure exposed to combined waves and in-line current. The aim is to investigate the fluid flow (and the associated hydrodynamic force) reduction relative to ambient fluid flow due to the presence of the jacket structure as an obstacle array, interpreted as wave–current blockage. Transient focussed wave groups, and embedded wave groups in a smaller regular wave background are generated in a towing tank, and the jacket is towed under different speeds opposite to the wave direction to simulate wave loading with different in-line uniform currents. The measurements are compared with numerical predictions using Computational Fluid Dynamics (CFD), with the actual jacket represented in a three-dimensional numerical wave tank as a porous tower modelled as a uniformly distributed Morison stress field. Good agreement is achieved, both in terms of incident surface elevation as well as total force time histories, all using a single set of Morison drag ( C d ) and inertia ( C m ) coefficients. Substantial force reduction is observed under transient large crest relative to prediction from the present industry design guideline with the same Morison coefficients. We demonstrate the generality of our findings: without influence of Keulegan–Carpenter (KC) number effect, a single invariant set of C d and C m is all that is required to numerically explain and reproduce the measured total force time histories on a realistic jacket model for a large range of wave heights and non-zero current speeds.

This paper describes an experimental and numerical investigation of the Iberdrola TLP wind turbine concept, TLPWIND, in realistic wind and wave conditions. The TLP was coupled to the NREL 5 MW reference turbine and was designed to operate in a water depth of 70 m. The test campaign included free oscillation tests, tests in regular and irregular waves and simulated wind conditions. A Software-in-the-loop approach was adopted to account for the time-varying aerodynamic forces produced by the turbine during the physical experiments. The effect of wind was found to have a significant contribution to the overall response of the platform whilst variation in wave conditions was found to have a relatively small effect on the platform response. A comparison of results from physical and numerical simulations show that, the numerical predictions from FAST were very close to the results obtained from the experiments in some cases, but in other cases the numerical model failed to accurately predict the platform response. The results from both studies show the benefits of such TLP structures in terms of motions which are vital to obtain a high power output from a floating offshore wind turbine.

This study describes the development of an approach for performance pr ediction for a sailing dinghy . Key modelling issues addressed include sail depowering for sailing dinghies which cannot reef; effect of crew physique on sailing performance, components of hydrodynamic and aerodynamic drag , decoupling of heel angle from heeling momen t, and the importance of yaw moment equilibrium. In order to illustrate the approaches described, a customised velocity prediction program (VPP) is developed for a Laser dinghy . Results show excellent agreement with measured data for upwind sailing , and correctly predict some phenomena observed in practice . Some discrepancies are found in downwind condition s, but it is speculated that this may be related at least in part to the sailing conditions in which the measured data was gathered. The ef fect of crew weight is studied by comparing time deltas for crews of different physique relative to a baseline 80kg sailor. R esults show relatively high sensitivity of the performance around a race course to the weight of the crew, with a 10kg change contr ibuting to time deltas of more than 60 seconds relative to the baseline sailor over a race of one hour duration at the extremes of the wind speed range examined.

The study reported in this paper is focused on experimental investigation of the hull girder loads on an intact and damaged naval ship DTMB 5415 at zero speed. The experimental campaign was carried out in head and beam regular waves at the University of Strathclyde. The effect of the use of moorings in the model experimental setup was investigated in the context of loads assessment, and the moorings are shown to influence the measured hull girder loads at some wave frequencies compared to the free drift case. Therefore the tests in beam seas are performed with free drifting model while the moored model setup was adopted for head seas. The results for ship motions are compared with those from a previous campaign giving an insight into repeatability and uncertainty of measurements. The roll decay of the ship in both intact and damaged conditions is analysed and the linear and quadratic extinction coefficients for the model and the ship scale are reported and detailed discussion on intact-versus-damaged ship roll damping behaviour is given. The results for the hull girder loads are presented for intact and damaged ship. An investigation of the nonlinear effects due to wave height variation in the range wave height to wave length from 1/50 to 1/22 on the shear force and bending moment values was carried out for a range of wave lengths to ship length ratios from 0.8 to 1.4. The results of the extensive campaign are compared against similar experimental studies forming a benchmark data for validation of numerical methods.

The main objective of this paper is to investigate theoretically and numerically how much interactions are expected between two ships travelling in waves. The theoretical estimation is based on asymptotic far-field wave patterns produced by a translating and oscillating source. The far-field wave pattern is governed by the parameter τ=ωeu0/g; For values of the parameter τ>0.25 there exist a fan-shaped quiescent region in front of the vessel. As τ increases, the range of the fan-shaped quiescent region will be expanded. The critical line between the quiescent and wake region can be estimated by the asymptotic expressions theoretically. It is expected that there is no hydrodynamic interaction if the two ships are located in each other's fan-shaped quiescent region. But due to the near-field local waves produced by the 3-D ships, the critical line could be different from that estimated from asymptotic wave pattern. Therefore, we developed a 3-D panel method based on Rankine-type Green function to investigate the hydrodynamic interaction effects for several combinations of parameters, including oscillation frequency, forward speed and transverse distance between two ships. Finally, the critical line calculated numerically was presented and compared to the theoretical estimation.

An improved characterisation of the hydrodynamic blade loads due to onset turbulence is essential in order to mitigate premature failures, reduce excessive levels of conservativeness and ultimately ensure the commercial viability of tidal turbines. The literature focussing on the turbulence in fast flowing tidal streams and of the unsteady loads that are subsequently imparted to rotors has previously been very limited. However, increased activity in the tidal energy community has led to new investigations and insights which are reported in this paper.It has been found that through the use of acoustic Doppler-based sensors, the streamwise turbulence intensities generally tend to a value of approximately 6–8% at the mid-depth of proposed tidal energy sites. Evidence that the anisotropic structure and scales of the turbulence are more consistent with open-channel-based models than atmospheric-based correlations has also been found. Rapid distortion theory has been applied to estimate that the standard deviation of the streamwise turbulent velocity fluctuations in the onset free-stream flow may be amplified significantly by 15% due to the presence of a turbine. The turbulent fluctuations have also been predicted to remain well correlated over the outer span of the blades at the rotational frequency of the rotor.Recent model-scale experiments have enabled the unsteady hydrodynamic loading to be isolated from the steady-flow loading. For cases where the boundary layer remains primarily attached across the blades, this has enabled linear transfer functions to be developed and applied to model the response to a multi-frequency forcing. It has also been found that phenomena consistent with delayed separation and dynamic stall can result in a blade root bending moment that exceeds the steady value by 25%, and this needs to be taken into account in design to reduce the probability of failure.

This paper examines impact forces resulting from wave-in-deck processes from two separate series of experiments: one with a generic solid deck model, and the other with a combined jacket and deck model, both were conducted with and without an I-beam grillage in-place below the solid deck. A range of inundation levels from 2.1 to 7.1 cm at 1:80 scale is considered. The focus is on global impact forces, which are considered more relevant for integrity assessment of overall bottom-founded structures when survivability is in question and local slamming is not addressed. The objective is to characterise the resultant impact forces as well as to investigate whether there is any interaction between the flows through the jacket and hitting the deck. Focussed wave groups were generated to impinge on the models which were suspended from a carriage over a towing tank. The motion of the support carriage mimics uniform current in-line with the incident waves. Both undisturbed surface elevations as well as impact force time histories were measured. From the first series of tests, a large increase in peak forces as well as high frequency oscillations (force spikes) is observed with the grillage in-place. As soon as the jacket model is in-place for the second series of tests, albeit with a different mounting support arrangement, such a large difference vanishes, which could likely be due to the effect of frequency-dependent transfer functions. We provide experimental evidence of the presence of the jacket in modifying the wave impact on the deck through a significant reduction in the total horizontal impulse. The effects of current on the wave impact forces are also investigated. A simple analytical model based on a momentum argument is used to describe the scaling of horizontal peak force with currents and inundation levels. Finally, the importance of the short duration force spikes as well as vertical impact loads on a real structure at full-scale is discussed based on the same analytical model.

Experimental and numerical studies have shown that operating an LNG Carrier in extreme bow-up trim conditions can lead to substantial savings of over 25% in nominal ship resistance. The present study applies the Extreme Trim Concept to RANSE self-propulsion simulations including the prediction of propeller cavitation. It was investigated how the transient cavitation location and volume changed with varying ship displacements and trim angles over a range of ship speeds. Further, the effect of extreme trim and cavitation development on the ship delivered power was analysed. Results have shown that by operating an LNG Carrier in extreme trim, power consumption and the extent of cavitation were reduced considerably. This study proved that the Extreme Trim Concept can be a valuable operating approach for reducing the environmental impact of LNG Carriers.

The paper presents a numerical roll damping assessment of the intact DTMB 5415 naval ship at zero speed. Free model motions from four experimental roll decays with initial heeling angle of 4.0, 13.5, 19.58 and 24.50 deg, performed previously at the University of Strathclyde, Glasgow, have been analysed and the one with 19.58 deg initial heeling has been chosen for the Computational Fluid Dynamic (CFD) analysis. All calculations are performed using CD Adapco Star CCM + software investigating the accuracy and efficiency of the numerical approach for case of high initial heeling angle of bare hull. In the numerical procedure the verification analysis of mesh refinement and time step was performed with the aim to investigate the numerical error/uncertainty. For grid refinement and time step, validation and verification procedure has been performed according to the Grid Convergence Index (GCI) method. Moreover, to verify the main source of the modelling error/uncertainty, the effect of degrees of freedom are evaluated, comparing the numerical results with the experimental results. Conclusions are identifying best practice for roll decay simulations commenting the accuracy of numerical results and required calculation time.

The application of Computational Fluid Dynamics (CFD) is the fastest developing area in marine fluid dynamics as an alternative to Experimental Fluid Dynamics (EFD). While EFD employs well-established methods for predicting a ship's performance, CFD is still challenged to reach a reliable level of accuracy in a reasonable amount of time. In the present study, this issue is addressed in the context of trim optimization by exploring the combination of time-inexpensive potential flow simulations with high-fidelity Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations. This approach allowed covering a broad fore body design space by running a large number of potential flow simulations while at the same time important flow effects due to viscous forces were included by running URANS simulations over the full speed range for a small set of simulations. The KCS baseline design results were validated against an experimental towing tank dataset ensuring a valid CFD setup and thus demonstrating its competitiveness to EFD.

The stability of the damaged ship is influenced by several factors including the encountered waves and its response to them, the floodwater behaviour and its interaction with the ship’s motions. The behaviour of floodwater is highly nonlinear and therefore the model testing is one of the best ways to assess the actual behaviour of the damaged ship. The present study addresses mainly the experimental study of the stability in intact and damage condition of a combatant vessel in beam waves. The tests were carried out at the Kelvin Hydrodynamics Laboratory of the University of Strathclyde, using a model of the well-known DTMB 5415, equipped with a double bottom. A 1/51-scale model was used. Free rolling decay tests with and without restricted constraint were implemented in calm water, with the model restrained at the bow and stern during the wave excited oscillation tests. In order to investigate the performance of the damaged ship, an opening was made at the starboard side near the midship through which two internal compartments were flooded. The obtained results show how in the damage condition and the floodwater dynamics the compartments impact on the motion responses of the ship and forces acting on the ship’s hull. Nonlinear behaviour of the RAOs of all tests are given to provide the benchmark results for prediction with CFD methods further.

Speed optimisation or speed management has been an attractive topic in the shipping industry for a long time. Traditional methods rely on masters’ experience. Some recent methods are more efficient but have many constraints, which preclude obtaining an optimum speed profile. This paper introduces a relatively advanced model for global speed optimisation towards energy efficient shipping in various weather conditions and shows the effect when the method is employed. With this model, if a ship type, departure and destination ports and fixed ETA (Estimated Time Arrival) are given, the stakeholders can be provided with a more reasonable speed operation plan for a certain commercial route, which leads to lower fuel consumption. Weather conditions and, hence, routing plays a very important role in this process. Several case studies over different shipping conditions are considered to validate the model.

This paper summarises extensive research work on the accurate calculation of extreme loads from waves and current on space-frame offshore structures. Although relevant to new builds, improved prediction of extreme loads is also key to the re-assessment of old and ageing offshore platforms.Current blockage is a field effect. Due to the presence of the rest of the structure, the flow velocity on each structural member is reduced on average leading to smaller overall loads. The first model to account for this ‘current blockage’ was first proposed by Taylor [1], and incorporated into standard industry practice (API, DNV and ISO). This is a simple improvement to the original Morison equation (Morison et al. [2]), which predicts forces using the undisturbed open ocean flow properties.New work shows that unsteady large waves on top of a steady current introduces additional blockage, interpreted as wave-current blockage. Large-scale laboratory experiments have been used to validate numerical force calculations. This paper describes a numerical Computational Fluid Dynamics (CFD) model of a porous block with embedded Morison drag and inertia stresses distributed over the enclosed volume of the space-frame as a global representation. At a local member scale, the standard Morison equation is used, but on the local flow. This local flow speed is reduced because of overall interaction between the structural members interpreted as resulting from a distributed array of obstacle. Since the Morison equation is semi-empirical, drag and inertia coefficients are still required, consistent with present industry practice. This new method should be useful for assessing the overall structural load resistance and integrity in extreme wave and current conditions when survivability is in question.Results are presented from recent large-scale experiments on a scaled (1:80) jacket model in the Kelvin Hydrodynamics Laboratory in Glasgow. These tests cover force measurements on both a jacket (stiff, statically-responding) and the same model restrained on springs to mimic structural dynamics (the first mode of a deep-water jacket, the second mode of a compliant tower or the first mode of a jack-up). For a jacket structure under all range of wave and current conditions, only a single pair of values of Morison drag and inertia coefficients is required to reproduce the complete total force-time histories on the jacket model. This is in contrast to the present industry practice whereby different Morison drag coefficients are required in order to fit the measured peak forces over the wide range of cases considered. For the dynamic tests, we find that the relative velocity formulation of the Morison equation for space-frame structures is valid for dynamically sensitive structures. All of these effects can be captured using our numerical porous block model.

With a typical investment in excess of 100 million for each project, the installation phase of offshore wind farms (OWFs) is an area where substantial cost-reductions can be achieved; however, to-date there have been relatively few studies exploring this. In this paper, we develop a mixed-method framework which exploits the complementary strengths of two decision-support methods: discrete-event simulation and robust optimisation. The simulation component allows developers to estimate the impact of user defined asset selections on the likely cost and duration of the full or partial completion of the installation process. The optimisation component provides developers with an installation schedule that is robust to changes in operation durations due to weather uncertainties. The combined framework provides a decision-support tool which enhances the individual capability of both models by feedback channels between the two, and provides a mechanism to address current OWF installation projects. The combined framework, verified and validated by external experts, was applied to an installation case study to illustrate the application of the combined approach. An installation schedule was identified which accounted for seasonal uncertainties and optimised the ordering of activities. (C) 2017 Elsevier B.V. All rights reserved. University of Strathclyde Technology and Innovation Centre

One key step of the industrial development of a tidal energy device is the testing of scale prototype devices within a controlled laboratory environment. At present, there is no available experimental protocol which addresses in a quantitative manner the differences which can be expected between results obtained from the different types of facilities currently employed for this type of testing. As a consequence, where differences between results are found it has been difficult to confirm the extent to which these differences relate to the device performance or to the test facility type. In the present study, a comparative “Round Robin” testing programme has been conducted as part of the EC FP VII MaRINET program in order to evaluate the impact of different experimental facilities on the test results. The aim of the trials was to test the same model tidal turbine in four different test facilities to explore the sensitivity of the results to the choice of facility. The facilities comprised two towing tanks, of very different size, and two circulating water channels. Performance assessments in terms of torque, drag and inflow speed showed very similar results in all facilities. However, expected differences between the different tank types (circulating and towing) were observed in the fluctuations of torque and drag measurements. The main facility parameters which can influence the behaviour of the turbine were identified; in particular the effect of blockage was shown to be significant in cases yielding for high thrust coefficients, even at relatively small blockage ratios.

International audience; This paper reviews key issues in the physical and numerical modelling of marine renewable energy systems, including wave energy devices, current turbines, and offshore wind turbines. The paper starts with an overview of the types of devices considered, and introduces some key studies in marine renewable energy modelling research. The development of new International Towing Tank Conference (ITTC) guidelines for model testing these devices is placed in the context of guidelines developed or under development by other international bodies as well as via research projects. Some particular challenges are introduced in the experimental and numerical modelling and testing of these devices, including the simulation of Power-Take-Off systems (PTOs) for physical models of all devices, approaches for numerical modelling of devices, and the correct modelling of wind load on offshore wind turbines. Finally, issues related to the uncertainty in performance prediction from model test results are discussed.The paper is based on the report of the International Towing Tank Conference specialist committee on Hydrodynamic Modelling of Marine Renewable Energy Devices to the 27th ITTC held in Copenhagen, Denmark in 2014 (ITTC Specialist Committee on Hydrodynamic Modelling of Marine Renewable Energy Devices, 2014a. Final Report and Recommendations to the 27th ITTC Proc. 27th International Towing Tank Conference, Copehagen, Denmark, vol. 2, pp. 680–725).

There has been a lot of interest in trim optimisation to reduce fuel consumption and emissions of ships. Many existing ships are designed for a single operational condition with the aim of producing low resistance at their design speed and draft with an even keel. Given that a ship will often sail outside this condition over its operational life and moreover some vessels such as LNG carriers return in ballast condition in one leg, the effect of trim on ships resistance will be significant. Ship trim optimization analysis has traditionally been done through towing tank testing. Computational techniques have become increasingly popular for design and optimization applications in all engineering disciplines. Computational Fluid Dynamics (CFD), is the fastest developing area in marine fluid dynamics as an alternative to model tests. High fidelity CFD methods are capable of modelling breaking waves which is especially crucial for trim optimisation studies where the bulbous bow partially emerges or the transom stern partially immerses. This paper presents a trim optimization study on the Kriso Container Ship (KCS) using computational fluid dynamics (CFD) in conjunction with towing tank tests. A series of resistance tests for various trim angles and speeds were conducted at 1:75 scale at design draft. CFD computations were carried out for the same conditions with the hull both fixed and free to sink and trim. Dynamic sinkage and trim add to the computational cost and thus slow the optimisation process. The results obtained from CFD simulations were in good agreement with the experiments. After validating the applicability of the computational model, the same mesh, boundary conditions and solution techniques were used to obtain resistance values for different trim conditions at different Froude numbers. Both the fixed and free trim/sinkage models could predict the trend of resistance with variation of trim angles; however the fixed model failed to measure the absolute values as accurately as the free model. It was concluded that a fixed CFD model, although computationally faster and cheaper, can find the optimum trim angle but cannot predict the amount of savings with very high accuracy. Results concerning the performance of the vessel at different speeds and trim angles were analysed and optimum trim is suggested.

Slender offshore structures possess multiple natural frequencies in different directions which can lead to different resonance conditions when undergoing vortex-induced vibration (VIV). This paper presents an experimental and numerical investigation of a two-degree-of-freedom VIV of a flexibly mounted circular cylinder with variable in-line-to-cross-flow natural frequency ratio. A mechanical spring-cylinder system, achieving a low equivalent mass ratio in both in-line and cross-flow directions, is tested in a water towing tank and subject to a uniform steady flow in a sub-critical Reynolds number range of about 2×103–5×104. A generalized numerical prediction model is based on the calibrated Duffing-van der Pol (structure-wake) oscillators which can capture the structural geometrical coupling and fluid-structure interaction effects through system cubic and quadratic nonlinearities. Experimental results for six measurement datasets are compared with numerical results in terms of response amplitudes, lock-in ranges, oscillation frequencies, time-varying trajectories and phase differences of cross-flow/in-line motions. Some good qualitative agreements are found which encourage the use of the implemented numerical model subject to calibration and the sensitivity analysis of empirical coefficients. Moreover, comparisons of the newly-obtained and published experimental results are carried out and discussed, highlighting a good correspondence in both amplitude and frequency responses. Various patterns of figure-of-eight orbital motions associated with dual two-to-one resonances are observed experimentally as well as numerically: the forms of trajectories are noticed to depend on the system mass ratio, damping ratio, reduced velocity parameter and natural frequency ratio of the two-dimensional oscillating cylinder.

This paper presents an extensive study on the experimental prediction of motions for the well-known 5415 frigate hull in intact and damaged conditions. The experimental campaign is conducted for two geosim models, 1/100 and 1/51 scale, at zero speed in head, beam and quartering seas. All experimental results for 1/51 model are presented as 1st and 2nd order RAO, commenting on physical reasons for second order response occurrences. The results show the changes in motion responses when a ship hull is in damaged condition, they highlight the model scale effects and demonstrate the comparisons between the tests in which the model may freely drift and those in which the mean position of the model is restrained. For damaged ship in free drift tests the damage opening orientation is varied and its effect on RAO and free drift velocity is commented.

Characterisation of the unsteady hydrodynamic loads is essential for accurate predictions of the fatigue life and ultimate loads of tidal turbine blades. This paper analyses a set of experimental tests of the hydrodynamic blade root out-of-plane bending moment response to planar oscillatory motion, chosen as an idealised representation of the unsteadiness imparted by waves and turbulence. Phenomena associated with dynamic stall are observed which are sensitive to the oscillatory frequency and velocity amplitude. Flow separation is shown to result in loads significantly greater in magnitude than that for steady flow. Following flow reattachment, the load cycles compare relatively well with Theodorsen's theory for a two-dimensional foil oscillating in heave, suggesting that circulation due to the shed wake dominates the unsteadiness in phase with acceleration, over added mass effects. For attached flow, the effect of unsteadiness is comparatively much smaller. At low frequencies a phase lead over the velocity is observed, compared to a lag at higher frequencies. Multiple frequency oscillations are also briefly considered. Reconstruction of the multi-frequency response using both the steady flow measurements, and the single frequency measured response, is shown to offer a relatively good fit when the flow is attached, for lower frequency combinations.

International audience; This study examines the relative merits of physical testing techniques which may be used in early stage design for assessment of the resistance of high-performance sailing vessels. The hull chosen as a benchmark form is a high-speed hard-chine sailing dinghy. The hull proportions and shape are typical of modern trends in skiff design, but may also be considered to be broadly similar to some high performance yacht hulls. The 4.55m hull was tested at full scale in a moderate size towing tank, at 1:2.5 scale in the same tank, and at full-scale by towing on open water. Results show the mean discrepancy in the measured resistance between the open water towing and the full-scale tank test is around 4%. The challenges of full-scale open-water testing are discussed and several improvements identified for future work. Comparison of the full-scale results suggests that blockage and depth correction for the full-scale hull in the tank do not present a substantial problem for subcritical speeds. Larger discrepancies were found between resistance from the model scale and the full scale tank tests at higher speeds; it was speculated that these discrepancies relate to the differences in the detailed geometry of the model and full-scale boat, particularly in the region of the chines.