Design of a Horizontal Axis Open-Centre Tidal Stream Turbine using Computational Fluid Dynamics

Tidal energy is one of the most promising emerging renewable energy sources which remains largely untapped, due primarily to the challenges of submerged operation within sensitive marine environments. Extracting kinetic energy from dense and energetic flow streams which vary in height, reverse flow direction roughly twice a day and carry sediment as well as marine life requires a unique application of engineering knowledge. A variety of tidal turbine technologies have been developed in response, although as yet the industry is far from mature and there remains great potential for improvement. The research presented in this study introduces a new type of turbine design which has been developed specifically to address the issue of balancing marine friendly technology with efficient energy harvest. This is accomplished through the use of an open-centre concept which houses the blades between the hub and shroud, thus minimizing the risk of blade tip impact and providing free passage through the central aperture. In this study several iterations of the design are tested using the methods of computational fluid dynamics (CFD), each one featuring a different helical blade geometry of varying length and twist angle. A numerical model of the new design is presented in which the energy generation potential is assessed by measuring the amount of torque produced by a stationary blade placed in a steady flow. The torque is calculated by determining the pressure force acting on each blade surface and the resulting moment generated about the rotation axis of the turbine. This method allows for a great number of geometries to be tested under simulated turbine operating conditions, without requiring a prohibitive amount of computational resources. The initial assessment of this new type of turbine is promising, indicating that certain blade geometries produce a greater amount of torque than a model of the conventional open-centre turbine developed by OpenHydro

Numerical simulation and flow visualization using soap film of the self-organized vortex structure in the wake of an array of cylinders

With the aid of computational fluid dynamics (CFD) and simple flow visualization technique using flowing soap-film, we present here the wake structures behind an array of cylinders for Reynolds numbers corresponding to both laminar and turbulent flow regimes. The image results illustrate interesting vortex interactions past these equally spaced cylinders; for low Reynolds number flow, well-organized wake pattern persists and manifests unsteadily to different symmetry states. An increase of free stream flow velocity causes the wake transition, resulting in the formation of asymmetric flow wake with chaotic mixing at the far wake. Observations from both the numerical simulations and soap-film are in good agreement at least qualitatively

Research priorities in the field of posttraumatic pain and disability: Results of a transdisciplinary consensus-generating workshop

© Copyright 2016 David M.Walton et al. Background. Chronic or persistent pain and disability following noncatastrophic \u27musculoskeletal\u27 (MSK) trauma is a pervasive public health problem. Recent intervention trials have provided little evidence of benefit from several specific treatments for preventing chronic problems. Such findings may appear to argue against formal targeted intervention for MSK traumas. However, these negative findings may reflect a lack of understanding of the causal mechanisms underlying the transition from acute to chronic pain, rendering informed and objective treatment decisions difficult. The Canadian Institutes of Health Research (CIHR) Institute ofMusculoskeletalHealth and Arthritis (IMHA) has recently identified better understanding of causalmechanisms as one of three priority foci of their most recent strategic plan. Objectives. A 2-day invitation-only active participation workshop was held inMarch 2015 that included 30 academics, clinicians, and consumers with the purpose of identifying consensus research priorities in the field of trauma-relatedMSK pain and disability, prediction, and prevention. Methods. Conversations were recorded, explored thematically, and member-checked for accuracy. Results. From the discussions, 13 themes were generated that ranged from a focus on identifying causal mechanisms and models to challenges with funding and patient engagement. Discussion. Novel priorities included the inclusion of consumer groups in research from the early conceptualization and design stages and interdisciplinary longitudinal studies that include evaluation of integrated phenotypes and mechanisms

COVID-19 in pregnancy in South Africa : tracking the epidemic and defining the natural history

South Africa (SA) has seen a rapid increase in COVID-19 infections in recent weeks, with cases exceeding 40 000 in early June and anticipated to escalate rapidly as lockdown is eased. The country also has the largest HIV burden globally, and poor maternal and child health indices in many parts. Although early indications were that COVID-19 infection does not worsen pregnancy and birth outcomes, recent reports have raised fresh concerns. Preterm birth, neonatal pneumonia[9-11] and cases of vertical transmission and postpartum infections have been reported, including in SA. Some maternal deaths related to COVID-19 have occurred, possibly linked to haemodynamic changes immediately postpartum and/or to the thrombogenic nature of both pregnancy and COVID- 19. Maternal wellbeing in pregnant women with COVID-19 infection is a major concern, as these women often have high anxiety about infecting their newborn child, and may experience challenging interactions with healthcare providers and community stigma. Most evidence on COVID-19 and pregnancy to date is limited to case series, involves only symptomatic women without HIV, and is almost exclusively from high-income countries. Cohort data across a range of settings and population groups are the only means of fully understanding the natural history, clinical disease spectrum and risks of COVID-19 in pregnant women, fetuses and infants.http://www.samj.org.zaam2021Obstetrics and Gynaecolog

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat