585 research outputs found
Transient Thermal Stresses in FG Porous Rotating Truncated Cones Reinforced by Graphene Platelets
Full text linkThe present work studies an axisymmetric rotating truncated cone made of functionally graded (FG) porous materials reinforced by graphene platelets (GPLs) under a thermal loading. The problem is tackled theoretically based on a classical linear thermoelasticity approach. The truncated cone consists of a layered material with a uniform or non-uniform dispersion of GPLs in a metal matrix with open-cell internal pores, whose effective properties are determined according to the extended rule of mixture and modified Halpin–Tsai model. A graded finite element method (FEM) based on Rayleigh–Ritz energy formulation and Crank–Nicolson algorithm is here applied to solve the problem both in time and space domain. The thermo-mechanical response is checked for different porosity distributions (uniform and functionally graded), together with different types of GPL patterns across the cone thickness. A parametric study is performed to analyze the effect of porosity coefficients, weight fractions of GPL, semi-vertex angles of cone, and circular velocity, on the thermal, kinematic, and stress response of the structural member
Three-Dimensional Buckling Analysis of Functionally Graded Saturated Porous Rectangular Plates under Combined Loading Conditions
Full text linkThe present work studies the buckling behavior of functionally graded (FG) porous rectangular plates subjected to different loading conditions. Three different porosity distributions are assumed throughout the thickness, namely, a nonlinear symmetric, a nonlinear asymmetric and a uniform distribution. A novel approach is proposed here based on a combination of the generalized differential quadrature (GDQ) method and finite elements (FEs), labeled here as the FE-GDQ method, while assuming a Biot’s constitutive law in lieu of the classical elasticity relations. A parametric study is performed systematically to study the sensitivity of the buckling response of porous structures, to different input parameters, such as the aspect ratio, porosity and Skempton coefficients, along with different boundary conditions (BCs) and porosity distributions, with promising and useful conclusions for design purposes of many engineering structural porous member
Editorial
No full textCorresponding Author: Masoud Mirzaei
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Single-molecule magnets within polyoxometalate-based frameworks
No full textTwo polyoxometalate-based frameworks containing holmium and terbium are synthesized. Their single-molecule magnet (SMM) properties are investigated, where weak field-induced SMM behaviour is observed at low temperatures in dynamic magnetic studies.As an extension of our interest in polyoxometalates (POMs) and lanthanoids, we report the design and synthesis of two polyoxometalate-based frameworks under hydrothermal conditions; [Ho 4 (PDA) 4 (H 2 O) 11 ][(SiO 4 )@W 12 O 36 ]·8H 2 O (1) and [Tb 4 (PDA) 4 (H 2 O) 12 ][(SiO 4 )@W 12 O 36 ]·4H 2 O (2) (H 2 PDA = 1,10-phenanthroline-2,9-dicarboxylic acid). Both hybrids have been characterized by elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and powder/single-crystal X-ray diffraction. According to the structural analysis, 1 and 2 consist of 2D-cationic coordination polymers based on the respective lanthanoids and PDA 2− as well as Keggin anions that reside in the interspaces between two adjacent layers as discrete counterions connected by extensive hydrogen bonding. Although the overall structures of 1 and 2 are composed of cationic and anionic layers, there are many differences in the cationic layers such as various coordination modes of PDA 2− , different void shapes, and the existence of dinuclear Tb( iii ) units only in 2. Frameworks 1 and 2 were further characterized by dc and ac magnetic measurements and both exhibit slow relaxation of magnetization at low temperatures under an applied dc field. Their single-molecule magnet (SMM) properties are investigated, where weak field-induced SMM behaviour is observed at low temperatures in dynamic magnetic studies.Two polyoxometalate-based frameworks containing holmium and terbium are synthesized. Their single-molecule magnet (SMM) properties are investigated, where weak field-induced SMM behaviour is observed at low temperatures in dynamic magnetic studies.As an extension of our interest in polyoxometalates (POMs) and lanthanoids, we report the design and synthesis of two polyoxometalate-based frameworks under hydrothermal conditions; [Ho 4 (PDA) 4 (H 2 O) 11 ][(SiO 4 )@W 12 O 36 ]·8H 2 O (1) and [Tb 4 (PDA) 4 (H 2 O) 12 ][(SiO 4 )@W 12 O 36 ]·4H 2 O (2) (H 2 PDA = 1,10-phenanthroline-2,9-dicarboxylic acid). Both hybrids have been characterized by elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and powder/single-crystal X-ray diffraction. According to the structural analysis, 1 and 2 consist of 2D-cationic coordination polymers based on the respective lanthanoids and PDA 2− as well as Keggin anions that reside in the interspaces between two adjacent layers as discrete counterions connected by extensive hydrogen bonding. Although the overall structures of 1 and 2 are composed of cationic and anionic layers, there are many differences in the cationic layers such as various coordination modes of PDA 2− , different void shapes, and the existence of dinuclear Tb( iii ) units only in 2. Frameworks 1 and 2 were further characterized by dc and ac magnetic measurements and both exhibit slow relaxation of magnetization at low temperatures under an applied dc field. Their single-molecule magnet (SMM) properties are investigated, where weak field-induced SMM behaviour is observed at low temperatures in dynamic magnetic studies
Free Vibration Analysis of Thick Annular Functionally Graded Plate Integrated with Piezo-Magneto-Electro-Elastic Layers in a Hygrothermal Environment
Full text linkThe present work aims at investigating the hygrothermal effect on the natural frequencies of functionally graded (FG) annular plates integrated with piezo-magneto-electro-elastic layers resting on a Pasternak elastic foundation. The formulation is based on a layer-wise (LW) theory, where the Hamiltonian principle is used to obtain the governing equation of the problem involving temperature- and moisture-dependent material properties. The differential quadrature method (DQM) is applied here as a numerical strategy to solve the governing equations for different boundary conditions. The material properties of FG annular plates are varied along the thickness based on a power law function. The accuracy of the proposed method is, first, validated for a limit-case example. A sensitivity study of the free vibration response is, thus, performed for different input parameters, such as temperature and moisture variations, elastic foundation, boundary conditions, electric and magnetic potential of piezo-magneto-electro-elastic layers and geometrical ratios, with useful insights from a design standpoint
Multiscale Wavelet and Upscaling-Downscaling for Reservoir Simulation
Full text linkThe unfortunate case of hydrocarbon reservoirs being often too large and filled with
uncertain details in a large range of scales has been the main reason for developments of
upscaling methods to overcome computational expenses. In this field lots of approaches
have been suggested, amongst which the wavelets application has come to our attention.
The wavelets have a mathematically multiscalar nature which is a desirable property
for the reservoir upscaling purposes. While such a property has been previously used
in permeability upscaling, a more recent approach uses the wavelets in an operator-coarsening-
based upscaling approach. We are interested in enhancing the efficiency in
implementation of the second approach. the performance of an wavelet-based operator
coarsening is compared with several other upscaling methods such as the group
renormalization, the pressure solver and local-global upscaling methods.
An issue with upscaling, indifferent to the choice of the method, is encountered while
the saturation is obtained at coarse scale. Due to the scale discrepancy the saturation profiles are too much averaged out, leading to unreliable production curves. An idea is
to downscale the results of upscaling (that is to keep the computational benefit of the
pressure equation upscaling) and solve the saturation at the original un-upscaled scale.
For the saturation efficient solution on this scale, streamline method can then be used.
Our contribution here is to develop a computationally advantageous downscaling
procedure that saves considerable time compared to the original proposed scheme in the
literature. This is achieved by designing basis functions similar to multiscale methods
used to obtain a velocity distribution.
Application of our upscaling-downscaling method on EOR processes and also comparing
it with non-uniform quadtree gridding will be further subjects of this study
Integrated Carbon Sequestration–Geothermal Heat Recovery:Performance Comparison Between Open and Close Systems
No full textIn this paper, the lateral boundaries for a theoretical homogeneous, isotropic, horizontal, 3-dimensional sedimentary hot aquifer were prescribed by either unhindered open to fluid and heat flow, or compartmentalised fully close boundary conditions. CO2 injection was administered through three well patterns of varying well spacing and numbers: 3 × 3 (5 injection wells and 4 production wells, 750-m well spacing), 5 × 5 (13 injection wells and 12 production wells, 500-m well spacing), and 7 × 7 (25 injection wells and 24 production wells, 375-m well spacing). To assess the effects of boundary conditions and well spacing on a combined carbon sequestration–geothermal heat recovery process, number of output metrics such as net cumulative CO2 stored, volumetric storage efficiency, geothermal heat recovery and pressure build-up were quantified in 54 simulation runs. Based on the assumption made and conditions that the simulation, it was shown that for a typical and more common fewer well number cases, the open versus close boundaries have critical role in determining the effectiveness of operation. (a) Open boundary conditions may counter-intuitively lead to heat recovery relative deficiencies if the pressure gradient stays largely towards the outside of the system (pressure of system > pressure of surrounding). This, however, will benefit CO2 injectivity and storage efficiency by providing escape paths for fluids (CO2 and brine). (b) Close boundary conditions will universally be beneficial for fluid and heat production purposes; however, the excessive pressure build-up can significantly affect the operation duration length. For economically unjustifiable cases with high number of wells, the effects of boundary conditions were shown to be reduced by effective fluid extraction from the medium, thereby enhancing the geothermal heat recovery and avoiding pressure build-up. The research delineated no significant effect of boundary conditions on salt precipitation.</p
Background data for: "The instantaneous structure of a turbulent wall-bounded flow influenced by freestream turbulence: streamwise evolution"
No full textThis data set contains planar Particle Image Velocimetry measurement fields for the experiments described in the article titled "The instantaneous structure of a turbulent wall-bounded flow influenced by freestream turbulence: streamwise evolution" (doi:10.1017/jfm.2024.1008).
The experiments were conducted in a water channel at the Norwegian University of Science and Technology. The setup includes an active grid to control freestream conditions. To analyze the evolution of the flow, the boundary layer was tested at four different streamwise locations for three grid sequences with freestream turbulence intensities up to 10.9%. Careful preprocessing was implemented to ensure high accuracy and minimal uncertainties.
This work was funded by the Research Council of Norway (see funding information): Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the Research Council of Norway. The granting authority cannot be held responsible for them.</p
Optimization of Pin-Fins for a Heat Exchanger by Entropy Generation Minimization and Constructal Law
No full textP.O. Box 552, Xi’an 710072, Shaanxi, China
Masoud Asadi
Department of Mechanical Engineering, Azad Islamic University Science and Research Branch, Tehran 1615918683, Iran e-mail: [email protected]
Giulio Lorenzini
Full Professor Department of Industrial Engineering, University of Parma, Parco Area delle Scienze, 181A, Parma 43124, Italy
1 Introduction
Employing pin-fins on a heated surface promotes heat transfer performance. Given their inexpensive and simple structure, pin- fins have extensive applications in cooling ranges from electronic equipment to the automobile industry. In diesel engines, about two-thirds of the input energy is wasted through the exhaust gas and cooling water. In this sense, it is important that a serious effort should be launched for conserving this energy. A pin-fin heat exchanger is an excellent choice for recovering waste energy in an automobile with diesel engine. Traditional methods for design- ing the exchanger are not very applicable because of relatively high pressure drop. Effective optimization methods are therefore necessary to enhance heat transfer performance with low pressure drop. Although there exist various methods for optimization of designs of heat exchangers, such optimizations were considered as manual designs by using different optimization algorithm rather than based on nature design from the standpoint of thermodynam- ics. This study focuses on the optimization of pin-fin geometry for a new heat exchanger by using EGM and CL.
EGM is widely used to evaluate thermal and energy systems in view of thermodynamic imperfection [1,2]. For example, Saffari- pour and Culham [3] presented a new nonintrusive method for the measurement of entropy production in microscale thermal-fluid devices. The entropy generation map was also obtained by post- processing the velocity and temperature distribution data. They used microparticle image velocimetry and laser-induced fluores- cence methods to measure data. Li and Kleinstreuer [4] analyzed the entropy generation in trapezoidal microchannels. They found that there existed an optimal Reynolds number range in order to
1Corresponding author.
Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received March 22, 2014; final manuscript received June 25, 2014; published online March 17, 2015. Assoc. Editor: Cesare Biserni.
Optimization of Pin-Fins for a Heat Exchanger by Entropy Generation Minimization and Constructal Law
Pin-fins are considered as one of the best elements for heat transfer enhancement in heat exchangers. In this study, the topology of pin-fins (length, diameter, and shape) is opti- mized based on the entropy generation minimization (EGM) theory coupled with the con- structal law (CL). Such pin-fins are employed in a heat exchanger in a sensible thermal energy storage (TES) system so as to enhance the rate of heat transfer. First, the EGM method is used to obtain the optimal length of pin-fins, and then the CL is applied to get the optimal diameter and shape of pin-fins. Reliable computational fluid dynamics (CFD) simulations of various constructal pin-fin models are performed, and detailed flow and heat transfer characteristics are presented. The results show that by using the proposed system with optimized pin-fin heat exchanger the stored thermal energy can be increased by 10.2%
Publisher Correction: Multi-step ahead forecasting of electrical conductivity in rivers by using a hybrid Convolutional Neural Network-Long Short-Term Memory (CNN-LSTM) model enhanced by Boruta-XGBoost feature selection algorithm
Full text linkCorrection to: Scientific Reportshttps://doi.org/10.1038/s41598-024-65837-0, published online 01 July 2024 In the original version of this Article, Changhyun Jun and Aitazaz Ahsan Farooque were omitted as corresponding authors. The correct corresponding authors for this Article are Masoud Karbasi, Changhyun Jun and Aitazaz Ahsan Farooque. The original Article has been corrected. © The Author(s) 2024
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