Parametric impact characterisation of a solid sports ball, WITH a view to developing a standard core for the GAA Sliotar

The main aim of this research was to characterise the dynamic impact behaviour of the sliotar core. Viscoelastic characterisation of the balls was conducted for a range of impact speeds. Modern polymer balls exhibited strain and strain-rate sensitivity while traditional multi-compositional balls exhibited strain dependency. The non-linear viscoelastic response was defined by two values of stiffness, initial and bulk stiffness. Traditional balls were up to 2.5 times stiffer than the modern types, with this magnitude being rate-dependent. The greater rate of increase of traditional ball stiffness produced a more non-linear COR velocity-dependence compared to modern balls. The dynamic stiffness results demonstrated limited applicability of quasi-static testing and springtheory equations. Analysis of ball deformation behaviour demonstrated that centre-of mass displacement and diameter compression values were not consistently equivalent for all ball types. The contribution of manufacturing conditions to ball performance was investigated by conducting extensive prototyping experiments. Manufacturing parameters of temperature, pressure and material composition were varied to produce a range of balls. Polymer hardness affected stiffness but not energy dissipation, with increased hardness increasing ball stiffness. The nucleating additive influenced ball COR, with increased additive tending to reduce ball COR, but this effect was sensitive to polymer grade. The impact response of the ball was simulated using three mathematical models. The first model was shown to replicate ball behaviour to only a limited degree, despite being used previously with reported success for other ball types. The second model exhibited a reasonable representation of ball impact response that was universally applicable to all tested ball types; however, the accuracy in terms of predicting force-displacement response was not as high as required for broad range implementation. The third model exhibited significantly better accuracy in simulating ball response. The force values generated from this model exhibited up to 95% agreement with experimental data

The dynamic viscoelastic characterisation of the impact behaviour of the GAA sliotar

In recent years variability in behaviour of the sliotar, a small leather-bound ball used in the Irish sport of hurling, became evident in championship matches. The current standard has not provided adequate repeatability of ball performance. A new method for assessing the dynamic impact behaviour of approved sliotar cores has been characterised. This test system was developed to measure the performance characteristics, such as coefficient of restitution, deformation and contact time, and the viscoelastic properties of dynamic stiffness and hysteresis energy dissipation. In this paper, the relationship between the viscoelastic properties and the coefficient of restitution is presented

Analysis of landfill gas migration by use of autonomous gas monitoring platforms

Autonomous gas sensing platforms have been developed to facilitate the long-term continuous monitoring of landfill gas concentrations. The analysis of a municipal landfill site in Ireland forms part of an on-going collaboration with the Environmental Protection Agency in monitoring the migration of greenhouse gases, i.e. methane and carbon dioxide, emanating from the landfill site. Target gas concentrations were automatically recorded via infrared gas sensors calibrated for the respective gases, with this data being logged remotely every six hours to a central base-station. The autonomous platform with its web-based portal interface provides a flexible alternative to the existing labor-intensive, manual monitoring routines. Frequent occurrences of 70% v/v methane and 6% v/v carbon dioxide were substantially in breach of the regulatory limits of 1.5% v/v and 1.0% v/v, respectively. These excessive levels of gas migration were analyzed with respect to SCADA flare data, on-site measurements and meteorological data

Distributed environmental monitoring

With increasingly ubiquitous use of web-based technologies in society today, autonomous sensor networks represent the future in large-scale information acquisition for applications ranging from environmental monitoring to in vivo sensing. This chapter presents a range of on-going projects with an emphasis on environmental sensing; relevant literature pertaining to sensor networks is reviewed, validated sensing applications are described and the contribution of high-resolution temporal data to better decision-making is discussed

Viscoelastic impact characterisation of solid sports balls used in the Irish sport of Hurling

In recent years, variability in behaviour of the sliotar, a small leather-bound ball used in the Irish sport of hurling, has become evident in championship matches. The inconsistency in performance was attributed to the range of constructions and material compositions of currently approved ball types. With a view to adopting a standard core, a new methodology has been commissioned to assess the dynamic impact behaviour of approved sliotar cores. In this paper, the relationship between the dynamic stiffness and the coefficient of restitution is presented with regard to material properties, ball construction and viscoelastic strain and strain-rate dependencies. The modern polymer ball types were shown to exhibit strain-rate sensitivity, while the performance of the traditional multi-compositional ball types exhibited lesser strain-rate dependence. The traditional balls types were shown to be up to 2.5 times stiffer than the modern ball types, with this finding having implications for ball energy dissipation

Landfill gas monitoring network - development of wireless sensor network platforms

A wireless sensor network has been developed for the application of landfill gas monitoring, specifically sensing methane, carbon dioxide and extraction pressure. This collaborative work with the Irish Environmental Protection Agency has been motivated by the need to reduce greenhouse gas emissions as well as aiming to improve landfill gas management and utilisation. This paper describes the preliminary findings of an ongoing trial deployment of multiple sensing platforms on an active landfill facility; data has been acquired for nine months to date. The platforms have operated successfully despite adverse on-site conditions, with validity demonstrated by reasonably strong correlation with independent on-site measurements. The increased temporal and spatial resolution provided by distributed sensor platforms is discussed with regard to improving landfill gas management practice

Distributed chemical sensor networks for environmental sensing

Society is increasingly accustomed to instant access to real-time information, due to the ubiquitous use of the internet and web-based access tools. Intelligent search engines enable huge data repositories to be searched, and highly relevant information returned in real time. These repositories increasingly include environmental information related to the environment, such as distributed air and water quality. However, while this information at present is typically historical, for example, through agency reports, there is increasing demand for real-time environmental data. In this paper, the issues involved in obtaining data from autonomous chemical sensors are discussed, and examples of current deployments presented. Strategies for achieving large-scale deployments are discussed

Web-based monitoring of gas emissions from landfill sites using autonomous sensing platforms

Executive Summary Numerous initiatives that are policy driven by national, European and global agencies target the preservation of our environment, human society’s health and our ecology. Ireland’s EPA 2020 Vision outlines a mandate to prepare for the unavoidable impact of climate change, the reduction of greenhouse gas (GHG) emissions, the control of air-emissions standards, the sustainable use of resources and the holding to account of those who flout environmental laws. These strategies are echoed in the Europe 2020: Resource-efficient Europe Flagship Initiative, which also advocates the creation of new opportunities for economic growth and greater innovation. The promotion of research and technical development is central to each of these strategies – specifically the achievement of accurate environmental monitoring technologies that will inform policy-makers and effect change. This is described in the EPA Strategic Plan 2013–2015 as the provision of ‘high quality, targeted and timely environmental data, information and assessment to inform decision making at all levels’. Specific to landfills, the Environmental Protection Agency’s (EPA) Focus on Landfilling in Ireland stipulates the management of landfill gas to eliminate environmental harm and public nuisance, to promote energy generation where possible and to avoid liabilities in site closure and aftercare. It was in this context that the EPA STRIVE programme granted funding for this research project on developing autonomous sensor platforms for the real-time monitoring of gases generated in landfill facilities. Managing landfill gas is one of the crucial operations in a landfill facility, where gases (primarily methane [CH4] and carbon dioxide [CO2] generated from the decomposition of biodegradable waste) are extracted and combusted in a flare or preferably an engine (as biogas fuel). These gases, classified as greenhouse gases (GHGs), also pose localised hazards due to fire risk and asphyxiation, and are indicative of odorous nuisance compounds. Gas-monitoring on site is conducted to (i) ensure against gas migration into the local environment and to (ii) maintain the thorough gas extraction and optimum composition for combustion. This is becoming more relevant because of the numerous landfill closures brought by Europe-wide changes in waste-management policy. Even for landfills no longer actively receiving waste, substantial gas generation remains ongoing for years and even decades. Despite diminished financial resources and reduced manpower, management of this gas must be maintained. Traditionally, monitoring involves taking manual measurements using expensive handheld equipment and requiring laborious travel over difficult and expansive terrain. Consequently, it is conducted relatively infrequently – typically once a month. These issues can be addressed by adopting distributed continuous monitoring systems. These low-cost remotely deployable sensor platforms offer a valuable complementary service to operators and the EPA. They enable easier adherence to their licence criteria, the prevention of expensive remediation measures and the potential boost in revenue from increasing energy production through the use of biogas. Challenges arise in terms of achieving a long-term monitoring performance in a harsh environment while maintaining accuracy, reliability and cost-effectiveness. To meet these challenges, this project developed cost- effective autonomous sensor platforms to allow long- term continuous monitoring of gas composition (methane and carbon dioxide) and extraction pressure. The project’s work represents one of the only developments of autonomous sensor technology in this space; the few other market alternatives tend to be expensive or difficult to implement for remotely deployable continuous monitoring. Beyond the development of a platform technology, the challenge was to apply this technology to the adverse environmental conditions. The project delivered a total of 14 autonomous sensor platforms in deployments involving Irish landfill sites, a Scottish landfill site and a Brazilian wastewater treatment plant. The analysis and interpretation of acquired data, coupled with local meteorological data and on-site operational data, provided the translation from raw environmental data to meaningful conclusions that could inform decision-making. This report presents a number of case studies to illustrate this. Characteristics of site gas dynamics could be identified; for example, it was possible to show if excessive gas concentrations in a perimeter well could be resolved by increasing the flare extraction rate for a particular well. Furthermore, the potential for quantifying methane generation potential at distributed locations within the landfill was identified in addition to diagnosing the effectiveness of the extraction network – hence aiding in field-balancing and landfill gas utilisation. The extensive wealth of data enabled by this platform technology will help better-informed decision-making and improve operational practices in managing gas emissions. In landfills, this signifies alleviating gas migration with perimeter monitoring and enhancing flare/ engine operation by evaluating gas quality at distributed locations within the gas field. While landfilling is becoming outmoded as a waste-management process, the need for continuous monitoring will be relevant for many years to come. Indeed, a number of existing facilities are considering retrofitting engines because of the significant potential for additional landfill gas utilisation being identified by Sustainable Energy Authority Ireland in 2010. Furthermore, the technology’s low-cost and autonomous nature would benefit the hundreds of historical and legacy landfills if any were deemed to be problematic in terms of their environmental impact. Beyond landfills, this work pertains to other applications within the waste sector, as demonstrated by measuring emissions from wastewater treatment plant lagoons. With some further development, this technology could apply to efforts in dealing with climate change (e.g. in evaluating GHG inventories), where applications include managed peatlands (one case study is presented in this report and future efforts could also be targeted at carbon sinks/storage) and agriculture (Ireland’s greatest contributor to GHGs). Further scope could also be pursued in air-quality monitoring, particularly relevant at present with 2013 being dubbed the ‘Year of Air’ by European leaders. Throughout this project, the commercial prospect of this technology was affirmed with positive feedback from landfill operators, environmental regulators and private consultancies. Continual technical developments and refinements in mechanical/electronic design delivered a platform with expanded functionality and reduced price-point, thus becoming more viable for scaled-up deployments and commercial feasibility. Ultimately, this innovative development shows good promise as a high-potential commercial venture, with this work continuing under Enterprise Ireland’s Commercialisation Fund

Simulation of the impact response of a sliotar core with linear and non-linear contact models

Static and dynamic models of the characteristic responses of sliotar cores made of both cork and polyurethane were studied in this work in order to understand their constitutive behaviour. Data from quasi-static tests at 10 mm/s and from dynamic impacts at speeds from 5 to 25 m/s were used to develop and evaluate the models. The quasi-static response was described well by Hertzian theory. A non-linear HunteCrossley model and a modified linear KelvineVoigt model were used to predict the dynamic response with set mass and shape coefficient parameters. The HunteCrossley model predicted well both the maximum force and maximum deflection for each ball type. The HunteCrossley model generally captured the experimental contact times well with a mean difference between experimental and model contact times of 8.3%. The mean difference between the KelvineVoigt model and experimental contact times was 7.6%, while the corresponding mean difference for the coefficient of restitution was 13.1%. Overall, the modified KelvineVoigt model predicted the parameters of contact time and coefficient of restitution well. Contact time and coefficient of restitution prediction in this linear model were not particularly sensitive to the strain rate