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Challenge 3 of the 2022 NIST additive manufacturing benchmark (AM-Bench) experiments asked modelers to submit predictions for solid cooling rate, liquid cooling rate, time above melt, and melt pool geometry for single and multiple track laser powder bed fusion process using moving lasers. An in-house developed Additive Manufacturing Computational Fluid Dynamics code (AM-CFD) combined with a cylindrical heat source was implemented to accurately predict these experiments. Heuristic heat source calibration was proposed relating volumetric energy density (ψ) based on experiments available in the literature. The parameters of the heat source of the computational model were initially calibrated based on a Higher Order Proper Generalized Decomposition- (HOPGD) based surrogate model. The prediction using the calibrated heat source agreed quantitatively with NIST measurements for different process conditions. A scaling law based on keyhole formation was also utilized in calibrating the parameters of the cylindrical heat source and predicting the challenge experiments. In addition, an improvement on the heat source model was proposed to relate the Volumetric Energy Density (VEDσ) to the melt pool aspect ratio. The model showed further improvement in the prediction of the experimental measurements for the melt pool including cases at higher VEDσ. Overall, it was concluded that the appropriate selection of parameterization scheme along with the heat source model was crucial in the accurate prediction of melt pool geometry and thermal measurements while bypassing the expensive computational simulations that consider increased physics equations.

Thermal residual stress is identified as one of the major reasons of stress concentration in material’s microstructures which initiates failure in the microstructure. Considering the details of microstructural features (inclusions shape, size, and distri-bution) can provide better understanding of the thermal residual stress developed in the materials due to the temperature change. In this paper, we have extended the self-consistent clustering analysis (SCA) method for efficient and accurate modeling of thermal residual stress for thermoelastic heterogeneous materials. The governing equations of the thermoelasticity has been implemented through a eigenstrain problem and solved using a Fast Fourier Transform (FFT) based solution scheme and later extended for SCA formulation. The thermoelastic formulation of SCA method has been verified for a single inclusion (homogeneous and inhomoge-neous) problem with the analytical solution of Eshelby and the FFT-based solution for multiple clusters. An example problem with multiple inhomogeneous inclusions has been solved for different temperatures and the residual stress developed has been analyzed. Results show that the thermoelastic formulation of SCA can have order of hundred times speed up compare to the traditional FFT-based solution scheme. The proposed methodology can be implemented in thermomechanical problems and provide efficient multiscale capabilities for prediction of thermal residual stress.

Stanene, two-dimensional, graphene-like buckled honeycomb structure, has been deemed as a potential material for the next generation nano-electronics application. In electronic applications, the materials are subjected to both thermal and mechanical loadings. In addition, structural defects are inevitable during synthesis of nanomaterials. Therefore, it is essential to study the mechanical and thermal properties of stanene with various structural defects. We investigated the effects of point vacancy, bivacancy and Stone-Wales defects on tensile response and thermal transport of single-layer bulk stanene sheets using classical molecular dynamics (MD) simulations. MEAM potential is used to describe the inter-atomic forces in order to predict the properties of the stanene adequately. We probed the deformation process of defective bulk stanene by applying uniaxial tensile loading. Our study suggests that tensile strength and elastic modulus of stanene decrease with the increment of defect concentrations. Moreover, stanene sheet with Stone-Wales defect shows less in-plane stiffness to the loading. Using non-equilibrium molecular dynamics (NEMD) method, we found that, the phonon thermal conductivity of stanene is highly sensitive to defect concentrations. Only 0.1% of defect concentrations result in about 40% reduction in thermal conductivity. To elucidate the underlying mechanism responsible for this reduction, vibrational density of states (vDOS) are calculated. Overall, our reported results provide an insight into the effect of defects in mechanical and thermal properties of defective bulk stanene and will facilitate further tailoring of the design of stanene based nanoelectronics device.

In this paper, compressive loading effects on the plasticity of Al-Cu alloy varying the crystal orientation of Al and alloying element (Cu) percentage are investigated using molecular dynamics approach. The alloying percentage of Cu are varied up to 10% in , and crystal loading direction of Al. Our results indicate that the alloy nanopillar has highest first yielding strength and strain along and direction, respectively. Further, the dislocation density and dislocation interaction are studied to explain the compressive stress strain behavior of the alloy nanopillar., Comment: 9 pages of main manuscript and 7 pages of supplementary, Physica B: Condensed Matter (2017)

Purpose The purpose of this investigation is to determine the nature of the flow field, temperature distribution and heat and mass transfer in a triangular solar collector enclosure with a corrugated bottom wall in the unsteady condition numerically. Design/methodology/approach Non-linear governing partial differential equations (i.e. mass, momentum, energy and concentration equations) are transformed into a system of integral equations by applying the Galerkin weighted residual method. The integration involved in each of these terms is performed using Gauss’ quadrature method. The resulting non-linear algebraic equations are modified by the imposition of boundary conditions. Finally, Newton’s method is used to modify non-linear equations into the linear algebraic equations. Findings Both the buoyancy ratio and thermal Rayleigh number play an important role in controlling the mode of heat transfer and mass transfer. Originality/value Calculations are performed for various thermal Rayleigh numbers, buoyancy ratios and time periods. For each specific condition, streamline contours, isotherm contours and iso-concentration contours are obtained, and the variation in the overall Nusselt and Sherwood numbers is identified for different parameter combinations.

Graphene and some graphene like two dimensional materials; hexagonal boron nitride (hBN) and silicene have unique mechanical properties which severely limit the suitability of conventional theories used for common brittle and ductile materials to predict the fracture response of these materials. This study revealed the fracture response of graphene, hBN and silicene nanosheets under different tiny crack lengths by molecular dynamics (MD) simulations using LAMMPS. The useful strength of these large area two dimensional materials are determined by their fracture toughness. Our study shows a comparative analysis of mechanical properties among the elemental analogues of graphene and suggested that hBN can be a good substitute for graphene in terms of mechanical properties. We have also found that the pre-cracked sheets fail in brittle manner and their failure is governed by the strength of the atomic bonds at the crack tip. The MD prediction of fracture toughness shows significant difference with the fracture toughness determined by Griffth's theory of brittle failure which restricts the applicability of Griffith's criterion for these materials in case of nano-cracks. Moreover, the strengths measured in armchair and zigzag directions of nanosheets of these materials implied that the bonds in armchair direction has the stronger capability to resist crack propagation compared to zigzag direction., 21 pages, 7 figures

Nanostructures have the immense potential to supplant the traditional metallic structure as they show enhanced mechanical properties through strain hardening. In this paper, the effect of grain sizes on the hardening mechanism of an Al-Cu nanostructure is elucidated by molecular dynamics simulation. The Al-Cu (50–54% Cu by weight) nanostructure having an average grain size of 4.57 to 7.26 nm are investigated for tensile simulation at different strain rates using embedded atom method (EAM) potential at a temperature of 50~500 K. It is found that the failure mechanism of the nanostructure is governed by the temperature, grain size, and strain rate applied. At the high temperature of 300–500 K, the failure strength of the Al-Cu nanostructure increases with the decrease of average grain size following Hall-Petch relation. Dislocation motions are hindered significantly when the grain size is decreased which play a vital role in the hardening of the nanostructure. The failure is always found to initiate at a particular Al grain due to its weak link and propagates through grain boundary (GB) sliding, diffusion, dislocation nucleation, and propagation. We also visualize the dislocation density at different grain sizes to show how the dislocation affects the material properties at the nanoscale. These results will further aid investigation on the deformation mechanism of other nanostructures.

A lid-driven L -shaped cavity filled with a porous medium is analyzed. The Galerkin weighted residual method is applied to obtain numerical solutions. The effect of the Reynolds number ( Re = 1–100), Grashof number ( Gr = 10 3 –10 5 ) and Darcy number ( Da = 10 −5 –10 −3 ) on the velocity and temperature fields is examined. For the vertical wall, a higher heat transfer rate is observed when a low Grashof number, higher Darcy number and higher Reynolds number are applied, but the opposite characteristic is found in the horizontal wall. It is evident that heat transfer decreases up to 63% in the horizontal wall when the flow has a high Reynolds number ( Re = 100).

In this study magneto-hydrodynamic convection in a half-moon shaped cavity filled with ferrofluid has been analyzed numerically. The cavity has two semi-circular bottom heaters and effect of the distance between these two heaters ( λ = 0.1 , 0.4 ) has been thoroughly investigated. Numerical simulation has been carried out for a wide range of Rayleigh number ( Ra = 10 3 ∼ 10 7 ), Hartmann number ( Ha = 0 ∼ 100 ) and inclination angle of magnetic field ( γ = 0 ° ∼ 90 ° ) to understand the flow field, thermal field and entropy generation respectively. Cobalt-kerosene and Fe 3 O 4 -water ferrofluids are used for the present investigation and considered as a single phase fluid. Galerkin weighted residual method of finite element analysis has been used for numerical solution. The code validation and grid independency test have been carried out to justify the numerical accuracy. It has been observed that increment of magnetic field reduces the heat transfer rate, whereas increment of heater distance augments the heat transfer rate significantly. Results are discussed on the basis of Nusselt number ( Nu ), Bejan number ( Be ) and shown by contours and 3D plots. It has also been found that λ = 0.4 always shows better heat transfer rate and entropy optimization.

Simulation of reasonable timescales for any long physical process using molecular dynamics (MD) is a major challenge in computational physics. In this study, we have implemented an approach based on multi-fidelity physics informed neural network (MPINN) to achieve long-range MD simulation results over a large sample space with significantly less computational cost. The fidelity of our present multi-fidelity study is based on the integration timestep size of MD simulations. While MD simulations with larger timestep produce results with lower level of accuracy, it can provide enough computationally cheap training data for MPINN to learn an accurate relationship between these low-fidelity results and high-fidelity MD results obtained using smaller simulation timestep. We have performed two benchmark studies, involving one and two component LJ systems, to determine the optimum percentage of high-fidelity training data required to achieve accurate results with high computational saving. The results show that important system properties such as system energy per atom, system pressure and diffusion coefficients can be determined with high accuracy while saving 68% computational costs. Finally, as a demonstration of the applicability of our present methodology in practical MD studies, we have studied the viscosity of argon-copper nanofluid and its variation with temperature and volume fraction by MD simulation using MPINN. Then we have compared them with numerous previous studies and theoretical models. Our results indicate that MPINN can predict accurate nanofluid viscosity at a wide range of sample space with significantly small number of MD simulations. Our present methodology is the first implementation of MPINN in conjunction with MD simulation for predicting nanoscale properties. This can pave pathways to investigate more complex engineering problems that demand long-range MD simulations., 23 pages, 17 figures

In this paper, a mechanistic-based data-driven approach, MAP123-EP, is proposed for numerical analysis of elastoplastic materials. In this method, stress-update is driven by a set of one-dimensional stress–strain data generated by numerical or physical experiments under uniaxial loading. Numerical results indicate that combined with the classical strain-driven scheme, the proposed method can predict the mechanical response of isotropic elastoplastic materials (characterized by J2 plasticity model with isotropic/kinematic hardening and associated Drucker–Prager model) accurately without resorting to the typical ingredients of classical model-based plasticity, such as decomposing the total strain into elastic and plastic parts, as well as identifying explicit functional expressions of yielding surface and hardening curve. This mechanistic-based data-driven approach has the potential of opening up a new avenue for numerical analysis of problems where complex material behaviors cannot be described in explicit function/functional forms. The applicability and limitation of the proposed approach are also discussed.

Nanoindentation is a useful technique to measure mechanical properties of a material such as the elastic modulus and hardness etc. In this paper, the effects of crystallographic orientation, indentation speed, indentation depth and indenter size has been studied for pure Aluminum (Al) using dislocation nucleation and propagation mechanism in atomistic simulation. The materials properties like hardness and reduced modulus are also calculated from the atomistic simulations. Nanoscale finite element (FE) simulations in Al are carried out using molecular dynamics tensile test data as input parameters and compared with atomistic results. The proposed methodology reduces the computational time and cost and reproduces the material properties with reasonable accuracy. The investigations of atomistic simulations include the load-displacement analysis, dislocation density and dislocation loops nucleation and propagation, von-Mises stress distribution and surface imprint. This study provides a pathway to obtain the materials properties for nanoscale materials without performing large scale atomistic simulation and can be applied for other mechanical properties such as fatigue, creep simulation of materials.

Functionally graded material (FGM) is a class of advanced materials, consisting of two (or more) different constituents, that possesses a continuously varying composition profile. With the advancement of nanotechnology, applications of FGMs have shifted from their conventional usage towards sophisticated micro and nanoscale electronics and energy conversion devices. Therefore, the study of mechanical and vibrational properties of different FGM nanostructures is crucial in exploring their feasibility for different applications. In this study, for the first time, we employed molecular dynamics (MD) simulations to investigate the mechanical and vibrational properties of radially graded Cu-Ni FGM nanowires (NW). Distribution of Cu and Ni along the radial direction follows power-law, exponential and sigmoid functions for FGM NWs under consideration. Our results demonstrate that, distribution function parameters play an important role in modulating the mechanical (elastic modulus and ultimate tensile strength) and vibrational (natural frequency and quality factor) properties of FGM NWs. The study also suggests that, elastic moduli of FGM NWs can be predicted with relatively good accuracy using Tamura and Reuss micromechanical models, regardless of NW diameter. We found that, Euler-Bernoulli beam theory under-predicts the natural frequencies of FGM NWs, whereas He-Lilley model closely approximates the MD results. Interestingly, FGM NWs are always found to exhibit beat vibration because of their asymmetrical cross sections. Finally, this is the first atomistic scale study of FGMs that directly compares MD simulations with continuum theories and micromechanical models to understand the underlying mechanisms that govern the mechanical and vibrational properties of FGM NWs in nanoscale., Comment: 45 pages, 11 figures

A numerical study is carried out to analyze both heat and mass transfer phenomena in the presence of an external magnetic field inside a square cavity with an isothermal hollow circular insert located at the centre of the cavity. In the present work, the effects of Hartmann number, Lewis number and buoyancy ratio at constant Rayleigh and Prandtl numbers are investigated simultaneously to understand the importance of these parameters on the characteristics of double diffusive natural convection. Galerkin finite element method is employed for the numerical simulations. Grid sensitivity test and code validation are performed prior to confirm the numerical accuracy of the solution. Quantitative comparison is presented by showing the influence of Hartmann and Lewis numbers for different buoyancy ratios on average Nusselt and Sherwood numbers. It is found that increment of Hartmann number results in lower heat and mass transfer rates. Higher value of Lewis number produces elevated mass transfer rate. However, Lewis number has negative impact on heat transfer rate. Moreover, buoyancy ratio has significant effect on heat and mass transfer inside the cavity.

Sn–Ag–Cu, commonly known as SAC, is considered to be among the most promising of all lead-free solder alloys. Research aimed at making electronic components smaller has pointed to the possible use of nanosized solder joints in the future. In this study, for the first time, molecular dynamics simulations were used to analyze the thermomechanical properties of SAC solder materials at the nanoscale. The modified embedded-atom method (MEAM) potential was utilized in the simulations of the SAC solder materials. The dimensions of the structures considered were 55 × 55 × 59 A. Four different SAC solders were studied, with Ag percentages ranging from 1% to 4% (SAC105, SAC205, SAC305, and SAC405). Thus, the effects of the Ag percentage on the thermomechanical properties of the solder at the nanoscale were identified. The impacts of the temperature on the uniaxial tensile properties and coefficient of thermal expansion (CTE) values of the SAC solder materials were investigated by performing simulations of the materials at different temperatures. Results suggest that as the Ag percentage increases, the uniaxial tensile strength and CTE of the solder increase whereas the failure strain and thermal conductivity decrease. The results presented should prove useful in the electronic packaging industry.

Silicene has become a topic of interest nowadays due to its potential application in various electro-mechanical nanodevices. In our previous work on silicene, fracture stresses of single crystal and polycrystalline silicene have been investigated. Existence of defects in the form of cracks reduces the fracture strength of silicene nanosheets to a great extent. In this study, an engineering way has been proposed for improving the fracture stress of silicene nanosheets with a pre-existing crack by incorporating auxiliary cracks symmetrically in a direction perpendicular to the main crack. We call this mechanism the “Failure shielding mechanism”. An extensive molecular dynamics simulation based analysis has been performed to capture the atomic level auxiliary crack-main crack interactions. It is found that the main crack tip stress distribution is significantly changed with the presence of auxiliary cracks for loading along both armchair and zigzag directions. The effects of temperature and the crack propagation speed of silicene have also been studied. Interestingly, in the case of loading along the zigzag direction, SW defect formation is observed at the tip of main crack. This leads to a reduction of the tip stress resulting in a more prominent failure shielding in case of zigzag loading than in armchair loading. Moreover, the position and length of the cracks as well as the loading directions have significant impacts on the tip stress distribution. Finally, this study opens the possibilities of strain engineering for silicene by proposing an engineering way to tailor the fracture strength of silicene.

The mechanical properties of indium phosphide (InP) nanowires are an emerging issue due to the promising applications of these nanowires in nanoelectromechanical and microelectromechanical devices. In this study, molecular dynamics simulations of zincblende (ZB) and wurtzite (WZ) crystal structured InP nanowires (NWs) are presented under uniaxial tension at varying sizes and temperatures. It is observed that the tensile strengths of both types of NWs show inverse relationships with temperature, but are independent of the size of the nanowires. Moreover, applied load causes brittle fracture by nucleating cleavage on ZB and WZ NWs. When the tensile load is applied along the [001] direction, the direction of the cleavage planes of ZB NWs changes with temperature. It is found that the {111} planes are the cleavage planes at lower temperatures; on the other hand, the {110} cleavage planes are activated at elevated temperatures. In the case of WZ NWs, fracture of the material is observed to occur by cleaving along the (0001) plane irrespective of temperature when the tensile load is applied along the [0001] direction. Furthermore, the WZ NWs of InP show considerably higher strength than their ZB counterparts. Finally, the impact of strain rate on the failure behavior of InP NWs is also studied, and higher fracture strengths and strains at higher strain rates are found. With increasing strain rate, the number of cleavages also increases in the NWs. This paper also provides in-depth understanding of the failure behavior of InP NWs, which will aid the design of efficient InP NWs-based devices.

Lid-driven mixed convection has been given immense importance due to its wide range of applications. A T-shaped cavity is introduced and pertinent parameters controlling mixed convection phenomenon are analyzed in this paper. Water-Al2O3 nanofluid is considered inside the cavity to augment heat transfer rate. Galerkin weighted residual method of finite element analysis is applied for the numerical simulations. Numerical solution is obtained for different solid volume fractions of nanofluid, (ϕ = 0-0.15), Grashof numbers (Gr = 0.1-5000) and Reynolds numbers (Re = 0.31-1000) in laminar flow regime. Special attention is given on the analysis of flow at the pure mixed convection regime. It is found that Grashof, Reynolds and Richardson numbers along with solid volume fraction of nanofluid have significant effect on heat transfer characteristics inside the cavity. Results are presented using streamline and isotherm contours along with related variation of average Nusselt numbers of the heated wall and average fluid temperature inside the cavity.

In this paper unsteady magnetohydrodynamic convection has been analyzed using numerical and statistical techniques for a semicircular-shaped enclosure filled with ferrofluid. Cobalt–kerosene ferrofluid is considered for the present investigation. Galerkin weighted residuals method of finite element ananlysis is adopted for the numerical simulation. The effects of Rayleigh number (Ra), solid volume fraction (ϕ) of ferrofluid and Hartmann number (Ha) are considered as pertinent parameters and varied for a wide range of values (Ra = 105–107, ϕ = 0–0.15, Ha = 0–50) to capture the flow and thermal interaction phenomena for unsteady situation. It is observed that higher ferrofluid solid volume fraction escalates the heat transfer rate. Enhancing the intensity of external magnetic field (by increasing Ha) retards the heat transfer rate while increment of Ra exhibits improvement on the heat transfer. It is also found that there exists a strong interacion between ferromagnetic particle (cobalt) and base fluid (kerosene) in the presence of magnetic field which can be utilized properly for desired heat transfer augmentation. If ϕ = 0 (or ϕ = 0.15) and Ra is changed from 105 to 107, the linear dependence of Ψmax on time changes significantly from positive to negative.

Numerical study of heat transfer phenomena has become a major field of research nowadays. In engineering applications, different boundary conditions arise which have various effects on heat transfer characteristics. For the present work, a triangular-shape cavity has been analyzed for the sine-squared thermal boundary condition which is common in practical cases. The augmentation of heat transfer has been done by introducing a nanofluid inside the cavity. Different solid volume fractions (φ = 0, 0.05, 0.1, 0.2) of water-CuO, water-Al2O3, and water-TiO2 nanofluid have been tested for the cavity with a wide range of Rayleigh number (Ra = 105–108) and for dimensionless time (τ = 0.1 to 1). The Galerkin weighted residual finite-element method has been applied for the numerical solution, and numerical accuracy has been checked by code validation. The heat transfer augmentation for different nanofluids has been done in the light of local (NuL) and overall Nusselt number (Nuav), and the results have been present...

The determination of shear based properties of Nickel (Ni) has a great importance since it is more likely to fail by shear than tension due to its ductile nature. It also features a wide variety of applications in structure, thin film, tubes, and plates due to its unique thermal and electrical properties. Molecular Dynamics Simulations were performed on Ni nano-plate subjected to shear loading to study the effect of voids in the structure using embedded atom method (EAM) potential. The shear stress-strain behavior was observed for Ni nano-plate with voids of 1.0 nm, 1.5 nm, and 2.0 nm radius. Snapshots taken at different strains show the formation of slip planes, crack propagation, and dislocation activity. Simulation results show that the modulus of rupture decreases with the increase of void radius due to more dislocation activity for larger void. Lastly, the effect of different void size on the shear modulus of rigidity is also incorporated.The determination of shear based properties of Nickel (Ni) has a great importance since it is more likely to fail by shear than tension due to its ductile nature. It also features a wide variety of applications in structure, thin film, tubes, and plates due to its unique thermal and electrical properties. Molecular Dynamics Simulations were performed on Ni nano-plate subjected to shear loading to study the effect of voids in the structure using embedded atom method (EAM) potential. The shear stress-strain behavior was observed for Ni nano-plate with voids of 1.0 nm, 1.5 nm, and 2.0 nm radius. Snapshots taken at different strains show the formation of slip planes, crack propagation, and dislocation activity. Simulation results show that the modulus of rupture decreases with the increase of void radius due to more dislocation activity for larger void. Lastly, the effect of different void size on the shear modulus of rigidity is also incorporated.

The mechanical properties of Indium Phosphide (InP) nanowire is an emerging issue due to its application as optoelectronic material. In this paper, atomistic simulations are conducted to find thermo-mechanical properties of Indium Phosphide (InP) nanowire under uniaxial tension. Vashishta potential is employed to define the atomic interactions between the atoms. The effect of variation of temperatures (100K-500K) on the tensile response of the InP nanowires is investigated in this study. Also, size effect is investigated for the temperature of 300 K by varying the cross sectional area of the nanowire. Results suggest that increment of temperature results in the failure of InP nanowire at a lower value of stress (from 8.60 GPa at 100K to 6.50 GPa at 500K) along with the decrement of Young’s modulus. Results also suggest that size has little effect on the tensile properties of this nanowire. Finally, failure mechanisms of indium phosphide nanowire are also investigated from the atomic images obtained from the simulation results.

In this paper, natural convection heat transfer has been analyzed for a C -shaped cavity filled with ferrofluid. Cobalt-kerosene ferrofluid is selected here for different solid volume fractions (φ = 0 ~ 0.15). Galerkin weighted residual method is applied to obt ain the numerical solution. Simulations are carried out for a wide range of R ayleigh (Ra = 10 3 ~ 10 7 ) and Hartmann (Ha = 0 ~ 100) numbers for both the ferrofluid and the plain fluid. From this work, it is found that higher Rayleigh number enhances the heat transfer rate significantly, whereas presence of magnetic field tries to retard convection. Moreover, addition of 15% solid volume fraction of nanoparticle can augment the heat transfer rate up to 52.65% at moderate Rayleigh number compared to the base fluid. By an optimization of these parameters, effective h eat transfer control equipment can be developed. Results are interpreted on the basis of streamline and isotherm patterns, and average Nusselt number of the heated wall and average fluid temperature of the cavity.

Magneto-hydrodynamic convection has been gaining attention due to its wide range of application. In this paper magneto-hydrodynamic convection in a half-moon (semi-circular) shaped cavity has been analysed. The cavity has two semi-circular bottom heaters and effect of distance between this two heaters has been thoroughly investigated for two different cases ( λ = 0.1, 0.4). Numerical simulation has been carried out for a wide range of Rayleigh number ( Ra = 10 3 ∼ 10 7 ) and for Hartmann number ( Ha = 0 ∼ 100) to understand the flow and thermal field. Galerkin weighted residual method of finite element analysis has been adopted for numerical solution along with code validation and grid independency test to ensure the numerical accuracy. It has been found that strengthening of magnetic field tries to reduce the heat transfer rate, whereas increment of heater distance augments the heat transfer rate. Results analysed on the basis of Nusselt number and average fluid temperatures are shown by related contours, plots and graphical analysis. Therefore, higher heat transfer rate has been achieved for λ = 0.4.

Solar thermal collectors have significant importance due to its wide use in solar thermal technology. Augmentation of heat transfer is a key challenge for solar thermal technology. A quarter circular solar thermal collectors is investigated throughout the paper introducing carbon nanotube (CNT)–water nanofluid in the cavity. Tilt angle of this type of collector plays a vital role and heat transfer can be maximized for a particular tilt angle and solid volume fraction of the nanofluid. Galerkin weighted residual of FEM has been applied for the numerical solution of the problem. Grid independency test and code validation have been assessed for the accuracy of numerical solution. In this paper a wide range of solid volume fraction (δ = 0 to δ = 0.12) and tilt angle (ϕ = 0 to ϕ = 60°) has been investigated for Rayleigh number (Ra = 105–108) with varying dimensionless times. It has been found that both solid volume fraction and tilt angle play vital roles for the augmentation of heat transfer and a good heat transfer characteristic can be obtained by compromising between these two parameters. The results are shown using streamline, isotherm contour and related graph and chart.

A half-moon shape enclosure which has a very wide range of practical applications in heat transfer is introduced for the first time in this article. The heat transfer is analyzed introducing different commercially available nanofluids such as water–Al2O3, water–Cu, water–TiO2 in this half-moon enclosure. A variable thermal boundary condition is assigned to the model, and the finite-element method is used for the numerical solution of the problem. The effect of solid volume fraction φ, along with a wide range of Rayleigh numbers (Ra = 105–107), are evaluated in various dimensionless times τ. The performance of the shape is described by using streamfunctions, isotherms, charts, and related graphs. It is found that heat transfer in the cavity can be enhanced up to 30% by to the presence of nanoparticles.

Nanofluids have been introduced for the enhancement in the heat transfer phenomena in the last few years. In this paper a corrugated bottom triangular solar collector has been studied introducing water based nanofluids inside the enclosure. The corrugated bottom is kept at a constant high temperature whereas the side walls of the triangular enclosure are kept at a low temperature. Three types of nanoparticles are taken into consideration: Cu, Al2O3, and TiO2. The effect of solid volume fraction (ϕ) of the nanoparticle of nanofluid has been studied numerically by Galerkin weighted residual method of finite element for a wide range of Grashof number (Gr) 104–106. Calculations are carried out for ϕ = 0, 0.05, 0.08, and 0.1 and dimensionless time, τ = 0.1, 0.5, and 1. For the specified conditions streamlines and isotherm contours are obtained and detailed results of the interaction between different parameters are studied using overall Nusselt number. It has been found that both Grashof number and solid volume fraction have significant influence on streamlines and isotherms in the enclosure. It is also found that heat transfer increased by 24.28% from the heated surface as volume fraction ϕ increases from 0% to 10% at Gr = 106 and τ = 1 for copper water nanofluid.

In this study, magneto-hydrodynamic (MHD) mixed convection flow through a channel with a round cavity at bottom wall using non-Newtonian power law fluid is analysed numerically. The cavity is kept at uniformly high temperature whereas rest of the bottom wall is insulated and top wall of the channel is maintained at a temperature lower than cavity temperature. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method is appointed to solve the continuity, momentum and energy equations. The problem is solved for wide range of pertinent parameters like Rayleigh number (Ra= 103 – 105), Hartmann number (Ha= 0 - 60) and power law index (n= 0.5 – 1.5) at constant Richardson number Ri= 1.0. The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given study is illustrated by average Nusselt number plots. Result of this investigation indicates that heat transfer is highest for dilatant fluids at this configuration and they perform better (47% more heat transfer) in absence of magnetic field. The retardation of heat transfer is offset by shear thickening nature of non-Newtonian fluid.In this study, magneto-hydrodynamic (MHD) mixed convection flow through a channel with a round cavity at bottom wall using non-Newtonian power law fluid is analysed numerically. The cavity is kept at uniformly high temperature whereas rest of the bottom wall is insulated and top wall of the channel is maintained at a temperature lower than cavity temperature. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method is appointed to solve the continuity, momentum and energy equations. The problem is solved for wide range of pertinent parameters like Rayleigh number (Ra= 103 – 105), Hartmann number (Ha= 0 - 60) and power law index (n= 0.5 – 1.5) at constant Richardson number Ri= 1.0. The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given study is illustrated by average Nusselt number plots. Result of thi...

Stanene is a two-dimensional, graphene-like honeycomb structure material, has been synthesized in a recent experimental study. Theoretically, it is expected to have a super conductive property near room temperature due to its spin orbital coupling effect. It is a potential material for the next generation nano-electronics application. Therefore, studying its thermal property is of particular interest. In this paper, we investigated the effect of different types of defects on the thermal conductivity of stanene nanosheets. Molecular Dynamics simulations are performed to calculate the thermal conductivity as a function of various types of defects. MEAM potential is used to describe the inter-atomic forces. It has been found that the presence of defects reduces the thermal conductivity significantly. Finally, vibrational density of states (DOS) are calculated to elucidate the underlying mechanisms of the reduction of thermal conductivity.

Uniaxial tensile properties of hexagonal boron nitride nanoribbons and dependence of these properties on temperature, strain rate, and the inclusion of vacancy defects have been explored with molecular dynamics simulations using Tersoff potential. The ultimate tensile strength of pristine hexagonal boron nitride nanoribbon of 26 nm x 5 nm with armchair chirality is found to be 100.5 GPa. The ultimate tensile strength and strain have been found decreasing with increasing the temperature while an opposite trend has been observed for increasing the strain rate. Furthermore, the vacancy defects reduce ultimate tensile strength and strain where the effect of bi-vacancy is clearly dominating over point vacancy.

P (proportional), PI (proportional-integral), and PID (proportional-integral-derivative) controllers are popular means of controlling industrial processes. Due to superior response, accuracy, and stable performance, PID controllers are mostly used in control systems. This paper presents a mathematical model and subsequent response analysis regarding regulation of flow in mixed convection through a T-shaped open cavity by temperature dependent controllers. The T-shaped cavity has cold top and hot bottom walls, while air is flowing through the inlet at surrounding temperature. The inflow is regulated by a controlled gate which operates according to the signal received from the controller. Values of proportional gain (kp), integral gain (ki), and derivative gain (kd) are varied to obtain the desired system response and to ensure a stable system with fastest response. At first, only P controller is used and eventually PI and finally PID control scheme is applied for controller tuning. Tuning of different cont...

This paper demonstrates magneto-hydrodynamic (MHD) mixed convection flow through a channel with a rectangular obstacle at the entrance region using non-Newtonian power law fluid. The obstacle is kept at uniformly high temperature whereas the inlet and top wall of the channel are maintained at a temperature lower than obstacle temperature. Poiseuille flow is implemented as the inlet velocity boundary condition. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method has been appointed to solve the continuity, momentum and energy equations. The problem has been solved for wide range of pertinent parameters like Richardson number (Ri = 0.1 - 10) at a constant Reynolds number (Re = 100), Hartmann number (Ha = 0 - 100), power index (n = 0.6 - 1.6). The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given st...

Entropy optimization is a major concern for designing modern thermal management system. In the present work, entropy analysis in a square cavity with an isothermal hollow cylinder at the center is carried out for magneto-hydrodynamic (MHD) double diffusive convection. Galerkin weighted residuals method of finite element formulation is adopted for the numerical solution. Entropies due to fluid flow, heat, and mass transfer are computed for wide range of Hartmann (0 ≤ Ha ≤ 50) and Lewis numbers (1 ≤ Le ≤ 15), and buoyancy ratios (−5 ≤ N ≤ 5) at constant Rayleigh and Prandtl numbers. It is found that the influence of buoyancy ratio is prominent on entropy generation, which also depends on both Lewis and Hartmann numbers. The ratio N = -1 shows minimum entropy generation for any combination of Lewis and Hartman numbers. Visualization of isentropic contours and the variation of total entropy with the governing parameters provide remarkable evidences of entropy optimization.