Radiative MHD Research Articles

LTNE effect on non-linear radiative MHD mixed convective flow in an annular porous medium: Intelligent Computing Paradigm

In this study, the back-propagated Levenberg-Marquardt algorithm-based neural network intelligent computing paradigm is used to examine the influence of non-linear thermal radiation, induced magnetic field and local thermal non-equilibrium effect on the magnetohydrodynamic mixed convective flow in the vertical annular porous region. In the annular porous region the inner cylinder is considered as electrically conducting and the outer cylinder as electrically non-conducting. The heat transfer is expected due to mixed convection and non-linear thermal radiation. The Galerkin finite element method is adopted to solve the governing equations. In the vertical annulus an increase in the magnetic Prandtl and Hartmann number reduces the velocity and induced magnetic field due to a strong external magnetic field and the Lorentz force. The higher Brinkmann values decelerate the conduction of heat generated by viscous dissipation hence, the temperature increases. The fluid and solid temperature increase with the buoyancy parameter. The non-linear radiation term enhances the fluid temperature, whereas it decelerates the solid temperature. The ANN model utilises finite element method output for training, validating and testing to predict the heat transfer characteristics. The performance of the BLM-NN algorithm is assessed using mean square error, error histogram and regression.

Double stratification impact on radiative MHD flow of nanofluid toward a stretchable cylinder under thermophoresis and brownian motion with multiple slip

In this paper, numerical investigations have been performed on intricate double stratification impact with a radiative mixed convective nanofluid over a cylinder. Double stratifications comprise heat transfer used in many practical applications like power station engineering, ground-water reservoirs, thermal stratification of reservoirs, and rivers, density stratification of atmosphere, oceans, different heterogeneous mixtures, and manufacturing processing. Characteristics of heat and mass transfer have also been considered. The developing mathematical expression for momentum, energy transportation, and nano-concentration involving Brownian motion and thermophoresis inspiration are considered. The modeled equations are formulated into ordinary differential equations by applying a suitable similarity approach, which is then tackled numerically via MATLAB. Graphical illustrations of dimensionless velocity, energy, and volumetric concentration distribution are drawn against a few values of appropriate parameters. Results elucidate that enhancement occurs in the concentration profile, whereas decrement is noted for the temperature field for different values of thermophoresis and thermal stratification parameters. Our results elucidate good agreement as compared with the previously published one. The higher value of Hartmann number indicates a higher coefficient of friction.

Performance of magnetic dipole contribution on ferromagnetic non-Newtonian radiative MHD blood flow: An application of biotechnology and medical sciences

Casson flow ferromagnetic liquid blood flow over stretching region is studied numerically. The domain is influence by radiation and blood flow velocity and thermal slip conditions. Blood acts an impenetrable magneto-dynamic liquid yields governing equations. The conservative governing nonlinear partial differential equations, reduced to ODEs by the help of similarity translation technique. The transport equations were transformed into first order ODEs and the resultant system are solved with help of 4th order R-K scheme. Performing a magnetic dipole with a Casson flow across a stretched region with Brownian motion and Thermophoresis is novelty of the problem. Significant applications of the study in some spheres are metallurgy, extrusion of polymers, production in papers and rubber manufactured sheets. Electronics, analytical instruments, medicine, friction reduction, angular momentum shift, heat transmission, etc. are only few of the many uses for ferromagnetic fluids. As ferromagnetic interaction parameter value improves, the skin-friction, Sherwood and Nusselt numbers depreciates. A comparative study of the present numerical scheme for specific situations reveals a splendid correlation with earlier published work. A change in blood flow velocity magnitude has been noted due to Casson parameter. Increasing change in blood flow temperature noted due to Casson parameter. Skin-friction strengthened and Nusselt number is declined with Casson parameter. The limitation of current work is a non-invasive magnetic blood flow collection system using commercially available magnetic sensors instead of SQUID or electrodes.

Chromospheric Heating from Local Magnetic Growth and Ambipolar Diffusion under Nonequilibrium Conditions

The heating of the chromosphere in internetwork regions remains one of the foremost open questions in solar physics. In the present study, we tackle this old problem by using a very-high-spatial-resolution simulation of quiet-Sun conditions performed with radiative MHD numerical models and interface region imaging spectrograph (IRIS) observations. We have expanded a previously existing 3D radiative MHD numerical model of the solar atmosphere, which included self-consistently locally driven magnetic amplification in the chromosphere, by adding ambipolar diffusion and time-dependent nonequilibrium hydrogen ionization to the model. The energy of the magnetic field is dissipated in the upper chromosphere, providing a large temperature increase due to ambipolar diffusion and nonequilibrium ionization (NEQI). At the same time, we find that adding the ambipolar diffusion and NEQI in the simulation has a minor impact on the local growth of the magnetic field in the lower chromosphere and its dynamics. Our comparison between synthesized Mg ii profiles from these high-spatial-resolution models, with and without ambipolar diffusion and NEQI, and quiet-Sun and coronal hole observations from IRIS now reveal a slightly better correspondence. The intensity of profiles is increased, and the line cores are slightly broader when ambipolar diffusion and NEQI effects are included. Therefore, the Mg ii profiles are closer to those observed than in previous models, though some differences still remain.

Dynamics of neutron star accretion columns in split-monopole magnetic fields

ABSTRACT We perform 2D axisymmetric radiative relativistic MHD simulations of radiation pressure supported neutron star accretion columns in split-monopole magnetic fields. The accretion columns exhibit quasi-periodic oscillations, which manifest in the luminosity power spectrum as 2–10 kHz peaks, together with broader extensions to somewhat higher frequencies. The peak frequency decreases for wider columns or higher mass accretion rates. In contrast to the case of shorter columns in uniform magnetic fields, pdV work contributes substantially to maintaining the radiation pressure inside the column against sideways radiative cooling. This is in part due to the compression associated with accretion along the converging magnetic field lines towards the stellar surface. Propagating entropy waves which are associated with the slow-diffusion photon bubble instability form in all our simulations. Radial advection of radiation from the oscillation itself as well as the entropy waves is also important in maintaining radiation pressure inside the column. The time-averaged profile of our fiducial simulation accretion is approximately consistent with the classical 1D stationary model provided one incorporates the correct column shape. We also quantify the porosity in all our accretion column simulations so that this may also in principle be used to improve 1D models.

Impact of radiation on the MHD couple stress hybrid nanofluid flow over a porous sheet with viscous dissipation

The investigation is carried to observe the impact of radiation on the MHD couple stress hybrid nanofluid over porous sheet with dissipation. The water based MHD couple stress hybrid nanofluid flow due to porous shrinking sheet with thermal radiation and viscous dissipation has range of engineering applications dealing with energy distribution, solar energy storage, chemical reactors and polymer production. The flow problem is mathematically modelled into nonlinear partial differential equations, which are transformed into set of ordinary differential equations via similarity variable. The analytical solutions are derived in the form of hypergeometric functions. These results are in line with the existing classical results. The physical insights on the impact of MHD, mass transpiration, Eckert number, Couple stress, porosity and thermal radiation on velocity and temperature profiles are provided by means of graphs.

Mixed Convection Nanofluid Flow using Lie Group Scaling with the Impact of MHD Radiation Thermophoresis and Brownian Motion

The present study concerns with the mixed convection nanofluid flow across a vertical wedge with Radiation, MHD, Brownian motion, thermophoresis effects using Lie Group scaling analysis. The governing set of highly nonlinear partial differential equations are non-dimensionalized through appropriate transformations and transformed into ordinary differential equations using Lie Group Scaling, which is solved numerically using Shooting method along with bvp4c scheme. The radiation heat flux approximated with the Rosseland approximation has been implemented in the flow equations. The influence of mixed convection, magnetic, Brownian motion, radiation, Lewis number and thermophoresis parameter on the flow profiles are examined. For establishing the efficiency of our adopted numerical technique, we made comparisons with the earlier published works and we found them to be in very good agreement.

How Fluid Particle Interaction Affects the Flow of Dusty Williamson Fluid

A model of two-phase flow involving non-Newtonian fluid is described to be more reliable to present the fluid that involves industrial applications due to the special characteristics in its behavior. Many models of non-Newtonian fluid were discovered in the last few decades but the model that captured the most attention is the Williamson model. The consideration of the existing particles in the Williamson flow (two-phase Williamson fluid) will make the model more interesting to investigate. Hence, this paper is aimed to explore the flow of two-phase Williamson fluid model in the presence of MHD and thermal radiation circumstances. The obtained ordinary differential equations after the transformations are solved using the Runge-Kutta Fehlberg (RKF45) method. The flow is considered asymmetric since it moves over a vertical stretching sheet with external stimuli. The result displays variation in dust phases compared to the fluid phase under distribution of velocity and temperature. It can be concluded that the fluid–particle interaction (FPI) parameter lessening the motion of fluid and heating characteristics. In addition, the upsurges on skin friction and heat transfer are resulting from the rising FPI. Furthermore, the presence of Williamson parameter increases the skin friction while causing degenerations on heat transfer of flow.

Применение к радиационной акустике метода Уитхэма для анализа волновых явлений в намагниченной плазме

The exact governing equation of radiative acoustics in radiating grey gas is derived in this work, taking into account the influence of the transverse magnetic field. The radiative MHD is described by three equations of hydrodynamics and two equations of radiation momentum with extensive use of the formalism of radiative thermodynamics. In order to describe the propagation of linear radiative magneto-acoustic perturbation waves with scattering and attenuation, radiation-thermal dissipation conditions, radiation drag force, and magnetic force and Joule heat are introduced into these equations. The Eddington approximation is used, which allows us to study the modes of radiative magneto-hydrodynamic waves in two asymptotic cases - optically thin and thick gas. The exact governing equation derived in this paper allows, using the heuristic Whitham method, to obtain a set of approximate governing equations of lower order, each of which is part of a reliable approximation to the exact equation in a certain region of the independent time variable. The relatively simple form of such equations allows, without formally solving the full problem, to investigate the physical processes occurring in each radiative magneto-hydrodynamic linear travelling wave.

EFFECTS OF RADIATION AND CHEMICAL REACTION ON MHD CASSON NANOFLUID FLOW PAST A POROUS STRETCHING SURFACE

The present investigation aims to study the influence of thermal radiation and chemical reaction on the unsteady magnetized flow of Casson fluid with immersed nanoparticles. The flow is past a permeable stretching surface. The nanofluid heat transmission characteristics are described with the Buongiorno model. The governing system of non-linear partial differential equations (PDEs) is converted into non-linear ordinary differential equations (ODEs) with a similarity group of transformations. The reduced ODEs are numerically solved with an effective shooting strategy along with the standard R-K fourth-order method. The graphical illustration for the immerging parameters on non-dimensional velocity, temperature, and concentration is obtained through bvp4c using MATLAB. The code validation is provided by comparing the numerical outcomes of a few parameters with recently published work. The result shows that the thermal radiation boosts the energy supply in the flow field, and hence, the thermal regime enhances quickly. Due to the rise in chemical activity and Schmidt number, the concentration profile declines. The flow velocity declines with higher magnetic flux.

Influence of Thermophoresis and Brownian Motion of Nanoparticles on Radiative Chemically-Reacting MHD Hiemenz Flow over a Nonlinear Stretching Sheet with Heat Generation

In this study, a radiative MHD stagnation point flow over a nonlinear stretching sheet incorporating thermophoresis and Brownian motion is considered. Using a similarity method to reshape the underlying Partial differential equations into a set of ordinary differential equations (ODEs), the implications of heat generation, and chemical reaction on the flow field are described in detail. Moreover a Homotopy analysis method (HAM) is used to interpret the related mechanisms. It is found that an increase in the magnetic and velocity exponent parameters can damp the fluid velocity, while thermophoresis and Brownian motion promote specific thermal effects. The results also demonstrate that as the Brownian motion parameter is increased, the concentration values become smaller.

Radiative MHD Nanofluid Flow Due to a Linearly Stretching Sheet with Convective Heating and Viscous Dissipation

This article describes a two-dimensional steady laminar boundary layer flow and heat mass transfer caused by a non-Newtonian nanofluid due to a horizontally stretching sheet. The non-dimensional parameters take into consideration and regulate the effects of convective boundary condition, slip velocity, Brownian motion, thermophoresis and viscous dissipation. The thermal radiation, which affects the flow’s thermal conductivity and the nanofluid’s variable viscosity are also taken into consideration. We propose that a hot fluid could exist beneath the stretching sheet’s bottom surface, which could aid in warming the surface via convection. The physical boundary conditions are non-dimensionalized, as are the governing transport set of nonlinear partial differential equations. By using the shooting approach, numerical values for dimensionless velocity, temperature and nanoparticle concentration are achieved. Distributions of velocity, temperature and concentration are plotted against a number of newly important governing factors, and the outcomes are then provided in accordance with those graphs. Additionally, the local skin-friction coefficient, the local Sherwood number and the local Nusselt number are discussed in order to further clarify and thoroughly explain the current problem. In order to validate the numerical results, comparisons are made with previously published data in the literature. There is a really good accord. Additionally, the current work has implications in the nanofluid applications.

FEM computations and Taguchi optimization in nonlinear radiative MHD MWCNT-MgO/EG hybrid nanoliquid flow and heat transfer over a 3D wedge surface

The problems concerning to heat transport in hybrid nanofluids on a wedge surfaces are of great interest due to their relevance in applications such as solar panels, drying processes, cooling of electronic equipment, heat exchangers, and air heaters. Therefore, the present study explores the nonlinear thermal radiative heat transport features and three-dimensional rheological characteristics of MWCNT-MgO/EG hybrid nanofluid flowing over a wedge considering the variable magnetic field, and multiple slip boundary conditions. The single-phase model comprising of the experimental data with their dependency on temperature and nanoparticle weight fraction is used for thermal conductivity and viscosity of composite nanomaterial. Rosseland and Boussinesq approximations are accounted. The wedge surface is maintained at thermal jump condition, whereas the ambient state is considered at a constant temperature. The governing conservation laws are transformed into a system of ordinary differential equations via space type similarity transformations, and then are solved using the Galerkin finite element method. The L16 orthogonal array-based Taguchi method is applied to determine the optimal setting of governing parameters are determined for maximum heat transport rate. The contribution of physical parameters in the enhancement of heat transport rate is also estimated. The temperature jump condition has the maximum contribution (51.72%), among the selected four physical parameters whereas the nanoparticle weight fraction has the least (10.02%). The nonlinear thermal radiation has the maximum heat transfer rate compared to the linear one.

Impacts of uniform and sinusoidal heating in a nanofluid saturated porous chamber influenced by the thermal radiation and the magnetic field

A numerical investigation on the impacts of heater length increased from left corner along with the bottom wall in a Cu-water nanofluid-filled porous cavity in the existence of MHD and thermal radiation is performed out. The bottom wall is heated with two different types of heater (both uniform and nonuniform) separately. Three various lengths of heater are considered. Constant cold upper horizontal wall moves in the positive direction. The other sidewalls and excluding the heating portion of the bottom wall are considered to be adiabatic. The system of dimensionless form of governing equations is solved by finite volume method (FVM) with appropriate boundary and initial conditions and SIMPLE algorithm has been employed for the pressure term. For both types of heating, the highest heat transfer is attained with the length of heater for all taken Richardson number. The effect of magnetic field is very low on heat transfer with the thermal source length and nonuniform heating in free convection regime. On increasing the heater length in nonuniform heating, overall heat transfer rate is decreased first and then raised. The percentage of increasing of average Nusselt number with an increase of thermal radiation parameter in nonuniform heating is higher than uniform heating. The effect of magnetic field is significant for all taken solid volume fraction in uniform heating than the nonuniform heating with heater length

Impacts of Cattaneo–Christov heat flux on the radiative MHD nanofluid flow past a stretched cylinder under multiple slip conditions

AbstractThis investigation explores the features of velocity distribution, mass and heat transmissions of nanoliquid stream over a permeable cylinder accompanied by Cattaneo–Christov heat model and thermal radiation with nonlinear sort. Multiple slip conditions have been also encountered here. A magnetic force is oriented along vertically upward. The existence of thermophoresis together with Brownian motion has been assumed here. The foremost equations and associated boundary conditions have been normalized through the similarity technique. Then we solve the system numerically along with the fourth‐order Runge–Kutta shooting scheme by using the software MAPLE‐17 and round it with our preassigned accuracy level. The obtained outcomes are epitomized by tables and graphs. All of the impacts have been compared in suction and injection correspondingly and explained with proper reasoning. In charts, the physical consignments (such as Sherwood number, Nusselt number and skin friction) reveal the transference of mass and temperature and amount of friction by nanoparticles in the nanocomposition. For suction, the nanofluidic temperature gradually diminished due to the advanced thermal relaxation, whereas the contrary fact is exhibited in injection. The relaxation parameter of concentration provides a positive influence on mass transmission. The rates of amplification of this transportation are 1.99% and 3.87%, measured in consideration of injection and suction, respectively. Thermal radiation influenced the fluid's temperature in a positive direction. It increases Nusselt number with 41.75% in suction, and 45.21% is recorded for injection.

Numerical simulation of 3D Darcy–Forchheimer fluid flow with the energy and mass transfer over an irregular permeable surface

The Jeffrey fluid model is capable of accurately characterizing the stress relaxation behavior of non-Newtonian fluids, which a normal viscous fluid model is unable to perform. The primary objective of this paper is to provide a comprehensive investigation into the effects of MHD and thermal radiation on the 3D Jeffery fluid flow over a permeable irregular stretching surface. The consequences of the Darcy effect, variable thickness and chemical reaction are also considered. The phenomena have been modeled as a nonlinear system of PDEs. Using similarity substitution, the modeled equations are reduced to a dimensionless system of ODEs. The parametric continuation method (PCM) is used to determine the numerical solution to the obtained sets of nonlinear differential equations. The impact of physical parameters on temperature, velocity and mass profiles are presented through Figures and Tables. It has been noticed that the energy profile magnifies with the increment of porosity term, thermal radiation and heat source term, while diminishing with the flourishing upshot of power index and Deborah number. Furthermore, the porosity term and wall thickness parameter enhance the skin friction.

Mass Transfer of a Thermally Radiative MHD Cattaneo-Christov Nanofluid between Two Stretchable Spinning Disks

The investigation on the impacts of magnetic field, thermal radiation, generation of heat and mass transfer in a porous-medium-embedded homogenous nanofluid flow between two stretchable spinning disks is crucial since spinning disks are prevalent in many engineering and technological applications. The objective of this research was to analyze the influences of these parameters using the Cattaneo-Christov heat flux model against the flow’s temperature, velocity and concentration profiles. Temperature profile is a decreasing function of thermal relaxation time parameter due to the particles require a longer period to transfer heat to the next particles. The rates of heat transfer at both spinning disks decrease as values of heat generation, Eckert number, Prandtl number, Brownian diffusion, thermophoresis diffusion and rotation ratio increase. The disks’ rates of mass transfer decrease with more thermophoresis diffusion, heat generation, heat transfer dissipation, and momentum diffusivity, but they increase with thermal radiation parameter. The current work attempts to include the transport profile of a Buongiorno’s nanofluid embedded in a Darcian porous medium between dual spinning disks with magnetic field, thermal radiation and generation of heat using the heat flux model of Cattaneo-Christov’s. Von Karman transformations are utilized to transform the nonlinear partial differential equations of fluid dynamics into coupled nonlinear ordinary differential equations (ODEs). These coupled ODEs are later solved by employing a shooting method with MATLAB bvp4c algorithm. All numerical evidences from this investigation are conferred through tables and figures after validation of present computations.

Where is the base of the Transition Region? Evidence from TRACE, SDO, IRIS and ALMA observations

Classic solar atmospheric models put the Chromosphere-Corona Transition Region (CCTR) at ∼2 Mm above the τ5000=1 level, whereas radiative MHD (rMHD) models place the CCTR in a wider range of heights. However, observational verification is scarce. In this work we review and discuss recent results from various instruments and spectral domains. In SDO and TRACE images spicules appear in emission in the 1600, 1700 and 304 Å bands and in absorption in the EUV bands; the latter is due to photo-ionization of H i and He i, which increases with wavelength. At the shortest available AIA wavelength and taking into account that the photospheric limb is ∼0.34 Mm above the τ5000=1 level, we found that CCTR emission starts at ∼3.7 Mm; extrapolating to λ=0, where there is no chromospheric absorption, we deduced a height of 3.0±0.5 Mm, which is above the value of 2.14 Mm of the Avrett and Loeser model. Another indicator of the extent of the chromosphere is the height of the network structures. Height differences produce a limbward shift of features with respect to the position of their counterparts in magnetograms. Using this approach, we measured heights of 0.14±0.04 Mm (at 1700 Å), 0.31±0.09 Mm (at 1600 Å) and 3.31±0.18 Mm (at 304 Å) for the center of the solar disk. A previously reported possible solar cycle variation is not confirmed. A third indicator is the position of the limb in the UV, where IRIS observations of the Mg ii triplet lines show that they extend up to ∼2.1 Mm above the 2832 Å limb, while AIA/SDO images give a limb height of 1.4±0.2 Mm (1600 Å) and 5.7±0.2 Mm (304 Å). Finally, ALMA mm-λ full-disk images provide useful diagnostics, though not very accurate, due to their relatively low resolution; values of 2.4±0.7 Mm at 1.26 mm and 4.2±2.5 Mm at 3 mm were obtained. Putting everything together, we conclude that the average chromosphere extends higher than homogeneous models predict, but within the range of rMHD models..

Estimation of chemical properties of single- and multi-wall carbon nanotubes (SWCNT/MWCNT) in the suspended nanofluids flow over a thin moving needle

ABSTRACT The aim of the current study is to analyze the flow and heat transport mechanism in carbon nanotubes (CNTs) in the suspended nanofluids flow due to a thin needle. The influence of MHD, activation energy, and thermal radiation are also incorporated while developing boundary layer equations governing the nanofluid flow. The governing partial differential equations (PDEs) problem are reduced into a set of nonlinear ordinary differential equations (ODEs) using an appropriate similarity transformation and then computed numerically through the Runge–Kutta–Fehlberg fifth-order (RKF-5) numerical method with a shooting scheme. The sway of significant parameters on velocity, temperature, and concentration evaluations are examined in detail, and the results are shown graphically. The quantities of physical interest, such as local skin friction coefficient, local Nusselt number, and local Sherwood number, are also investigated for pertinent parameters. When the size of needle thickness expands, the surface drag force increases for single- and multi-wall carbon nanotubes. Furthermore, heat transfer rate enhances by rising values of Eckert number for first and second branch solutions. The results also revealed that the higher values of the chemical reaction parameter diminish the concentration distribution for both solutions.

Radiative MHD flow of Rivlin–Ericksen nanofluid of grade three through porous medium with uniform heat source

BackgroundThe paper investigates the analytical and numerical solution of the radiation effect on MHD flow of Rivlin–Ericksen nanofluid of grade three through a porous medium with a uniform heat source between two vertical flat plates. The governing equations are solved analytically using multi-step differential transform method (MDTM) and numerically using finite difference method (FDM) and shooting method by designing MATLAB and Mathematica algorithms. The study discovered that the MDTM, FDM, and shooting methods are effective for solving nonlinear differential equations like this one.ResultsGraphs and tables show the influence of different parameters on velocity and temperature. Figures and tables show the comparisons between current outcomes and previous results that are accessible.ConclusionsThe present results showed that the analytical and numerical solutions agree well with previously published outcomes.