Wake impacting on a horizontal axis wind turbine

Offshore wind is set to contribute a significant portion of the UK’s renewable energy production. In order to achieve this, installation costs must be reduced and energy density optimised, but this must be balanced with the increase in maintenance costs resulting from fatigue due to wake impact. The aim of this thesis is to investigate the effects of horizontal axis wind turbine wake impact on a downstream rotor. A force-free wake implementation of the unsteady vortex lattice method has been developed in order to simulate the flow around the downstream rotor, including the effects of an upstream rotor wake, uncorrelated wind field and the dynamic inflow response of the turbine wake. In addition, a series of wind tunnel experiments were undertaken to characterise the wake of a horizontal axis wind turbine and measure time histories of the turbine thrust and blade root bending moments in uniform and turbulent inflow and upstream rotor wake impact. Comparisons are made between the model and wind tunnel experiments for a range of flow cases: uniform inflow, turbulent inflow and operation in an upstream rotor wake at varying degrees of lateral offset. The upstream flow field is modelled on a Cartesian grid, following the assumption of frozen turbulence. For both the turbulent flow and upstream rotor wake, a simplified model is used as a starting point and then refined to better model the effect of turbulence. Ambient turbulence is found to have minimal impact on the mean response of the rotor, suggesting that a linearised approach can be taken in the numerical modelling of turbulence effects. The simple model better predicts the low frequency response, but does not capture the per revolution frequencies identified by the refined model, which also better predicts the admittance. The response of the rotor to an aligned upstream rotor wake is found to be dominated by the wake turbulence, although the proposed model does not reproduce the measured response. However, for laterally offset upstream rotor wakes the mean velocity deficit is the dominant factor and the model captures the response, including the shift to higher bending moment cycles which will contribute to increased fatigue.Open Acces

Derby Fisheries, Individual Quotas, and Transition in the Fish Processing Industry

Processors adapt to the pulse of landings in derby fisheries by investing in large-scale facilities capable of preserving and storing fish products. In fisheries where the pulse of landings suppresses the ability of processors to meet consumer demand for fresh product, the imposition of individual quota (IQ) systems transforms the associated fish processing industry. The cost of fresh fish processing is generally lower and more malleable than that for preserved fish, and consumers may pay a price premium for fresh product, which creates an opportunity for entry by fresh-fish processors and results in higher equilibrium ex-vessel prices. Incumbent firms are likely to experience an economic dislocation due to a diminished value of nonmalleable capital used to preserve and store fish products. Our paper generalizes and provides a modeling framework for the observed changes in the British Columbian halibut harvester/processor industry complex following the introduction of an IQ system.Derby fishery, individual quotas, pulse of landings, fish processing, fresh fish, preserved fish, product forms, ex-vessel price, wholesale fish price, processing capital, malleability, Resource /Energy Economics and Policy, Q13, Q22,

A Cost Comparison of Treatments of Moderate to Severe Psoriasis

This study of the efficacy and cost-effectiveness of moderate to severe psoriasis treatments compared phototherapy, oral systemic agents, and biologics from a managed health care systems perspective. A literature review was conducted to identify published studies reporting Psoriasis Area and Severity Index (PASI) percentage improvement from baseline (PASI%) for selected treatments. The researchers then calculated total annualized costs. For each treatment, annualized cost-effectiveness was calculated by dividing total annualized costs of treatment by PASI%. The costs necessary to achieve clinically meaningful outcomes (PASI50 and PASI75) were then calculated. Of 3886 articles examined, 16 studies met inclusion criteria. Oral systemic medications, UV therapy, and UV therapy combined with acitretin appear to be the most cost-effective therapies for moderate to severe psoriasis

A three-phase analysis of the prevention of recreational softball injuries

Recreational sports injuries are expensive to society. Prevention of such injuries must be a major public health goal. In a previous retrospective study, base sliding was found to be responsible for 71 % of recreational softball injuries. Because most injuries occurred during rapid deceleration against stationary bases, quick-release (break-away) bases were evaluated as a means to modify this mechanism of injury. In a prospective study, 633 softball games were played on break-away base fields and 627 games were played on stationary base fields. Forty-five sliding injuries occurred on the station ary base diamonds (1 injury for every 13.9 games) and only two sliding injuries occurred on the break-away fields (1 injury for every 316.5 games). The medical costs for injuries on the stationary base fields was 79 times greater than that on the break-away fields. In a 1035 game follow-up study performed on all fields equipped with break-away bases, two sliding injuries occurred (1 injury for every 517.5 games). Installing break-away bases in fields used by recrea tional leagues would achieve a significant reduction of serious softball injuries (98%) and, therefore, should be mandatory. Based on our findings, the Centers for Disease Con trol has estimated 1.7 million injuries would be pre vented nationally per year, saving $2.0 billion per year nationally in acute medical care costs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67297/2/10.1177_036354659001800613.pd

Serving GODAE Data and Products to the Ocean Community

The Global Ocean Data Assimilation Experiment (GODAE [http:// www.godae.org]) has spanned a decade of rapid technological development. The ever-increasing volume and diversity of oceanographic data produced by in situ instruments, remote-sensing platforms, and computer simulations have driven the development of a number of innovative technologies that are essential for connecting scientists with the data that they need. This paper gives an overview of the technologies that have been developed and applied in the course of GODAE, which now provide users of oceanographic data with the capability to discover, evaluate, visualize, download, and analyze data from all over the world. The key to this capability is the ability to reduce the inherent complexity of oceanographic data by providing a consistent, harmonized view of the various data products. The challenges of data serving have been addressed over the last 10 years through the cooperative skills and energies of many individuals

Strategies for Testing the Impact of Natural Flood Risk Management Measures

Natural Flood Management (NFM) is an approach that seeks to work with natural processes to enhance the flood regulating capacity of a catchment, whilst delivering a wide range of ecosystem services, from pollution assimilation to habitat creation and carbon storage. This chapter describes a tiered approach to NFM, commencing with strategic modelling to identify a range of NFM opportunities (tree-planting, distributed runoff attenuation features, and soil structure improvements), and their potential benefits, before engagement with catchment partners, and prioritisation of areas for more detailed hydrological modelling and uncertainty analysis. NFM measures pose some fundamental challenges in modelling their contribution to flood risk management because they are often highly distributed, can influence multiple catchment processes, and evidence for their effectiveness at the large scale is uncertain. This demands we model the ‘upstream’ in more detail so that we can assess the effectiveness of many small-scale changes at the large-scale. We demonstrate an approach to address these challenges employing the fast, high resolution, fully-distributed inundation model JFLOW, and visualisation of potential benefits in map form. These are used to engage catchment managers who can prioritise areas for potential deployment of NFM measures, where more detailed modelling may be targeted. We then demonstrate a framework applying the semi-distributed Dynamic TOPMODEL in which uncertainty plays an integral role in the decision-making process

Models of everywhere revisited: a technological perspective

The concept ‘models of everywhere’ was first introduced in the mid 2000s as a means of reasoning about the environmental science of a place, changing the nature of the underlying modelling process, from one in which general model structures are used to one in which modelling becomes a learning process about specific places, in particular capturing the idiosyncrasies of that place. At one level, this is a straightforward concept, but at another it is a rich multi-dimensional conceptual framework involving the following key dimensions: models of everywhere, models of everything and models at all times, being constantly re-evaluated against the most current evidence. This is a compelling approach with the potential to deal with epistemic uncertainties and nonlinearities. However, the approach has, as yet, not been fully utilised or explored. This paper examines the concept of models of everywhere in the light of recent advances in technology. The paper argues that, when first proposed, technology was a limiting factor but now, with advances in areas such as Internet of Things, cloud computing and data analytics, many of the barriers have been alleviated. Consequently, it is timely to look again at the concept of models of everywhere in practical conditions as part of a trans-disciplinary effort to tackle the remaining research questions. The paper concludes by identifying the key elements of a research agenda that should underpin such experimentation and deployment

Seasonal total methane depletion in limestone caves

Methane concentration in caves is commonly much lower than the external atmosphere, yet the cave CH4 depletion causal mechanism is contested and dynamic links to external diurnal and seasonal temperature cycles unknown. Here, we report a continuous 3-year record of cave methane and other trace gases in Jenolan Caves, Australia which shows a seasonal cycle of extreme CH4 depletion, from ambient ∼1,775 ppb to near zero during summer and to ∼800 ppb in winter. Methanotrophic bacteria, some newly-discovered, rapidly consume methane on cave surfaces and in external karst soils with lifetimes in the cave of a few hours. Extreme bacterial selection due to the absence of alternate carbon sources for growth in the cave environment has resulted in an extremely high proportion 2-12% of methanotrophs in the total bacteria present. Unexpected seasonal bias in our cave CH4 depletion record is explained by a three-step process involving methanotrophy in aerobic karst soil above the cave, summer transport of soil-gas into the cave through epikarst, followed by further cave CH4 depletion. Disentangling cause and effect of cave gas variations by tracing sources and sinks has identified seasonal speleothem growth bias, with implied palaeo-climate record bias

Parental depression and child cognitive vulnerability predict children\u27s cortisol reactivity

Risk for depression is expressed across multiple levels of analysis. For example, parental depression and cognitive vulnerability are known markers of depression risk, but no study has examined their interactive effects on children\u27s cortisol reactivity, a likely mediator of early depression risk. We examined relations across these different levels of vulnerability using cross-sectional and longitudinal methods in two community samples of children. Children were assessed for cognitive vulnerability using self-reports (Study 1; n = 244) and tasks tapping memory and attentional bias (Study 2; n = 205), and their parents were assessed for depression history using structured clinical interviews. In both samples, children participated in standardized stress tasks and cortisol reactivity was assessed. Cross-sectionally and longitudinally, parental depression history and child cognitive vulnerability interacted to predict children\u27s cortisol reactivity; associations between parent depression and elevated child cortisol activity were found when children also showed elevated depressotypic attributions as well as attentional and memory biases. Findings indicate that models of children\u27s emerging depression risk may benefit from the examination of the interactive effects of multiple sources of vulnerability across levels of analysis