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Inverse force determination is commonly used to determine input forces when they are not directly measurable. If transfer functions are measured with the source component attached, the inversely determined forces are, by definition, blocked forces. The primary advantage of using blocked forces is that the receiving structure may be modified and blocked forces, in theory, are unchanged. In this research, blocked forces are determined for a plastic engine cover connected to a base plate and a compressor attached to two different structures. At lower frequencies, blocked forces are determined using routine approaches where phase is included in both transfer function and operational response measurements. At high frequencies, it is demonstrated that predictions are improved if phase is ignored and blocked forces are assumed to be uncorrelated with respect to each other. It is also shown that the uncorrelated blocked forces are still valid even when changes are made to the receiving structure.

The vehicle acoustic overall performance optimization in an undertaking to determine the difficulty of sound techniques turned into created the noise within the cabin. In this paper to audit the advancements so far did in the discipline of optimization thinks approximately on lower of noise within the truck cabins with the aid of the use of acoustic materials. In mild of this, it’s miles to analyze the opportunity of acoustic substances as aluminum, steel metallic and carbon fiber with plan to improve the cabin noise by NVH evaluation may be finished via using ansys and hypermesh software program’s. By locating the analysis values of frequency, sound and weighted sound can be concluded the acoustic materials are excellent for quieter programs.

Still today, the issue of safely and efficiently avoiding the atmospheric release of the nano-particles produced by combustion and incineration processes is a critical and open challenge. This study addresses the conception, the technological realization and the first experimental testing of a new device suitable for in-duct filtration and separation of nano particles dispersed into flue-gas streams. The active filtering material is a membrane made from ptfe foil, in origin impermeable but suitable to allow creation, once properly stretched, of an inner texture of permeable micro- and nano-tubes, thus inducing activation of van der Waals effects to the advantage of improved particles’ sticking. The experimental tests confirm attainment of a remarkable filtration capacity, way better than the so-called ‘absolute filters’. Moreover, the filtration material allows to undergo a simple and safe “regeneration cleaning” process by which the particles can be re-collected off-duct without any filter dismantling., Le problème de la prévention des émissions à l'atmosphère des nano-particules produites par les procédés de combustion et de incinération est un défi toujours ouvert. L'étude présente la conception, la technologie de construction et les premiers essais expérimentaux d'un nouveau dispositif approprié pour la filtration et la séparation des nano particules dans les flux de gaz. Le substrat actif est une membrane en PTFE film: même si il est initialement imperméable, il permet la création, à l'intérieur, d'un réseau dense, mais perméable au gaz, de micro-et nano-tubes lorsque la membrane est soumis à une opération d'étirage planaire. De cette façon, sont également provoqué des actions induisant des effets de van der Waals à l'avantage de l’amélioration de l'adhésion moléculaire. Les tests expérimentaux confirment la réalisation d'une grande capacité de filtrage de micro- et de nano-particules, bien mieux que les ’filtres absolus’. En outre, le filtre à membrane peut être “régénéré” par des impulsions de pression, donc le particules sont remobilisés et séparés sans avoir à démonter le filtre., Il problema di impedire la emissione atmosferica delle nano-particelle prodotte dai processi di combustione e di incenerimento rappresenta una sfida tuttora aperta. Lo studio riguarda la concezione, la realizzazione tecnologica e le prime prove sperimentali di un nuovo dispositivo atto alla filtrazione e separazione di nano particelle presenti in flussi gassosi. Il substrato attivo è una membrana realizzata in pellicola di PTFE: essa, in origine impermeabile, consente la creazione, al suo interno, di una fitta trama di micro- e nano-tubi se sottoposta ad un processo di stiramento planare. In tal modo vengono altresì indotti importanti effetti di adesione molecolare riferibili alle forze di van der Waals. Le prove sperimentali confermano il raggiungimento di una notevole capacità di filtraggio delle nano particelle, in modo nettamente migliore dei cosiddetti 'filtri' assoluti. Inoltre, la membrana filtrante consente di essere “rigenerata” in modo semplice e sicuro tramite impulsi di pressione, le particelle entro i micro-pori vengono ri-mobilizzate e separate senza smontare il filtro., EQA - International Journal of Environmental Quality; Vol 8 (2012); 9-20

This paper presents different modeling technique approaches of the single-link uniform cross-sectional shape manipulators. Three different materials of manipulators which are epoxy-glass and carbon-fiber for composite manipulators and steel manipulator are considered for both simulation and experimental analyses. Three different modelling techniques which are solid, beam and shell models are used for both manipulators. The study consists of three steps. In the first step, the manipulators are modeled in ANSYS for finite element analyses. In the second step, modal analysis is carried out in order to find the frequencies of the manipulators. In the third step, transient analysis is performed to investigate the success of different modeling approaches with experimental results. It is observed that the simulation results with three different modeling approaches have well matched with the experimental results and then, elapsed times for the transient analyses are investigated to find the appropriate modeling technique for the manipulator. © 2020 Institution of Structural Engineers

This article presents an experimental study on the torsional behavior of composite tubes subjected to impact loadings. Four types of composite tubes with the winding angle of 30°, 45°, 60°, and 75° ([±30]FW, [±45]FW, [±60]FW, and [±75]FW) were produced with the filament winding method. Besides, a [0,90]PP composite tube was manufactured with the prepreg wrapping technique. After the composite tubes were impacted at 2.5 J, 5.0 J, and 7.5 J, non-impacted and impacted composite tubes were tested under torsional loading. Contact force–deformation curves of impacted tubes are presented. Torsional moment–twist angle relations for both impacted and non-impacted composite tubes were obtained. In addition, front view and side view of the impacted zone of composite tubes are given. The results showed that sample [±60]FW had the best impact performance with regard to absorbed energy. The impacted samples of [±60]FW and [±75]FW had the lowest torsional strength for each energy level.

In this study, mixed convection in a phase change material filled square cavity under the effect of a rotating cylinder was numerically investigated. The vertical walls are kept at constant temperatures while the horizontal walls are adiabatic. The effects of angular rotational speed of the cylinder (between −7.5 and 7.5), vertical location of the cylinder (between 0.25 and 0.75) and two different cylinder sizes (0.05 and 0.1) on the fluid flow and heat transfer were numerically investigated in detail. It was observed that rotating cylinder parameters can be used to control the heat transfer and melting process in the cavity. For angular rotational speed of cylinder at ( ω = 7.5 ) compared to motionless cylinder ( ω = 0 ), average heat transfer enhances by about 22.50 % . The highest value of the average heat transfer for different vertical locations of the cylinder depends on the angular rotational speed of the cylinder. The average Nusselt number increases 10 % when a large cylinder is used compared to smaller one for clockwise rotation of the cylinder and it is 19.8 % for the stationary cylinder configuration.

In the current study, magnetohydrodynamics mixed convective flow of Ag–MgO/water hybrid nanofluid in a triangular shaped partitioned cavity involving a porous layer is numerically investigated by using the finite element method. In the numerical simulation, various effects of pertinent parameters such as Richardson number (between 0.01 and 100), Hartmann number (between 0 and 60), magnetic field inclination angle (between 0 and 90), Darcy number (between $$10^{-4}$$ and $$5 \times 10^{-2}$$ ), location of the vertex of triangular porous region (between 0.2 and 0.8 H) and hybrid nanoparticle solid volume fraction ( $$\phi _1$$ between 0 and 0.01, $$\phi _2$$ between 0 and 0.01) on the fluid flow and convective heat transfer features are examined. It was observed that a large vortex is established below the main vortex near the upper wall for the lowest value Ri number. At the highest magnetic field strength, multi-recirculation flow pattern is seen in the right bottom corner. The average heat transfer enhances with higher values of permeability of the porous medium, magnetic field inclination angle, distance of the porous layer vertex from the hot wall and solid nanoparticle volume fraction of each particles in the hybrid nanofluid. The impact is reverse for higher values of Richardson number and Hartmann number. In the current work, significant changes in the average Nusselt number are obtained by varying the location of the porous medium. The triangular shaped porous compound can be used as an excellent tool for convective heat transfer control.

Heat reveals during the bone drilling operations in orthopedic surgery because of friction between bone and surgical drill bit. The heating causes extremely important damages in bone and soft tissues. The heating has a critical threshold and it is known as 47∘C. If bone temperature value exceeds 47∘C, osteonecrosis occurs in bones and soft tissues. Many factors such as surgical drill bit geometry and material, drilling parameters, coolant has important roles for the temperature rise. Many methods are used to decrease the temperature rise. The most effective method among them is to use the coolant internally. Numeric simulations of a new driller system to avoid the overheating during the orthopedic operating processes were performed in this study. The numerical simulation with/without coolant was also performed using the finite element based software. Computer aided simulation studies were used to measure the bone temperatures occurred during the bone drilling processes. The outcomes from the simulations were compared with the experimental results. A good temperature level agreement between the experimental results and FEA simulations was found during the bone drilling process.

Purpose This paper aims to numerically examine the mixed convection of SiO2-water nanofluid flow in a three-dimensional (3D) cubic cavity with a conductive partition considering various shapes of the particles (spherical, cylindrical, blade, brick). The purpose is to analyze the effects of various pertinent parameters such as Richardson number (between 0.1 and 10), Hartmann number (between 0 and 10), solid nanoparticle volume fraction (between 0 and 0.04), particle shape (spherical, cylindrical, blade, brick) and different heights and lengths of the conductive partition on the fluid flow and heat transfer characteristics. Design/methodology/approach The numerical simulation was performed by using Galerkin-weighted residual finite element method for various values of Richardson number, Hartmann number, solid nanoparticle volume fraction, particle shape (spherical, cylindrical, blade, brick) and different heights and lengths of the conductive partition. Two models for the average Nusselt number were proposed for nanofluids with spherical and cylindrical particle by using multi-layer feed-forward neural networks. Findings It was observed that the average Nusselt number reduces for higher values of Richardson number and Hartmann number, while enhances for higher values of nanoparticle volume fraction. Among various types of particle shapes, blade ones perform the worst and cylindrical ones perform the best in terms of heat transfer enhancement, but this is not significant which is less than 3 per cent. The average Nusselt number deteriorates by about 6.53per cent for nanofluid at the highest volume fraction of spherical particle shapes, but it is 11.75per cent for the base fluid when Hartmann number is increased from 0 to 10. Conductive partition geometrical parameters (length and height) do not contribute to much to heat transfer process for the 3D cavity, except for the case when height of the partition reaches 0.8 times the height of the cubic cavity, the average Nusselt number value reduces by about 25per cent both for base fluid and for nanofluid when compared to case with cavity height which is 0.2 times the height of the cubic cavity. Originality/value Based on the literature survey, a 3D configuration for MHD mixed convection of nanofluid flow in a cavity with a conductive partition considering the effects of various particle shapes has never been studied in the literature. This study is a first attempt to use a conductive partition with nanofluid of various particle shapes to affect the fluid flow and heat transfer characteristics in a 3D cubic cavity under the influence of magnetic field. Partial or all findings of this study could be used for the design and optimization of realistic 3D thermal configurations that are encountered in practice and some of the applications were already mentioned above. In this study, thermal performance of the system was obtained in terms of average heat transfer coefficient along the hot surface, and it is modeled with multi-layer feed-forward neural networks.

Numerical study of natural convection and melting in a corrugated square cavity filled with CNT-water nanofluid under the influence of inclined magnetic field was performed. The left and right walls of the cavity are kept at constant temperatures while the horizontal wall is adiabatic. Galerkin weighted residual finite element was used. The effects of Hartmann number (between 0 and 40), magnetic inclination angle (between 0° and 90°), nanoparticle volume fraction (between 0 and 4%), number (between 1 and 20) and height (between 0.002 H and 0.16 H) of the corrugation on the convective heat transfer features and melting in the square cavity were examined. Magnetic field was found to dampen the fluid motion, and less movement of the melt front in the upper part of the cavity is observed. By using the CNT nanoparticles in the base fluid, significant enhancement in the heat transfer and faster propagation of the melt front is observed in the absence and presence of magnetic field. Average heat transfer enhancements are around 118% and 95% when nanofluid at the highest particle volume fraction is compared with water in the absence and presence of magnetic field. The heat transfer is reduced and melt front curve characteristics are affected when the number and height of corrugation waves are increased. © 2019, Akadémiai Kiadó, Budapest, Hungary.

Purpose The purpose of this study is to numerically analyze the convective heat transfer features for cooling of an isothermal surface with a cavity-like portion by using CuO-water nano jet. Jet impingement cooling of curved surfaces plays an important role in practical applications. As compared to flat surfaces, fluid flow and convective heat transfer features with jet impingement cooling of a curved surface becomes more complex with additional formation of the vortices and their interaction in the jet wall region. As flow separation and reattachment may appear in a wide range of thermal engineering applications such as electronic cooling, combustors and solar power, jet impingement cooling of a surface which has a geometry with potential separation regions is important from the practical point of view. Design/methodology/approach Numerical simulations were performed with a finite volume-based solver. The study was performed for various values of the Reynolds number (between 100 and 400), length of the cavity (between 5 w and 40 w), height of the cavity (between w and 5w) and solid nano-particle volume fraction (between 0 and 4 per cent). Artificial neural network modeling was used to obtain a correlation for the average Nusselt number, which can be used to obtain fast and accurate predictions. Findings It was observed that cavity geometrical parameters of the cooling surface can be adjusted to change the flow field and convective heat transfer features. When the cavity length is low, significant contribution of the inclined wall of the cavity on the average Nusselt number is achieved. As the cavity length and height increase, the average Nusselt number, respectively, reduce and slightly enhance. At the highest value of cavity height, significant changes in the convective flow features are obtained. By using nanofluids instead of water, enhancement of average heat transfer in the range of 35-46 per cent is obtained at the highest particle volume fraction. Originality/value In this study, jet impingement cooling of an isothermal surface which has a cavity-like portion was considered with nanofluids. Addition of this portion to the impingement surface has the potential to produce additional vortices which affects the fluid flow and convective features in the jet impingement heat transfer. This geometry has the forward-facing step for the wall jet region with flow separation reattachment in the region. Based on the above literature survey and to the best of the authors’ knowledge, jet impingement cooling for such a geometry has never been reported in the literature despite its importance in practical thermal engineering applications. The results of this study may be useful for design and optimization of such systems and to obtain best performance in terms of fluid flow and heat transfer characteristics.

Numerical study for the effects of an inner stationary cylinder having an elastic rod like extension on the mixed convection of CNT-water nanofluid in a three dimensional vented cavity was performed by using finite element method. Effects of various pertinent parameters such as Reynolds number (between 100 and 1000), elastic modulus of the flexible rod (between 10 5 and 10 8 ), size of the elastic rod (between 0.05H and 0.3H), size of the circular cylinder (between 0.025H and 0.25H), inclination angle of the left vertical surface of the cavity (between 0° and 30°) and CNT-nanoparticle solid volume fraction (between 0 and 4 % ) on the convective flow features in a 3D vented cavity were analyzed. It was observed that with the installation of the obstacle (cylinder + elastic rod) and changing its geometrical and other parameters (elasticity of the rod) affect the variations of established multiple re-circulation zones and isotherms with the three dimensional vented cavity. The average heat transfer rate for the left vertical surface deteriorated with higher inclination angle of the side surface of the cavity while the variations in the average heat transfer rate for the upper surface was found to be slight. Inclusion of the CNT nanoparticle results in average heat transfer enhancement which is about 60 % at the highest nanoparticle solid volume fraction and the rate of enhancement was found to be independent of obstacle geometrical parameters, elasticity of the flexible wall and side surface inclination angle of the cavity. A correlation for the average Nusselt number is obtained in polynomial form for the configurations in the presence and absence of obstacles.

In current text, we developed CVFEM code for nanomaterial hydrothermal management through a permeable compound cavity including two temperature model. Radiation and Lorentz source terms were added in formulations. Impacts of radiation parameter, Rayleigh, Hartmann number, interface heat transfer parameter and nanoparticles’ shape on nanofluid behavior were demonstrated. Contours indicate that convective mode becomes stronger with augment of buoyancy term. By increasing Nhs, conduction becomes more effective and Nusselt number reduces. As radiation term enhances, Nusselt number augments. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

International audience; The reactivity of water with Li-rich layered Li2RuO3 and partial exchange of Li2O with H2O within the structure is studied under aqueous (electro)chemical conditions. Upon slow delithiation in water over long time periods, micron-sized Li2RuO3 particles structurally transform from an O3 structure to an O1 structure with a corresponding loss of 1.25 Li ions per formula unit. The O1 stacking of the honeycomb Ru layers is imaged using high-resolution high-angle annular dark-field scanning transmission electron microscopy, and the resulting structure is solved by X-ray powder diffraction and electron diffraction. In situ X-ray absorption spectroscopy suggests that reversible oxidation/reduction of bulk Ru sites is realized on potential cycling between 0.4 and 1.25 VRHE in basic solutions. In addition to surface redox pseudocapacitance, the partially delithiated phase of Li2RuO3 shows high capacity, which can be attributed to bulk Ru redox in the structure. This work demonstrates that the interaction of aqueous electrolytes with Li-rich layered oxides can result in the formation of new phases with (electro)chemical properties that are distinct from the parent material. This understanding is important for the design of aqueous batteries, electrochemical capacitors, and chemically stable cathode materials for Li-ion batteries.

The purpose of this work is to check if additive manufacturing technologies are suitable for reproducing porous samples designed for sound absorption. The work is an inter-laboratory test, in which the production of samples and their acoustic measurements are carried out independently by different laboratories, sharing only the same geometry codes describing agreed periodic cellular designs. Different additive manufacturing technologies and equipment are used to make samples. Although most of the results obtained from measurements performed on samples with the same cellular design are very close, it is shown that some discrepancies are due to shape and surface imperfections, or microporosity, induced by the manufacturing process. The proposed periodic cellular designs can be easily reproduced and are suitable for further benchmarking of additive manufacturing techniques for rapid prototyping of acoustic materials and metamaterials. ispartof: Additive Manufacturing vol:36 status: Published online

Numerical study for mixed convection of CNT-water nanofluid flow in a branching channel with annulus at the junction and a rotating surface was performed by using finite volume method. This geometry can be used in a variety of engineering applications such as in geothermal, gas pipelines, in pharmaceutical, fuel cells and many others. The numerical simulations are performed for various values of pertinent parameters such as Richardson number, angular rotational velocity of the inner surface at the annulus junction, solid nanoparticle volume fraction and diameter of the inner rotating. It was observed that the recirculation regions established within the annulus and separated fluid zones on the walls of the branching channel near the junction are strongly influenced by the by rotation of the inner surface at the annulus. The average Nusselt number enhancements up to 64% are obtained for the nanofluid containing the highest particle volume fraction for Ri = 0.01 and Ri = 1 when the inclination angle of the lower branching channel is 45°. Finally, ANFIS modeling technique with triangular-shaped membership function and 48 fuzzy rules are used to predict the average Nusselt numbers for the hot walls of the channel and annulus part. © 2018 Elsevier Ltd

Numerical study of double jet impingement cooling of an isothermal surface with Al2O3-water nanofluid under the influence of magnetic field was performed. Galerkin-weighted residual finite element method was utilized for the solution of the governing equations. The numerical simulations were performed for various values of Reynolds number (between 100 and 400), solid particle volume fraction (between 0 and 4%), and Hartmann number (between 0 and 2.5). The ratio of the slot-to-plate distance was varied between 4 and 16 whereas ratio of the distance between the slots to slot width was varied between 5 and 22.5. It was observed that magnetic field retarded the fluid flow and reduced the local and average heat transfer. At the highest value of the Hartmann number, the fluid cannot reach the stagnation point. Depending on the distance between the slots and slots to plate distance, average heat transfer enhances by about 46% and its value increases linearly with nanoparticle volume fraction. This study is particularly important where magnetic field is present and weakens the convective heat transfer characteristics in jet impingement cooling whereas it is possible to enhance its thermal performance by utilization of nanoparticles. © 2018, © 2018 Taylor & Francis Group, LLC.

In this study, the role of magnetic field and surface corrugation on the natural convective transfer characteristics in a three dimensional, CuO-water nanofluid filled trapezoidal cavity was numerically investigated with finite element method. Influence of various pertinent parameters such as Rayleigh number (between 104 and 106), Hartmann number (between 0 and 40), number (between 0 and 16) and height (between 0 and 0.5H) of triangular wave form and solid nanoparticle volume fraction (between 0 and 0.04) on the fluid flow and thermal characteristics were analyzed. It was observed that when corrugation height and number of corrugation waves enhance, local and average heat transfer reduce. The use of CuO nanoparticles is advantageous when heat transfer is effective and for the configurations without magnetic field. 26.86% increase in the average Nusselt number is obtained when magnetic field is imposed at Hartmann number of 30 whereas 40.72% of increment in the average heat transfer is attained in the absence of magnetic field when 4% of CuO nanoparticles are added to the water. A mathematical model based on proper orthogonal decomposition and polynomial interpolation among modal coefficients is developed that could be used to reconstruct the whole flow and thermal field and perform thermal predictions for the 3D corrugated cavity. © 2018 Elsevier Ltd

In this study, mixed convection in a lid driven trapezoidal cavity filled with Al2O3–water nanofluid under the effect of an inclined magnetic field was numerically investigated for various electrical conductivity models. The top and bottom wall of the trapezoidal cavity were maintained at constant cold and hot temperatures and the top wall is moving at a constant speed in positive x direction. The governing equations are solved with finite element method. Numerical simulations were performed for different values of Richardson numbers (between 0.01 and 25), strength and orientation of the uniform magnetic field (Hartmann number (between 0 and 40), magnetic inclination angle (between 0 o and 90 o )) and solid volume fraction of the nanofluid (between 0 and 0.03) for different electrical conductivity models. It was observed that as the value of the Richardson number, strength of the magnetic field and solid particle volume fractions enhance, discrepancy between the average Nusselt number increases for systems with different electrical conductivity models. Magnetic inclination angle for which the difference between average heat transfer rate is minimized for different electrical conductivity models depends on the side wall inclination angle of the trapezoidal cavity. After performing an optimization study, it was found that the optimum value of magnetic inclination angle is dependent on the electrical conductivity model.

In this study, a numerical and experimental study was carried out to determine the effects of variables such as curvature and foam properties on the natural frequencies of the sandwich panels. Sandwich panels consist of laminated E/glass epoxy face sheets with [0 degrees/90 degrees/-45 degrees/+45 degrees] stacking sequences and PVC foam cores with AIREX C70.55, C70.90, C70.200 and C70.250. A group of sandwich panels with radii of curvature ranging from 90 to 200 mm were analysed by ANSYS software. Vibration characteristics were obtained for clamped square sandwich panels. The results indicate that the natural frequencies increase with the increasing curvature and foam density. However, the increment in the natural frequency due to an increase in the magnitude of curvature decreases with increasing foam density. The highest increase in natural frequency due to increasing foam properties is seen in the flat panels. Also, it is found that in values beyond a specific curvature; increasing of the foam properties causes reduction in the natural frequencies. (C) 2017 Elsevier Ltd. All rights reserved.

Numerical study of mixed convection in a lid-driven 3D flexible walled trapezoidal cavity with nanofluids was performed by using Galerkin weighted residual finite element method. Effects of various pertinent parameters such as Richardson number (between 0.05 and 50), elastic modulus of the side surfaces (between 1000 and 10 5 ), side wall inclination angle (between 0° and 20°) and solid particle volume fraction (between 0 and 0.04) on the fluid flow and heat transfer characteristics in a 3D lid-driven-trapezoidal cavity were numerically examined. It was observed that these characteristics are influenced when the pertinent parameters change. Flexible side surface can be used as control element for heat transfer rate. Increment and reduction in the space which are provided by the flexible side walls result in heat transfer enhancement and deterioration for side wall inclination angle of 0° and 10°. Average Nusselt number enhances by about 9.80 % when the value of the elastic modulus is increased from 1000 to 10 5 for side wall inclination angles of θ = 0°. Adding nanoparticles to the base fluid results in linear increment of heat transfer and at the highest volume fraction, 25.30 % of heat transfer enhancement is obtained. A polynomial type correlation for the average Nusselt number along the hot wall was proposed and it has a fourth order polynomial dependence upon the Richardson number and first order dependence upon the solid particle volume fraction.

The effect of comonomer on structure and relaxation of flow-induced precursors was investigated in a series of isotactic polypropylene and random propylene–ethylene copolymers. The polymers were subjected to flow by fiber pulling and allowed to relax above their nominal melting temperature for specific times. The type of morphology developed after cooling revealed whether flow-induced precursors were still present or the melt had fully re-equilibrated. Precursors were long-lived and, at fixed temperature, decayed significantly faster with higher ethylene content. The critical time for precursor relaxation followed an Arrhenius-type dependence with temperature. The apparent energy of activation for precursor dissolution decreased with increasing comonomer content, indicating that the rate-limiting step of the relaxation process becomes less difficult with higher ethylene fraction. This effect is attributed to ethylene counits acting as disruptors of precursor structure and is discussed in terms of quasi-cr...

In this study, laminar forced convection of pulsating nanofluid flow over a backward-facing step with a corrugated bottom wall was numerically examined by using finite volume method. Part of the bottom wall downstream of the step was corrugated and kept at constant temperature. Effects of Reynolds number, length and height of the surface corrugation wave, nanoparticle volume fraction, amplitude and frequency of flow pulsation on the fluid flow and heat transfer were numerically investigated. It was observed that average Nusselt number enhances as the Reynolds number, length and height of the corrugation wave increase. Average Nusselt number versus Strouhal number shows a resonant type behavior and flow pulsation amplitude increment results in heat transfer enhancement. Average heat transfer rate increases with the inclusion of the nanoparticles but the rate of enhancement depends on the nanoparticle solid volume fraction interval. An efficient computational strategy for the thermal performance prediction of the system was developed by using proper orthogonal decomposition and artificial neural networks. © 2017 Elsevier Ltd

Heat transfer aspects of a typical flat-plate solar collector utilizing water-based nanofluids as the working fluid were analyzed numerically. Water-based nanofluids of various compositions containing metallic Al2O3 and Cu nanoparticles with volume fractions ranging from 1% to 5% were examined, and the effects of the nanofluids on the heat transfer were quantified. Relevant parameters such as the heat flux, Reynolds number, and the collector tilt angle were calculated and compared to each other at different boundary conditions. The flat-plate solar collector geometry was simplified, and only a fluid carrying pipe with an absorber surface was chosen as a numerical model with a particular at ention to symmetry, instead of taking the entire collector geometry. The numerical model was controlled and confirmed by applying it to similar studies existing in the pertinent literature. All numerical solutions were carried out by using a commercial finite volumes of ware package called ANSYS Fluent. The results show that the nanofluids increase the heat transfer rate ranging from 1% to 8%, when compared to water as a working fluid. © 2017 by Begell House, Inc.

The photovoltaic panels are one of the most efficient energy systems that generate electricity by absorbing the solar radiation. Nevertheless, when the sun's rays are converted to electricity, a high amount of waste heat is generated. Therefore, the efficiency of photovoltaic (PV) panels needs to be studied to minimize the amount of waste heat. There is a non-linear relationship between the temperature, the current and the voltage values produced by the PV panels. In the present study, the performance of 75 W PV panels with polycrystalline cell structure under Elazig, Turkey climatic conditions were experimentally investigated. The system performances such as temperature, power and efficiencies were analyzed by applying different fin parameters (length, sequences) to PV panels. The aluminum fins were applied with 10 different configurations as given by A1-A10. The cell temperatures, output powers, power loss ratios and energy-exergy efficiencies were calculated based on measurements of the experimental study. It was observed that the temperature did not distributed homogeneously on the PV panel. In terms of the efficiency, the fins are designed as staggered array and the 7 cm × 20 cm dimensions showed the best results. The highest energy and exergy efficiencies values of the finned panels (A5) were calculated as 11.55%, and 10.91%, respectively.

International audience; Energy is vital to the profitable growth of every nation and to stimulate new research. Only natural resources can meet the growing energy demand in recent years, biodiesel has become very interested in the energy as well as environmental advantages that it can be combined with mineral diesel fuel in any quantity. The research focuses on the study of the replacement of diesel with a safflower methyl ester. The engine tests shall be performed using the safflower methyl ester as fuel in the DI diesel engine. The combustion, emission and performance characteristics were studied using alternative fuels and mixtures. SAfflower Methyl Ester 80% (SAME80) and SAME100 have high heat release rates. Nitrogen oxides were higher by about 50%, carbon monoxide decreased by 10%, unburnt hydrocarbon was slightly higher and the thermal efficiency was higher for the SAME than for diesel fuel.

WOS:000384779300059; International audience; This paper illustrates the morphing of flow architecture toward greater performance in a counterflow heat exchanger. The architecture consists of two plenums with a core of counterflow channels between them. Each stream enters one plenum and then flows in a channel that travels the core and crosses the second plenum. The volume of the heat exchanger is fixed while the volume fraction occupied by each plenum is variable. Performance is driven by two objectives, simultaneously: low flow resistance and low thermal resistance. The analytical and numerical results show that the overall flow resistance is the lowest when the core is absent, and each plenum occupies half of the available volume and is oriented in counterflow with the other plenum. In this configuration, the thermal resistance also reaches its lowest value. These conclusions hold for fully developed laminar flow and turbulent flow through the core. The curve for effectiveness vs number of heat transfer units (N-tu) is steeper (when N-tu \textless 1) than the classical curves for counterflow and crossflow. (C) 2016 Elsevier Ltd. All rights reserved.

This article contains the experimental investigations of different cooling methods used for photovoltaic (PV) panels. Phase change material (PCM), thermoelectric (TE) and aluminum fins were chosen as the cooling methods. The CaCl2·6H2O is chosen as one of the PCM which is widely used in the cooling of PVs and the other is the PCM with melting temperature above the surface temperature of the PV panel. By using TE material in different numbers (6, 8 and 12) and aluminum fins in different layouts, surface temperatures and output powers of PV panels were compared. It is observed that the PCM which is not chosen appropriately has insulation feature in the PV panel and enhances the temperature of the panel and decreases the output power. When the most successful cooling methods were tested under the same environmental conditions, PV with fin system produced the highest power generation of 47.88 W while PV with PCM and TEM produced the lowest power generation of 44.26 W. © 2020 Elsevier Ltd

In the present study, laminar forced convective nanofluid flow over a backward-facing step was numerically investigated. The bottom wall downstream of the step was flexible, and finite element method was used to solve the governing equations. The numerical simulation was performed for a range of Reynolds number (between 25 and 250), elastic modulus of the flexible wall (between 104 and 106), and solid particle volume fraction (between 0 and 0.035). It was observed that the flexibility of the bottom wall results in the variation of the fluid flow and heat transfer characteristics for the backward-facing step problem. As the value of Reynolds number and solid particle volume fraction enhances, local and average heat transfer rates increase. At the highest value of Reynolds number, heat transfer rate is higher for the case with the wall having lowest value of elastic modulus whereas the situation is reversed for other value of Reynolds number. Average Nusselt number reduces by about 9.21% and increases by about 6.1% for the flexible wall with the lowest elastic modulus as compared to a rigid bottom wall for Reynolds number of 25 and 250. Adding nano-additives to the base fluid results in higher heat transfer enhancements. Average heat transfer rates enhance by about 35.72% and 35.32% at the highest solid particle volume fraction as compared to nanofluid with solid volume fraction of 0.01 for the case with wall at the lowest and highest elastic modulus. A polynomial type correlation for the average Nusselt number along the flexible hot wall was proposed, which is dependent on the elastic modulus and solid particle volume fraction. The results of this study are useful for many thermal engineering problems where flow separation and reattachment coupled with heat transfer occur. Control of convective heat transfer for such configurations with wall flexibility and nanoparticle inclusion to the base fluid was aimed in this study to find the effects of various pertinent parameters for heat transfer enhancement.

We characterize the transient response of semi-dilute wormlike micellar solutions under an imposed steady shear flow in a cone-plate geometry. By combining conventional rheometry with 2-D Particle Image Velocimetry (PIV), we can simultaneously correlate the temporal stress response with time-resolved velocimetric measurements. By imposing a well defined shear history protocol, consisting of a stepped shear flow sweep, we explore both the linear and nonlinear responses of two surfactant solutions: cetylpiridinium chloride (CPyCl) and sodium salicylate (NaSal) mixtures at concentrations of [66:40] mM and [100:60] mM, respectively. The transient stress signal of the more dilute solution relaxes to its equilibrium value very fast and the corresponding velocity profiles remain linear, even in the strongly shear-thinning regime. The more concentrated solution also exhibits linear velocity profiles at small shear rates. At large enough shear rates, typically larger than the inverse of the relaxation time of the fluid, the flow field reorganizes giving rise to strongly shear-banded velocity profiles. These are composed of an odd number of shear bands with low-shear-rate bands adjacent to both gap boundaries. In the non-linear regime long transients (much longer than the relaxation time of the fluid) are observed in the transient stress response before the fluid reaches a final, fully-developed state. The temporal evolution in the shear stress can be correlated with the spatiotemporal dynamics of the multiple shear-banded structure measured using RheoPIV. In particular our experiments show the onset of elastic instabilities in the flow which are characterized by the presence of multiple shear bands that evolve and rearrange in time resulting in a slow increase in the average torque acting on the rotating fixture.

14th International Symposium on Solid Oxide Fuel Cells, SOFC 2015; held as part of the Electrochemical Society, ECS Conference on Electrochemical Energy Conversion and Storage -- 26 July 2015 through 31 July 2015 -- -- 113202, Solid oxide fuel cells (SOFCs) operate at high temperatures and produce electricity and heat energy from fuels in an electrochemical way. Membrane electrode assembly (MEA) composed of a dense electrolyte coated with two porous electrodes on each side is generally constructed on the electrolyte. However, high operation temperatures are required to obtain acceptable performance values due to high electrolyte resistance as a result of the use of thick electrolyte layer as a mechanical support for MEA. Alternatively, the cells can be fabricated as anode-supported where the anode is responsible for supporting the cell mechanically. By doing so, the operation temperature can be lowered due to reduced electrolyte thickness. In this study, the effects of isostatic press parameters i.e. temperature and pressure for NiO/YSZ anode support on the anode-supported cell performance and the microstructure of the anode support are investigated. The experimental results reveal that the cell performance is strongly influenced by the pressing parameters. In this aspect, the optimum pressing temperature and pressure are found to be 50°C and 40 MPa, respectively. © The Electrochemical Society.

WOS:000350080000074; International audience; Here we document the effect of flow configuration on the heat transfer performance of a helically shaped pipe embedded in a cylindrical conducting volume. The helix is wrapped on an imaginary cylinder. Several configurations of helices with fixed volume of fluid are considered. We found the optimal spacings between the helical turns such that the volumetric heat transfer rate is maximal. Next, we extended the study by varying the volume (length) of the embedded pipe. We found that the optimized features of the heat transfer architecture are robust with respect to changes in several physical parameters. We compared the performance for both helical 3D and 20 designs. We found that the 2D designs offer greater heat transfer density than the 3D designs. (C) 2014 Elsevier Ltd. All rights reserved.

Induced uncertainties during the filament winding process may cause a significant stochastic variation in the mechanical behaviour of composite shells. This paper aims to develop a novel and deep uncertainty quantification (UQ), sensitivity and reliability analyses of filament wound shells considering manufacturing uncertainties. Firstly, a progressive damage analysis is performed to estimate their deterministic burst pressure. Then, a signal-to-noise (SNR) approach is employed using the Taguchi method for sensitivity analysis and screening uncertainties arising from manufacturing. Initial results reveal that the shells are more sensitive to thickness uncertainties for thinner structures. Then, probabilistic and reliability analyses are carried out using the Boosted Decision Trees Regression (BDTR) approach from machine learning algorithms. Despite the complexity and non-linear relationships in the problem, the developed BDTR-based metamodel shows powerful predictive performance. A comparative study shows that ply thickness uncertainty leads to a significant underestimation of failure probability. For expensive and time-consuming models in that only a few runs can be affordable, a modified approximation method for reliability analysis is proposed. Results indicate a high capability at estimating failure probability with high accuracy.

openaire: EC/H2020/723246/EU//RAMSSES Funding Information: Open Access funding provided by Aalto University. This research was funded by Aalto University, Meyer Turku Oy, and the RAMSSES project (funded by the European Union’s Horizon 2020, grant agreement No. 723246), and the CaNeLis project (funded by the Business Finland, grant No. 3409/31/2022). The financial support is gratefully acknowledged. Publisher Copyright: © 2023, The Author(s). Thisresearch studies the influence of local weld notch parameters on fatigue crack initiation sites in laser-hybrid butt welds, utilizing high-resolution 3D scans and fatigue tests to failure. The suitability of different local geometric weld notch parameters for fatigue strength characterization is investigated, and the current challenges associated with their measurements are highlighted. The weld notch shapes were found to fluctuate significantly, resulting in considerable variation in notch parameters over short intervals. Undercut depth was found to determine the critical location for crack initiation. There were several instances where the fatigue crack initiated from notches with large radii despite the presence of sharper notches, contrary to what is expected on the basis of previous investigations. The results of the present study indicate that the undercut depth is a suitable fatigue strength indicator for high-quality laser-MAG hybrid welds, overcoming the practical limitations of notch radius measurement.

This study aimed to investigate the effect of different activations on the properties of bio-based activated carbons (BACs) for water treatment. BACs were produced via pyrolysis by the carbonization stage and were followed by four different activation procedures. Chemical activation included the introduction of metal oxides or alkali on the structure of the sawdust-derived BACs, resulting in iron-activated carbon (BAC-Fe), copper-activated carbon (BAC-Cu), and sodium-activated carbon (BAC-Na). The physical activation was conducted in a CO2 environment with the usage of two types of locally available biomasses, resulting in husk-activated carbon (HAC) and wood-activated carbon (WAC). Depending on the activation, BACs can be developed with high porosity, active sites, and different additional functionalities such as antimicrobial and magnetic. The adsorption of natural organic matter (NOM) with chemically activated BACs yielded high removal percentages (97, 87, and 80% for BAC-Fe, BAC-Cu, and BAC-Na, respectively). The physically activated BACs demonstrated high adsorption capacities for dye – 278 mg/g for WAC and 213 mg/g for HAC. This outlines a wide range of BAC production possibilities with advanced functionalities.

The impacts of Cr-TiB2 addition on densification, hardness, microstructure, phase transformation, and corrosion were examined. The results indicated an even and uniform dispersion of TiB2 particles in the titanium matrix, with no noticeable interfaces throughout the sintering process. The relative density of the sintered titanium-based composites dropped, with an increase in TiB2 percentage. The microhardness result indicated that Ti6Al4V has 326 HV0.5, while the maximum hardness was 598 HV0.5, produced from 20 wt.% TiB2 ceramic particles. The Ti6Al4V alloy depicts α-phase forms parallel plates in the prior β-grain borders and expands into the β-grain to create α-colonies, while the addition of 5–20 wt.% Cr-TiB2 resulted in a microstructural transformation characterized by equiaxed α-precipitates embedded within the β-phase matrix, for all samples. The electrochemical behaviour revealed that the Ecorr decreased as TiB2 increased, while the icorr was higher. However, samples containing 5Cr and 5Cr-5TiB2 moved to a more positive Ecorr region, whereas the icorr altered to a more negative area. This meant that the presence of ceramic reinforcements increased the corrosion resistance of the alloys and that higher concentrations of titanium diboride provided less protection against ion attack in a chloride environment.

International audience; This work aims at a better understanding and modeling of the failure of carbonitrided pinions made out of 20MnB5 steel. Carbonitriding is a thermochemical treatment inducing high surface hardness while preserving significant core ductility. This results in graded microstructure and properties which makes the prediction of failure particularly complex: brittle external layer, ductile core material. A test bench was specifically designed to load one tooth of the studied pinions with a lateral force until complete failure. In situ observations were performed and the load-displacement curve recorded, showing a variety of behaviors as a function of the teeth engagement depth. The presence of the carbonitrided layer induces only a slight force and toughness increase. The main failure mechanism comes from shear failure of the ductile core material which will therefore be studied in this paper. Experimental tests with various stress states were conducted to measure plastic properties as well as to calibrate fracture criteria for the core steel. Von Mises plasticity and a simple strain hardening curve fit very well all these experiments. As fracture criteria from the literature were unable to predict failure correctly for all the mechanical tests, an adapted criterion has therefore been proposed as an outcome of this extensive mechanical testing campaign. Fracture simulations in LS Dyna were performed using the element erosion technique, the limitations of which are discussed. Comparison with the experimental tooth fracture allows evaluation of the proposed failure criteria, and enables to highlight and discuss the present limits of the simulation. Abstract This work aims at a better understanding and modeling of the failure of carbonitrided pinions made out of 20MnB5 steel. Carbonitriding is a thermochemical treatment inducing high surface hardness while preserving significant core ductility. This results in graded microstructure and properties which makes the prediction of failure particularly complex: brittle external layer, ductile core material. A test bench was specifically designed to load one tooth of the studied pinions with a lateral force until complete failure. In situ observations were performed and the load-displacement curve recorded, showing a variety of behaviors as a function of the teeth engagement depth. The presence of the carbonitrided layer induces only a slight force and toughness increase. The main failure mechanism comes from shear failure of the ductile core material which will therefore be studied in this paper. Experimental tests with various stress states were conducted to measure plastic properties as well as to calibrate fracture criteria for the core steel. Von Mises plasticity and a simple strain hardening curve fit very well all these experiments. As fracture criteria from the literature were unable to predict failure correctly for all the mechanical tests, an adapted criterion has therefore been proposed as an outcome of this extensive mechanical testing campaign. Fracture simulations in LS Dyna were performed using the element erosion technique, the limitations of which are discussed. Comparison with the experimental tooth fracture allows evaluation of the proposed failure criteria, and enables to highlight and discuss the present limits of the simulation.

Date of Conference: 11–13 October 2017 Conference Name: ASME 2017 Dynamic Systems and Control Conference, DSCC 2017 The paper presents an approach to the Model Reference Adaptive Control (MRAC) design for nonlinear dynamical systems. A nonlinear reference system is considered such that its response is designed to be stable via Successive Approximation Approach (SAA). Having designed the stable reference model through the SAA, MRAC is then formulated for nonlinear plant dynamics with a new adaptation rule to guarantee the convergence of the nonlinear plant response to that of the response of the nonlinear reference model. The proposed design methodology is illustrated with examples for different case studies.

International audience; There is growing interest in superconducting machinery design in AC regime such as generators, motors, and magnets. High-temperature superconductors are used as tapes or cables for the machine windings. Therefore, AC losses have to be evaluated efficiently for an optimal design. Moreover, non-linearities, arising from the power law characterizing the electrical behaviour of superconductor, have to be also dealt with. The development of efficient numerical methods is therefore critical to model high-temperature superconductors. Although numerous methods have already been proposed, the finite element method applied on the time-dependent curl-curl–based H-formulation remains the mostly used. It uses edge elements of Nedelec to naturally ensure the continuity of the tangential components of H. To take into account non-linearities from superconductors, a linearisation of the superconductors constitutive power law E=ρ(J)J was implemented. Discontinuous Galerkin finite element method provides an interesting alternative to edge elements for the time-dependent H-formulation. Indeed, the curl-curl operator is written as a div operator and the interior penalty approach defines numerical fluxes at the interfaces. Those fluxes will ensure the continuity of the tangential components of H. The resistivity ρ(J) is explicitly evaluated at the previous iteration with such an approach leading to convergence. In this paper, both numerical approaches implementation will be presented. We will also compare the numerical results from those methods applied to 3D modelling of simple superconducting geometries in AC regime.

Numerical study of jet impingement cooling of a corrugated surface with water–SiO2 nanofluid of different nanoparticle shapes was performed. The bottom wall is corrugated and kept at constant surface temperature, while the jet emerges from a rectangular slot with cold uniform temperature. The finite volume method is utilized to solve the governing equations. The effects of Reynolds number (between 100 and 500), corrugation amplitude (between 0 and 0.3), corrugation frequency (between 0 and 20), nanoparticle volume fraction (between 0 and 0.04), and nanoparticle shapes (spherical, blade, brick, and cylindrical) on the fluid flow and heat transfer characteristics were studied. Stagnation point and average Nusselt number enhance with Reynolds number and solid particle volume fraction for both flat and corrugated surface configurations. An optimal value for the corrugation amplitude and frequency was found to maximize the average heat transfer at the highest value of Reynolds number. Among various nanoparticle shapes, cylindrical ones perform the best heat transfer characteristics in terms of stagnation and average Nusselt number values. At the highest solid volume concentration of the nanoparticles, heat transfer values are higher for a corrugated surface when compared to a flat surface case.

SUMMARY The method of weighted residuals can efficiently enforce time-periodic solutions of flexible structures experiencing unilateral contact. The harmonic balance method (HBM) based on Fourier expansion of the sought solution is a common formulation, although wavelet bases that can sparsely define nonsmooth solutions may be superior. This hypothesis is investigated using a full three-dimensional blade with unilateral contact conditions on a set of Nc discrete contact points located at its tip. The unilateral contact conditions are first regularized, and a distributional formulation in time is introduced, allowing L2(S1)N trial functions to properly approximate in the time domain the solution to the governing equations. The mixed wavelet Petrov–Galerkin solutions are found to yield consistent or better results than HBM, with higher convergence rates and seemingly more accurate contact force prediction. Copyright © 2014 John Wiley & Sons, Ltd.

15th International Conference on Metal Forming 2014 -- 21 September 2014 through 24 September 2014 -- -- 110734, For the process modeling, material properties such as anisotropy values at different orientation are very important. The most commonly used method for the determining of the anisotropy values is the tensile test that is performed for samples are prepared at different orientation. Besides the tensile test, the anisotropy parameters of TRIP 800 steel are measured with the hole-expansion test. The effects of the test methods on the yield surfaces are determined for using two different anisotropic yield criteria are Hill-48 and Barlat-89. Results illustrated that a significant difference is observed in the yield surfaces for the two test methods. The material under biaxial deformation is deformed plastically faster than the uniaxial deformation mode. © (2014) Trans Tech Publications, Switzerland.

Kolmogorov's first similarity hypothesis (or KSH1) stipulates that two-point statistics have a universal form which depends on two parameters, the kinematic viscosity ν and the mean energy dissipation rate ⟨e⟩. KSH1 is underpinned by two assumptions: the Reynolds number is very large and local isotropy holds. To disentangle the intricacies of these two requirements, we assess the validity of KSH1 in a flow where local isotropy is a priori tenable, i.e. decaying grid turbulence. The main question we address is how large should the Reynolds number be for KSH1 to be valid over a range of scales wider than, say, five Kolmogorov scales. To this end, direct numerical simulations based on the lattice Boltzmann method are carried out in low Reynolds number grid turbulence. The results show that when the Taylor microscale Reynolds number Rλ drops below about 20, the Kolmogorov normalised spectra deviate from those at higher Rλ; the deviation increases with decreasing Rλ. It is shown that at Rλ ≃ 20, the contributi...

International audience; The present work proposes a Chebyshev-collocation Fourier-Galerkin pseudospectral method for simulating unsteady, three-dimensional, fluid flows in cylindrical geometries with pressure-driven flow through permeable boundaries. Such systems occur in diverse applications and are challenging to simulate due to an additional velocity-pressure coupling on the permeable walls through Darcy's law. The present work extends the projection method of Raspo et al. (2002) to assure Darcy's law is satisfied exactly. A multidomain solver allows the efficient treatment of open boundary conditions that necessitate permeability buffers and a sponge layer. The method is spectrally convergent, and we demonstrate that pressure-prediction is necessary to obtain second-order temporal accuracy. The ability of the method to simulate complicated physical systems is demonstrated by simulating subcritical and supercritical flows in rotating filtration in Taylor-Couette cells. For subcritical cases, numerical results show excellent agreement with analytical solutions. For supercritical cases, the numerical method accurately resolves convectively and absolutely unstable flows with traveling toroidal and helical vortical structures that are in good agreement with a local linear stability analysis and experimental observations.

In this study, mixed convective flow of nanofluid in an inclined L-shaped cavity which has elastic walls is numerically analyzed under the effects of internal heat generation and magnetic field by using the finite element technique with the Arbitrary-Lagrangian–Eulerian method. Simulations are performed for different values Richardson number (between 0.03 and 30), inclination angle of the cavity (between 0°and 180°), Hartmann number (between 0 and 50), orientation angle of the magnetic field (between 0°and 90°), internal Rayleigh number (between 1 0 4 and 1 0 6 ), solid nanoparticle volume fraction (between 0 and 0.04), flexible wall elastic modulus (between 1 0 4 and 1 0 8 ) and aspect ratio (between 0.2 and 0.7) of the L-shaped cavity. It was observed that the effects of elastic wall on the convective heat transfer features are significant for the lowest value of Richardson number and lowest values of elastic modulus while 11% of discrepancy is obtained in the average Nusselt number when cavity with elastic and rigid walls is compared. The impact of the magnetic inclination angle is significant when compared to magnetic field strength for the variation of the average Nusselt number. Cavity inclination angle has significant impacts on the variation of the average Nusselt number for water and nanofluid. A higher size of the cold wall (aspect ratio) increases the heat transfer rate while the internal Rayleigh number reduces it. Enhancement in the average Nusselt number is about 15%–19% at highest nanoparticle volume fraction of the nanofluid while the trends in the convective heat transfer features with respect to changes in the pertinent parameters are similar for water and nanofluid.

This research reports on the microstructural characterization and nanomechanical evaluation of hybrid aluminium-based composite, fabricated by reinforcing pure aluminium matrix with zirconia (ZrO2) and ferrotitanium (TiFe) particles. The composites were consolidated using the spark plasma sintering technique, and the properties of the reinforced composites were examined and compared with pure aluminium samples fabricated using the same sintering parameters. The formation of new phases in the hybrid composites was ascertained using the X-ray diffraction technique, while the morphologies of the starting powders and as-sintered specimens were analysed using optical and scanning electron microscopes. Mechanical tests such as Vickers microhardness and frictional coefficient were determined to ascertain the respective strength and tribological performance. Nanoindentation test was also carried out to evaluate the nanomechanical properties such as penetration depth, elastic modulus, work indentation, and indentation creep. The results from this study revealed that mixing and sintering the admixed powders at sufficiently high temperature resulted in the formation of new phases which contributed to improved mechanical performance of the hybrid composites. The absence of pinning effect in loading and unloading curves from the nanoindentation test conducted confirmed the homogeneous dispersion of the reinforcement particles. Overall, the sample reinforced with 5% TiFe and 5% ZrO2 exhibited the most improved mechanical properties, while the unreinforced aluminium sample recorded the least mechanical and nanomechanical performance.

Microelectromechanical systems accelerometers have opened new possibilities for vibration monitoring of a rotating machinery. They enable mounting accelerometers directly to the rotating component of the machine, e.g., shaft. This enables not only the measurement of a lateral vibration but also a torsional vibration of the machine. This increases the vibration data gathered from the machine by one measurement instrument. This article presents an on-shaft wireless universal measurement unit (UMU) with innovative combination of features, such as a high measurement range and easy mounting. The UMU has a two-sensor configuration where two accelerometers are mounted to the opposite sides of a shaft. This enables to utilize a novel signal processing method to separate torsional and lateral vibration from the data. The signal processing method combines and modifies methods presented in the published literature. The results presented in this article demonstrate that the UMU together with the presented signal processing method can measure frequencies of torsional and lateral vibration accurately. However, the amplitude comparison between the UMU and reference sensors cannot be done adequately because they are measuring either different components of the machine or different physical properties.

Funding Information: This research was supported by the Academy of Finland (343192), Business Finland (HeatStock project), and Technology Industries of Finland Centennial Foundation and Jane and Aatos Erkko Foundation (Future Makers 2019 Program). The research used characterization equipment in OtaNano Nanomicroscopy Center (NMC). The authors wish to acknowledge M.Sc. Irina Annenkova for her contribution in DSC measurements and material preparation. Publisher Copyright: © 2022 The Authors. Published by American Chemical Society. A new cold crystallizing material (NaPP) is analyzed for long-term thermal energy storage (TES). NaPP comprises a mixture of erythritol and mannitol as the binary phase change material (PCM) in the scaffold of polyvinyl alcohol (PVA) cross-linked with sodium citrate (SC). The material demonstrates a unique behavior of stable supercooling and vitrification during cooling and cold crystallization during subsequent heating, which enables a reliable long-term storage of the melting enthalpy and a controllable heat release. The use of several components in the material composition, however, impedes optimization of the thermal properties for the storage. As such, differential scanning calorimetry (DSC) was applied to expose the effect of the material components on the thermal properties, and the mixture experimental methodology (MEM) was used to model and optimize these properties. Successful modeling yielded a linear response for the thermal performance, which was significantly affected by the content of SC. Increasing the amount of SC (from 0 to 18 wt %) elevated the ionic strength of the system, which caused reduction in the amount of active PCM (confirmed by X-ray diffraction and DSC) and coarsening of the surface morphology (revealed by optical and scanning electron microscopies). This was also manifested as gradual disappearance of cold crystallization which limits the use of the material to compositions with the glass-transition temperature below -15 °C. MEM identified the optimal composition as 88.9 wt % PCM and 11.1 wt % SC, which showed a melting enthalpy of 194 J/g at 105 °C. Yet, the composition comprising 80 wt % PCM, 10 wt % PVA, and 10 wt % SC showed both high melting enthalpy (176 J/g) and shape stability facilitating larger scale applications. These compositions demonstrated a temperature increase of 10-20 °C during cold crystallization of a 10 g sample, confirming the suitability of the optimization model and the operation of the new material for long-term TES.

International audience; Dynamic mode decomposition (DMD) has been applied to the wake of a NREL-5MW wind turbine, to characterize the most dynamically relevant coherent structures characterizing this flow. The decomposition has been applied on a snapshot dataset obtained by Large-Eddy Simulation of the flow impinging on the wind turbine, whose tower and nacelle are modeled by the immersed boundary method, whereas rotor blades are modeled using the actuator line method. The Sparsity-Promoting DMD algorithm allows one to select a limited number of dynamic modes optimally reconstructing the snapshot sequence. Among the largest-amplitude selected modes, we found the tip vortices, oscillating at an angular frequency equal to three times the rotational frequency of the turbine. Interestingly, the remaining selected modes are characterized by low frequencies and large-scale spatial structures, reaching the frequency range of the wake meandering. This small set of dynamic modes is highly relevant for the formulation of reduced-order models.

This study explores various uses of engineering as a tool for solving problems and improving the quality of life. The experiments in the article show that competitive athletes swim with their fingers spread slightly, because this configuration generates greater speed, the research being based on a principle known as constructional law. The constructional law has been applied to predict all the key features of the design of animal locomotion, which includes human running and swimming. In engineering, the discovery expands a domain of constructal-design results that has been growing fast. Bodies that generate heat volumetrically are endowed with maximum heat transfer density when the spacing between the solid surfaces internal to the volume have certain sizes that are smaller in forced convection than in natural convection. The volumetric cooling of future electronics, avionics, and self-cooling materials rests on this class of constructal designs. The swimming with spread fingers is the corresponding design of a body for maximum momentum transfer density.