Mixed convective heat transfer to flexible viscosity nanofluid over a radially elongated convective exterior with temperature dependent heat source and Arrhenius activation energy Naveen Joshi, Vijaya Lakshmi R., Jitendra Kumar Singh World Journal of Engineering, 2026 Purpose This study aims to explore the collective influence of several factors, namely, thermal radiation, Brownian motion, magnetic field and variable viscosity parameter, on the boundary layer flow, heat and mass transfer of an electrically steering nanofluid over a radially stretching exterior subjected to convective heating. In addition, the impacts of thermal and solutal buoyancy forces and activation energy are taken into account. The enlarging velocity is assumed to vary linearly with radial distance. Design/methodology/approach Through the similarity transformation technique, the governing highly nonlinear partial differential equations are transformed into a set of nonlinear ordinary differential equations, which are then numerically solved using the Runge–Kutta–Fehlberg method with a shooting technique. Findings Graphical depictions are provided to analyze the velocity, temperature and nanoparticle concentration fields under the influence of various pertinent parameters. Furthermore, local skin friction, local Nusselt and Sherwood numbers are quantitatively presented and discussed. A comparison with previous results demonstrates good agreement. Originality/value This study uniquely integrates multiple factors influencing boundary layer flow in electrically conducting nanofluids, offering a nuanced understanding of heat and mass transfer over radially stretching surfaces. By using advanced numerical methods, it provides valuable insights and quantitative data that can inform practical applications in engineering and materials science.
Unsteady MHD Natural Convective Flow of a Rotating Walters'-B Fluid over an Oscillating Plate with Fluctuating Wall Temperature and Concentration J. K. Singh, N. Joshi, P. Rohidas Journal of Mechanics, 2018 In the present study, unsteady MHD boundary layer flow of a rotating Walters’-B fluid (viscoelastic fluid) over an infinite vertical porous plate embedded in a uniform porous medium with fluctuating wall temperature and concentration taking Hall and ion-slip effects into consideration is discussed. The MHD flow in the rotating fluid system is induced due to the non-torsional oscillations of the plate in its own plane and the buoyancy forces arises from temperature and concentration differences in field of gravity. The partial differential equations governing the fluid motion are solved analytically by using regular perturbation and variable separable methods by assuming very small viscoelastic parameter. Solution for velocity field in the case when natural frequency due to rotation and Hall current is equals to the frequency of oscillations i.e. in the case of resonance is also obtained. In order to note the influences of various system parameters and to discuss the important flow characteristics, the numerical results for fluid velocity in the non-resonance case, temperature and species concentration are computed and depicted graphically versus boundary layer parameter whereas skin friction, Nusselt number and Sherwood number at the plate are computed and presented in tabular form. An interesting observation recorded that there arises flow reversal in the primary flow direction due to high rotation. When natural frequency is greater than the frequency of oscillations the fluid velocity in the primary flow direction is maximum at the plate whereas incase when natural frequency is smaller than the frequency of oscillations, it is maximum in the neighborhood of the plate.
Unsteady Magnetohydrodynamic Couette-Poiseuille flow within porous plates filled with porous medium in the presence of a moving magnetic field with hall and ion-slip effects J. Singh, Naveen Joshi, S. Begum International Journal of Heat and Technology, 2016 A study on the effects of Hall current, ion-slip and permeability on unsteady Magnetohydrodynamic Couette-Poiseuille flow within porous plates filled with porous medium in the presence of a moving uniform transverse magnetic field which is fixed relative to the moving porous plate is carried out. Flow within the channel is generated due to accelerated movement of the lower plate of the channel along x-axis and by an applied constant pressure gradient acting along x-axis. An exact solution of the governing equations is found by Laplace transform method. Numerical values of analytical solution for fluid velocity and that of shear stress at the moving porous plate of the channel are depicted for various values of pertinent flow parameters. It is noticed from the numerical result that, for the pure fluid regime, suction tends to enhance fluid velocity in the primary flow direction whereas injection has reverse effect on it. For the small permeable regime, suction tends to enhance fluid velocity in the primary flow direction in the upper half of the channel whereas injection has reverse effect on it.
Unsteady hydromagnetic heat and mass transfer natural convection flow past an exponentially accelerated vertical plate with hall current and rotation in the presence of thermal and mass diffusions Jitendra Kumar Singh, Naveen Joshi, Shik Ghousia Begum, C. T. Srinivasa Frontiers in Heat and Mass Transfer, 2016 In the present analytical study, we have considered unsteady hydromagnetic heat and mass transfer natural convection flow of an electrically conducting, heat absorbing and chemically reacting fluid past an exponentially accelerated vertical plate in a uniform porous medium taking Hall current and rotation into account. The species concentration near the plate is considered to be varies linearly with time. Two particular cases for plate temperature are considered i.e. (i) plate temperature is uniform and (ii) plate temperature varies linearly with time and after some time it is maintained at uniform temperature. The coupled partial differential equations governing the fluid flow problem are solved analytically for fluid velocity, temperature and species concentration using Laplace transform method. To examine the physical characteristic of this problem the graphs for velocity, temperature, species concentration, skin friction, Nusselt number and Sherwood number distributions are computed and generated for various values of different pertinent flow parameters. It is observed that for small thermal diffusion, the free stream value of velocity and temperature are achieved nearer to the plate in comparison to that for large thermal diffusion.
Unsteady MHD hartmann-couette flow due to time dependent movement of the plate of a darcian channel with hall current and ion-slip effects Jitendra K. Singh, Naveen Joshi, S. Ghousia Begum International Journal of Fluid Mechanics Research, 2015 Unsteady MHD Hartmann−Couette flow of a viscous, incompressible and electrically conducting fluid within parallel plate porous Darcian channel with Hall current and ion-slip effects is carried-out. Fluid flow within the channel is induced due to time dependent movement of the upper plate of the channel and by a constant pressure gradient applied along the axis of the plates of the Darcian channel. Fluid flow within the Darcian channel is permeated by a uniform transverse magnetic field, which is fixed relative to the stationary plate. Laplace transform technique is used to obtain an exact solution of the governing equations. The expression for the shear stress at the moving plate due to primary and secondary flows is also derived. To highlight the transient approach to the final steady state flow and the effects of Hall current, ion-slip, magnetic field, permeability and suction/injection, asymptotic behavior of the solution is analyzed for small and large values of time. It is noticed that, at the starting stage, secondary velocity is independent of permeability and there are no flows in the secondary flow direction in the absence of Hall current. At the final stage, fluid flow is in quasi-steady state. Steady state flow executes spatial oscillations in the flow-field whereas unsteady state flow exhibits spatial as well as inertial oscillation in the flow-field. Inertial oscillations in the flow-field are due to presence of Hall current. Numerical values of primary and secondary fluid velocities and that of shear stress at the moving plate of the Darcian channel due to primary and secondary flows are represented graphically for various values of pertinent flow parameters.
