Effects of thermal radiation on Casson fluid flow and heat transfer over an unsteady stretching surface subjected to suction/blowing

The unsteady flow of a Casson fluid and heat transfer over a stretching surface in presence of suction/blowing are investigated.The transformed equations are solved numerically by using the shooting method.The exact solution corresponding to the momentum equation for the steady case is obtained.Fluid velocity initially decreases with the increase of unsteadiness parameter.Due to an increasing Casson parameter the velocity field is suppressed.Thermal radiation enhances the effective thermal diffusivity and the temperature rises.     

Heat transfer effects on Hiemenz flow of nanofluid over a porous wedge sheet in the presence of suction/injection due to solar energy: Lie group transformation

The objective of the present work is to investigate theoretically the Hiemenz flow and heat transfer of an incompressible viscous nanofluid past a porous wedge sheet in the presence of suction/injection due to solar energy (incident radiation). The wall of the wedge is embedded in a uniform Darcian porous medium in order to allow for possible fluid wall suction or injection and has a power-law variation of the wall temperature. The partial differential equations governing the problem under consideration are transformed by a special form of Lie symmetry group transformations viz. one-parameter group of transformation into a system of ordinary differential equations, which are solved numerically using Runge-Kutta-Gill based shooting method. The conclusion is drawn that the flow field and temperature are significantly influenced by thermal radiation, nanoparticle volume fraction, and porosity of the sheet.     

Series solution of unsteady free convection flow with mass transfer along an accelerated vertical porous plate with suction

The problem of unsteady free convection flow is considered for the series solution (analytic solution). The flow is induced by an infinite vertical porous plate which is accelerated in its own plane. The series solution expressions for velocity field, temperature field and concentration distribution are presented. The influence of important parameters is seen on the velocity, temperature, concentration, skin friction coefficient and temperature gradient with the help of graphs and tables. Convergence is also properly checked for different values of the important parametes for velocity field, temperature and concentration with the help of ħ-curves.     

Convective heat transfer flow of nanofluid in a porous medium over wavy surface

In this letter, water base nanofluid flow over wavy surface in a porous medium of spherical packing beds is investigated. The copper oxides particles are taken into account. These properties are rehabilitated when fluid interacts with porous walls. For porous medium, Dupuit–Forchheimer model; an extension of Darcy's law model is utilized. The natures of velocity and temperature profiles of nanofluid are discussed graphically whereas the values of convection heat transfer coefficient in the presence of different nanoparticles concentrations in porous medium is presented in tabular form. The obtained results illustrate that convection heat transfer is improved by nanoparticles concentration but reduces when fluid attract to pores structured medium. On the other hand, when particles are added in fluid, convection heat transfer rate is improved but flow velocity is declined.     

Marangoni flow and mass transfer of power-law non-Newtonian fluids over a disk with suction and injection

We scrutinize the approximate analytical solutions by the optimal homotopy analysis method (OHAM) for the flow and mass transfer within the Marangoni boundary layer of power-law fluids over a disk with suction and injection in the present paper. Concentration distribution on the surface of a disk varies in a power-law form. The non-Newtonian fluid flow is due to the surface concentration gradient without considering gravity and buoyancy. According to the conservation of mass, momentum and concentration, the governing partial differential equations are established, and the appropriate generalized Kármán transformation is found to reduce them to the nonlinear ordinary differential equations. OHAM is used to access the approximate analytical solution. The influences of Marangoni the number, suction/injection parameters and power-law exponent on the flow and mass transfer are examined.     

Heat transfer in fluctuating flow of an elastico-viscous fluid past an infinite plate with constant suction

An analysis of heat transfer in a two dimensional flow of an elastico-viscous fluid (Walters liquid B) past an infinite porous plate has been carried out under the following conditions: (1) constant suction, (2) free stream oscillates in time about a constant mean, (3) the plate is thermally insulated. Approximate solutions to the temperature field have been derived on taking into consideration viscous dissipative terms. The mean wall temperature has been shown graphically and it is observed that it decreases with increasing frequency.     

超声波对多孔介质中两相流动的影响

近年来，超声技术已被应用于采油工程中，在油井解堵，水井增注等方面发挥了重要的作用。     

Heat and mass transfer analysis on the flow of a second grade fluid in the presence of chemical reaction

The laminar flow problem of convective heat transfer for a second grade fluid over a semi-infinite plate in the presence of species concentration and chemical reaction is investigated. The governing equations are transformed into a dimensionless system of three non-linear coupled partial differential equations. These equations have been solved analytically subject to the relevant boundary conditions by employing a homotopy analysis method (HAM). It is noted that for the arising system, the HAM performs extremely well in terms of efficiency and simplicity. The influence of dimensionless pertinent parameters on the velocity, temperature and concentration fields has been examined carefully.     

Modeling of flow and mass transport in granular porous media

The scope of this work is to estimate the effective mass-transfer coefficient in a two-phase system of oil and water fluid droplets, both being in a porous medium. To this end, a tracer is advected from the flowing aqueous phase to the immobile non-aqueous one. Partitioning at the fluid-fluid interface and surface diffusion are also taken into account. By using spatial/volume-averaging techniques, the appropriately simplified boundary-value problems are described and numerically solved for the flow velocity field and for the transport problem. The problem was found to be controlled by the Peclet number of the flowing phase, the dimensionless parameter Λ, containing both diffusion and partition in the two phases, as well as the geometrical properties of the porous structure. It is also verified that the usually involved unit cell-configurations underestimate the mass transport to the immobile phase.     

Heat and mass transfer of MHD convective boundary layer flow past a stretching porous wall embedded in a porous medium

The hydromagnetic convective boundary layer flow past a stretching porous wall embedded in a porous medium with heat and mass transfer in the presence of a heat source and under the influence of a uniform magnetic field is studied. Exact solutions of the basic equations of motion, heat and mass transfer are obtained after reducing them to nonlinear ordinary differential equations. The reduced equations of heat and mass transfer are solved using a confluent hypergeometric function. The effects of the flow parameters such as a suction parameter (N), magnetic parameter (M), permeability parameter (K _p ), wall temperature parameter (r), wall concentration parameter (n), and heat source/sink parameter (Q) on the dynamics are discussed. It is observed that the suction parameter appears in the boundary condition ensuring the variable suction at the surface. Transverse component of the velocity increases only when magnetic field strength exceeds certain value, but the thermal boundary layer thickness and concentration distribution increase for all values. Results presented in this paper are in good agreement with the work of the previous author and also in conformity with the established theory.     

NMR-propagator measurements in porous media in the presence of surface relaxation and internal fields

We measure the probability distribution P(zeta)--the propagator--of molecular displacements on Stokes flow through a pack of microporous glass beads and a carbonate rock. An optimized sampling of q-space is introduced for the measurement of a P(zeta) and its first moment zeta. Our results delineate and provide an understanding of the experimental regimes where background fields and surface relaxation distort the measured propagators.     

Magnetohydrodynamic free convection and mass transfer flow in micropolar fluid with constant suction

An analysis is presented for the problem of free convection with mass transfer flow for a micropolar fluid bounded by a vertical infinite surface under the action of a transverse magnetic field. Approximate solutions of the coupled nonlinear governing equations are obtained for different values of the microrotation- and the magnetic-parameters. Numerical calculations are carried out for the various parameters entering into the problem. Velocity, angular velocity, temperature and concentration profiles are shown graphically. The numerical values of the skin friction, the wall couple stress, the rate of heat transfer and the concentration gradient at the wall are entered in tables.     

Heat transfer by laminar flow of an elastico-viscous liquid along a plane wall with periodic suction

The problem of heat transfer by the laminar flow of an elastico-viscous liquid along a plane wall with periodic suction has been considered. A perturbation technique has been used to obtain an approximate solution of the differential equations. The flow phenomenon has been characterized by the non-dimensional parameters like the elastic number (S), the Reynolds number (R), the Prandtl number (P) and the Eckert number (E). The effects of these parameters on the temperature distributions and the rate of heat transfer at the wall have been studied.     

Heat and mass transfer on unsteady three-dimensional convective MHD flow past a porous plate moving in a parallel free stream

The unsteady three-dimensional convective flow of a viscous incompressible, electrically conducting fluid over a vertical, insulated, porous surface moving in a parallel free stream has been investigated, which flows belong to a separate class of problem of boundary layer theory. The effects of heat and mass transfer on this unsteady laminar flow past porous surface with transverse sinusoidal suction and oscillatory wall temperature have been analysed and discussed.     

Casson fluid flow: Free convective heat and mass transfer over an unsteady permeable stretching surface considering viscous dissipation

The present study investigates a Casson fluid flow in the presence of free convection of combined heat and mass transfer toward an unsteady permeable stretching sheet with thermal radiation, viscous dissipation and chemical reaction. The governing partial differential equations are reduced to a system of nonlinear ordinary differential equations and then solved by an efficient Runge–Kutta–Fehlberg method. The dimensionless velocity is decreased by increasing values of the chemical reaction and magnetic parameter while fluid temperature is significantly reduced by increasing values of the Prandtl number. The heat transfer rate is reduced with increasing values of thermal radiation and magnetic parameters.     

Heat and mass transfer at ignition of liquid fuel droplets spreading over the surface of massive hot bodies

Processes of heat and mass transfer with phase transitions and chemical reactions at the ignition of a liquid fuel droplet colliding with the surface of a hot metal substrate are numerically investigated. The droplet ignition delay times are found. The scale of the influence of the temperature of the substrate, droplet, and oxidizer, and also the droplet size and spreading rate on the ignition inertia is determined. Conditions in which the liquid fuel droplet spread plays an important role in the ignition process are found.     

Effect of melting heat transfer and thermal radiation on Casson fluid flow in porous medium over moving surface with magnetohydrodynamics

In this study, the effects of variable fluid properties on heat transfer in MHD Casson fluid melts over a moving surface in a porous medium in the presence of the radiation are examined. The relevant similarity transformations are used to reduce the governing equations into a system of highly nonlinear ordinary differential equations and those are then solved numerically using the Runge–Kutta–Fehlbergmethod. The effects of different controlling parameters, namely, the Casson parameter,melting and radiation parameters, Prandtl number,magnetic field, porosity, viscosity and the thermal conductivity parameters on flow and heat transfer are investigated. The numerical results for the dimensionless velocity and temperature as well as friction factor and reducedNusselt number are presented graphically and discussed. It is found that the rate of heat transfer increases as the Casson parameter increases.