Numerical simulation of the loading characteristics of straight and helical-bladed vertical axis tidal turbines

The stress and deflection of straight and helical-bladed vertical axis turbines was investigated using hydrodynamic and structural analysis models. Using Double Multiple Streamtube (DMS) and Computational Fluid Dynamics (CFD) models, the hydrodynamic forces and pressures on the turbines were modelled for three rotational rates from startup to over speed conditions. The results from these hydrodynamic models were then used to determine stress and total deflection levels using beam theory and Finite Element Analysis (FEA) methods. Maximum stress and deflection levels were found when the blades were in the furthest upstream region, with the highest stresses found at the blade-strut joints for the turbines studied. The helical turbine exhibited on average 13% lower maximum stress levels than the straight-bladed turbine, due to the helical distribution of the blades around the rotational axis. All simulation models offered similar accuracy when predicting maximum blade stress and deflection levels; however for detailed analysis of the blade-strut joints the more computationally demanding CFD-FEA models were required. Straight-bladed, rather than helical turbines, are suggested to be more suited for tidal installations, as for the same turbine frontal area they produce higher power output with only 13% greater structural stress loading

Using a community of practice to evaluate falls prevention activity in a residential aged care organisation: a clinical audit

Objective This study evaluates whether a community of practice (CoP) could conduct a falls prevention clinical audit and identify gaps in falls prevention practice requiring action. Methods Cross-sectional falls prevention clinical audits were conducted in 13 residential aged care (RAC) sites of a not-for-profit organisation providing care to a total of 779 residents. The audits were led by an operationalised CoP assisted by site clinical staff. A CoP is a group of people with a shared interest who get together to innovate for change. The CoP was made up of self-nominated staff representing all RAC sites and comprised of staff from various disciplines with a shared interest in falls prevention. Results All 13 (100%) sites completed the audit. CoP conduct of the audit met identified criteria for an effective clinical audit. The priorities for improvement were identified as increasing the proportion of residents receiving vitamin D supplementation (mean 41.5%, s.d. 23.7) and development of mandatory falls prevention education for staff and a falls prevention policy, as neither was in place at any site. CoP actions undertaken included a letter to visiting GPs requesting support for vitamin D prescription, surveys of care staff and residents to inform falls education development, defining falls and writing a falls prevention policy. Conclusion A CoP was able to effectively conduct an evidence-based falls prevention activity audit and identify gaps in practice. CoP members were well positioned, as site staff, to overcome barriers and facilitate action in falls prevention practice

Three-dimensional numerical simulations of straight-bladed vertical axis tidal turbines investigating power output, torque ripple and mounting forces

Three straight-bladed vertical axis turbine designs were simulated using Three-Dimensional (3D) transient Computational Fluid Dynamics (CFD) models, using a commercial Unsteady Reynolds Averaged Navier–Stokes (URANS) solver. The turbine designs differed in support strut section, blade-strut joint design and strut location to evaluate their effect on power output, torque fluctuation levels and mounting forces. Simulations of power output were performed and validated against Experimental Fluid Dynamics (EFD), with results capturing the impacts of geometrical changes on turbine power output. Strut section and blade-strut joint design were determined to significantly influence total power output between the three turbine designs, with strut location having a smaller but still significant effect. Maximum torque fluctuations were found to occur around the rotation speed corresponding to maximum power output and fluctuation levels increased with overall turbine efficiency. Turbine mounting forces were also simulated and successfully validated against EFD results. Mounting forces aligned with the inflow increased with rotational rates, but plateaued due to reductions in shaft drag caused by rotation and blockage effects. Mounting forces perpendicular to the inflow were found to be 75% less than forces aligned with the inflow. High loading force fluctuations were found, with maximum values 40% greater than average forces

The influence of turbulence model and two and three-dimensional domain selection on the simulated performance characteristics of vertical axis tidal turbines

The influence of Computational Fluid Dynamics (CFD) modeling techniques on the accuracy of vertical axis turbine power output predictions was investigated. Using Two-Dimensional (2D) and Three-Dimensional (3D) models, as well as the Baseline-Reynolds Stress Models (BSL-RSM) model and the k-ω Shear Stress Transport (k-ω SST) model in its fully turbulent and laminar-to-turbulent formulation, differences in power output modeling accuracy were evaluated against experimental results from literature. The highest correlation with experimental power output was found using a 3D domain model that fully resolved the boundary layer combined with the k-ω SST laminar-to-turbulent model. The turbulent 3D fully resolved boundary layer k-ω SST model also accurately predicted power output for most rotational rates, at a significantly reduced computational cost when compared to its laminar-to-turbulent formulation. The 3D fully resolved BSL-RSM model and 3D wall function boundary layer k-ω SST model were found to poorly simulate power output. Poor output predictions were also obtained using 2D domain k-ω SST models, as they were unable to account for blade tip and strut effects. The authors suggest that 3D domain fully turbulent k-ω SST models with fully resolved boundary layer modeling are used for predicting turbine power output given their accuracy and computational efficiency

Numerical investigation of the influence of blade helicity on the performance characteristics of vertical axis tidal turbines

Previous research has shown that helical vertical axis turbines exhibit lower torque fluctuation levels than straight-bladed turbines; however little is known of the impact of blade helicity on turbine performance characteristics. To investigate these relationships the hydrodynamic characteristics of straight and helical-bladed vertical axis turbines were investigated using Three-Dimensional (3D) Computational Fluid Dynamics (CFD) models using a commercial Unsteady Reynolds Averaged Navier-Stokes (URANS) solver. Simulations of power output, torque oscillations, and mounting forces were performed for turbines with overlap angles from 0° to 120° and section inclination angles from −15° to 45°. Results indicated that straight-bladed turbines with 0° blade overlap generated the highest power output. Helical turbines were found to generate decreasing power outputs as blade overlap angle increased due to the resultant blade inclination to the inflow. Blade section inclination to the inflow was also found to influence power output. Some benefits of helical-bladed turbines over their straight-bladed counterparts were established; helical turbine torque oscillation levels and mounting forces were reduced when compared to straight-bladed turbines. For both straight and helical-bladed turbines maximum mounting force levels were found to exceed the average force levels by more than 40%, with large cyclical loading forces identified

Mechanisms underpinning interventions to reduce sexual violence in armed conflict: A realist-informed systematic review

Sexual violence is recognised as a widespread consequence of armed conflict and other humanitarian crises. The limited evidence in literature on interventions in this field suggests a need for alternatives to traditional review methods, particularly given the challenges of undertaking research in conflict and crisis settings. This study employed a realist review of the literature on interventions with the aim of identifying the mechanisms at work across the range of types of intervention. The realist approach is an exploratory and theory-driven review method. It is well suited to complex interventions as it takes into account contextual factors to identify mechanisms that contribute to outcomes. The limited data available indicate that there are few deterrents to sexual violence in crises. Four main mechanisms appear to contribute to effective interventions: increasing the risk to offenders of being detected; building community engagement; ensuring community members are aware of available help for and responses to sexual violence; and safe and anonymous systems for reporting and seeking help. These mechanisms appeared to contribute to outcomes in multiple-component interventions, as well as those relating to gathering firewood, codes of conduct for personnel and legal interventions. Drawing on pre-existing capacity or culture in communities is an additional mechanism which should be explored. Though increasing the risk to offenders of being detected was assumed to be a central mechanism in deterring sexual violence, the evidence suggests that this mechanism operated only in interventions focused on gathering firewood and providing alternative fuels. The other three mechanisms appeared important to the likelihood of an intervention being successful, particularly when operating simultaneously. In a field where robust outcome research remains likely to be limited, realist methods provide opportunities to understand existing evidence. Our analysis identifies the important potential of building in mechanisms involving community engagement, awareness of responses and safe reporting provisions into the range of types of intervention for sexual violence in crises

Wetdeck slamming loads on a developed catamaran hullform – experimental investigation

Catamaran wetdeck slamming has been experimentally investigated using a servo hydraulic slam testing system. A series of controlled-speed water impacts was undertaken on a rigid catamaran bow section with two interchangeable centrebows. Entry into the body of water was at two fixed trim angles: 0° and 5°. The vertical velocity was varied from 3 to 5 m/s in 0.5 m/s increments. This study presents a new dataset of pressure distributions and slam forces on the arched wetdeck structure of catamaran vessels. The relationships between the peak force magnitudes, relative impact angle and vertical velocity are observed, with a small reduction in slam force for an amended centrebow. Limited pressure measurements along the archway were not found to be representative of wetdeck slamming loads

The evolution of strategic environmental assessment from the Law 20.417

La evaluación ambiental estratégica se incorporó el año 2010, como instrumento de gestión ambiental a través de la Ley N° 20.417, que creó el Ministerio del Medio Ambiente, el Servicio de Evaluación Ambiental y la Superintendencia del Medio Ambiente, la cual introdujo reformas importantes en la regulación del medio ambiente. Casi seis años más tarde, el reglamento para la Evaluación Ambiental Estratégica, fue aprobado mediante el Decreto 32/2015 del Ministerio del Medio Ambiente. Durante la ausencia de norma reglamentaria, Contraloría General de la República dio ciertas directrices a seguir por los Órganos Responsables al momento de evaluar ambientalmente los Instrumentos de Planificación Territorial, Planes y Políticas, estableciendo como ley supletoria para llevar a cabo el procedimiento administrativo a la Ley N° 19.880. Con ello se debió implementar abruptamente la EAE considerando ciertos vacíos legales que con la llegada del Reglamento se esperaban resolver.The strategic environmental assessment was incorporated in 2010 as an instrument of environmental management through the Law N° 20.417, that created the Ministry, the Environment Assessment Authority and the Superintendence, which made on the environment regulation, important reforms. Nearly six years later, the strategic environmental assessment regulation, was approved by Decree 32/2015 of the Environment Ministry. During the absence of regulatory standard, Contraloría General gave some guidelines to be followed by the responsible institutions that have to elaborate the strategic environmental assessment of the Territorial Planning Instruments, Plans and Public Policies, establishing as a suppletive law to this administrative procedure, the Law N° 19.880. This was an abrupt implementation, considering certain loopholes that are expected to be solved with the recently approved regulation

Experimental drop test investigation into wetdeck slamming loads on a generic catamaran hullform

A series of drop-test experiments was performed to investigate the hydrodynamic loads experienced by a generic wave-piercer catamaran hullform during water impacts. The experiments, which focus on the characterisation of the unsteady slam loads on an arched wetdeck, were conducted using a Servo-hydraulic Slam Testing System (SSTS) that allows the model to enter the water at a range of constant speeds up to 10 m/s. The systematic and random uncertainties associated with the drop test results are quantified in detail. The relationships between water-entry velocity and both slam force and pressure distributions are presented and discussed with a strong relationship between the slam force peak magnitudes and impact velocity being observed. In addition the three dimensionality of the water flow in these slam impact events is characterised

A systematic literature review of undergraduate clinical placements in underserved areas.

Context: The delivery of undergraduate clinical education in underserved areas is increasing in various contexts across the world in response to local workforce needs. A collective understanding of the impact of these placements is lacking. Previous reviews have often taken a positivist approach by only looking at outcome measures. This review addresses the question: What are the strengths and weaknesses for medical students and supervisors of community placements in underserved areas? Methods: A systematic literature review was carried out by database searching, citation searching, pearl growing, reference list checking and use of own literature. The databases included MEDLINE, EMBASE, PsycINFO, Web of Science and ERIC. The search terms used were combinations and variations of four key concepts exploring general practitioner (GP) primary care, medical students, placements and location characteristics. The papers were analysed using a textual narrative synthesis. Findings: The initial search identified 4923 results. After the removal of duplicates and the screening of titles and abstracts, 185 met the inclusion criteria. These full articles were obtained and assessed for their relevance to the research question; 54 were then included in the final review. Four main categories were identified: student performance, student perceptions, career pathways and supervisor experiences. Conclusions: This review reflects the emergent qualitative data as well as the quantitative data used to assess initiatives. Underserved area placements have produced many beneficial implications for students, supervisors and the community. There is a growing amount of evidence regarding rural, underserved areas, but little in relation to inner city, deprived areas, and none in the UK