• On bypass transition in separation bubbles: a review

      Yang, Zhiyin; School of Mechanical Engineering and the Built Environment, College of Engineering and Technology, University of Derby (Elsevier, 2019-01-14)
      Transition from laminar flow to turbulent flow is of great practical interest as it occurs in many engineering flows and often plays a critical role in aerodynamics and heat transfer performance of those flow devices. There could be many routes through transition, depending on flow configuration, geometry and the way in which transition is initiated by a wide range of possible background disturbances such as free-stream turbulence, pressure gradient, acoustic noise, wall roughness and obstructions, periodic unsteady disturbance and so on. This paper presents a brief overview of wall bounded flow transition in general and focuses more on the transition process in the free shear layer of separation bubbles, demonstrating that at elevated free-stream turbulent intensity the so called bypass transition could occur in geometrically induced separation bubbles where the separation point is fixed.
    • On secondary instability of a transitional separation bubble.

      Yang, Zhiyin; Abdalla, Ibrahim E.; University of Derby; Jubail University College (Elsevier, 2018-12-01)
      It is well established in the natural transition of an attached boundary layer that the transition process starts with a two–dimensional primary instability (Tollmien–Schlichting wave, denoted as TS wave), followed by usually a three-dimensional secondary instability (fundamental mode or subharmonic mode) leading to the breakdown to turbulence. However, the transition process of a separation bubble (laminar flow or laminar boundary layer at separation and transition occurs downstream of the separation, leading to turbulence at reattachment) is less well understood, especially on the nature of secondary instability. The focus of this paper is on trying to advance our understanding of secondary instability of a transitional separation bubble on a flat plate with a blunt leading edge (separation is induced geometrically at the leading edge) under a very low free-stream turbulence level (< 0.1%). Large-Eddy Simulation (LES) is employed in the current study with a dynamic sub-grid-scale model. The numerical flow visualisation together with the spectral analysis has indicated that a three dimensional secondary instability, the elliptical instability, which occurs for fundamental frequency is the main mechanism at work whereas the subharmonic mode in the form of vortex-pairing is hardly active. There is no evidence for the existence of hyperbolic instability in the braid region either.
    • On transition process in separated-reattached flows

      Langari, Mostafa; Yang, Zhiyin; University of Derby (Pushpa Publishing House, 2010-10)
      Laminar-to-turbulent transition in shear layer of separated flows is of practical importance. A thorough understanding of transition process is crucial for its prediction and control; to delay the turbulent phase where laminar flow characteristics are desirable or to accelerate it where high mixing and heat transfer rates of turbulent flow are of interest. This paper presents a review of transition process and unsteady behavior of shear layer in separated flows. Despite decades of intensive research in this area the transition process is still not fully understood. However, significant progress has been made with the simulation tools such as Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS). This paper will discuss several important issues such as instability, vortex shedding, coherent structures and so on in separated shear layer transition, trying to provide the current status of understanding and an appraisal of possible future developments.
    • Operational precise irrigation for cotton cultivation through the coupling of meteorological and crop growth models.

      Tsakmakis, Ioannis; Kokkos, Nikolaos; Pisinaras, Vassilios; Papaevangelou, Vasiliki; Hatzigiannakis, Evangelos; Arampatzis, George; Gikas, Georgios, D.; Linker, Raphael; Zoras, Stamatis; Evagelopoulos, Vasilis; et al. (Springer, 2016-11-19)
      In this paper, we tested the operational capacity of an interoperable model coupling system for the irrigation scheduling (IMCIS) at an experimental cotton (Gossypium hirsutum L.) field in Northern Greece. IMCIS comprises a meteorological model (TAPM), downscaled at field level, and a water-driven cultivation tool (AquaCrop), to optimize irrigation and enhance crop growth and yield. Both models were evaluated through on-site observations of meteorological variables, soil moisture levels and canopy cover progress. Based on irrigation management (deficit, precise and farmer’s practice) and method (drip and sprinkler), the field was divided into six sub-plots. Prognostic meteorological model results exhibited satisfactory agreement in most parameters affecting ETo, simulating adequately the soil water balance. Precipitation events were fairly predicted, although rainfall depths needed further adjustment. Soil water content levels computed by the crop growth model followed the trend of soil humidity measurements, while the canopy cover patterns and the seed cotton yield were well predicted, especially at the drip irrigated plots. Overall, the system exhibited robustness and good predicting ability for crop water needs, based on local evapotranspiration forecasts and crop phenological stages. The comparison of yield and irrigation levels at all sub-plots revealed that drip irrigation under IMCIS guidance could achieve the same yield levels as traditional farmer’s practice, utilizing approximately 32% less water, thus raising water productivity up to 0.96 kg/m3.
    • Optimisation nozzle design for mixing fluid using computational fluid dynamics.

      Chenery, Thomas; Harmanto, Dani; University of Derby (Industrial Engineering and Operations Management Society (IEOM), 2018-03)
      The mixing of different chemicals has traditionally been achieved using a rotating paddle in a tank. An alternate option to mix chemicals together is using jet nozzles to spray them into the tank. This paper presents different setups that could be potentially used for selected tank and find the optimal design. The aspects that are changed in the report where the inlet pipe location, the outlet pipe location and the inlet fluid speed. By using SolidWorks to create the models and Star CCM+ to run the simulations, the results of each test where generated and analysed. The validation had been conducted prior to the simulation. When analysing the results, the primary area of interest was the location and size of any dead zones that occurred in the tank during the running of the simulation. The results show that the optimal design for this tank is a side entry inlet pipe at the top of the tank with a side exit outlet pipe at the bottom of the tank, perpendicular to the inlet pipe. It was also shown that a slower inlet speed improved the quality of the mixing process.
    • Optimum compressive strength of hardened sandcrete building blocks with steel chips

      Omoregie, Alohan; University of Bolton (Multidisciplinary Digital Publishing Institute (MDPI), 2013-02)
      The recycling of steel chips into an environmentally friendly, responsive, and profitable commodity in the manufacturing and construction industries is a huge and difficult challenge. Several strategies designed for the management and processing of this waste in developed countries have been largely unsuccessful in developing countries mainly due to its capital-intensive nature. To this end, this investigation attempts to provide an alternative solution to the recycling of this material by maximizing its utility value in the building construction industry. This is to establish their influence on the compressive strength of sandcrete hollow blocks and solid cubes with the aim of specifying the range percent of steel chips for the sandcrete optimum compressive strength value. This is particularly important for developing countries in sub-Saharan Africa, and even Latin America where most sandcrete blocks exhibit compressive strengths far below standard requirements. Percentages of steel chips relative to the weight of cement were varied and blended with the sand in an attempt to improve the sand grading parameters. The steel chips variations were one, two, three, four, five, ten and fifteen percent respectively. It was confirmed that the grading parameters were improved and there were significant increases in the compressive strength of the blocks and cube samples. The greatest improvement was noticed at four percent steel chips and sand combination. Using the plotted profile, the margin of steel chips additions for the optimum compressive strength was also established. It is recommended that steel chip sandcrete blocks are suitable for both internal load bearing, and non-load bearing walls, in areas where they are not subjected to moisture ingress. However, for external walls, and in areas where they are liable to moisture attack after laying, the surfaces should be well rendered. Below ground level, the surfaces should be coated with a water proofing agent like bitumen and cement containing waterproofing agents be used in the manufacture, laying, and rendering of steel chip sandcrete blocks.
    • Performance Investigation of a Commercial Wind Catcher with Horizontally-Arranged Heat Transfer Devices (HHTD).

      Calautit, John Kaiser; O'Connor, Dominic; Hughes, Ben; Shahzad, Sally; University of Sheffield; University of Derby (2015)
      The aim of this study was to conduct numerical Computational Fluid Dynamics (CFD) and experimental analysis of the performance of a wind catcher with Horizontally-arranged Heat Transfer Devices (HHTD) for hot climate conditions. A detailed experimental prototype was created using 3D printing and tested in a closed-loop low speed wind tunnel. An accurate geometrical representation of the wind tunnel test setup was recreated in the numerical modeling. The airflow supply velocity was measured and compared with the numerical data and good correlation was observed. Flow visualisation testing was conducted to analyse the airflow within the device and also inside the ventilated space. The results of the numerical analysis showed that the wind catcher with HHTD was capable of reducing the air temperature by up to 12 K within the micro-climate depending on the outdoor conditions. The technology presented here is subject to a UK patent application (1321709.6).
    • Performance Investigation of a Commercial Wind Catcher with Horizontally-arranged Heat Transfer Devices (HHTD). 

      Calautit, John Kaiser; O'Connor, Dominic; Hughes, Ben; Shahzad, Sally; University of Sheffield; University of Derby (2015)
      The aim of this study was to conduct numerical Computational Fluid Dynamics (CFD) and experimental analysis of the performance of a wind catcher with Horizontally-arranged Heat Transfer Devices (HHTD) for hot climate conditions. A detailed experimental prototype was created using 3D printing and tested in a closed-loop low speed wind tunnel. An accurate geometrical representation of the wind tunnel test setup was recreated in the numerical modeling. The airflow supply velocity was measured and compared with the numerical data and good correlation was observed. Flow visualisation testing was conducted to analyse the airflow within the device and also inside the ventilated space. The results of the numerical analysis showed that the wind catcher with HHTD was capable of reducing the air temperature by up to 12 K within the micro-climate depending on the outdoor conditions. The technology presented here is subject to a UK patent application (1321709.6).
    • A plate model for compressive strength prediction of delaminated composites

      Choudhry, Rizwan Saeed; Rhead, Andrew T.; Nielsen, Mark W.D.; Butler, Richard; University of Derby; University of Bath (Elsevier, 2018-11-24)
      Damage tolerance is of critical importance to laminated composite structures. In this paper, we present a new semi-analytical method for predicting the strain at which delamination propagation will initiate following sublaminate buckling. The method uses a numerical strip model to determine the thin-film buckling strain of an anisotropic sub-laminate created by delamination, before evaluating the strain energy release rate for delamination propagation. The formulation assumes that all energy is available for propagation in a peeling mode (Mode I); avoiding an approximate mixed-mode criterion. Results are compared with twelve experimentally obtained propagations strains, covering a variety of laminates each containing a circular PTFE delamination. Comparison shows agreement to within 12% for balanced sublaminate tests in which delamination propagation occurred before intra-ply cracking. The method can be used to significantly improve the damage tolerance of laminates, opening up new opportunities for structural efficiency using elastic tailoring, non-standard ply angles and material optimisation.
    • Polycentric cultural framework for infrastructure procurement in Nigeria

      Omoregie, Alohan; Radford, Dennis; De Montfort Univeristy (Association of Researchers in Construction Management, 2006-09-06)
      The high failure rate of most infrastructures in sub-Saharan Africa is alarming, particularly in Nigeria, where the dearth and deterioration of infrastructure constantly imposes severe constraints on economic growth and development. Consequently, existing institutions or strategies which are designed to reproduce effective infrastructures in areas that lack them have been mostly unsuccessful. A carefully conducted survey covering the six geopolitical zones in Nigeria identified inadequate maintenance and inconsistent procurement strategies as the major factors responsible for unsustainable infrastructure delivery. In view of the fact that a stable infrastructure is an essential prerequisite for sustainable development, this paper presents a polycentric cultural framework for infrastructure maintenance and procurement in Nigeria, a framework which emphasises the integration of infrastructure users throughout the process, from conceptualization to actual delivery of infrastructure, by taking the recipients’ culture, beliefs and values into account. It also emphasises the use of systemic referendum amongst users and stakeholders via the traditional consultative processes before the actual delivery of infrastructure and services.
    • Portable inflated solar power cold storage house technology as a supporting facility to increase the production and marketing of fishery fishermen.

      Setiawan, M. Ikhsan; Ade, Reswada T.; Harmanto, Dani; University of Derby; Universitas Narotama (IEOM Society, 2018-03)
      Indonesia is a maritime country and fourth largest fish exporter in the world. Currently Indonesia exported fish worth around 35,4 billion US dollars in 2012 and continue to rise. The post -catching is the most important aspect of the process to ensure the fish quality will be meeting the standard export. Most of the post-catching process is a home industry based and fridge/freezer had been used to store the fish before sending them to the exporter for further process. Therefore, paper presents the design and development of the Solar Power Cold Storage House for the fishermen. The general purpose is to support production facilities for cheaper alternative which increasing the fishermen profitable for the mass production. The research purpose is to developed a prototype Portable Inflated Solar Power Cold Storage House as a production support facility and fishery marketing that meets aspects of strength, speed, effectiveness, convenience, so that Portable Inflated Solar Power Cold Storage House products also increase the absorption of National Fish. The paper will describe the design process, testing process such as material strength, rapid deployment of the cold storage, environment test and mechanical test.
    • Portable urban agriculture technology and soil nutrient drive app that support farmers profit.

      Nasihien, Ronny D.; Dhaniarti, Iswachyu; Muhibuddin, Anton; Hasyim, Cholil; Setiawan, M. Ikhsan; Wulandari, Diah Ayu Restuti; Zacoeb, Archfas; Harimurti; Sudapet, Nyoman; Napitupulu, Darmawan; et al. (Science Publishing Corporation, 2018)
      A narrow land farmed urban Agriculture. It used for daily fresh vegetables and fruit for the housing community in urban areas. Portable Urban Agriculture Technology as a support facility to increase production of Urban Agriculture, the Greenhouse portable system could be built and transferred to a specific location is convenient, safe, fast, lightweight structural material (PVC 0.55mm Tarpaulin) so that the Urban Agricultural Products closer to residential consumers in urban. The impact was the price was cheaper but quality. The objective was to plan, build and test prototype Water inflated tent activity as a facility to strengthen Greenhouse's strength, speed, effectiveness and comfort. Application method stages of the Cup or SDN on a former tin mining land, with Portable Urban Agriculture Technology support soil nutrient drive are as follows: first Reconstruction of the land in the form of land arrangement in accordance contours and irrigation channels that exist in the field is very important to support the success of the method SDN; second Management of top soil in the form of top soil enriched with organic material will support environmental compliance in the soil, especially for the growth and development of VAM hyphae and root system; third Soil Amendment to improve the physical and chemical properties of former mining land; fourth Activities vegetation of mined land with SDN method optimizes the achievement of the goals replanting of sustainable of native vegetation for erosion and runoff, repair and restoration of biodiversity, landscape aesthetics that will impact habitat improvement fauna, biodiversity, soil productivity and water quality. Tree plant species such as Acacia mangium, Acacia auriculiformis and Leucaena diversifolia microbes that have been infected with mycorrhizal fungi (VAM) will be very effective and support this effort. Vegetation activities with SDN method includes the following steps: first Seedling plants with VAM; second Preparation of arable land that supports the development of VAM in the soil; third Planting of the first cup with VAM; fourth Incubate 1 month; fifth Planting of the second cup with VAM; sixth 1 month incubation; and seventh The planting of the main crop.
    • Predicting the effect of voids on mechanical properties of woven composites.

      Choudhry, R. S.; Sharif, Tahir; Khan, Kamran A.; Khan, Sohaib Z.; Hassan, Abid; Khan, Muhammad A.; University of Derby; Khalifa University of Science Technology and Research (KUSTAR), UAE; Islamic University of Madinah; Pakistan Petroleum Limited; et al. (IOP Publishing, 2018-09-21)
      An accurate yet easy to use methodology for determining the effective mechanical properties of woven fabric reinforced composites is presented. The approach involves generating a representative unit cell geometry based on randomly selected 2D orthogonal slices from a 3D X-ray micro-tomographic scan. Thereafter, the finite element mesh is generated from this geometry. Analytical and statistical micromechanics equations are then used to calculate effective input material properties for the yarn and resin regions within the FE mesh. These analytical expressions account for the effect of resin volume fraction within the yarn (due to infiltration during curing) as well as the presence of voids within the composite. The unit cell model is then used to evaluate the effective properties of the composite.
    • Printing morphology and rheological characteristics of lead-free Sn-3Ag-0.5Cu (SAC) solder pastes.

      Sharma, Ashutosh; Mallik, Sabuj; Ekere, Nduka N.; Jung, Jae-Pil; University of Seoul; University of Greenwich; University of Wolverhampton (The Korean Microelectronics and Packaging Society, 2014-12-30)
      Solder paste plays a crucial role as the widely used joining material in surface mount technology (SMT). The understanding of its behaviour and properties is essential to ensure the proper functioning of the electronic assemblies. The composition of the solder paste is known to be directly related to its rheological behaviour. This paper provides a brief overview of the solder paste behaviour of four different solder paste formulations, stencil printing processes, and techniques to characterize solder paste behaviour adequately. The solder pastes are based on the Sn-3.0Ag-0.5Cu alloy, are different in their particle size, metal content and flux system. The solder pastes are characterized in terms of solder particle size and shape as well as the rheological characterizations such as oscillatory sweep tests, viscosity, and creep recovery behaviour of pastes.
    • The private versus public infrastructure in Sub-Saharan Africa: An empirical validation

      Omoregie, Alohan; Ebohon, Obas John; Radford, Dennis; De Montfort University (International Council for Research and Innovation in Building and Construction, 2005-11-17)
      The macroeconomics of the relationship between the private and public infrastructure in sub-Saharan Africa has been very unpredictable due to the region’s ineffective planning and policy formulation for infrastructure and service delivery. This paper examines the relationship between public and private infrastructure in subSaharan Africa. It also demonstrates that sub-Saharan Africa consumes more and invests less when compared to the industrialised world and that the present domestic investments in sub-Saharan Africa are actually more in the hands of the private sector. Lastly, an inference relationship for measuring and comparing economic stability between countries and regions was formulated, with the industrialised countries as a reference value.
    • Process optimisation of non-cyanide Ag–PTFE metal matrix composite electroplating for threaded connections

      Sieh, Raymond; Le, Huirong; Cree, Alistair; University of Plymouth (2015-02-11)
    • Profitability through cleaner production

      Peiris, V. R. Sena; Liyanage, Kapila; Jatunarachchi, Sumudu Sajeewareka; The Open University of Sri Lanka (University of Sri Jayewardenepura, Sri Lanka, 2006)
      Cleaner Production (CP) is an integrated, continuous and preventive environment strategy applied to processes, products and services to increase efficiency, minimize waste and reduce risks to humans and the environment. CP should be an essential part of any comprehensive environmental management system at an enterprise or national level. Cleaner production is now seen as a major approach for industry to achieve environmental improvements while remaining competitive and profitable. CP is being increasingly recognized as a definite route towards sustainable development. CP concepts are growing in popularity throughout the world. European countries and some of the Asian countries such as Thailand, India have already applied this concept appropriately and reaped benefits, which have greater impact on their economy and environment. However, Sri Lankan industries are far behind in this respect. Therefore, there is a strong need to introduce CP concept to local industries. Training and education for cleaner production have become essential for most professions. This paper summarizes some of the outcomes and successful lessons learned from the recent CP projects carried out in Sri Lanka since the case studies are an effective means of demonstrating the economic benefits of Cleaner Production. In addition, this paper also emphasizes the necessity for promoting cleaner production concept through education and training in order to achieve sustainable production of goods and services in Sri Lankan industries and promote sustainable consumption among the members of the community.
    • Progress and challenges in large eddy simulation of gas turbine flows.

      Yang, Zhiyin; University of Derby (Shenyang Blower Research Institute ( 沈阳鼓风机研究所), 2018)
      Gas turbine flows are complex and very difficult to be predicted accurately not only due to that they are inherently unsteady but also because the presence of many complex flow phenomena such as transition, separation, substantial secondary flow, combustion and so on. Those complex flow phenomena cannot be captured accurately by the traditional Reynolds-Averaged Navier-Stokes (RANS) and Unsteady RANS (URANS) methods although they have been the main numerical tools for computing gas turbine flows in the past decades due to their computational efficiency and reasonable accuracy. Therefore, the desire for greater accuracy has led to the development and application of high fidelity numerical simulation tools for gas turbine flows. Two such tools available are Direct Numerical Simulation (DNS) which captures directly all details of turbulent flow in space and time, and Large Eddy Simulation (LES) which computes large scale motions of turbulent flow directly in space and time while the small scale motions are modelled. DNS is computationally very expensive and even with the available most powerful supercomputers today or in the foreseeable future it is still prohibitive to apply DNS for gas turbine flows. LES is the most promising simulation tool which has already reasonably widely used for gas turbine flows. This paper will very briefly review first the applications of LES in turbomachinery flows and then focus on two gas turbine combustor related flow cases, summarizing the current status of LES applications in gas turbines and pointing out the challenges that we are facing.
    • Quantitative evaluation of voids in lead free solder joints.

      Mallik, Sabuj; Njoku, Jude; Takyi, Gabriel; Unviersity of Derby; University of Greenwich; Kwame Nkrumah University (Trans Tech Publications Inc., 2015-07)
      Voiding in solder joints poses a serious reliability concern for electronic products. The aim of this research was to quantify the void formation in lead-free solder joints through X-ray inspections. Experiments were designed to investigate how void formation is affected by solder bump size and shape, differences in reflow time and temperature, and differences in solder paste formulation. Four different lead-free solder paste samples were used to produce solder bumps on a number of test boards, using surface mount reflow soldering process. Using an advanced X-ray inspection system void percentages were measured for three different size and shape solder bumps. Results indicate that the voiding in solder joint is strongly influenced by solder bump size and shape, with voids found to have increased when bump size decreased. A longer soaking period during reflow stage has negatively affectedsolder voids. Voiding was also accelerated with smaller solder particles in solder paste.