1642 research outputs found
Sort by
Flume tank testing of offshore wind turbine dynamics with foundation scour and scour protection
No full textScour erosion processes can occur at seabed level around offshore wind turbine monopile foundations. These scour processes are often especially severe at sites where mobile sediments, such as sands, are present in the superficial seabed soils. Loss of local soil support to the monopile, caused by scour erosion, can lead to significant changes in the dynamic characteristics of the wind turbine support structure. This can result in accelerated fatigue damage, owing to the applied cyclic loads from the wind turbine generator, especially at the rotor frequency. Although scour erosion can be controlled by appropriate scour protection systems, there is a lack of knowledge to support the design and optimization of these protection measures, to ensure that the dynamic performance of the wind turbine support structure remains within acceptable limits. This paper describes an experimental campaign conducted on a 1:20 scale model of a driven monopile foundation and wind turbine support structure, founded in a prepared sand test bed in the Fast Flow Facility flume (HR Wallingford, UK). Scour processes were induced by applying cycles of flow. Experiments were conducted to investigate the influence that these scour processes, and selected concepts for preventative and remedial scour protection, have on the dynamic characteristics of the monopile–tower system. The paper describes the experimental procedures that were adopted, and provides an assessment of the results
The origins of large dam engineering and factors contributing to dam longevity
No full textThe history of dam building dates back some 5000 years and covers most civilisations around the globe. It encompasses every type of engineered dam structure, from simple masonry walls and earthen embankments, to complex concrete and composite dams, and covers many differing societal needs. By studying the successes and failures of dam building throughout history, we can trace the development of the engineering from an ‘art’ to a science. The authors describe the results of a literature review to establish the oldest dam, the oldest large dam, the dams with the longest periods of operation and finally, the oldest large dam still in operation today. From studying historical accounts, and carrying out site visits and interviews with dam owners, the authors establish consistent themes for sustainability, and conclude the most important factors contributing to the longevity of large dams
Forecasting the impact of drought on water resources using seasonal rainfall forecasts
No full textWater is considered to be one of the main mechanisms through which people will experience climate change, with the number of people estimated to become exposed to water scarcity projected to increase sharply in the future (United Nations World Water Assessment Programme, 2011). Water resource managers in the UK have access to a range of meteorological and hydrological indicators of drought. However, these data are limited in their utility to directly forecast how systems should be managed to reduce impacts on water users. At present, forecasts are typically used in a qualitative manner, with seasonal forecasts not widely used to inform operational or planning decisions.
To increase uptake in the use of seasonal forecasts, water resources managers need concise visualisation of the data in a format which can readily be communicated and understood by both their management and customers. This requires inclusion of key historical information and metrics which are used across the industry to assess the current water resources status.
The European Centre for Medium-Range Weather Forecasts (ECMWF) implements the Copernicus Climate Change Service (C3S) on behalf of the European Union. At the heart of the C3S infrastructure is the Climate Data Store (CDS), which provides information on the past, present, and future climate. We have explored the potential of these data to support UK water companies manage their resources in periods of prolonged dry weather and droughts.
We combined C3S data with both operational practices and the latest UK water resources planning developments to provide metrics of value tailored to the needs of water resource managers. This analysis is presented via an app. Our app is currently operational and being updated with new forecast data as they are made available each month. It has been tested and trialled over the summer by three UK water company stakeholders.
The App allows users to view and analyse seasonal forecasts and explore how valuable these forecasts are in relation to predicting potential upcoming droughts based on historical performance. Forecasts are put into context against key industry metrics of value and meaning to water resources managers. Verification metrics are presented to help the users understand how well the forecasts have performed in the past. Visualisation of results has been developed in collaboration with industry stakeholders to ensure maximum value
Sediment flushing from reservoirs: a review
No full textSustainable use of natural resources is of great importance worldwide. For reservoirs, the loss of storage to sedimentation is a major challenge to their sustainable use. Several management options exist that can improve sustainability of reservoirs, one of them is the removal of the accumulated sediment by means of hydraulic flushing. Based on a comprehensive review of literature, this paper presents a review of factors related to feasibility of sediment flushing. These factors have been grouped into seven topics: availability of water for flushing and cost of flushing operations; timing of flushing; limitations posed by reservoir geometry, in particular the width of the reservoir and the presence of bends; the effects of sediment properties; sizing and positioning of evacuation outlets; downstream impacts of flushing and control of operation. For each topic, the technical and environmental issues that arise as well as ways to address them are presented. Some of the factors are competing, which further stresses the need for careful planning and evaluation of flushing operations
Open web-distributed integrated geographic modelling and simulation to enable broader participation and applications (Position paper)
No full textIntegrated geographic modelling and simulation is a computational means to improve understanding of the environment. With the development of Service Oriented Architecture (SOA) and web technologies, it is possible to conduct open, extensible integrated geographic modelling across a network in which resources can be accessed and integrated, and further distributed geographic simulations can be performed. This open web-distributed modelling and simulation approach is likely to enhance the use of existing resources and can attract diverse participants. With this approach, participants from different physical locations or domains of expertise can perform comprehensive modelling and simulation tasks collaboratively. This paper reviews past integrated modelling and simulation systems, highlighting the associated development challenges when moving to an open web-distributed system. A conceptual framework is proposed to introduce a roadmap from a system design perspective, with potential use cases provided. The four components of this conceptual framework - a set of standards, a resource sharing environment, a collaborative integrated modelling environment, and a distributed simulation environment - are also discussed in detail with the goal of advancing this emerging field
Hydrodynamic loads on buildings in floods
No full textEvaluating the vulnerability of buildings lying in flood-prone areas is an essential component of the assessment of flood-induced risk, particularly because of the severe consequences that damage and collapse of building may have on loss of life during most extreme events. Despite its importance, a comprehensive methodology for use in the assessment of the potential damage to buildings caused by dynamic loads during floods is still missing. After a brief overview of flood-induced hydrodynamic loads on buildings, this paper describes a new set of experiments designed to improve understanding of the dynamics of flood-induced loads, critically reviews existing methods in light of new experimental evidence and proposes a generic formulation for the evaluation of dynamic loads for use in the assessment of the vulnerability of existing structures and the design of new flood-resilient buildings
Selection and integration of earth observation-based data for an operational disease forecasting system
Get PDFThe current increase in the volume and quality of Earth Observation (EO) data being collected by satellites offers the potential to contribute to applications across a wide range of scientific domains. It is well established that there are correlations between characteristics that can be derived from EO satellite data, such as land surface temperature or land cover, and the incidence of some diseases. Thanks to the reliable frequent acquisition and rapid distribution of EO data it is now possible for this field to progress from using EO in retrospective analyses of historical disease case counts to using it in operational forecasting systems.
However, bringing together EO-based and non-EO-based datasets, as is required for disease forecasting and many other fields, requires carefully designed data selection, formatting and integration processes. Similarly, it requires careful communication between collaborators to ensure that the priorities of that design process match the requirements of the application.
Here we will present work from the D-MOSS (Dengue forecasting MOdel Satellite-based System) project. D-MOSS is a dengue fever early warning system for South and South East Asia that will allow public health authorities to identify areas at high risk of disease epidemics before an outbreak occurs in order to target resources to reduce spreading of epidemics and improve disease control. The D-MOSS system uses EO, meteorological and seasonal weather forecast data, combined with disease statistics and static layers such as land cover, as the inputs into a dengue fever model and a water availability model. Water availability directly impacts dengue epidemics due to the provision of mosquito breeding sites. The datasets are regularly updated with the latest data and run through the models to produce a new monthly forecast. For this we have designed a system to reliably feed standardised data to the models. The project has involved a close collaboration between remote sensing scientists, geospatial scientists, hydrologists and disease modelling experts. We will discuss our approach to the selection of data sources, data source quality assessment, and design of a processing and ingestion system to produce analysis-ready data for input to the disease and water availability models
The D-MOSS Dengue Fever Forecasting System
No full textDengue fever now occurs in 141 countries and it is estimated that half of the world’s population are now at risk from the disease. 122,000 cases were reported in Vietnam in 2016 and this was followed by major outbreaks in 2017 and 2019 across the whole of South East Asia. Studies have emphasised significant links between climate variability and infectious diseases such as dengue fever, highlighting the potential for the development of modelling systems with the capability of predicting the probability of disease outbreaks several months in advance, and therefore helping health agencies and practitioners to target actions to manage and prevent outbreaks.
A new Dengue Forecasting Model Satellite‑based System (D-MOSS) has been developed which has potential to bring benefits to the fight against dengue. D-MOSS is the first fully integrated dengue fever forecasting system incorporating Earth Observation (EO) data and seasonal climate forecasts to issue warnings on a routine basis. D-MOSS integrates multiple stressors (such as water availability, land-cover, precipitation and temperature) with surveillance data on dengue cases and the UK Met Office’s GloSea5 seasonal climate forecast into a statistical model which produces probabilistic dengue fever forecasts from one to six months ahead. D-MOSS is now operational in Vietnam, and used by local agencies to plan and implement preventative actions. The system is also being introduced to three other countries in South and South East Asia.
Here, we describe the D-MOSS system and the benefits it can bring to support dengue prevention and control activities in the region through the provision of:
probabilistic forecasts of dengue outbreaks on a monthly basis, up to seven months in advance;
visualisation of forecast numbers of dengue cases, disease incidence, transmission months, probability of exceeding outbreak thresholds; and
supporting information on recommended actions to be taken by decision makers.
The development of D-MOSS has been funded by the UK Space Agency’s International Partnership Programme
Observations of nearbed turbulence over mobile bedforms in combined, collinear wave-current flows
No full textCollinear wave-current shear interactions are often assumed to be the same for currents following or opposing the direction of regular wave propagation; with momentum and mass exchanges restricted to the thin oscillating boundary layer (zero-flux condition) and enhanced but equal wave-averaged bed shear stresses. To examine these assumptions, a prototype-scale experiment investigated the nature of turbulent exchanges in flows with currents aligned to, and opposing, wave propagation over a mobile sandy bed. Estimated mean and maximum stresses from measurements above the bed exceeded predictions by models of bed shear stress subscribing to the assumptions above, suggesting the combined boundary layer is larger than predicted by theory. The core flow experiences upward turbulent fluxes in aligned flows, coupled with sediment entrainment by vortex shedding at flow reversal, whilst downward fluxes of eddies generated by the core flow, and strong adverse shear can enhance near-bed mass transport, in opposing currents. Current-aligned coherent structures contribute significantly to the stress and energy dissipation, and display characteristics of wall-attached eddies formed by the pairing of counter-rotating vortices. These preliminary findings suggest a notable difference in wave-following and wave-opposing wave-current interactions, and highlight the need to account for intermittent momentum-exchanges in predicting stress, boundary layer thickness and sediment transport
D-MOSS: An integrated dengue early warning system in Vietnam driven by Earth Observations
Get PDFDengue is the fastest-growing mosquito-borne viral infection in the world today. It is present in over 150 countries, meaning that around 40 percent of the world’s population now live in countries where dengue is a daily risk. It has been estimated that annually dengue affects 390 million people and has a global cost of almost US$9 billion per year. Since 2000, there has been an increase of over 100% in the number of cases of dengue fever in Vietnam, with approximately 185,000 cases occurring in 2017 alone. In Vietnam, there is currently no system for forecasting future dengue outbreaks.
D-MOSS is the first fully integrated dengue fever forecasting system incorporating Earth Observation data and seasonal climate forecasts to issue warnings on a routine basis. D-MOSS integrates multiple stressors such as water availability, land-cover, precipitation and temperature with data on past dengue fever incidents. This information is used to develop statistical models of disease incidence, that can then be used to forecast dengue outbreaks based on seasonal weather and hydrological forecasts as well as other factors. An overview of the D-MOSS web page and the forecasts it produces are shown in the accompanying figure.
D-MOSS takes the form of a web-based platform. The system’s architecture is based on open and non-proprietary software, where possible, and on flexible deployment into platforms including cloud-based virtual storage and application processing. D-MOSS is currently being piloted in Vietnam. When the system becomes fully operational it should assist the Vietnamese Ministry of Health, to meet its goal of actively to forecast, detect early and prevent the occurrence of epidemics, especially major ones.
The project is funded by the UK Space Agency’s International Partnership Programme and we have been recently awarded with an extension to our grant to implement D-MOSS to another six countries in South East Asia