• The effect of fine droplets on laminar propagation speed of a strained acetone-methane flame: Experiment and simulations

      Fan, Luming; Tian, Bo; Chong, Cheng Tung; Jaafar, Mohammad Nazri Mohd; Tanno, Kenji; McGrath, Dante; Oliveira, Pedro M.de; Rogg, Bernd; Hochgreb, Simone; University of Derby; et al. (Elsevier, 2021-07-31)
      In this study, we investigate the effect of the presence of fuel droplets, their size and concentration, on stretched laminar flame speeds. We consider premixed strained methane/air mixtures, with the addition of small acetone droplets, and compare the flame velocity field behaviour to that of the fully vaporized mixture. An impinging stagnation flame configuration is used, to which a narrowly distributed polydisperse mist of acetone droplets is added. Total acetone molar concentrations between 9% and 20% per mole of methane are used, corresponding to 18.6% and 41.4% of the total fuel energy. The Sauter Mean Diameter (SMD) of acetone droplets is varied from 1.0 to 4.7 μm by carefully tuning the air flow rate passing through an atomizer. The droplet size distribution is characterized by a Phase Doppler Anamometry (PDA) system at the outlet of the burner. The flame propagation speed is measured using Particle Image Velocimetry (PIV) for overall equivalence ratios ranging from 0.8 to 1.4 at various strain rates, and the result is compared with a reference case in which acetone was fully vaporized. Unlike the fully vaporized flame, a two-stage reaction flame structure is observed for all droplet cases: a blue premixed flame front followed by a reddish luminous zone. Comparison of the results between gas-only and droplet-laden cases shows that the mean reference burning velocity of the mixture is significantly enhanced when droplets are present under rich cases, whereas the opposite is true for stoichiometric and lean cases. The mean droplet size also changes the relationship between flame speed and strain rate, especially for rich cases. The result suggests that with typical conditions found in laminar strained flames, even for the finest droplets that may have been vaporized before reaching the flame front, the resulting inhomogeneities may lead the flame to behaves differently from the well-premixed gaseous counterpart. Simulations at similar conditions are performed using a two-phase counterflow flame model to compare with experimental data. Model results of reference velocities do not compare well with observations, and the possible reasons for this behaviour are discussed, including the difficulties in determining the pre-vaporization process and thus the boundary conditions, as well as the fidelity of the current point-source based 1D model.
    • Thermal Fatigue Life of Ball Grid Array (BGA) Solder Joints Made From Different Alloy Compositions

      Depiver, Joshua Adeniyi; Sabuj, Mallik; Amalu, Emeka H; University of Derby; Teeside University (Elsevier, 2021-04-27)
      As temperature cycling drives fatigue failure of solder joints in electronic modules, characterisation of the thermal fatigue response of different solder alloy formulations in BGA solder joints functioning in mission-critical systems has become crucial. Four different lead-free and one eutectic lead-based solder alloys in BGA solder joints are characterised against their thermal fatigue lives (TFLs) to predict their mean-time-to-failure for preventive maintenance advice. Five finite elements (FE) models of the assemblies of the BGAs with the different solder alloy compositions are created with SolidWorks. The models are subjected to standard IEC 60749-25 temperature cycling in ANSYS mechanical package environment. Plastic strain, shear strain, plastic shear strain, and accumulated creep energy density responses of the solder joints are obtained and inputted into established life prediction models – Coffin Manson, Engelmaier, Solomon and Syed – to determine the lives of the models. SAC405 joints have the highest predicted TFL of circa 13.2 years, while SAC387 joints have the least life of circa 1.4 years. The predicted lives are inversely proportional to the magnitude of the areas of stress-strain hysteresis loops of the BGA solder joints. The prediction models are significantly not consistent in predicted magnitudes of TFLs across the solder joints. With circa 838% variation in the magnitudes of TFL predicted for Sn63Pb37, the damage parameters used in the models played a critical role and justifies that a combination of several failure modes drives solder joints damage. This research provides a technique for determining the preventive maintenance time of BGA components in mission-critical systems. It proposes developing a new life prediction model based on a combination of the damage parameters for improved prediction.
    • On wind turbine power fluctuations induced by large-scale motions

      Ahmadi, Mohammad; Yang, Zhiyin; University of Derby (Elsevier, 2021-04-21)
      Our current understanding on the dynamic interaction between large-scale motions in the approaching turbulent flow and wind turbine power is very limited. To address this, numerical studies of a small-scale three-bladed horizontal axis wind turbine with cylinders placed in front of it to produce energetic coherent structures of varying scale relative to the turbine size have been carried out to examine the temporary variations of the turbine power. The predicted spectra reveal a strong interaction between large-scale turbulent motions generated by cylinders and the instantaneous turbine power. More specifically, it shows how the large dominant turbulent scales of incoming flow affect the spectral characteristics of turbine power, i.e, determining the level and trend of the turbine power spectrum. Comparisons reveal that there are two critical frequencies recognisable in the turbine power spectrum: the first one, close to the turbine rotational frequency, above which the coupling of upstream flow and turbine power disappears; the second one, identified for the first time and related to the dominant large-scale motions which dictate the level and trend of the turbine power spectrum. This study also shows that the strong scale-to-scale interaction between the upstream flow and turbine power reported previously does not appear at high Reynolds numbers.
    • Self-healing of bio-cementitious mortar incubated within neutral and acidic soil

      Esaker, Mohamed; Hamza, Omar; Souid, Adam; Elliott, David; University of Derby (Springer Science and Business Media LLC, 2021-04-14)
      The efficiency of bio self-healing of pre-cracked mortar specimens incubated in sand was investigated. The investigation examined the effect of soil pH representing industrially recognised classes of exposure, ranging from no risk of chemical attack (neutral pH≈7) to very high risk (pH≈4.5). Simultaneously, the soil was subjected to fully and partially saturated cycles for 120 days to resemble groundwater-level fluctuation. Bacillus Subtilis with nutrients were impregnated into perlite and utilised as a bacterial healing agent. The healing agent was added to half of the mortar specimens for comparison purposes. Mineral precipitations were observed in both control and bio-mortar specimens, and the healing products were examined by SEM-EDX scanning. The healing ratio was evaluated by comparing (i) the repair rate of the crack area and (ii) by capillary water absorption and sorptivity index - before and after incubation. The results indicated that bacteria-doped specimens (bio-mortar) exhibited the most efficient crack-healing in all incubation conditions i.e. different chemical exposure classes. In the pH neutral soil, the average healing ratios for the control and bio-mortar specimens were 38% and 82%, respectively. However, the healing ratio decreased by 43% for specimens incubated in acidic soil (pH≈4) compared with specimens incubated in neutral soil (pH≈7). The study implies that bio self-healing is generally beneficial for concrete embedded within the soil; however, aggressive ground conditions can inhibit the healing process.
    • The cradle to gate life-cycle assessment of thermoelectric materials: A comparison of inorganic, organic and hybrid types

      Soleimani, Zohreh; Zoras, Stamatis; Ceranic, Boris; Shahzad, Sally; Cui, Yuanlong; University of Derby; Sheffield University (Elsevier, 2021-02-18)
      Using thermoelectric generators to convert waste heat into electricity is a renewable alternative to fossil energy sources. As thermoelectric materials are the main element of thermoelectric generators, so far numerous studies have attempted to optimize their energy conversion efficiency. However, no single study to date has examined their life cycle impacts, whilst it is the most important feature of any renewable technology. Accordingly, the aim of the present study is to assess the life cycle impacts of thermoelectric materials at their production stage (cradle to gate) using a life cycle assessment tool called GaBi v.4.4. Thus, the thermoelectric materials were categorized into inorganic, organic, and hybrid types. The five investigated impact categories were resource consumption, emission, waste, primary energy demand, and global warming potential. The results confirmed that the inorganic type caused significantly greater environmental impacts than the other two types. The only inorganic exception was Bi 2 Te 3 that its environmental impact was by far the lowest among all the studied thermoelectric materials. Notably, the inorganic type caused major harm to the environment due to its extremely energy-intensive manufacturing process. However, the core environmental drawback of the organic and hybrid types was driven from their raw materials supply.
    • Blockchain application in supply chain chemical substance reporting - a Delphi study

      Takhar, Sukhraj Singh; Liyanage, Kapila; University of Derby (Inderscience, 2021-02-08)
      Blockchains utilise digital ledger technology to enable data to be traced in a more efficient manner than traditional paper-based systems. Smart contracts extend the capabilities of a blockchain by defining specific obligations. Chemical regulations impose the need on industry to record and report the use of hazardous chemicals within products. The process of collating supply chain chemical substance reporting information is a manually intensive and lengthy process in order to identify potential business risks and reporting of information to employees, consumers and chemical regulators. The research question answered in this paper relates to use of a blockchain with a smart contract to enable the automated collation of supply chain chemical substance information. This paper presents the findings from a Delphi study and a proposed 'supply chain chemical substance reporting' (SCCSR) blockchain. The SCCSR blockchain enables industry to implement greater efficiencies in collecting the required chemical substance information.
    • Biodiesel sustainability: The global impact of potential biodiesel production on the energy–water–food (EWF) nexus

      Chong, Cheng Tung; Loe, Ting Yu; Wong, Kang Yao; Ashokkumar, Veeramuthu; Lam, Su Shiung; Chong, Wen Tong; Borrion, Aiduan; Tian, Bo; Ng, Jo-Han; Shanghai Jiao Tong University, Lingang, Shanghai 201306, China; et al. (Elsevier, 2021-02-01)
      A data-driven model is used to analyse the global effects of biodiesel on the energy–water–food (EWF) nexus, and to understand the complex environmental correlation. Several criteria to measure the sustainability of biodiesel and four main limiting factors for biodiesel production are discussed in this paper. The limiting factors includes water stress, food stress, feedstock quantity and crude oil price. The 155-country model covers crude oil prices ranging from USD10/bbl to USD160/bbl, biodiesel refinery costs ranging from -USD0.30/L to USD0.30/L and 45 multi-generation biodiesel feedstocks. The model is capable of ascertaining changes arising from biodiesel adoption in terms of light-duty diesel engine emissions (NO, CO, UHC and smoke opacity), water stress index (WSI), dietary energy supply (DES), Herfindahl–Hirschman index (HHI) and short-term energy security. With the addition of potential biodiesel production, the renewable energy sector of global primary energy profile can increase by 0.43%, with maximum increment up to 10.97% for Malaysia. At current crude oil price of USD75/bbl and refinery cost of USD0.1/L, only Benin, Ireland and Togo can produce biodiesel profitably. The model also shows that water requirement varies non-linearly with multi-feedstock biodiesel production as blending ratio increases. Out of the 155 countries, biodiesel production is limited by feedstock quantity for 82 countries, 47 are limited by crude oil price, 20 by water stress and 6 by food stress. The results provide insights for governments to set up environmental policy guidelines, in implementing biodiesel technology as a cleaner alternative to diesel.
    • Compression and buckling after impact response of resin-infused thermoplastic and thermoset 3D woven composites

      Shah, S.Z.H; Megat-Yusoff, P.S.M; Karuppanan, S; Choudhry, Rizwan Saeed; Din, I.U; Othman, A.R; Sharp, K; Gerard, P; Universiti Teknologi PETRONAS, 32610, Bandar Seri Iskandar, Perak, Malaysia; University of Derby; et al. (Elsevier, 2020-12-29)
      Damage tolerance of a unique resin-infused thermoplastic (Elium) 3D fibre-reinforced composite (3D-FRC) is compared with the conventional resin-infused thermoset (Epoxy) 3D-FRC using compression after impact (CAI) tests and finite element simulations. Higher damage tolerance is demonstrated for the thermoplastic 3D-FRC as its CAI failure strength and CAI stiffness is nearly insensitive to the impact energy levels and subsequent damage, while in contrast, both these properties for the thermoset 3D-FRC get compromised significantly. The buckling performance shows a gradual, almost linear, reduction in critical buckling (44.5% reduction in 0–100 J) for the thermoplastic 3D-FRC. In comparison, the thermoset 3D-FRC shows a much steeper drop in critical buckling, which becomes more pronounced for the higher impact energy cases (84.5% reduction in 0–100 J). It is postulated that the local plastic deformation of the thermoplastic matrix at the impact site as well as better interfacial adhesion is responsible for its better damage tolerance.
    • Machinability of INCONEL718 alloy with a porous microstructure produced by laser melting powder bed fusion at higher energy densities

      Wood, Paul K; Díaz-Álvarez, Antonio; Díaz-Álvarez, José; Miguélez, María Henar; Rusinek, Alexis; Williams, Gavin; Bahi, Slim; Sienkiewicz, Judyta; Płatek, Paweł; Gunputh, Urvashi Fowdar; et al. (MDPI, 2020-12-15)
      Products produced by additive manufacturing (AM) seek to exploit net shape manufacturing by eliminating or minimizing post-process stages such as machining. However, many applications which include turbo machinery components with tight dimensional tolerances and a smooth surface finish will require at least a light machine finishing stage. This paper investigates the machinability of the additively fabricated INCONEL718 (IN718) alloy produced by laser melting powder bed fusion (LM-PBF) with different levels of spherical porosity in the microstructure. The literature suggests that the band width for laser energy density, which combines the various scan process parameters to obtain a low spherical type porosity in the LM-PBF IN718 alloy (~1%), has wide breadth. With the increasing laser energy density and above a threshold, there is a rapid increase in the spherical pore size. In this paper, three tube samples each with different levels of spherical porosity were fabricated by varying the laser energy density for LM-PBF of the IN718 alloy within the stable and higher energy density range and the porosity measured. A low laser energy density was avoided due to balling up, which promotes highly irregular lack of fusion defects and poor consolidation within the alloy microstructure. An orthogonal turning test instrumented, with a three-component dynamometer to measure the cutting forces, was performed on AM produced IN718 tube samples under light cut conditions to simulate a finish machining process. The orthogonal turning tests were also performed on a tube sample obtained from the wrought extruded stock. The machining process parameters, which were studied include varying the cutting speed at three levels, at a fixed feed and under dry cut conditions for a short duration to avoid the tool wear. The results obtained were discussed and a notable finding was the higher rate of built-up-edge formation on the tool tip from the AM samples with a higher porosity and especially at a higher cutting speed. The paper also discusses the mechanisms that underpin the findings.
    • Computational study of flow around 2D and 3D tandem bluff bodies

      Charles, Terrance; Yang, Zhiyin; Lu, Yiling; University of Derby (Shahid Chamran University of Ahvaz, 2020-11-21)
      Numerical simulations have been carried out to advance our current understanding of flow around two dimensional (2D) and three dimensional (3D) square shaped tandem bluff bodies at a Reynolds number of 22,000, especially to shed light on the sudden change of the downstream body’s drag coefficient. The Reynolds-Averaged Navier-Stokes (RANS) approach has been employed in the present study and the predicted drag coefficients compare reasonably well with available experimental data. Better understanding of flow fields has been achieved by analyzing streamlines, velocity vectors for both 2D and 3D cases in a horizontal plane and a vertical symmetric plane. The sudden jump in drag coefficient for the 2D case is well captured numerically, which is due to the flow over the upstream body impinging onto the front face of the downstream body at a critical gap size between those two bodies. For the 3D case the drag coefficient is predicted to increase gradually, consistent with the previous experimental finding. This is due to the fact that the vortical structures formed in the 3D case are very different, resulting in a reasonably smooth change of the flow field around the upstream body and hence leading to gradual, not sudden, increase in the drag coefficient of the downstream body.
    • Effective solder for improved thermo-mechanical reliability of solder joints in ball grid array (BGA) soldered on printed circuit board (PCB)

      Depiver, Joshua Adeniyi; Sabuj, Mallik; Amalu, Emeka H; University of Derby; Teeside University (Springer, 2020-11-05)
      Ball grid array (BGA) packages have increasing applications in mobile phones, disk drives, LC displays and automotive engine controllers. However, the thermo-mechanical reliability of the BGA solder joints challenges the device functionality amidst component and system miniaturisation as well as wider adoption of lead-free solders. This investigation determines the effective BGA solders for improved thermo-mechanical reliability of the devices. It utilised a conducted study on creep response of a lead-based eutectic Sn63Pb37 and four lead-free Tin-Silver-Copper (SnAgCu) [SAC305, SAC387, SAC396 and SAC405] solders subjected to thermal cycling loadings and isothermal ageing. The solders form the joints between the BGAs and printed circuit boards (PCBs). ANSYS R19.0 package is used to simulate isothermal ageing of some of the assemblies at -40℃, 25℃, 75℃ and 150℃ temperatures for 45 days and model the thermal cycling history of the other assemblies from 22℃ ambient temperature for six cycles. The response of the solders is simulated using Garofalo-Arrhenius creep model. Under thermal ageing, SAC396 solder joints demonstrate possession of least strain energy density, deformation and von-Mises stress in comparison to the other solders. Under thermal cycle loading conditions, SAC405 acquired the lowest amount of the damage parameters in comparison. Lead-free SAC405 and SAC387 joints accumulated the lowest and highest energy dissipation per cycle, respectively. It is concluded that SAC405 and SAC396 are the most effective solders for BGA in devices experiencing isothermal ageing and temperature cycling during operation, respectively. They are proposed as the suitable replacement of eutectic Sn63Pb37 solder for the various conditions.
    • Comparing and benchmarking fatigue behaviours of various sac solders under thermo-mechanical loading

      Depiver, Joshua Adeniyi; Mallik, Sabuj; Amalu, Emeka H; University of Derby (IEEE, 2020-10-23)
      While the fatigue behaviours (including fatigue life predictions) of lead-free solder joints have been extensively researched in the last 15 years, these are not adequately compared and benchmarked for different lead-free solders that are being used. As more and more fatigue properties of lead-free solders are becoming available, it is also critical to know how fatigue behaviours differ under different mathematical models. This paper addresses the challenges and presents a comparative study of fatigue behaviours of various mainstream lead-free Sn-Ag-Cu (SAC) solders and benchmarked those with lead-based eutectic solder. Creep-induced fatigue and fatigue life of lead-based eutectic Sn63Pb37 and four lead-free SAC solder alloys: SAC305, SAC387, SAC396 and SAC405 are analysed through simulation studies. The Anand model is used to simulate the inelastic deformation behaviour of the solder joints under accelerated thermal cycling (ATC). It unifies the creep and rate-independent plastic behaviour and it is used to predict the complex stress-strain relationship of solders under different temperatures and strain rates, which are required in the prediction of fatigue life using the fatigue life models such as Engelmaier, Coffin-Mason and Solomon as the basis of our comparison. The ATC was carried out using temperature range from −40°C to 150°C. The fatigue damage propagation is determined with finite element (FE) simulation, which allows virtual prototyping in the design process of electronics devices. The simulation was carried out on a BGA (36 balls, 6 × 6 matrix) mounted onto Cu padded substrate. Results are analysed for plastic strain, Von mises stress, strain energy density, and stress-strain hysteresis loop. The simulation results show that the fatigue behaviours of lead-based eutectic Sn63Pb37 solder is comparable to those of lead-free SAC solders. Among the four SAC solders, SAC387 consistently produced higher plastic strain, strain energy and stress than the other solders. The fatigue life’s estimation of the solder joint was investigated using Engelmaier, Coffin-Manson, and Solomon models. Results obtained show that SAC405 has the highest fatigue life (25.7, 21.1 and 19.2 years) followed by SAC396 (18.7, 20.3 and 17.9 years) and SAC305 (15.2, 13.6 and 16.2 years) solder alloys respectively. Predicting the fatigue life of these solder joints averts problems in electronics design for reliability and quality, which if not taken care of, may result in lost revenue. Predictive fatigue analysis can also considerably reduce premature failure, and modern analysis technique such as one used in this research is progressively helping to provide comprehensive product life expectancy data.
    • Detection of Cover Collapse Doline and Other Epikarst Features by Multiple Geophysical Techniques, Case Study of Tarimba Cave, Brazil

      Hussain, Yawar; Uagoda, Rogerio; Borges, Welitom; Prado, Renato; Hamza, Omar; Cárdenas-Soto, Martín; Havenith, Hans-Balder; Dou, Jie; Clemson University, Clemson, SC 29634, USA; University of Brasilia, Brasilia 70910-900, Brazil; et al. (MDPI, 2020-10-12)
      Reliable characterization of the karst system is essential for risk assessment where many associated hazards (e.g., cover-collapse dolines and groundwater pollution) can affect natural and built environments, threatening public safety. The use of multiple geophysical approaches may offer an improved way to investigate such cover-collapse sinkholes and aid in geohazard risk assessments. In this paper, covered karst, which has two types of shallow caves (vadose and fluvial) located in Tarimba (Goias, Brazil), was investigated using various geophysical methods to evaluate their efficiency in the delineation of the geometry of sediments filled sinkhole. The methods used for the investigation were Electrical Resistivity Tomography (ERT), Seismic Refraction Survey (SRS), Seismic Refraction Tomography (SRT) and the Very Low-Frequency Electromagnetic (VLF-EM) method. The study developed several (2D) sections of the measured physical properties, including P-wave velocity and electrical resistivity, as well as the induced current (because of local bodies). For the analysis and processing of the data obtained from these methods, the following approaches were adopted: ERT inversion using a least-square scheme, Karous-Hjelt filter for VLF-EM data and time-distance curves and Vp cross-sections for the SRS. The refraction data analysis showed three-layered stratigraphy topsoil, claystone and carbonate bedrock, respectively. The findings obtained from ERT (three-layered stratigraphy and sediment-filled doline), as well as VLF-EM (fractured or filled caves as a positive anomaly), were found to be consistent with the actual field conditions. However, the SRS and SRT methods did not show the collapsed material and reached the limited depth because of shorter profile lengths. The study provides a reasonable basis for the development of an integrated geophysical approach for site characterization of karst systems, particularly the perched tank and collapse doline.
    • Characterization of Sobradinho landslide in fluvial valley using MASW and ERT methods

      Hussain, Yawar; Hamza, Omar; Cárdenas-Soto, Martín; Borges, Welitom Rodrigues; Dou, Jie; Rebolledo, Juan Félix Rodriguez; Prado, Renato Luiz; Clemson University, South Carolina, USA; University of Derby; Universidad Nacional Autónoma de México; et al. (FapUNIFESP (SciELO), 2020-09-30)
      Landslides can substantially impact the fluvial systems, which is why the continuous mapping of their extent, evolution and stability assessment is crucial. However, in such environments, material identification (e.g. colluvium) and subsurface characterization by the methods used for geologic mapping and geotechnical investigation is often a challenging task. Thus, these classical invasive methods may benefit from geophysical techniques to enable and enhance our understanding of the subsurface in these areas. To examine such integrated approach, Multi-Channel Analysis of Surface Waves (MASW) combined with Electrical Resistivity Tomography (ERT) were applied on a geomorphologically active fluvial valley in Sobradinho (the Federal District of Brazil). The subsurface materials showed a specific range of resistivity values as dry soil, saprolite, and landslide slip surface. The 1D shear wave velocity (Vs) model showed an increasing trend of Vs with depth at a location away from the landslide mass, while the longitudinal profile (over the landslide) showed an anomalous change in Vs (~ 250 to 400 m/sec). Based on the existing information about the landslide, the ERT appeared to be an effective method over MASW. This study shows how the integration of geophysical data with the geological and geotechnical investigation helps to obtain a more realistic or unambiguous model of the subsurface.
    • Optimal design of cold roll formed steel channel sections under bending considering both geometry and cold work effects

      Qadir, Sangar; Nguyen, Van Bac; Hajirasouliha, Iman; Cartwright, Brian; English, Martin; University of Derby; University of Sheffield; Hadley Industries plc (Elsevier, 2020-09-17)
      Optimal design of a structural member is a design process of selecting alternative forms to obtain its maximum strength while maintaining the same weight, leading to the most economical and efficient structure. Amongst steel structures, cold rolled steel ones can effectively gain this requirement as they are thin-walled structures that offer the high ratio of strength over weight. However, the design is very challenging as these members are prone to buckling and failure at low loads. In this paper, the buckling and ultimate strength of cold rolled channel sections was studied using numerical modelling. In order to improve the section strength, the development of various alternative cold rolled formed sections included additional bends such as intermediate stiffeners. The section strength was optimised through a practical approach which altered the stiffener’s position and shape and searched for maximum buckling and ultimate strength under bending. In this approach, a nonlinear Finite Element model was first developed for an industrial channel beam subjected to four-point bending tests and this model was validated against experimental test data. The verified model was then used to conduct a parametric study in which the effects of a stiffener’s properties on the section strength including its position, shape, size and material properties by the cold work at bends were investigated in detail. Several different cold rolled channel sections having intermediate stiffeners at web and flanges with and without the cold work effect on material properties at the stiffener’s bends were considered for this investigation. In addition, a design method, the Direct Strength Method (DSM), was utilised to take into account the effects of a stiffener’s properties on the section strength and results were compared with the Finite Element modelling results. It was found that some significant improvements were obtained for the section strength of the optimised sections in comparison to the original sections. An optimal shape for the channel section with maximum ultimate strength in distortional buckling could be obtained with both the stiffeners’ position, shape, size and quantity, and the cold work effect. The cold work effect was found most significant in the cases of changing the width of the web stiffeners and the position of the flange stiffeners. It also revealed that, the currently available DSM beam design curve for distortional buckling provided good agreement in predicting buckling load and ultimate strength capacity for most of the considered sections with and without the cold work effect included; however, the DSM provided overestimate results compared to the Finite Element model results in the sections with web intermediate stiffeners, in particular, when the tip of web intermediate stiffener moved away from the web-flange junction in the horizontal direction.
    • Assessment of drag reduction devices mounted on a simplified tractor-trailer truck model

      Charles, Terrance; Yang, Zhiyin; Lu, Yiling; Coventry University; University of Derby (Shahid Chamran University of Ahvaz, 2020-09-14)
      Aerodynamic drag reduction of tractor-trailer combination trucks is critically important to improve their fuel consumption which consequently results in lower emissions. One practical method to reduce aerodynamic drag of a truck is by mounting drag reduction devices on the truck. This paper presents a numerical study of turbulent flow over a simplified tractortrailer truck with different drag reduction devices mounted on the truck using the Reynolds Averaged Navier-Stokes (RANS) approach to assess the effectiveness of those devices in drag reduction around the tractor-trailer gap region. Three cases with different drag reduction devices have been studied and significant drag reduction (above 30%) has been achieved for all three cases. Detailed analysis of the flow field has been carried out to understand drag reduction mechanisms, and it shows that no matter what drag reduction devices are deployed the drag reduction is mainly due to the reduced pressure on the front face of the trailer, and a small proportion of the drag reduction is due to the reduced turbulent kinetic energy in the gap region.
    • The challenges of teaching design in the 21st century, the age of the fourth industrial revolution

      Sole, Martin; Barber, Patrick; Harmanto, Dani; University of Derby (The Design Society - Institution of Engineering Designers, 2020-09-12)
      There is an ever-growing demand from industry for qualified design engineers. Many of these design engineers are trained at universities and colleges. This paper will explore how to keep this training as up to date and relevant as possible. It will look at the modern techniques and methods used by world-leading industries during the 21st century. This century, known also as the Fourth Industrial Revolution, or the Information Technology Revolution. It will show how these techniques and methods can be applied in academia. A challenge is also highlighted, how to get students to design to industry standards but at the same time make it possible to assess their work to satisfy the needs of academia and awarding bodies. These modern techniques and methods will be applied to actual university students and an assessment made of the results. Use of group working will be explored and an algorithm developed to grade the completed group work. What do students need now to equip them to become competent designers, and what will they need soon?
    • Large eddy simulation of the flow past a circular cylinder at super-critical Reynolds numbers

      Ahmadi, Mohammad; Yang, Zhiyin; University of Derby (ASME, 2020-09)
      Turbulent flow past a circular cylinder at super-critical Reynolds numbers is simulated using large eddy simulation in this study. A novel combination of O- and H-grid structures is used to reduce mesh cells and, in turn, the computational cost. To investigate the influence of sub-grid scale (SGS) models on the accuracy of simulations, four different SGS models are applied to simulate the flow. In this study, the effect of mesh resolution near the wall on the accuracy of results is also evaluated by applying different y+ values at the wall. The results show that due to the complexity of the flow around the cylinder particularly at high Reynolds numbers, using very high resolution mesh near the cylinder wall, can not guarantee the accuracy of results and other parameters such as mesh resolutions at the top and bottom shear layers and the wake shortly behind the cylinder should be considered appropriately.
    • Nature connectedness, human behaviours, and blue infrastructure: the water effect to people in historical and contemporary masterplanning

      Al-Wali, Wafaa; Tracada, Eleni; University of Derby (Water Efficiency Network, University of Bath, 2020-09)
      Most urban designers and planners have produced anthropocentric masterplans since early twentieth century. Today green infrastructure in cities, including blue infrastructure, primarily expresses people’s relationship to the environment in terms of resource management. Often the natural world is converted into urban green arrangement or a replica of nature mainly for the economic and cultural benefit of humans. Water and related ecosystems were only part of industry as necessity until late twentieth century. Nowadays, water is valued as a very important element of life. Most experts believe that by offering people the opportunity to participate in running and preserving certain ecosystems could have a very positive impact to human health and wellbeing. Environmental psychology suggests that we can provoke heightened experiences in people’s minds by designing dynamic flowing water patterns in urban context. Natural or artificial landscapes, such as green parks should intertwine with the built environment, displaying human creativity and inventiveness. The authors of this paper discuss the importance of water changing culture and behaviours in regenerated green parks in vulnerable urban areas, such as the case study of Arboretum Derby. This particular case study was reviewed by both authors (tutor and PhD student) who shared research with undergraduate students in Urban Design module in this academic year. The student projects reveal the importance of nature connectedness to people seeking happiness and mental balance to counterbalance lockdown hardship, employment loss and social deprivation.
    • Simultaneous two-phase flame velocity measurement using laser-induced incandescence particle image velocimetry (LII-PIV)

      Fan, Luming; Chong, Cheng Tung; Tian, Bo; Zheng, Yutao; Dante, McGrath; Hochgreb, Simone; University of Cambridge; Shanghai Jiao Tong University; Universiti Teknologi Malaysia; University of Derby (Elsevier, 2020-08-25)
      In a previous study we demonstrated a novel two-phase PIV technique based on the laser-induced incandescence (LII) signal from black submicron tungsten carbide particles (WC), which achieved velocity measurements for both dispersed-form (large water droplet) and continuous-form (gas). Submicron WC particles are intentionally seeded into a two-phase flow, and heated by a light sheet generated by a double-pulsed PIV laser running at high energy. The 200 nm diameter, light absorbing WC particles are heated to several thousand degrees to emit strong incandescence signals, whilst the temperature rise in liquid droplets or large particles remains negligible. The small particles follow the gas phase flow, unlike the droplets which may have a different velocity. Droplets are detected via the Mie scatter signal at the same incident wavelength, whereas the LII signal from small WC particles is detected at a suitably different wavelength within the LII emission spectrum, thus allowing discrimination of velocities between phases. The LII-PIV technique had been implemented with a low-speed CCD PIV camera in non-reacting flows. In flames, the strong flame luminosity saturated the second frame due to the long exposure time as the characteristics of the device. To solve this problem, in the present study, we synchronized two high-speed CMOS cameras to a low speed laser. One records the LII signal and the other records the Mie scatter signal from 36.6 µm water droplets. The scattering from WC particles appears only as a weak background signal in the Mie image, which can be easily removed by applying a high-pass filter. Simultaneous velocity measurements for both gas and liquid phase are demonstrated in an air jet, a cold impinging flow, and finally in a Bunsen flame. The last two cases are repeated using the traditional two-phase PIV technique based on image segmentation so as to conduct a fair comparison of both techniques. We show that LII-PIV can achieve the same level of accuracy as the segmentation method in non-reacting flows, and can be applied to measure in flames with two-phase flows with less stringent requirements regarding seeding quality.