Pramana最新文献

{"title":"Finite-element approximation for three-dimensional nanofluid flow with heat transfer over a non-linearly stretching sheet","authors":"Shahid Rafiq,&nbsp;Muhammad Asim,&nbsp;Muhammad Mustahsan,&nbsp;M Ijaz Khan","doi":"10.1007/s12043-024-02804-4","DOIUrl":"10.1007/s12043-024-02804-4","url":null,"abstract":"<div><p>This article uses a finite-element approximation approach for solving a three-dimensional flow problem of a nanofluid influenced by heat transfer due to nanoparticles over a non-linearly stretching sheet within an unbounded domain. Utilising similarity transformations, a well-posed coupled system of nonlinear ordinary differential equations is derived from the governing partial differential equations describing the flow and heat transfer processes. The resulting system is then solved by using quadratic Lagrange polynomials as basic functions over a mesh of different finite elements through the Galerkin finite element (GFE) technique. This implementation is based on a regular grid utilising Lagrange polynomials for solving the converted equations. The effects of various parameters of interest are efficiently discussed with the help of graphs and numeric tables. Both numerical and exact solutions are compared favourably, demonstrating a high level of accuracy. It is noteworthy that the GFE method emerges as a much more stable numerical technique than the other existing analytic and semi-analytical methods. Furthermore, the adopted finite-element method reduces the dimensionality of Sobolev's space's finite-dimensional subspace and also improves the solution's convergence rate. Moreover, the velocity is negative, and its magnitude increases as the stretching rates ratio increases due to the downward flow in the vertical direction. The temperature and heat transmission from the sheet are barely impacted by Brownian motion due to the dominance of other forces and length scales involved in the heat transfer process.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PT-invariant generalised non-local nonlinear Schrödinger equation: soliton solutions","authors":"Nirmoy Kumar Das,&nbsp;Dhanashri Barman,&nbsp;Ashoke Das,&nbsp;Towhid E Aman","doi":"10.1007/s12043-024-02827-x","DOIUrl":"10.1007/s12043-024-02827-x","url":null,"abstract":"<div><p>A new generalised non-local nonlinear Schrödinger (NLS) equation is introduced which possesses a Lax pair and is parity–time (<i>PT</i>)-symmetric. Thus, it is confirmed that the generalised non-local NLS equation is integrable. The inverse scattering transform for the generalised non-local NLS equation is developed using a Riemann–Hilbert problem for rapidly decaying initial data and an approach for finding pure soliton solutions is described. The analytical characteristics of the eigenfunctions, scattering data and their symmetries are discussed. Finally, using <i>Mathematica</i> some important two-dimensional plots of the wave solutions are shown to illustrate the dynamics of the model.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crystallisation of liquid silica under compression: a molecular dynamics simulation","authors":"Van Hong Nguyen,&nbsp;Hoang Anh Nguyen","doi":"10.1007/s12043-024-02839-7","DOIUrl":"10.1007/s12043-024-02839-7","url":null,"abstract":"<div><p>In this study, we employ molecular dynamics simulations to develop a large model (19,998 atoms) of liquid SiO₂ at 3500 K. We construct models at different pressures in the 0–100 GPa range using the Beest–Kramer–Santen (BKS) potential and periodic boundary conditions. The goal is to detail the structural transition from the polyamorphic liquid state of SiO₂ to the crystalline stishovite form, which occurs between 45 and 60 GPa. We analyse the polyamorphic state of liquid SiO₂ by examining the formation of SiO_<i>x</i> clusters from 2 to 60 GPa. Beyond 60 GPa, the pair radial distribution functions (PRDFs) for Si–O, O–O and Si–Si display multiple peaks, indicating the crystalline phase. This observation is further supported by examining the bond angle distribution, the fraction of SiO_<i>x</i> units and OSi_<i>x</i> linkages, Si–O bond lengths within SiO_<i>x</i> units, structural visualisations and the analysis of ring statistics in the liquid SiO₂ system, all of which underscore the comprehensive changes in the structure of the system.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142411205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Maximising OLED performance: Unleashing the power of stacking transport, injection and blocking layers along with different emissive materials","authors":"S Diana Emerald Aasha,&nbsp;Shanthi Prince","doi":"10.1007/s12043-024-02835-x","DOIUrl":"10.1007/s12043-024-02835-x","url":null,"abstract":"<div><p>The performance of multilayer organic light emitting diode (OLED) is studied by stacking poly(3,4-ethylenedioxythiophene) polystyrene sulphonate (PEDOT:PSS) as the hole transport layer (HTL), tris(4-carbazoyl-9-ylphenyl) amine (TCTA) as the hole injection layer (HIL) and bathophenanthroline (BPhen) as the electron transport layer (ETL). Modification is done in the emissive layer (EML) by the introduction of host–guest material which is bis[2-(4,6-difluorophenyl) pyridinato-C2,N](picolinato)iridium(III) (FlrPic) and bis[2-(diphenylphosphino) phenyl] ether oxide (DPEPO). Multiple devices are fabricated and the performance is compared in terms of turn-on voltage, current density, brightness and luminous efficiency. The device with co-deposition of guest and host materials has improved the luminous efficiency by 6.17% when compared to the other fabricated devices.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142411166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat transfer of MHD Eyring–Prandtl fluid flow past a moving permeable plate with shear flow","authors":"Abir Baidya,&nbsp;Swati Mukhopadhyay,&nbsp;G C Layek","doi":"10.1007/s12043-024-02829-9","DOIUrl":"10.1007/s12043-024-02829-9","url":null,"abstract":"<div><p>It is obvious that due to its higher viscosity, non-Newtonian fluid show better heat transport than the Newtonian fluid. Moreover, shear flow helps us to make our surrounding environment friendly. With this view point, an attempt has been taken in this paper to explore the two-dimensional flow of low electrically conducting Eyring–Prandtl fluid and heat transfer over a moving porous plate subject to suction/blowing with externally applied magnetic field. The flow is maintained due to the incoming shear away from the plate so that boundary layer type of flow is formed over the plate. This makes the problem new, not yet been addressed by any researcher. Similarity transformations are applied to obtain self-similar structure of the leading equations. However, similar solutions of the problem are attained for a specific power-law velocity (index, <span>(n=1/3)</span>) of the moving plate. The equations are solved numerically and compared with different flow quantities having different grid sizes. The data are plotted graphically to represent velocity, velocity gradient and temperature for different parametric values. The influences of suction/blowing parameter, fluid material parameters, Prandtl number and magnetic parameter on velocity, temperature and velocity gradient are shown and explained at length with physical explanations as far as practicable. The velocity decreases with increasing values of magnetic parameter due to the appearance of Lorenz force. However, temperature increases. So, the boundary layer flow can be controlled using a suitable magnetic field. It is found that fluid velocity rises with the growing suction/blowing parameter and fluid material parameter <span>(alpha )</span> but the temperature is found to diminish resulting in the reduction of heat transfer in fluid. The analysis reveals that blowing destabilises the flow, while the suction stabilises the boundary layer flow. This study explores the boundary layer flow structure of a fluid with low electrical conductivity along with heat transfer in the presence of suction/blowing, externally applied magnetic field and shear flow.\u0000</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142411167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A unified scheme of central symmetric shape-invariant potentials","authors":"T Koohrokhi,&nbsp;A Izadpanah,&nbsp;M Gerayloo","doi":"10.1007/s12043-024-02824-0","DOIUrl":"10.1007/s12043-024-02824-0","url":null,"abstract":"<div><p>Most physical systems, whether classical or quantum mechanical, exhibit spherical symmetry. Angular momentum, denoted as <span>(ell )</span>, is a conserved quantity that appears in the centrifugal potential when a particle moves under the influence of a central force. This study introduces a formalism in which <span>(ell )</span> plays a unifying role, consolidating solvable central potentials into a superpotential. This framework illustrates that the Coulomb potential emerges as a direct consequence of a homogeneous (<i>r</i>-independent) isotropic superpotential. Conversely, an <span>(ell )</span>-independent central superpotential results in a 3-dimensional harmonic oscillator (3-DHO) potential. Moreover, a local <span>(ell )</span>-dependent central superpotential generates potentials applicable to finite-range interactions such as molecular or nucleonic systems. Additionally, we discuss generalisations to arbitrary <i>D</i> dimensions and investigate the properties of the superpotential to determine when supersymmetry is broken or unbroken. This scheme also shows that the free-particle wave function in three dimensions is obtained from the spontaneous breakdown of supersymmetry and clarifies how a positive 3-DHO potential, as an upside-down potential, can have a negative energy spectrum. We also present complex isospectral deformations of the central superpotential and superpartners, which can have interesting applications for open systems in dynamic equilibrium. Finally, as a practical application, we apply this formalism to specify a new effective potential for the deuteron.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142410084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Traversable wormhole solutions with phantom fluid in modified f(R, T) gravity","authors":"Sourav Chaudhary,&nbsp;S K Maurya,&nbsp;Jitendra Kumar,&nbsp;Sweeti Kiroriwal","doi":"10.1007/s12043-024-02811-5","DOIUrl":"10.1007/s12043-024-02811-5","url":null,"abstract":"<div><p>In this work, we have obtained new phantom fluid-type traversable wormhole (WH) solutions in the context of <span>(f(mathcal {R}, T))</span> modified gravity. We investigate the potential that some equations of state (EoS), specifically phantom energy, which describes the accelerated expansion of the universe, could support the existence of traversable wormholes. This cosmic fluid thus offers us a plausible explanation for the occurrence of WH geometries. We construct two WH models with matter Lagrangian density <span>(mathcal {L}_{m}=-(-rho +mathcal {P}_{r}+2mathcal {P}_{t}))</span> and inspect numerous characteristics of these models under the WH geometry. The first WH solution (WH-I) is discovered by utilising a linear barotropic equation of state (EoS) connected with phantom energy <span>(omega &lt;-1)</span> indicating the presence of the phantom fluid and pointing to the Universe’s expansion, while in the second WH (WH-II) solution, we take into account an interesting EoS <span>(rho =eta (mathcal {P}_{t}-mathcal {P}_{r}))</span> to generate a WH model. Additionally, it showed that the phantom fluid WH-I solution violates the radial null energy condition (NEC) while tangential NEC is satisfied. On the other hand, for the WH-II solution, NEC is violated. Extensive detailed discussions of the matter components have been done via graphical analysis. The obtained WH geometries satisfy a stable WH’s physically acceptable criteria.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142414739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamical probing and multiple actions of linear offset boosting of constants in Josephson junction instigated by Wien bridge oscillator embedded in the microcontroller","authors":"Balakrishnan Sriram,&nbsp;Daniel Maoussi Godonou,&nbsp;Cyrille Ainamon,&nbsp;Isidore Komofor Ngongiah,&nbsp;Karthikeyan Rajagopal","doi":"10.1007/s12043-024-02816-0","DOIUrl":"10.1007/s12043-024-02816-0","url":null,"abstract":"<div><p>The dynamical probing and linear offset boosting of constants in Josephson junction (JJ) instigated by the Wien bridge oscillator (JJIWBO) are investigated in this paper. Via numerical simulations, the JJIWBO unveiled bistable periodic oscillations, bistable periodic doubling with an evolving path to bistable chaotic characteristics, monostable chaotic behaviours and monostable periodic characteristics. The numerical dynamics are realised by the microcontroller validation (MCV) scheme. Two constant parameters are introduced in the rate equations of JJIWBO to implement the linear offset boosting of constants based on the two voltage variables. It is demonstrated that the polarity of the chaotic voltage and phase difference signals can be flexibly changed by varying one of the two constant parameters which is different from zero and the other constant parameter is zero. When two constant parameters have the same value, the chaotic voltages and phase difference signals can switch between bipolar and unipolar signals flexibly by changing the unique constant parameter.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142414802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical study of unsteady reactive third-grade fluid flow in a microchannel through a porous medium subject to exothermic reaction","authors":"Idrees Khan,&nbsp;TIRI Chinyoka,&nbsp;Rozli Zulkifli,&nbsp;Emad A A Ismail,&nbsp;Fuad A Awwad,&nbsp;Ahmed M Hassan,&nbsp;Oluwole D Makinde,&nbsp;Zubair Ahmad","doi":"10.1007/s12043-024-02820-4","DOIUrl":"10.1007/s12043-024-02820-4","url":null,"abstract":"<div><p>The purpose of this study is to investigate the transient dynamics of a third-grade fluid, which can undergo exothermic reactions in a saturated porous microchannel. The adverse pressure gradient force constitutes the primary flow driver. In addition to exothermic reactions, the system is also subjected convective cooling at the microchannel boundaries. Newton’s law of cooling and Arrhenius kinetics are employed to model the boundary cooling and exothermic reactions, respectively. The temperature-dependent fluid viscosity is modelled via a Nahme-type law and the porous material between the parallel microchannels is assumed to have constant permeability. To account for this, the unsteady modified Darcy’s law is applied, effectively capturing the impact of porosity. Computational solutions are employed to solve the non-homogeneous partial differential equations (PDEs) for the flow temperature and velocity. These computational solutions are developed from efficient, convergent and unconditionally stable, semi-implicit finite difference (SIFD) methods. Examining the thermodynamic and fluid-dynamical consequences of variations in the numerical exponent <span>(aleph )</span> and exothermic reaction parameter <span>(delta _2)</span> are the principal motives of the study. A comparative evaluation of the thermal runaway susceptibility of the numerical exponent parameter for two distinct types of fluids is outlined, indicating that the ranking of susceptibility ranges from most to least susceptible in the bimolecular case, the Arrhenius case and the sensitised case. Newtonian fluids are the most prone to non-Newtonian fluids. Additionally, the study systematically explores the sensitivity of field variables to changes in different flow parameters through graphical representations and shows that the fluid variables increase with the increase in Reynolds number, viscosity parameter and Brinkman number, while decrease for the third-order parameter and porous medium parameter. The obtained results are qualitatively discussed and compared with the published data.\u0000</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142413307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impinging flow of a special third-grade nanofluid streaming over a porous receding sheet using the tri-temperature model","authors":"Palanisamy Gayathri,&nbsp;Nagarajan Nithyadevi,&nbsp;Krishnan Sathyasri,&nbsp;Naramgari Sandeep","doi":"10.1007/s12043-024-02802-6","DOIUrl":"10.1007/s12043-024-02802-6","url":null,"abstract":"<div><p>The heat transfer characterisation of the three-phase local thermal non-equilibrium analysis due to the nanofluid (solid particle phase and the base fluid phase) and the absorbing phase (due to the porous surface) is performed for a third-grade nanofluid impinging over a receding surface. The mathematical formulation of the physical model includes the Rivlin–Ericksen tensor for fluids of grade three with appropriate restriction to viscous flows and also incorporates the Buongiorno nanofluid model for studying the impact of thermophoresis and Brownian motion. The resultant governing time-dependent partial differential equations has been converted to ordinary differential equations by applying similarity transformation. The computational results are obtained using the finite-difference approach in the Matlab software. The non-Newtonian and the time-dependent flow phenomena demands an additional boundary condition to ensure the uniqueness of the solution. With a general third-grade assumption with the wall shrinking and unsteadiness, the resultant equations govern the occurrence of dual solution in the obtained numerical results. The stability investigation reports the existence of multiple (dual) solutions due to the unsteadiness imparted in the flow and the flow behaviour of both the stable and unstable solutions are revealed. The boundary layer characteristics are explored for various vital physical parameters, such as material parameter, porous permeability parameter, Brownian motion parameter, thermophoresis parameter, inter-phase heat transfer coefficient, modified thermal capacity ratio, modified thermal diffusivity ratio and buoyancy ratio parameter. The temperature distribution across different phases is analysed for the stable solutions.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"98 4","pages":""},"PeriodicalIF":1.9,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142413318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}