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

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

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

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

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

Assessing Communities of Practice in health policy : A conceptual framework as a first step towards empirical research

Peer reviewe

GP/GPN partner* perspectives on clinical placements for student nurses in general practice: can a community of practice help to change the prevailing culture within general practice?

Background: The UK Government document 5 year forward view describes the need to move chronic disease management from secondary to primary care, which will require a significant increase in the numbers of General Practice Nurses (GPNs). Until recently, there has been no specific recruitment strategy to address this increased need. In recent times, a number of solutions have been suggested to address this impending GPN recruitment crisis. For example, Health Education England (HEE) commission General Practitioners (GPs), who are members of the Advanced Training Practice Scheme (ATPS), to provide placements for student nurses within general practice. Methods: A descriptive qualitative study was undertaken, in which data were collected using semi-structured interviews with 16 GPs and 2 GPN partners∗. Qualitative analysis used a framework approach and themes were cross-checked within the team and member checking was undertaken with a convenience sample of GPs. The research had ethical approval and anonymity and confidentiality were maintained. Results: From the GP perspective, there were two key themes that emerged from the data. The first theme of 'fishing in the same small pond' included succession planning for the general practice workforce, the 'merry go round' of poaching staff from other practices, and the myths and misunderstandings that have grown up around general practice nursing. The second theme, 'growing your own', looked at the impact of the student nurse placements as a means to address the crisis in GPN recruitment. There was recognition of the need for cultural change in the way that GPNs are recruited, and that the ATPS was one way of helping to achieve that change. There were however a number of challenges to sustaining this cultural shift, such as the financial constrains placed upon the GP practice, and the need to function as a 'small business'. Conclusions: Despite all the challenges, the evidence is that, through the Community of Practice (CoP), the ATPS scheme is beginning to 'bear fruit', and there is a subtle but discernible move by GPs from a 'why would we?' to 'why wouldn't we?' invest in education and training for nurses in general practice. N.B. The term GPN partner∗denotes a GPN who is a 'full partner' in the practice business, holding the same NHS contracts and the same status as a GP. For the purposes of the paper itself, the term GP will be used to denote both types of partner

Widening access to medicine may improve general practitioner recruitment in deprived and rural communities:survey of GP origins and current place of work

BACKGROUND: Widening access to medicine in the UK is a recalcitrant problem of increasing political importance, with associated strong social justice arguments but without clear evidence of impact on service delivery. Evidence from the United States suggests that widening access may enhance care to underserved communities. Additionally, rural origin has been demonstrated to be the factor most strongly associated with rural practice. However the evidence regarding socio-economic and rural background and subsequent practice locations in the UK has not been explored. The aim of this study was to investigate the association between general practitioners’ (GPs) socio-economic and rural background at application to medical school and demographic characteristics of their current practice. METHOD: The study design was a cross-sectional email survey of general practitioners practising in Scotland. Socio-economic status of GPs at application to medical school was assessed using the self-coded National Statistics Socio-Economic Classification. UK postcode at application was used to define urban–rural location. Current practice deprivation and remoteness was measured using NHS Scotland defined measures based on registered patients’ postcodes. RESULTS: A survey was sent to 2050 Scottish GPs with a valid accessible email address, with 801 (41.5 %) responding. GPs whose parents had semi-routine or routine occupations had 4.3 times the odds of working in a deprived practice compared to those with parents from managerial and professional occupations (95 % CI 1.8–10.2, p = 0.001). GPs from remote and rural Scottish backgrounds were more likely to work in remote Scottish practices, as were GPs originating from other UK countries. CONCLUSION: This study showed that childhood background is associated with the population GPs subsequently serve, implying that widening access may positively affect service delivery in addition to any social justice rationale. Longitudinal research is needed to explore this association and the impact of widening access on service delivery more broadly

Integration of robotic surgery into routine practice and impacts on communication, collaboration, and decision making: A realist process evaluation protocol

Background: Robotic surgery offers many potential benefits for patients. While an increasing number of healthcare providers are purchasing surgical robots, there are reports that the technology is failing to be introduced into routine practice. Additionally, in robotic surgery, the surgeon is physically separated from the patient and the rest of the team, with the potential to negatively impact teamwork in the operating theatre. The aim of this study is to ascertain: how and under what circumstances robotic surgery is effectively introduced into routine practice; and how and under what circumstances robotic surgery impacts teamwork, communication and decision making, and subsequent patient outcomes. Methods and design: We will undertake a process evaluation alongside a randomised controlled trial comparing laparoscopic and robotic surgery for the curative treatment of rectal cancer. Realist evaluation provides an overall framework for the study. The study will be in three phases. In Phase I, grey literature will be reviewed to identify stakeholders' theories concerning how robotic surgery becomes embedded into surgical practice and its impacts. These theories will be refined and added to through interviews conducted across English hospitals that are using robotic surgery for rectal cancer resection with staff at different levels of the organisation, along with a review of documentation associated with the introduction of robotic surgery. In Phase II, a multi-site case study will be conducted across four English hospitals to test and refine the candidate theories. Data will be collected using multiple methods: the structured observation tool OTAS (Observational Teamwork Assessment for Surgery); video recordings of operations; ethnographic observation; and interviews. In Phase III, interviews will be conducted at the four case sites with staff representing a range of surgical disciplines, to assess the extent to which the results of Phase II are generalisable and to refine the resulting theories to reflect the experience of a broader range of surgical disciplines. The study will provide (i) guidance to healthcare organisations on factors likely to facilitate successful implementation and integration of robotic surgery, and (ii) guidance on how to ensure effective communication and teamwork when undertaking robotic surgery