scholarly journals Effectiveness of Hall current and exponential heat source on unsteady heat transport of dusty TiO2-EO nanoliquid with nonlinear radiative heat

2019 ◽  
Vol 6 (4) ◽  
pp. 551-561 ◽  
Author(s):  
Basavarajappa Mahanthesh ◽  
Nagavangala Shankarappa Shashikumar ◽  
Bijjanal Jayanna Gireesha ◽  
Isac Lare Animasaun
Keyword(s):  
Boundary Layer ◽  
Nusselt Number ◽  
Heat Source ◽  
Friction Factor ◽  
Skin Friction ◽  
Heat Transport ◽  
Radiative Heat ◽  
Hall Current ◽  
Dust Particles ◽  
Numeric Data

Abstract The problem of exponential heat source across a flowing nanofluid (TiO2-EO; titanium oxide-Engine oil) containing tiny dust particles on a deformable planar plate has been an open question in meteorology. In this paper, the boundary layer transient two-phase flow of dusty nanoliquid on an isothermal plate which is deforming with time-dependent velocity in the presence of exponential heat source is studied. The impacts of Hall current, nonlinear radiative heat and an irregular heat source (temperature based heat source and exponential space-based heat source) are also accounted. Dusty nanofluid is the composition of dust particles and nanoliquid (TiO2-EO). Using relevant transformations, the system of PDEs is rehabilitated to the system of ODEs and then treated numerically. Exploration of the impacts of pertinent parameters on velocity and temperature fields is performed via graphical illustrations. Numeric data for skin friction factor and the Nusselt number is presented and their characteristics are analyzed/quantified through the slope of linear regression via data points. Highlights Boundary layer flow of dusty nanoliquid past a isothermal plate is studied. Impacts of Hall current and irregular heat source are also accounted. Role of physical parameters are focused in momentum and heat transport distributions. Numeric data for skin friction factor and the Nusselt number is presented.

Exponentially Decaying Heat Source on MHD Tangent Hyperbolic Two-Phase Flows over a Flat Surface with Convective Conditions

2018 ◽  
Vol 387 ◽  
pp. 286-295 ◽  
Author(s):  
S.U. Mamatha ◽  
Chakravarthula S.K. Raju ◽  
Putta Durga Prasad ◽  
K.A. Ajmath ◽  
Mahesha ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Differential Equations ◽  
Heat Source ◽  
Thermal Boundary Layer ◽  
Energy Transport ◽  
Weissenberg Number ◽  
Dust Particles ◽  
Convective Conditions ◽  
Two Phase ◽  
Velocity Boundary Layer

The present framework addresses Darcy-Forchheimer steady incompressible magneto hydrodynamic hyperbolic tangent fluid with deferment of dust particles over a stretching surface along with exponentially decaying heat source. To control the thermal boundary layer Convective conditions are considered. Appropriate transformations were utilized to convert partial differential equations (PDEs) into nonlinear ordinary differential equations (NODEs). To present numerical approximations Runge-Kutta Fehlberg integration is implemented. Computational results of the flow and energy transport are interpreted for both fluid and dust phase with the support of graph and table illustrations. It is found that non-uniform inertia coefficient of porous medium decreases velocity boundary layer thickness and enhances thermal boundary layer. Improvement in Weissenberg number improves the velocity boundary layer and declines the thermal boundary layer.

Genesis and Features of Dust Devil-Like Vortices in Convective Boundary Layers – A Numerical Study Using LES and DNS

2020 ◽  
Author(s):  
Sebastian Giersch ◽  
Siegfried Raasch
Keyword(s):  
Boundary Layer ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Heat Transport ◽  
Vortex Core ◽  
Dust Particles ◽  
Dust Devil ◽  
Dust Devils ◽  
Convective Boundary ◽  
Rayleigh Numbers

<p>Dust devils are convective vortices with a vertical axis of rotation mainly characterized by a local minimum in pressure and a local maximum in vertical vorticity within the vortex core. They are made visible by entrained dust particles. That's why they occur primarily in dry and hot areas. Currently, there is great uncertainty about the extent to which dust devils contribute to the atmospheric aerosol and heat transport and thereby influence earth's radiation budget as well as boundary layer properties. Past efforts to quantify the aerosol or heat transport and to study dust devils' formation, maintenance, and statistics using large-eddy simulation (LES) as well as direct numerical simulation (DNS) have been of limited success. Therefore, this study aims to provide better statistical information about dust devil-like structures and to extend, prove or disprove existing theories about the development and maintenance of dust devils. Especially, the vortex strength measured through the pressure drop in the vortex core is regarded, which is, in past LES simulations, almost one order of magnitude smaller compared to the observed range of several hundreds Pascals. <br>So far, we are able to reproduce observed core pressures with LES of the convective boundary layer by using a high spatial resolution of 2m while considering a domain of 4km x 4km x 2km, a model setup with moderate background wind and a spatially heterogeneous surface heat flux. It is found that vortices mainly appear at the vertices and branches of the cellular pattern and at lines of horizontal flow convergence above the centers of the strongly heated patches. The latter result is in contrast to some older observations in which vortices seemed to be created along the patch edges. Also further statistical properties, like lifetimes, diameters or frequency of occurrence, fit quite well in the observed range. Nevertheless, statistics of dust devils from LES face the general problem that they are highly influenced by the used grid spacing and thereby by the structures that can be explicitly resolved. For example, the near surface layer, which plays a major role for the vortex development, is poorly resolved and turbulent processes in this layer are highly parameterized. DNS would overcome this problem. Therefore, dust devil-like structures are also investigated with DNS by simulating laboratory-like Rayleigh-Bénard convection with Rayleigh numbers up to 10<sup>12</sup>. Such high Rayleigh numbers have never been used in DNS studies of dust devils. The focus is on the vortex formation dependence on the used Rayleigh number and aspect ratio. First results of the laboratory-like Rayleigh-Bénard convection simulated with DNS confirm the existence of dust devil-like structures also on small scales with much lower Rayleigh numbers than in the atmosphere. <br>In a next step, detailed statistics of dust devil-like structures in Rayleigh-Bénard convection will be derived focusing on Rayleigh number and aspect ratio dependencies. Afterwards, results will be compared to LES simulations of dust devils and experimental data.</p>

scholarly journals MHD natural convection flow with radiative heat transfer past an impulsively moving vertical plate with ramped temperature in the presence of hall current and thermal diffusion

2013 ◽  
Vol 18 (4) ◽  
pp. 1201-1220
Author(s):  
G.S. Seth ◽  
G.K. Mahato ◽  
S. Sarkar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Skin Friction ◽  
Radiative Heat Transfer ◽  
Vertical Plate ◽  
Radiative Heat ◽  
Hall Current ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Flow Parameters

Abstract An investigation on an unsteady MHD natural convection flow with radiative heat transfer of a viscous, incompressible, electrically conducting and optically thick fluid past an impulsively moving vertical plate with ramped temperature in a porous medium in the presence of a Hall current and thermal diffusion is carried out. An exact solution of momentum and energy equations, under Boussinesq and Rosseland approximations, is obtained in a closed form by the Laplace transform technique for both ramped temperature and isothermal plates. Expressions for the skin friction and Nusselt number for both ramped temperature and isothermal plates are also derived. The numerical values of fluid velocity and fluid temperature are displayed graphically versus the boundary layer coordinate y for various values of pertinent flow parameters for both ramped temperature and isothermal plates. The numerical values of the skin friction due to primary and secondary flows are presented in tabular form for various values of pertinent flow parameters.

Analytical Investigation of Nusselt Number and Skin Friction of Fluid Flow Over a Stretching Sheet Using Optimal Homotopy Asymptotic Method

2020 ◽  
Vol 12 (5) ◽  
pp. 657-661
Author(s):  
Zohreh Aliannejadi
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Differential Equations ◽  
Skin Friction ◽  
Flow And Heat Transfer ◽  
Optimal Homotopy Asymptotic Method ◽  
The Magnetic Field

In many cases such as production of metal sheets, the behavior of fluid flow and heat transfer in the neighborhood of a hot plate is very important. The CFD simulation of fluid flow is a widespread study that reveals detail information about the fluid flow in the calculated domain. In this study, the flow and heat transfer of a specific fluid in the above area of a stretching plate is examined analytically to find the variation of skin friction and Nusselt number. For this purpose, the similarity transformations can be employed to achieve the ordinary differential equations from the governing partial differential equations. The optimal homotopy asymptotic method (OHAM) is used to solve the ordinary differential equations which is applicable in solving of nonlinear equations. The effects of magnetic field on the analytical results from solving the equations are evaluated in detail. It is found that the thickness of the flow boundary layer decreases and the thickness of the thermal boundary layer increases by increasing in the magnetic field. Moreover, the Nusselt number is lower and skin friction is higher for the higher values of the magnetic field.

scholarly journals MHD Free Convection Flow Across an Inclined Porous Plate in the Presence of Heat Source, ISoret Effect, and Chemical Reaction Affected by Viscous Dissipation Ohmic Heating

2021 ◽  
Vol 12 (5) ◽  
pp. 6280-6296
Keyword(s):  
Nusselt Number ◽  
Heat Source ◽  
Free Convection ◽  
Skin Friction ◽  
Chemical Reaction ◽  
Sherwood Number ◽  
Perturbation Technique ◽  
Porous Plate ◽  
Convection Flow ◽  
Free Convection Flow

This work studies the steady two-dimensional MHD free convection flow past an inclined porous plate embedded in the porous medium in the presence of heat source, iSoret effect, and chemical reaction. The non-dimensional governing equations are solved by the perturbation technique. The Rosseland approximation is utilized to describe the radiative heat flux in the energy equation. The effect of magnetic parameter, heat source parameter, radiation parameter, Grashofi number, modified Grashofi number, Schmidt number, Prandtl number, porosity parameter, Soreti number, and chemical reaction on velocity, temperature, concentration profiles, skin friction, Nusselt number, and Sherwood number are mainly focussed in discussion with the help of graphs. It is seen that velocity, concentration, and skin friction fall with the increasing value of chemical reaction. Further, temperature, Nusselt number, and Sherwood number increase with the increasing value of chemical reaction.

scholarly journals Perturbation analysis of thermophoresis, hall current and heat source on flow dissipative aligned convective flow about an inclined plate

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
G. Dharmaiah ◽  
O.D. Makinde ◽  
K.S. Balamurugan
Keyword(s):  
Mass Transfer ◽  
Heat Source ◽  
Skin Friction ◽  
Chemical Reaction ◽  
Magnetic Parameter ◽  
Hall Current ◽  
Perturbation Technique ◽  
Heated Plate ◽  
Inclined Plate ◽  
The Impact

This present examination researches the impacts of thermophoresis, heat source and Hall current on dissipative adjusted MHD joint convection stream about an inclined plate inserted in a permeable medium. Utilizing dimensionless variables, the system of partial differential equations is changed into dimensionless equations. By making use of perturbation technique, estimated solutions for velocity, temperature, concentration profiles, skin friction, rate of heat transfer and rate of mass transfer have been determined. The attained results are explained with an assistance of diagrams to examine the impact of distinct parameters such as Magnetic parameter (M), Aligned magnetic parameter (ξ), Schmidt number (Sc), Eckert number (Ec), inclined angle (α), Prandtl number (Pr), heat generation parameter (Q), and chemical reaction (Kr), assuming two cases viz. Case I: Gr < 0, Gm < 0 (flow on heated plate); Case II: when Gr > 0, Gm > 0(flow on cooled plate). Additionally, the impacts of the appropriate parameters on the skin-friction coefficient and rates of heat and mass transfer are numerically furnished in tabular form. Skin friction coefficients are firmly diminished as magnetic field rises. Sherwood and Nusselt numbers boost up as enhance in chemical reaction.

scholarly journals Impact of heat transfer analysis on Carreau fluid-flow past a static/moving wedge

2018 ◽  
Vol 22 (2) ◽  
pp. 809-820 ◽  
Author(s):  
Hashim Ali ◽  
Masood Khan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Skin Friction ◽  
Wedge Angle ◽  
Weissenberg Number ◽  
Heat Transfer Analysis ◽  
Carreau Fluid ◽  
Opposite Behavior ◽  
Moving Wedge

The foremost aspiration of the present endeavor is to investigate the boundary-layer flow of a generalized Newtonian Carreau fluid model past a static/moving wedge. In addition, the effects of heat transfer on the flow field are also taken into account. The governing equations of the problem based on the boundary-layer approximation are changed into a non-dimensional structure by introducing the local similarity transformations. The subsequent system of ODE has been numerically integrated with fifth-order Runge-Kutta method. Influence of the velocity ratio parameter, the wedge angle parameter, the Weissenberg number, the power law index, and the Prandtl number on the skin friction and Nusselt number are analyzed. The variation of the skin friction as well as other flow characteristics has been presented graphically to capture the influence of these parameters. The results indicate that the increasing value of the wedge angle substantially accelerates the fluid velocity while an opposite behavior is noticed in the temperature field. Moreover, the skin friction coefficient for the growing Weissenberg number significantly enhances for the shear thickening fluid and show the opposite behavior of shear thinning fluid. However, the local Nusselt number has greater values in the case of moving wedge. An excellent comparison with previously published works in various special cases has been made.

scholarly journals Convective conditions and dissipation on Tangent Hyperbolic fluid over a chemically heating exponentially porous sheet

2019 ◽  
Vol 8 (1) ◽  
pp. 407-418 ◽  
Author(s):  
Mamata Patil ◽  
Mahesha ◽  
C.S.K. Raju
Keyword(s):  
Boundary Layer ◽  
Differential Equations ◽  
Heat Source ◽  
Ordinary Differential Equations ◽  
Skin Friction ◽  
Chemical Reaction ◽  
Transfer Rate ◽  
Manufacturing Systems ◽  
Mass Transfer Rate ◽  
Tangent Hyperbolic Fluid

Abstract In this present analysis we investigated the steady-state magnetohydrodynamic boundary layer flow of tangent hyperbolic fluid over an exponentially stretching surface in the presence of heat source and chemical reaction. The chemical reaction with combination of exponential surface has significance in many industrial and manufacturing systems. The partial nonlinear differential equations are transformed into ordinary differential equations by using the similarity conversion and the accomplished boundary layer ordinary differential equations are elucidated numerically by using Shooting technique. The effects of numerous non-dimensional governing factors on velocity, temperature and concentration profiles were depicted graphically and analyzed in detail. The numerically computed results of Skin friction factor, Nusselt and Sherwood numbers are presented in tabular form for suction and injection cases separately.Heat transfer rate at the surface increases with increasing values of power law of index and whereas it declines with the magnetic field, heat source and chemical reaction parameters. It observed that Biot number enhances the skin friction, Nusselt number and decrease the Sherwood number.Heat transfer rate and mass transfer rate increases and skin friction decreases with increasing Eckert number.

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