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Experimental and numerical analysis of three-dimensional free-surface turbulent vortex flows with strong circulation
Full text linkStrong free-surface vortex flows are widely employed in various civil engineering and industrial applications. However, a review of the state-of-the-art suggests that a number of areas surrounding the underlying flow mechanics in these systems requires additional attention and are therefore explored in this study. The research focuses on experimental and numerical analysis as well as analytical investigations of the flow problem.\ud
Experimental modelling was performed in two phases: investigation into the effects of the approach flow geometry and an exploration of the mean three-dimensional velocity fields and secondary flow processes. Twelve geometries of a typical scroll type vortex chamber were constructed and independently tested in a customised hydraulic test rig. Model discharges were monitored using a magnetic flow meter and the approach flow depths and water surface profiles were monitored using a depth gauge apparatus. The horizontal velocity field in the far- to mid-field was measured using a 2D particle tracking velocimetry system. Particle streak velocimetry was employed to determine the near-field tangential and axial velocity fields. The results highlighted an explicit dependence of the circulation number NΓ and the discharge number NQ on the approach flow conditions. Two empirical auxiliary parameters \u1d458\u1d6fc and \u1d45b\u1d6fc were proposed and further modelled to yield an alternative depth-discharge equation. The model was validated using a scaled model and a prototype. Scale effects in the physical models were found to be negligible.\ud
The investigation of the primary flow field indicated that the tangential velocity field was independent of the sub-surface depth away from the tank boundaries. Using the available velocity data and laser-induced fluorescence images, the radial velocity was observed to be confined at the vessel floor and free-surface. The axial velocity appeared to be concentrated in a downward direction in the core region as well as in a newly observed upward direction at the tank periphery. Further analysis showed that the ideal irrotational tangential velocity model agrees with the experimental data in the far-field. However, large discrepancies were observed in the near-field close to the vortex core. Based on analytical and numerical analysis, it was proposed that the discrepancy was as a result of the axial velocity gradient in the core region which was not accounted for in the original assumptions of the model. As a result, an alternative tangential velocity profile was devised based on a correction multiplier containing the inverse of the circulation number and the empirical exponent \u1d45a. The model relieves the discrepancy of the ideal model by reducing it in areas of strong axial flow to within reasonable levels.\ud
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Three-dimensional numerical modelling of the strong free-surface vortex was performed using an Eulerian-Eulerian homogeneous multiphase flow model in the ANSYS CFX computational fluid dynamics code. The experimental data was used as a benchmark to compare the solutions of the numerical model for various test cases in a single model. The comparison showed that the maximum solution accuracy was obtained using a radially structured mesh and a solution independent mesh density was presented. The model was strongly dependent on the type of turbulence model used. Standard Reynolds averaged Navier-Stokes equations appeared to be highly dissipative and overestimated the generation of turbulence in the core region which generated significant errors in the solution. The modified shear stress transport with curvature correction as well as the Reynolds stress models delivered the greatest model accuracy. It was also found that transient modelling was necessary to resolve the unsteady features of the flow field, namely that of free-surface oscillations and the radial flow field. However, the final comparison using the Reynold Stress models nonetheless rendered a significant error in under predicting the free-surface and over predicting the tangential velocity distribution by approximately 12 and 22 % respectively. It was concluded that further refinement of the mesh at the free-surface and in the drop shaft region was required to further improve the numerical solution.\ud
In a final contribution, based on the experimental and numerical observations of the primary and secondary flow fields, an alternative description of the flow mechanics in a strong free-surface vortex was made based on the concept of a newly defined ‘virtual Taylor-Couette’ flow system. Based on this flow representation, a hypothetical description highlighting the likely stages of stability based on various states of the ‘Taylor-like’ vortices which occur in the secondary flow field was proposed. The overall description serves to provide a universal scientific understanding of both ‘weak’ and ‘strong’ free-surface vortices as well as the transitional dissipative state at a depth coinciding with the critical submergence
Low energy masonry buildings
No full textThis dissertation was carried out in order to evaluate three differing approaches to achieving low energy buildings using improved methods of traditional masonry construction. Spiralling greenhouse emissions and fuel costs have focused the industry towards the delivery of low energy buildings.\ud
Cavity wall Masonry construction is the favoured method of construction currently used in the construction of dwellings in Ireland. Partial fill rigid insulation which is installed within the cavity is a technique which has been seen to result in large gaps between the design performance levels and actual performance levels. Impending requirements to further reduce heat loss will result in restricted use of traditional methods in the future. The inherent structural properties of this method are reaching their limits due to the requirement of more comprehensive widths of insulation material within the cavity.\ud
A comprehensive examination of published literature was carried out in order to address the causes of the performance gap relevant to this topic. The research will assess the performance issues with the comparative approaches through the literature review and primary research in order to determine if the use of either approach could contribute to narrowing the performance gap. Primary research will be gathered in the form of structured interviews with Industry professionals with expertise in both practical aspects and theoretical based levels of expertise.\ud
The results indicate that Solid Wall Construction with External Insulation is seen to be the approach which could contribute to the delivery of low energy buildings in Ireland on a more consist basis from the three options. The primary reasons for this are owing to the simplicity of the construction form and division of trade responsibility. However as this approach lacks familiarity, it is believed that a training and skills issued would firstly need to be addressed as it is a relatively new technique.\ud
One of the most problematic areas concerned with partial fill insulation is the issue of thermal passage that occur. Insulating cavity walls internally is seen to increase construction times and involves multiple layers with sequencing issues and lack of accountability in addition to the increased hygrothermal risk associated with insulating internally. While the Super Wide Full fill cavity technique draws concerns to the structural implication concerning the distance between both leafs and implications around window and eave locations
Weather beaten archaeology conference: revealing, concealing and erasing. Book of abstracts
No full textCoastal archaeological sites have always been vulnerable to erosion. In recent years this vulnerability has become a contentious issue when a variety of archaeological sites across Northern Europe were impacted by the winter storms of 2013-14. Stone forts fell into the sea. Castles crumbled to the ground. Shipwrecks, middens, timber trackways and ancient drowned forests were revealed for the first time in centuries. Heritage venues were flooded and a large number of archaeological sites were washed away entirely. The annual winter storms now regularly require rescue work by governments and archaeologists, allow chance finds by members of the public and have necessitated the creation of citizen science schemes to report vulnerable / newly discovered sites. The Weather Beaten Archaeology Conference is the first of its kind and will establish a forum for the exchange of experiences of extreme weather events and their impact on archaeological sites
Leveraging institute of technology incubation centres in \ud the teaching of innovation: a case study
Full text linkThe overriding purpose of this on-going work is to contribute to the debate on the best pedagogical approach to developing undergraduate Mechanical Engineering skills to meet the requirements of contemporary complex working environments. The particular focus of this study is to develop the students’ appreciation of entrepreneurship and the development of a new venture. Enterprise Ireland has funded business incubation centres on college campuses across Ireland in order to provide a supportive environment for start-up companies and two centres have been located in the Galway-Mayo Institute of Technology (GMIT). The paper provides an example of collaboration between the Incubation Centre managers and a lecturer in GMIT in the teaching of innovation modules to final year students. The methodology of the paper involved a structured questionnaire followed by an interview with the management of the Innovation Hubs (the name given to the GMIT incubation centres). Working directly with the Innovation Hubs is a novel pedagogical approach that fosters entrepreneurial thinking and behaviour among the students. Furthermore key stakeholders (in this case the managers and staff of the Innovation Hubs) have engaged in the learning process. Both managers have been very supportive of the process as it meets their remit to involve the Innovation Hubs with the GMIT campus. The response to the structured questionnaire was positive but also provided suggestions for improving the process. Furthermore, the project supports a targeted action of the Campus Entrepreneurship Enterprise Network program, a partnership between a number of Institutes of Technology and Universities in Ireland
Visible-light activation of Ti02 photocatalysts: advances in theory and experiments
No full textThe remarkable achievement by Fujishima and Honda (1972) in the photo-electrochemical water splitting\ud
results in the extensive use of TiO2 nanomaterials for environmental purification and energy\ud
storage/conversion applications. Though there are many advantages for the TiO2 compared to other\ud
semiconductor photocatalysts, its band gap of 3.2 eV restrains application to the UV-region of the electromagnetic\ud
spectrum ( \ud
≤\ud
387.5 nm). As a result, development of visible-light active titanium dioxide\ud
is one of the key challenges in the field of semiconductor photocatalysis. In this review, advances in\ud
the strategies for the visible light activation, origin of visible-light activity, and electronic structure of\ud
various visible-light active TiO2 photocatalysts are discussed in detail. It has also been shown that if\ud
appropriate models are used, the theoretical insights can successfully be employed to develop novel\ud
catalysts to enhance the photocatalytic performance in the visible region. Recent developments in theory\ud
and experiments in visible-light induced water splitting, degradation of environmental pollutants,\ud
water and air purification and antibacterial applications are also reviewed. Various strategies to identify\ud
appropriate dopants for improved visible-light absorption and electron–hole separation to enhance the\ud
photocatalytic activity are discussed in detail, and a number of recommendations are also presented
Lean services: a systems thinking approach for achieving operational excellence and quality improvement in the Irish hotel sector.
No full textThe services economy is a significant element in the economic growth of most OECD countries, including Ireland (OECD 2012). Tourism is a key subsector of the services economy, with accommodation being a necessary component of the tourism product (Cooper et al. 2008). Hotels are one of the largest components of the accommodation sector within the Irish Tourism and Hospitality Industry (Melia and Robinson 2010). The environment in which Irish hotels operate is one of an increasingly competitive nature. The industry in recent years has been characterised by a dramatic level of overcapacity and rising number of insolvent hotels (Peter Bacon & Associates 2009). The re-emergence of domestic and international investment in the Irish hotel sector has positively impacted on reducing the number of insolvent hotels (IHF 2015).\ud
To manage the issues currently dominating the Irish and global hotel sector, hotel management must refocus efforts on formulating effective operations analysis to optimise hotel productivity and overall profitability in an increasingly competitive marketplace (Moncarz and Kron 1993; Imrie and Fyall 2001; Burgess 2007).\ud
Lean is a management methodology that emerged in the automobile industry in the late 1980s (Womack et al. 2007). Lean was popularised by MIT researchers, Womack et al. (2007) on the publication of “The Machine that Changed the World” in 1990. In “The Machine that Changed the World”, Womack et al. (2007) define in-depth “the Toyota way” (TPS), created by Eiji Toyoda and Taiichi Ohno of Toyota.\ud
The core principle of lean is to maximise customer value while minimising waste (Lean Enterprise Institute 2015). The ideology of lean is about creating added value for the customer whilst utilising less resources (Lean Enterprise Institute 2015). Lean is a total systems approach in optimising operational efficiency (Jadhav et al. 2014). Lean is increasingly being adopted by various industries beyond manufacturing as a performance improvement method (Jadhav et al. 2014). The concept of a “lean” operating system is continually being developed within the services industry (Hanna 2007). Some subsectors of the services industry have advanced lean initiatives more progressively than others, e.g. healthcare, software/IT (Kollberg et al. 2006; Staats et al. 2011). Healthcare as noted by Chase and Apte (2007) is considered a lean services champion for continuous efforts in adopting traditional operations management techniques, e.g. lean healthcare - Virginia Mason Production System.\ud
Coinciding with the lean philosophy, this research study aims to highlight the importance of systems thinking, which focuses on synthesis, understanding the “why” and interaction of elements within a process, as an alternative to analytical thinking, “how”, which simply provides knowledge (Ackoff 1979).\ud
This research study aims to understand the implementation and applicability of lean production principles in services. A key objective of this research study is the development and implementation of a lean services framework for the Irish hotel sector.\ud
By submission of this ‘Early Research’ abstract, it is envisioned that future THRIC research programmes will incorporate and advocate for the importance of service operations research
An augmented penetration testing framework for Mobile Devices on 802.11 ac Wireless Networks
Full text linkIn combination with the rapid growth of mobile device ownership worldwide and some reported high profile cybersecurity issues, rigorous security testing techniques are required to ensure that sensitive corporate and domestic end-user data is kept safe. The current wireless communication standard (801.11ac) forms the basis of the penetration testing framework for mobile devices on wireless networks presented here. Given a lack of a comprehensive mobile penetration testing framework, an augmentation of existing approaches is suggested. A series of progressive open source tools are used to analyze and exploit various weaknesses on mobile devices with a view to validating the efficacy of the framework. Advantages of this framework include the rapid identification and implementation the most appropriate solutions with a limited time scale and a significant contribution to the professional pentesters toolkit. Overall, this study shows that holistic, systems systems-oriented thinking is needed to more fully engage with the security issues surrounding mobile device security
An investigation into the commercialisation of final year projects within Creative Design courses
Full text linkThe aim of this study is to identify and investigate the barriers to commercialisation of Final Year Projects within Creative Design courses. The term Creative Design refers to Creative Design, Product Design and Industrial Design courses in the Republic of Ireland.\ud
How do Design courses in ROI address the issues of commercialisation? Failure to incorporate key course elements such as entrepreneurship, intellectual property law and business studies, as core studies, results in long term loss for both Institution and student.\ud
Research related to design education will be collected and organized through interviews with educators, students and practitioners of Creative Design.\ud
The research will be qualitative and quantitative. It will include a study of product identification and development methods within industry. The development of student product designs through to commercialisation will be monitored through ten Case Studies. It will also include statistical research of student major projects over the last five years.\ud
This research is important as there is a low rate of students successfully commercialising their work. Having completed their Degree, students will have acquired the necessary skills and capabilities of designing successful products yet these often fail to realise their full potential. There is a need for a system that encourages and supports students entering the professional world of design; in the current economic situation there is a clear need for such entrepreneurship. This research is aimed at identifying and recommending best practice for overcoming obstacles to students commercialising their college work.\ud
The aim of this study is to raise awareness of the issues and challenges facing undergraduate students in the transitional period between college and professionalism, as they attempt to commercialise their work. This research will consider the communication of complex ideas, and the difference between successful or unsuccessful products through a series of case studies
Density estimates of harbour porpoises phocoena phocoena at eight coastal sites in Ireland
Full text linkSingle platform line-transect surveys with distance sampling were carried out at eight sites between July and September 2008 to derive density and abundance estimates of harbour porpoises. Over 37 days at sea, a total of 475 track-lines were surveyed for a total distance of 20,623km. From the 332 sightings, a total of 618 individual harbour porpoise were recorded. Overall density estimates ranged from 0.53 to 2.03 porpoises km 2 (without correction for g(0)). Mean group size varied from 1.41 to 2.67. These data provide baseline information to help identify important habitats for harbour porpoise and reference values for monitoring future changes in harbour porpoise distribution and densities in Ireland
The challenge of work based learning: a role for academic mentors?
Full text linkPurpose - This paper explores the key challenge(s) experienced by employers, employees and academics during work based learning (WBL) programmes at undergraduate level. The idea of\ud
academic mentors is proposed as an aid to addressing the challenges common to WBL\ud
programmes.\ud
Design Methodology – The case study presented in this paper involves a large multinational organisation and a higher education institution (HEI), both of which are based in Ireland. Interviews were used to explore the outcome(s) of a WBL programme.\ud
Findings – The challenges associated with WBL place demands on the design and delivery of curriculum, pedagogy and accreditation. The use of academic mentors can help translate academic knowledge into workplace practice; and address challenges which are common in WBL programmes.\ud
Practical Implications – The understanding of best practice in the design of WBL programmes is\ud
enriched. A role for academics as mentors is identified and the implications explored.\ud
Originality/value - The success of WBL can be linked to the relationships that form between employers, employees and academics. There is evidence that the academic is central to the development of these relationships