Dual Flux Research Articles

Entropy optimization on Casson nanofluid flow with radiation and Arrhenius activation energy over different geometries: A numerical and statistical approach

This study employs numerical and statistical approaches to investigate the entropy optimization of steady Casson nanofluid flow over three different geometries subject to boundary conditions induced by convective flow. Multiple linear regression is employed to statistically examine. The present model incorporates several novel elements, such as Arrhenius activation energy, Brownian motion, the Cattaneo-Christov dual flux, thermophoresis, thermal radiation, and so on. Moreover, a comparison is presented between Newtonian and non-Newtonian fluids. By applying the proper similarity transformations, ordinary differential equations (ODEs) are obtained by converting foundational partial differential equations (PDEs). The Runge-Kutta fourth-order method is utilised to solve the obtained ODEs along with the shooting technique. The outcomes are visually depicted via tables and graphs. The velocity drops with increasing Grashof number, and the magnetic field becomes progressively more forceful as the suction parameter increases. The temperature gets reduced with the increase of the suction parameter, solute Grashof number increases with the magnetic field, thermophoresis, and radiation parameters. The entropy is observed to rise with the increase of the effective parameters (magnetic field, Brinkmann number and radiation). The MAD (mean absolute deviation), MSE (mean squared error), and RMSE (root mean square error) values are approaching zero, indicating that the derived outcomes are highly accurate. A lower MAPE (mean absolute percentage error) suggests that the model has a higher level of precision. Therefore, the outcomes of the present model are more precise and reliable. This study has various potential applications such as power plant heat exchangers, material processing industries, and solar thermal energy systems.

Dual magnetic curves and flux ruled surfaces

In this paper, we introduce the dual magnetic trajectories traced by the dual Frenet vectors of any dual curves in dual space via the dual Lorentz force, and then we give the characterizations of dual magnetic curves. Moreover, we define the dual flux ruled surfaces corresponding to the Killing vectors on the dual unit sphere and identify the conditions for these surfaces to be minimal or developable. Additionally, we present certain characterizations related to these surfaces. We demonstrate the visual representations of some dual flux ruled surfaces in some examples.

Modification of an oxyhalide solid-solution photocatalyst with an efficient O2-evolving cocatalyst and electron mediator for two-step photoexcitation overall water splitting.

Two-step photoexcitation overall water splitting based on particulate photocatalysts represents a promising approach for low-cost solar hydrogen production. The performance of an O2-evolution photocatalyst and electron mediator between two photocatalysts crucially influences the construction of an efficient two-step excitation water-splitting system. Bismuth-tantalum oxyhalides are emerging photocatalysts for O2 evolution reactions and can be applied in two-step water-splitting systems. In this study, a highly crystalline Bi4TaO8Cl0.9Br0.1 solid solution with microplatelet morphology was synthesized by the dual flux method. The light absorption intensity and charge transfer efficiency of the Bi4TaO8Cl0.9Br0.1 solid solution were higher than those of Bi4TaO8Cl and Bi4TaO8Br; thus, the sacrificial O2 evolution activity of Bi4TaO8Cl0.9Br0.1 photocatalyst was obviously enhanced. The two-step excitation water splitting with a solid-state electron mediator was successfully constructed using Bi4TaO8Cl0.9Br0.1 as the O2-evolution photocatalyst and Ru/SrTiO3:Rh as the H2-evolution photocatalyst. The CoOx cocatalyst and reduced graphene oxide decorations on the surface of Bi4TaO8Cl0.9Br0.1 promoted the catalytic O2 generation process on Bi4TaO8Cl0.9Br0.1 and electron transfer between CoOx/Bi4TaO8Cl0.9Br0.1 and Ru/SrTiO3:Rh photocatalysts, respectively. As a result, the apparent quantum yield for this overall water-splitting system was 1.26% at 420 nm, which surpassed the present performance of the two-step excitation water-splitting systems consisting of metal oxyhalide photocatalysts. This study demonstrates the validity of high-quality solid-solution photocatalysts with suitable surface modification for efficient solar hydrogen production from water splitting.

Numerical analysis of interfacial nanolayer thickness on Darcy-Forchheimer Casson hybrid nanofluid flow over a moving needle with Cattaneo-Christov dual flux

The interfacial nanolayer is a tinny coating of liquid molecules convened around the immersed solid nanoparticles in the base liquid which plays a vital role to control the flow and improve the thermophysical properties of the fluid. Features are more prominent for hybrid nanomaterials. Hence, the present analysis deals with the concomitant effects of an interfacial nanolayer of nanomaterials MWCNT and Ag during a viscous Darcy Forchheimer flow over a moving needle. Thermal radiation, Joule heating, and viscous dissipations concerning the Cattaneo-Christov thermosolutal flux have been introduced. An appropriate transition is applied to rationalize the substantially paired and nonlinear governing equations. Equations after similarity transformation are processed by the finite element method. The impression of different governing parameters on the governing systems in conjunction with entropy and Bejan number is displayed through graphs and tables. Graphs are drawn with an evaluation of general and hybrid nanofluids and different nanolayer thicknesses of nanoparticles. A similarity feature concerns existing literature with good promise. The thermal impact is more significant with the occurrence of Cattaneo-Christov heat flux and is further supported by thermal radiation and the Brinkman number. It has been found that Brinkman numbers boost the rate of heat transfer. Entropy generation is nonlinearly raised with advanced outcomes of radiation parameters, Brinkman number, and Reynolds number, while Bejan number shows the opposite behavior with respect to those parameters. The nanolayer thickness of the nanoparticles restricted the irreversibility phenomena of the system, and the same feature is supported by the Bejan number.

Entropy analysis along thermophoretic particle deposition on nanofluid flow through different geometries with thermal radiation

The current study analyses the entropy of nanofluid flow over three different geometries with thermophoretic particle deposition and thermal radiation. It is essential while considering heat exchangers, transpiration, fiber coating, and other similar processes, to have a solid understanding of the transfer of both heat and mass that occurs during MHD flows across three dissimilar shapes. A mathematical model will be utilized to explore magnetohydrodynamic flows including energy transfer with heat and mass variations. In this model, some of the innovative concepts include thermophoresis, Brownian motion, the Cattaneo–Christov dual flux with the application of an external magnetic field, and the entropy generation effect are considered. By the appropriate similarity transformations, fundamental PDE’s converted into ODE’s. To solve these ODE's, the Runge–Kutta fourth order is used along with the shooting technique. The results are displayed in graphs and tables. It is observed that the velocity gets decreases with the increase of the porous parameter and magnetic field and gets stronger with the increase of the Grashof number. The temperature increases with an increase in the magnetic field, radiation parameter, Brownian motion parameter, and thermophoresis parameter. Concentration increases with the increase in a magnetic field and Brownian motion parameter but reduces with the increase of other parameters. Entropy generation gets enhanced with an increase in the magnetic field, temperature difference, concentration difference and diffusion parameters. When a flow is directed through geometries the heat and mass transfer rates are both affected by a parameter known as the thermal relaxation parameter. The influence of skin friction, Nusselt number and Sherwood number were analyzed and results were discussed.

Entropy optimization of MHD Casson-Williamson fluid flow over a convectively heated stretchy sheet with Cattaneo-Christov dual flux

This work confers the comparative study of Casson-Williamson fluid flow over a heated porous stretchy sheet. The energy and mass transfer equations are modeled by Cattaneo-Christov theory. The governing flow models were altered into an ODE model with the use of suitable transformations. The HAM scheme is applied to find the series solutions. The response of diverse flow variables on fluid speed, fluid warmness, liquid concentration, skin friction coefficient, local Nusselt number, local Sherwood number, local entropy generation number and Bejan number are analyzed through graphs and charts. It is found that the fluid speed subsides when surging values of the magnetic field, porosity, Casson fluid, Williamson fluid and injection/suction parameters. The fluid warmness escalates for a high amount of radiation, convective heating and heat generation/absorption parameters and its suppresses when enriching the convective cooling parameter. The chemical reaction parameter leads to rise in the thickness of the solutal boundary layer. The higher quantity of skin friction coefficient occurs in Casson fluid compared to Williamson fluid. The local entropy generation decimates when growing the Casson and Williamson parameters and it aggravates when raising the Biot number. The Bejan number exalts when upgrading the Reynolds, Brinkman and Biot numbers.

Numerical and Analytical Investigation for Darcy-Forchheimer Flow of a Williamson Fluid over a Riga Plate with Double Stratification and Cattaneo-Christov Dual Flux

The Darcy-Forchheimer flow of a Williamson fluid over a Riga plate was analyzed in this paper. Energy and mass equations are modeled with Cattaneo-Christov theory and double stratifications. The governing PDE models are altered into ODE models. These models are numerically solved by MATLAB bvp4c and analytically solved by the homotopy analysis method. The impact of governing flow parameters on fluid velocity, fluid temperature, fluid concentration, skin-friction coefficient, local Nusselt number, and local Sherwood number is scrutinized via graphs and tables. We acknowledged that the speed of the fluid becomes diminishes for more presence of porosity parameter. Also, we noted that the thermal and solutal boundary layer thicknesses are waning due to their corresponding stratification parameters. In addition, the maximum decreasing percentage of skin friction is obtained when the suction/injection parameter varies from 0.0 to 0.4 for Williamson and viscous fluids. The maximum increasing percentage of local Nusselt number occurs when the suction/injection parameter varies from 0.4 to 0.8 for Williamson and viscous fluids.

A Discontinuous Galerkin Method for Three-Dimensional Poroelastic Wave Propagation: Forward and Adjoint Problems

We develop a numerical solver for three-dimensional wave propagation in coupled poroelastic-elastic media, based on a high-order discontinuous Galerkin (DG) method, with the Biot poroelastic wave equation formulated as a first order conservative velocity/strain hyperbolic system. To derive an upwind numerical flux, we find an exact solution to the Riemann problem, including the poroelastic-elastic interface; we also consider attenuation mechanisms both in Biot's low- and high-frequency regimes. Using either a low-storage explicit or implicit-explicit (IMEX) Runge-Kutta scheme, according to the stiffness of the problem, we study the convergence properties of the proposed DG scheme and verify its numerical accuracy. In the Biot low frequency case, the wave can be highly dissipative for small permeabilities; here, numerical errors associated with the dissipation terms appear to dominate those arising from discretisation of the main hyperbolic system. We then implement the adjoint method for this formulation of Biot's equation. In contrast with the usual second order formulation of the Biot equation, we are not dealing with a self-adjoint system but, with an appropriate inner product, the adjoint may be identified with a non-conservative velocity/stress formulation of the Biot equation. We derive dual fluxes for the adjoint and present a simple but illuminating example of the application of the adjoint method.

Impact of double-diffusion and second order slip on convection of chemically reacting Oldroyd-B liquid with Cattaneo-Christov dual flux

This article express the outcomes of mixed convective flow of a chemically reacting Oldroyd-B liquid (OBL) with Cattaneo-Christov double flux (CCDF) under the consequence of second order slip (SS), heat absorption (HA)/heat generation (HG) and Newtonian cooling (NC)/Newtonian heating (NH). The governing PDEs are converted into ODEs using suitable variables. The homotopy analysis method (HAM) is employed to solve these resultant equations. The outcomes of diverse physical parameters, like, relaxation time, retardation time, Richardson number, buoyancy ratio, Prandtl number, radiation, heat absorption/generation, Schmidt number, chemical reaction, suction/injection, slip and Newtonian heating are discussed.

Performance comparison and optimisation of dual mover linear permanent magnet flux switching machine

Short moving primary and rigid low-cost secondary are important requirements of linear machines designed for long stroke applications. In the race, linear permanent magnet flux switching machine (LPMFSM) is a competitive candidate by confining excitation sources to short mover, thus making stator robust and low cost (made of only iron). However, single-sided LPMFSM exhibit a demerit of high normal (attraction) force due to its topology. In order to rectify the problem and enhance thrust force profile, two novel double-sided LPMFSMs are proposed with dual stator and dual mover topologies. After stator pole study, both topologies with same design dimensions are analysed and compared by 2-D finite element method here. Detailed analysis revealed that 12/14 DMLPMFSM exhibit low numerical values of thrust force ripples and detent force while maintaining average thrust force value. Hence, 12/14 DMLPMFSM is selected and optimised by structure-based deterministic optimisation (SBDO) approach to further enhance thrust force profile. Finally, comparison of initial and optimised design of 12/14 DMLPMFSM is presented to validate optimisation procedure.

Design and analysis of an axial flux dual stator flux modulating synchronous reluctance machine

This work was supported in part by the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea, and in part by the BK21PLUS Program through the National Research Foundation of Korea within the Ministry of Education.

Design of a novel dual flux modulation machine with consequent-pole spoke-array permanent magnets in both stator and rotor

In this paper, a novel dual flux modulation (DFM) machine with consequent-pole spoke-array permanent magnets (PMs) in both stator and rotor is proposed to achieve a larger torque density than regular flux modulation machines. The stator has two portions of PMs, one is set next to the stator slot with circumferential magnetization, and the other is inserted between the stator yoke and flux bridge with radial magnetization. The rotor has consequent-pole spoke-array PMs and alternative flux bridges. The proposed DFMPM machine can be regarded as the combination of the flux switching PM (FSPM) machine and vernier PM (VPM) machine. First, the structure and operational principle are introduced. Then, the proposed 12-stator-slot/10-rotor-tooth dual flux modulation permanent magnet (DFMPM) machine is compared with the FSPM machine and VPM machine in terms of flux lines distribution, back-electromotive force (EMF), cogging torque and average torque. Finally, the four proposed DFMPM machines are optimized for maximum average torque and minimum ripple torque considering the effects of split ratio, slot opening ratio, PM depth, PM angle and iron angle.

A Scalar Conservation Law for Plume Migration in Carbon Sequestration

A quasi-linear hyperbolic partial differential equation with a discontinuous flux models geologic carbon dioxide (CO$_2$) migration and storage [M. Hesse, F. Orr, and H. Tchelepi, Fluid Mech., 611 (2008), pp. 35--60]. Two flux functions characterize the model, giving rise to flux discontinuities. One convex flux describes the invasion of the plume into pore space, and the other captures the flow as the plume leaves CO$_2$ bubbles behind, which are then trapped in the pore space. We investigate the method of characteristics, the structure of shock and rarefaction waves, and the result of binary wave interactions. The dual flux property introduces unexpected differences between the structure of these solutions and those of a scalar conservation law with a convex flux. During our analysis, we introduce a new construction of cross-hatch characteristics in regions of the space-time plane where the solution is constant, and there are two characteristic speeds. This construction is used to generalize the notion of the Lax entropy condition for admissible shocks and is crucial to continuing the propagation of a shock wave if its speed becomes characteristic.

Permanent-Magnet Coupled Power Inductor for Multiphase DC–DC Power Converters

Using a coupled power inductor (CPI) in a multiphase dc–dc power converter instead of using multiple single-phase power inductors (PIs) reduces the inductor size and achieves better steady state and transient performances. To further reduce the inductor size and weight used in multiphase power converters, this paper presents a two-phase CPI that utilizes a permanent magnet (PM) to achieve almost doubled saturation current with the same size or equivalently achieve significant size and weight reduction. Operation principle of the presented permanent magnet coupled power inductor (PMCI) and required PM dimensions are derived and used as a design guide. The three-dimensional physical model of the PMCI is developed by using ANSYS/Maxwell software package to “visualize” the saturation current doubling. The fabricated PMCI design, with specifications of 24 A/phase, ∼4.25 μH/phase equivalent steady-state inductance, and ∼2.3 μH equivalent transient inductance, is tested in a 4–8 V two-phase dc–dc boost power converter with up to 50 A input current. Results show that compared to a conventional CPI design with the same size, weight, and inductance, the fabricated PMCI almost doubles the saturation current (from 13 to 24 A/phase). Compared to another CPI with a larger size but with even a smaller saturation current (18 A/phase), the core volume of the PMCI is reduced to 51.9% and the core weight is reduced to 51.2%. In addition, the PMCI achieves ∼76.3% core size and ∼73.4% core weight reductions compared to two separate single-phase PIs with the same steady-state inductance and similar saturation current (∼22 A) due to the dual flux cancelation effect from the coupling and PM realized by the presented PMCI structure.

Dual rotor flux switching permanent magnet machines with phase-group concentrated-coil windings for high performance

This paper proposes a novel dual rotor radial field flux switching permanent magnet machine (FSPMM) with phase- group concentrated-coil (PGCC) windings and two misaligned rotors to obtain high performance, including high torque density and low cogging torque, as well as low torque ripple. The proposed FSPMM features a new combination of stator slots and rotor poles, which is determined by the winding configurations. The PGCC windings are adopted to obtain a unity displacement winding factor, and enhance the flux focusing effects together with the use of spoke-type PM constructions. The unaligned arrangement of two rotors will help to not only achieve further flux magnification by an alternate operating principle for PM flux concentration, but also suppress the cogging torque. To highlight the advantages of the proposed FSPMM, two conventional FSPMMs with typical machine configurations having concentrated windings are adopted for performance comparison based on a finite element method (FEM) using JMAG-Designer.

Analysis of curvilinear motion of tracked vehicles with electromechanical dual-flux turning mechanisms

The results of the numerical simulation of the curvilinear motion of tracked vehicles with electromechanical dual–flux mechanisms of the turning are given. The variants were studied of simple modernization of the mechanical step mechanisms of the turning and gears, which were installed on the tractors of the MTLB family produced in large quantities. These tracked vehicles until now display good results on reliability and passability, but they are substantially inferior to contemporary machines in specific power, protection and ergonomic parameters. The indicated modernization makes it possible to implement, at insignificant cost, a smooth controlled change in the turning radius of the old tracked vehicles, with partial recovery of deceleration energy. In so doing, the transition from controlling the turning with the aid of levers to the steering-wheel control is facilitated. As a result of conducted studies, it was established that: – for modernization without a considerable increase in the power of the diesel engine, the most rational appears to be the scheme with two electromotors that work predominantly in the brake mode, retaining the mechanical branch of a regular transmission of a vehicle; – with an increase in the specific power up to 24 hp/t, the decrease of gear ratios in the branches of the turning mechanism from 2,6 to 2 will make it possible to increase the turnability of the machine by 11–15 % even without introduction of an electric drive to the turning mechanisms. Obtained results make it possible, at a minimum cost, to draw the characteristics of the old vehicles on the turnability and ease of control closer to the new requirements and standards.

Grand Canonical Ensembles, Multiparticle Wave Functions, Scattering Data, and Lattice Field Theories.

We show that information about scattering data of a quantum field theory can be obtained from studying the system at finite density and low temperatures. In particular we consider models formulated on the lattice that can be exactly dualized to theories of conserved charge fluxes on lattice links. Apart from eliminating the complex action problem at nonzero chemical potential μ, these dualizations allow for a particle world line interpretation of the dual fluxes from which one can extract data about the two-particle wave function. As an example we perform dual MonteCarlo simulations of the two-dimensional O(3) model at nonzero μ and finite volume, whose nonperturbative spectrum consists of a massive triplet of particles. At nonzero μ particles are induced in the system, which at sufficiently low temperature give rise to sectors of fixed particle number. We show that the scattering phase shifts can be obtained either from the critical chemical potential values separating the sectors or directly from the wave function in the two-particle sector. We find that both methods give excellent agreement with the exact result. We discuss the applicability and generality of the new approaches.

Local error estimates for least-squares finite element methods for first-order system

We present local energy type error estimates for first-order system div least-squares (LS) finite element methods. The estimate shows that the local energy norm error is bounded by the local best approximation and weaker norms which account for the pollution. The estimate is similar to the one for the standard Galerkin methods. However, our estimate needs to consider the effect of error of dual (flux) variables since LS methods approximate the primary and dual variables simultaneously. The effect of error of the dual variables is shown to be of higher order. Moreover, our estimate shows the convergence behavior when locally enriched approximation spaces are used in the area of interest. As an elementary consequence of the estimate, asymptotically exact a posteriori error estimator is constructed for the local area of interest under mild assumptions.

Analysis of a New Dual Excitation Flux Switching Machine with Outer-Rotor Configuration for Direct Drive EV

This paper presents the design improvement and analysis of dual excitation flux switching machine (DEFSM) with outer-rotor configuration for direct drive electric vehicle (EV). Deterministic design improvement approach based on two-dimensional (2-D) finite element analysis (FEA) is applied to obtain optimal torque density and power density of the proposed machine to meet the requirement of direct drive propulsion of EV. The performance comparison of the original design machine with the improved design machine is also addressed. The improved design machine has achieved 10.19 Nm/kg and 4.74 kW/kg of maximum torque density and maximum power density, respectively..

Evaluating the six-point remainder function near the collinear limit

The simplicity of maximally supersymmetric Yang–Mills theory makes it an ideal theoretical laboratory for developing computational tools, which eventually find their way to QCD applications. In this contribution, we continue the investigation of a recent proposal by Basso, Sever and Vieira, for the nonperturbative description of its planar scattering amplitudes, as an expansion around collinear kinematics. The method of G. Papathanasiou, J. High Energy Phys.1311, 150 (2013), arXiv:1310.5735, for computing the integrals the latter proposal predicts for the leading term in the expansion of the six-point remainder function, is extended to one of the subleading terms. In particular, we focus on the contribution of the two-gluon bound state in the dual flux tube picture, proving its general form at any order in the coupling, and providing explicit expressions up to six loops. These are included in the ancillary file accompanying the version of this paper on the arXiv.