Entropy optimization analysis of Marangoni convective flow over a rotating disk moving vertically with an inclined magnetic field and nonuniform heat source

The present study investigates the Marangoni convective fluid flow over a rotating disk with an inclined magnetic field and in the presence of a nonuniform heat source when the disk moves upward/downward with nonconstant velocity with the incorporation of the second law of thermodynamics. The Keller-box method is applied to the reduced system of equations to draw graphical illustrations. The study of these illustrations to examine the effects of involved pertinent parameters, like, magnetic field, Marangoni number, angle of inclination, vertical disk movement parameter, heat source, and disk rotation, on velocity and temperature profiles, reveals some interesting findings. From the analysis, it can be concluded that the skin friction coefficient increases with more angle of inclination and the Marangoni number with the reverse trend in case of vertical disk movement. Also, the Marangoni number and vertical disk motion diminish the Nusselt number with a positive effect in the case of more angle of inclination. The rate of entropy generation is enhanced with the temperature ratio parameter while it diminishes with the inclined magnetic field of any strength. The current study in its reduced form is in excellent agreement with earlier published work to ensure the validity of the used numerical scheme.     

Boundary-layer flow of nanofluids over a moving surface in a flowing fluid

The steady boundary-layer flow of a nanofluid past a moving semi-infinite flat plate in a uniform free stream is investigated. The plate is assumed to move in the same or opposite directions to the free stream. The resulting system of nonlinear ordinary differential equations is solved numerically using the Keller-box method. Numerical results are obtained for the skin-friction coefficient, the local Nusselt number and the local Sherwood number as well as the velocity, temperature and the nanoparticle volume fraction profiles for some values of the governing parameters, namely, the plate velocity parameter, Prandtl number, Lewis number, the Brownian motion parameter and the thermophoresis parameter. The results indicate that dual solutions exist when the plate and the free stream move in the opposite directions.     

Steady flow of an Eyring Powell fluid over a moving surface with convective boundary conditions

In this article, the flow and heat transfer of Eyring Powell fluid over a continuously moving surface in the presence of a free stream velocity are investigated. Convective boundary conditions have been used in the problem formulation. The solution for velocity and temperature are computed by applying the homotopy analysis method (HAM). The effects of emerging fluid parameters (?), (δ) and Prandtl number (Pr) on the velocity and temperature are illustrated through graphs and tables for different values of λ. It is found that the boundary layer thickness is an increasing function of (?) and decreasing function of (δ). However the temperature and thermal boundary layer thickness decrease when the values of (?) and (δ) are increased.     

The heating of magnetic nanoparticles in a rotating magnetic field

ABSTRACT

The specific absorption rate of magnetic nanoparticles in a rotating magnetic field has been calculated taking into account both thermal fluctuations of the particle magnetic moments and strong magneto-dipole interactions in nanoparticle clusters with various filling factors. For an assembly of interacting superparamagnetic nanoparticles, the maximal values of the specific absorption rate in a rotating magnetic field are found to be 30–40% greater than that in alternating magnetic field. In addition, for the given filling factor and magnetic field amplitude in rotating magnetic field the nanoparticles in a wider range of diameters can effectively contribute to the energy absorption process. Therefore, the use of rotating magnetic field seems preferable in magnetic nanoparticle hyperthermia.     

Differential transformed approach of unsteady chemically reactive nanofluid flow over a bidirectional stretched surface in presence of magnetic field

This study investigates the consequences of steady and unsteady nanofluid flow over a bidirectional stretching sheet. Herein, the magnetic field is working in the normal direction. The Brownian motion together with thermophoresis is taken into consideration. Moreover, the chemical reaction within the nanoingredients also occupies a novel corner in this study. The leading equations of the considered model are transferred to nonlinear ordinary differential equations (ODEs) by an appropriate similarity transformation. The differential transformation method is used to solve the set of ODEs. We have used MAPLE‐17 software to solve this with the desired accuracy rate. Results are portrayed with graphs and tables. The corresponding physical consignments such as the Nusselt number, skin friction, and the Sherwood number are exhibited. Excellent improvement in heat and mass transport is observed, which can be visualized through tables. Outcomes reveal that both the temperature and x‐direction velocity are reduced for the stretching parameter. Heat transport escalates for stretching factor, but higher outcomes are marked for the unsteady flow as compared with the steady flow. The mass transfer also increases for the chemical reaction factor, but the rate of increment is higher for the unsteady flow.     

Impact of activation energy and gyrotactic microorganisms on flow of Casson hybrid nanofluid over a rotating moving disk

Many models of various non-Newtonian fluid flows for different geometries are available for analyzing the mass and heat transfer. Nevertheless, for researchers, it is challenging to choose the most suitable model for a specific geometry. Here, we have adopted a modified Buongiorno model to explore the impact of activation energy on the Casson hybrid nanofluid flow over an upward/downward-moving rotating disk filled with the gyrotactic microorganisms. Moreover, the external magnetic field can establish the magnetic effect, which normalizes the features of heat, mass transfer, and fluid flow. Here, we used silver and copper as nanoparticles suspended in human blood as the carrier fluid. The modeled partial differential equations are converted to ordinary differential equations by opting suitable similarity variables. The numerical solutions of these reduced equations are attained by means of Runge–Kutta–Fehlberg fourth-fifth-order method by adopting a shooting scheme. An investigation of the attained outcomes reveals that the flow field is affected appreciably by the activation energy, bioconvection, and magnetic effect. Peclet and concentration difference numbers diminish the microorganism's profile. A rise in values of the Brownian motion parameter leads to an increase in the rate of heat transfer.     

Flow and heat transfer in a moving fluid over a moving non-isothermal surface

Heat transfer characteristics for a boundary layer forced convective flow past a moving parallel flat non-isothermal surface in the presence of heat source/sink are obtained. The cases of surface temperature varying directly or inversely with power-law exponent are considered. The similarity solutions are obtained. The numerical results are validated by comparing them with the available results in the literature for some special cases. It is found that dual solutions exist when the surface and the fluid move in the opposite directions. Furthermore, exact and analytical solutions are provided for some parametric regimes.     

Analysis of a boundary layer flow over moving an exponentially stretching surface with variable viscosity and Prandtl number

Boundary layer flow phenomenons on a stretching sheet find numerous applications in industrial processes such as manufacture and extraction of rubber and polymer sheets. The current study focuses on two‐dimensional water boundary layer flow on exponential stretching surface with a vertical plate for variable physical properties of fluid such as viscosity and Prandtl number. The Quasilinearization technique has been used on governing equations to transform nonlinear to linear equations and these equations are discretized by finite difference techniques to get numerical solutions. The effect of buoyancy parameters (λ), velocity ratio parameter () and streamwise coordinator (ξ) on velocity profiles (F), temperature profiles (θ), local skin‐friction coefficient (C_fx(Re_Lξexp(ξ)^)1/2) and the local Nusselt number (Nu_x(Re_Lξexp(ξ)^)?1/2) has been analyzed graphically based on numerical outcome. The magnitude of velocity profiles increases and temperature profile decreases approximately by 4% and 16% with increases the buoyancy parameter from λ = 1 to λ = 3 at = 0.5 and ξ = 1.0. The skinfriction and heat transfer coefficient increases approximately by 22% and 27% with an increase in ξ from 0.5 to 1.0 at fixed = 0.5 and λ = 1.0. The variations of velocity profiles and temperature profiles have more impact with as compared to ξ and λ. The benchmark studies were carried out to validate the current results with previously published work and found to be in excellent agreement.     

Steady MHD mixed convection flow of a viscoelastic fluid over a magnetized convectively heated vertical surface with Hall current and induced magnetic field effects

In this paper, the steady magnetohydrodynamic mixed convection flow of a viscoelastic fluid over a magnetized vertical surface embedded in a uniform porous material with rotation is considered. The Hall and induced magnetic field effects are also considered in this investigation. The regular perturbation technique is used to find the solutions of flow governing equations. To analyze the consequences of flow-influencing parameters to the flow variables, numerical computation has been performed and the results are illustrated in graphical and tabular forms. It is interesting to note that magnetic diffusion leads to the increase of the fluid flow. It brings a decrement in the induced magnetic field in the vicinity of the magnetized vertical surface.     

Convection and instability of thermocapillary flow in a liquid bridge subject to a non-uniform rotating magnetic field

A three-dimensional liquid bridge is considered in this study to numerically investigate the effects of an external non-uniform rotating magnetic field (RMF) on the thermocapillary flow in semiconductor melt under microgravity. Simulations are carried out to examine the convection and instability features of the thermocapillary flow over a range of Marangoni numbers (Ma = 15–50) under a non-uniform RMF. The present results show that applying an external non-uniform RMF enhances the maximum tangential velocity and depresses the maximum axial velocity. As a consequence, an approximately axisymmetric flow is maintained in the melt under the effect of the non-uniform RMF, which is beneficial for growing high quality crystal. Further investigation of the thermocapillary flow subject to different non-uniform RMFs (corresponding to Taylor numbers Ta = 3.8 × 10²–1.86 × 10⁴ and Rotating Reynolds number Re_ω = 2.2 × 10⁴) reveals that the thermocapillary convection may undergo a transition from the approximately axisymmetric steady flow to a periodically oscillatory flow for Ma above a critical value. The critical Ma generally increases with the intensity of the non-uniform RMF.     

OHAM simulation of 3D transverse magnetic field in rotating flow of Maxwell nanofluid over a stretching sheet with chemical reaction and heat source/sink

In this article, we investigate the heat transfer characteristics of a Maxwell nanofluid along a stretching sheet with transverse magnetic field, considering the presence of heat source/sink and chemical reaction. We consider appropriate similarity transformation for transforming the governing nonlinear equations into nondimensional highly nonlinear coupled ordinary differential equations. The optimal homotopy analysis method is utilized for solving the resultant-coupled equations. The impact of all sundry parameters, like, Deborah number, Prandtl number, magnetic parameter, thermophoresis, rotation parameter, chemical reaction, velocity slip, Schmidt number, Brownian motion parameter, heat sources per sink, Biot number, and Eckert number, on the temperature, velocity, and concentration fields is reported, analyzed, and described through graphs and tables. It is noticed that higher values of magnetic parameter and Deborah number reduce the horizontal velocity field. Furthermore, it is observed that the Biot number and heat source/sink parameter enhance the temperature distribution.     

Magnetohydrodynamic free convection flow over a wedge in the presence of a transverse magnetic field

This paper presents the main results of a theoretical study focusing on the effects of a uniform magnetic field on the free convection flow of an electrically conducting fluid past an isothermal wedge. A very efficient numerical method has been used to solve the non-similar boundary layer equations. A range of values for the magnetic field parameter, wedge angle parameter and Prandtl number were considered. Flow and heat transfer characteristics are presented and discussed.     

On MHD and slip flow over a rotating porous disk with variable properties

The steady laminar magnetohydrodynamics (MHD) flow of a viscous Newtonian and electrically conducting fluid over a rotating disk with slip boundary condition is investigated taken into account the variable fluid properties (density, (ρ), viscosity, (μ) and thermal conductivity, (κ)). These fluid properties are taken to be dependent on temperature. The governing equations, which are partial and coupled, are transformed to ordinary ones by utilizing the similarity variables introduced by von Karman and the resulting equation system is solved numerically by using a shooting method. The resulting velocity and temperature distributions are shown graphically for different value of parameters entering into the problem. The numerical values of the radial and tangential skin-friction coefficients and the rate of heat transfer coefficient are shown in tabular form.     

Transient flow of a conducting fluid with heat transfer due to an infinite rotating disk

The unsteady MHD flow of an incompressible viscous electrically conducting fluid above an infinite rotating disk is studied with heat transfer. The effect of an external uniform magnetic field on the velocity and temperature distributions as well as the heat transfer is considered. Numerical solutions of the nonlinear equations which govern the magnetohydrodynamics and energy transfer are obtained.     

Convective nanofluid flow over a vertical cone with a rough surface

In recent literature, the analysis of a combined convective flow over a cone has received a lot of attention. To explore the convection effects of flow over a cone in greater detail, in this investigation, we have considered a cone with a rough surface, which is entirely a new flow problem. Recent studies have shown the influence of roughness on fluid flow over several geometries, but flow over a rough conical surface has not been studied so far. In addition, we have analyzed the effects of nanoparticles, magnetohydrodynamic (MHD), and suction/blowing, which could have significant impacts on characteristics of fluid flow over the cone with a rough surface. Initially, the governing equations, which are partial differential equations with a high degree of nonlinearity, are nondimensionalized through Mangler's transformations. Later, linear equations are obtained via the method of quasilinearization, which is then solved numerically through finite difference approximations. The roughness of the cone's surface has notable effects on fluid flow, that too away from the origin. In fact, the roughness increases the friction at the cone's surface. Furthermore, the magnetic field applied at the wall increases the surface friction. Thus, the combination of roughness and MHD helps delay the boundary layer separation. On the other hand, the suction reduces the temperature of the fluid and increases the energy transport strength, while the thermophoresis parameter exhibits the contrary nature. Therefore, the combined consideration of these two could enhance energy transport strength in several industrial applications.     

Unsteady stagnation-point flow over a plate moving along the direction of flow impingement

Unsteady plane and axisymmetric stagnation flow of an incompressible viscous fluid on the body that moves along the oncoming flow with a time-dependent velocity is studied in this work. Similarity solutions for the full Navier–Stokes equations are obtained and the results of the flow velocity, shear stress and stream lines are reported for both plane two dimensional flow and axisymmetric flow. The results show that the features of the similar boundary flow highly depends on a characteristic parameter β. There exists a critical value β_c below which no similarity solution to the flow is found. When β_c < β < 0, two solution branches exist and different flow patterns appear for each branch. Flow with monophonically growing velocity, reversed flow and flow with S-shaped velocity are obtained for various values of β. The boundary layer thickness of the plane and axisymmetric flows is tabulated, the streamlines of the flow are demonstrated, and the shear stress over the boundary layer is also discussed.     

Convective flow past an accelerated porous plate in rotating system in presence of magnetic field

Investigation on hydromagnetic convective flow of an incompressible homogeneous viscous liquid over an accelerated porous plate with suction/injection is presented using Laplace transform technique. The whole system is in a state of solid body rotation with constant angular velocity about z^′-axis normal to the plate. The boundary conditions of the problem are of physical significance and thus the problem may have some important and interesting characteristic features of hydromagnetic spin up flows. The effects of suction/injection parameter on the velocity field and of Prandtl number on temperature field are graphically shown.     

Upshot of radiative rotating Prandtl fluid flow over a slippery surface embedded with variable species diffusivity and multiple convective boundary conditions

Here, modeling and computations are performed to explore the impact of variable molecular diffusivity, nonlinear thermal radiation, convective boundary conditions, momentum slip, and variable molecular diffusivity on Prandtl fluid past a stretching sheet. By using the compatible transformation, the partial differential equations regarding momentum, energy, and concentration are reformed into ordinary differential equations and furthermore, these equations are handled numerically via the shooting method. The behavior of intricate parameters that emerge during numerical simulation is displayed in the form of tables and graphs. These outcomes are supplemented with the information for the heat transfer rate and surface drag coefficients. It is perceived that an uplift in the temperature profile occurs by virtue of augmentation in the temperature convection parameter, and furthermore, mass fraction field escalates owing to an amplification in the chemical reaction coefficient.     

Transient mixed convection flow arising due to thermal diffusion over a porous sensor surface inside a squeezing horizontal channel

A transient laminar mixed convection flow of viscous incompressible fluid generated by thermal buoyancy force, over a horizontal porous sensor surface placed inside a squeezing channel is analysed. The non-similar boundary layer equations for the flow and energy are solved numerically for different time regimes. The quantities of physical interest like skin friction coefficient, heat transfer coefficient, velocity and temperature profiles are calculated for different values of physical parameters, Pr, b, S and ξ. The implicit finite difference approximation together with Keller box method is employed for the solution for small and all time regime, where as, a series solution is found for large time regimes. A good agreement of the results computed by different methods has been observed.