enclosure filled with nanofluid. They found that the angle of turn has an important effect on the streamlines, isotherms and maximum or minimum values of local Nusselt number. Sheikholeslami et al. (2013, a) used the lattice Boltzmann method to examine free convection of nanofluids. They found that choosing copper as the nanoparticle leads to obtain the highest enhancement for this problem. The problem of steady, laminar, mixed convection flow of a non- Newtonian fluid past a preamble vertical flat plate embedded in a **porous** **medium** saturated with a nanofluid was considered by Rashad et al. (2013). They showed that the effects of Lewis number, Brownian motion or thermophoresis parameters are more pronounced on the local Sherwood number than on the local Nusselt number. Sheikholeslami et al. (2013, b) performed a numerical study to investigate natural convection in a square cavity with curve boundaries filled with Cu –water nanofluid. Their results proved that the change of inclination angle has a significant impact on the thermal and hydrodynamic flow fields. Recently several authors investigated about natural convection and effect of adding nanoparticle in the base fluid on flow and heat transfer (Khan et al. (2011), Vajravelu et al. (2011), Sheikholeslami et al. (2013, c), Sheikholeslami et al. (2013, d),

Mostrar mais
8 Ler mais

plate with variable suction. Alam et al. (2006a), (2006b) have studied the Dufour and Soret effects on MHD free convection and mass transfer flow past a vertical **porous** plate in a **porous** **medium**. They have discussed both the steady and unsteady cases. Diffusion-thermo and thermal-diffusion effects on free convective heat and mass transfer flow in a **porous** **medium** with time dependent temperature and concentration have been investigated by Alam et al. (2007). Manna et al. (2007) have studied an unsteady viscous flow past a flat plate in a rotating system. Thermal radiation effect on a transient MHD flow with mass transfer past an impulsively started vertical plate has been described by Alam and Sarmah (2009). Rajesh and Varma (2009) have presented the radiation and mass transfer effects on an MHD free convective flow past an exponentially accelerated vertical plate with variable temperature. Muthucumaraswamy et al. (2009) have studied an unsteady flow past an accelerated infinitely long vertical plate with variable temperature and uniform mass diffusion. Muthucumaraswamy et al. (2009) have also discussed the heat and mass transfer on the flow past an accelerated vertical plate with variable mass diffusion. Jha and Ajibade (2009) have investigated the diffusion-thermo effects on free convective heat and mass transfer flow in a vertical channel with symmetric boundary conditions. The combined effects of heat and mass transfer by mixed convective MHD flow past a **porous** plate with chemical reaction in the presence of heat source have been described by Ahamed and Zueco (2010). Rajesh and Varma (2010) have investigated the radiation effects on an MHD flow through a **porous** **medium** with variable temperature or variable mass diffusion. Makinde (2010) has discussed an MHD heat and mass transfer over a moving vertical plate with a convective surface boundary condition. The effects of thermal radiation on an MHD free convective flow past

Mostrar mais
15 Ler mais

The numerical results presented in the previous section show that the effect of the Forchheimer term on the velocity profiles strongly depends on Da values for Re ≥ 10. It becomes negligible for very small values of Da, i.e. Da < 0.001. Only in these situations, the analyt ical solution of Leont’ev [10] can be used. However, the final decision concerning the velocity profile that can be used for the flow past an impermeable cylinder embedded in a fluid saturated **porous** **medium** can be taken only after the following important problem is solved: for which values of Re and Da, are the macroscopic inertial terms from the generalized momentum balance equation negligible ?

Mostrar mais
7 Ler mais

Uddin et al. [13] studied free convective boundary layer flow of a nanofluid over a permeable upward horizontal plate in a **porous** **medium** with thermal convective boundary condition. Rana and Bhargava [14] studied the heat transfer enhancement in mixed convection flow along a vertical plate with heat source/sink utilizing nanofluids. Chamkha and Aly [15] focused on steady convection boundary layer flow of a nanofluid along a permeable vertical plate in the presence of magnetic field, heat generation/absorption and suction/injection effects. Recently, Rahman et al. [16] investigated hydromagnetic slip flow of water based nanofluid over a wedge with convective surface in the presence of heat generation or absorption. A similarity solution of the steady boundary layer near the stagnation-point flow on a permeable stretching sheet in a **porous** **medium** saturated with a nanofluid in the presence of heat generation/absorption is studied by Hamad and Pop [17]. An important numerical investigation on the convective heat transfer performance of nanofluids over a permeable stretching surface in the presence of partial slip, thermal buoyancy and internal heat generation or absorption was presented by Das [18].

Mostrar mais
21 Ler mais

Given the expressive applicability of ozone as protecting agent, it is fundamental to study parameters related to the distribution of the gas during grain fumigation, evaluating its saturation and decomposition kinetics in the **porous** **medium**. Gaseous ozone has half-life of 20 min at 20 ºC (Novak & Yuan, 2007) and rapidly reacts in **medium** containing organic material, decomposing into oxygen (Cullen et al., 2009). Temperature and moisture content are factors that influence ozone decomposition in **porous** **medium** containing grains, as reported by Alencar et al. (2011) and Pandiselvam et al. (2015). There are few reports on ozone saturation and decomposition in **porous** **medium** containing grains (Santos et al., 2007; 2016; Alencar et al., 2011; Pandiselvam et al., 2015; Roberto et al., 2016). For Alencar et al. (2011), parameters related to saturation and decomposition are fundamental to evaluate technical viability and to dimension grain ozonation systems. Due to the differences in chemical composition and physical properties, it is important to study these processes in the different grains. Hence, the present study aimed to evaluate ozone saturation and decomposition kinetics in **porous** **medium** with grains of different maize hybrids.

Mostrar mais
6 Ler mais

This paper discusses mathematically phenomenon of imbibition in double phase flow of two immiscible fluids in a homogeneous **porous** media with capillary pressure. The phenomenon arises due to the difference in the wetting abilities of the phases. It is assumed that the injection of a preferentially wetting fluid into a **porous** **medium** saturated with another non-wetting fluid is initiated by imbibition and the injected fluid and the native fluid form immiscible fluid phases of different wetting abilities, with respect to the **porous** **medium**.

5 Ler mais

Consider unsteady flow of a viscous incompressible fluid through a **porous** **medium** occupying a semi-infinite region of the space bounded by a vertical infinite **porous** surface in a rotating system under the action of a uniform magnetic field applied normal to the direction of flow. The temperature of the surface varies with time about a non-zero constant mean and the temperature at the free stream is constant. The **porous** **medium** is, in fact, a non-homoge- nous **medium** which may be replaced by a homogenous fluid having dynamical properties equal to those of a non-homogenous continuum. Also, we assume that the fluid properties are not affected by the temperature and concentration differences except by the density ρ in the body force term; the influence of the density variations in the momentum and energy equa- tions is negligible. It is assumed that the effect of viscous dissipation is negligible in the ener- gy equation and there is a first order chemical reaction between the diffusing species and the fluid. Initially the plate and the fluid are of same temperature T ∞ * and concentration C ∞ * . The plate temperature is raised to T and the species concentration level near the plate is made w * raise to C w ∗ .

Mostrar mais
12 Ler mais

We consider a two-dimensional MHD natural convection flow of an incompressible viscous and electrically conducting fluid through **porous** **medium** past a vertical impermeable flat plate is considered in presence of a uniform transverse magnetic field. The governing equations of velocity and temperature fields with appropriate boundary conditions are solved by the ordinary differential equations by introducing appropriate coordinate transformations. We solve that ordinary differential equations and find the velocity profiles, temperature profile, the skin friction and nusselt number. The effects of Grashof number (Gr), Hartmann number (M) and Prandtl number (Pr), Darcy parameter (D -1 ) on velocity profiles and temperature profiles are shown graphically. Keywords : Natural convection, Grashof number (Gr), Hartmann number (M) and Prandtl number (Pr), Darcy parameter (D -1 )

Mostrar mais
6 Ler mais

683 of rotating fluids which has applications in various technological situations which are governed by the action of coriolis force. The double diffusive convective problems of couple-stress fluid through an anisotropic **porous** **medium** considering rotational effect have been discussed in the references by Malashetty and Kollur (2011) and Malashetty et al. (2011). A major part of the universe is filled with charged particles and magnetic field is present in and around the heavenly bodies. Magnetic field plays a dominant role in several clinical purposes such as in neurology and orthopaedics for examining the internal organs of the body in various diseases like tumours detection, heart and brain diseases, stroke damage etc. The theory of magneto-hydrodynamics (MHD) has several scientific and practical applications in geophysics (in the study of earth’s core), atmospheric science (solar wind is governed by MHD), astrophysics, plasma physics, space sciences etc. Thermal instability problem of an electrically conducting couple-stress fluid heated from below through a **porous** **medium** in the presence of a uniform magnetic field has been investigated by Sharma and Thakur (2000). Sharma and Sharma (2004) have considered the effect of suspended particles on couple-stress fluid heated from below in the presence of vertical rotation and vertical magnetic field and noted that the effect of rotation is to stabilize the system, whereas suspended particles have destabilizing effects. Thermosolutal convective problem for a couple-stress fluid through a **porous** **medium** under the influences of uniform vertical magnetic field and uniform rotation has been studied by Singh and Kumar (2011), whereas the effect of suspended particles on couple-stress fluid heated and soluted from below through a **porous** layer has been noted by Sunil et al. (2004).

Mostrar mais
12 Ler mais

The purpose of this paper is to present a theoretical analysis of an unsteady hydromagnetic free convection flow of viscoelastic fluid (Walter’s B’) past an infinite vertical **porous** flat plate through **porous** **medium**. The temperature is assumed to be oscillating with time and the effect of the Hall current is taken into account. Assuming constant suction at the plate, closed form solutions have been obtained for velocity and temperature profiles. The effect of the various parameters, entering into the problem, on the primary, secondary velocity profiles, the axial and transverse components of skin-friction are shown graphically followed by quantitative discussion.

Mostrar mais
10 Ler mais

Let us consider the unsteady free convection flow of an incompressible viscous fluid over an infinite vertical plate embedded in a **porous** **medium**. The physical configuration of the problem is shown in Fig. 1. The x-axis is taken along the plate and the y-axis is taken normal to it. Initially, both the plate and fluid are at stationary conditions with the constant temperature T ? and concentration C ? . After time t~0

12 Ler mais

ABSTRACT: The one dimensional MHD unsteady magneto-hydrodynamics fluid flow past an infinite rotating vertical **porous** plate through **porous** **medium** with heat transfer considering hall current has been investigated numerically under the action of induced magnetic field. The numerical solution for the primary velocity field, secondary velocity field and temperature distributions are obtained by using the implicit finite difference method. The obtained results have been represented graphically for different values of parameters. Finally, the important findings of the investigation are concluded.

Mostrar mais
9 Ler mais

Keeping in mind the importance and applications in chemical engineering, biomechanics and various applications mentioned above, the effects of magnetic field and suspended particles on thermosolutal convection in Maxwellian viscoelastic fluid through **porous** **medium** has been considered in the present paper.

8 Ler mais

F.M. Mahfouz [2] has investigated a buoyancy driven flow and associated heat convection in an elliptical enclosure. The enclosure which is the space between two horizontal concentric confocal elliptic tubes is heated through its inner tube surface which is maintained at either uniform temperature or uniform heat flux. The induced buoyancy driven flow and the associated heat convection are predicted at different enclosure orientations. The full governing equations in terms of vorticity, stream function and temperature are solved numerically using Fourier Spectral Method. Khanafer and al. [3] studied a numerical investigation of natural convection heat transfer within a two-dimensional, horizontal annulus that is partially filled with a fluid-saturated **porous** **medium**. In addition, the **porous** sleeve is considered to be press fitted to the inner surface of the outer cylinder. Both cylinders are maintained at constant and uniform temperatures with the inner cylinder being subjected to a relatively higher temperature than the outer one. Moreover, the Forchheimer and Brinkman effects are taken into consideration when simulating the fluid motion inside the **porous** sleeve. Kumari and Nath [4] studied the unsteady natural convection flow from a horizontal cylindrical annulus filled with a non-Darcy **porous** **medium** .The unsteadiness in the problem arises due

Mostrar mais
8 Ler mais

Figures 1(a)-1(c) establishes the different values of permeability of the **porous** **medium** parameter (K) on velocɨty, temperature and concentration profiles, respectively. The values of K is taken to be K = 0.1, 0.6, 1.2, 2 and the other parameters are fixed as A = - 1, σt = 0.1, σb = 0.1, Q = 0.β, = 0.γ, = 0.γ, Le = 1, Pr = 0.7 and S = 2. It is noticed that, with the hype in the values of K from 0.1 to 2.0 then the velocity decreases consequently decreases the thickness of momentum boundary layer but the temperature and concentration of the fluid increases. The reason for this, the **porous** **medium** obstructs the fluid to move freely through the boundary layer. This leads to the raise in the thickness of thermal and concentration boundary layer. Figures 2(a)-2(c) establishes the different values of unsteadiness parameter (A) on velocɨty, temperature and concentration profiles, respectively. The values of A is taken to be A = - 1, - 2, - 3, - 4 and the other parameters are fixed as K = 0.5, Nt = 0.1, σb = 0.1, Q = 0.β, = 0.γ, = 0.γ, Le = 1, Pr = 0.7 and S = β. It is noticed that, with the hype in the values of A from -4 to -1 then the velocity, temperature and concentration profiles increases consequently enhanced the thickness of momentum, thermal and concentration boundary layer.

Mostrar mais
15 Ler mais

layer of a saturated **porous** have been investigated by Nield and Kuznetsov (2011). They found that the horizontal throughflow has no effect on the stability. When the permeability increases in the direction of the throughflow a small amount of throughflow may destabilize the transverse modes and so destabilize the layer as a whole. Reza and Gupta (2012) investigated the effect of throughflow on the onset of convection in a horizontal layer of electrically conducting fluid confined between two rigid permeable boundaries heated from below in the presence of uniform vertical magnetic field, they found that magnetic field inhabits the onset of steady convection, and a positive throughflow is more stabilizing than negative throughflow. Nield and Kuznetsov (2013) considering iso-flux and iso- temperature boundaries they investigated the effect of onset of convection in a layered **porous** **medium** with vertical throughflow and found that throughflow has a stabilizing effect whose magnitude may be increased or decreased by the heterogeneity. Throughflow and internal heating effects on anisotropic **porous** **medium** investigated by Vanishree et al. (2014). They have presented

Mostrar mais
9 Ler mais

it into (2.4), implying an evolution equation for the free surface, h(x, t). Therefore, the solution to our problem goes through a Dirichlet-to-Neumann operator. We will, however, avoid explicitly introducing it here, for the sake of simplicity and as we would not really gain much in doing so. Let us also point out here that the main diﬀerence between the equations governing the classical water-wave problem and those that govern the **porous** **medium** problem under consideration can be seen in (2.2), which in the last case is much simpler than in the former case, where it involves time- derivatives and nonlinear terms.

Mostrar mais
11 Ler mais

plane turbulent jets, cenainly one of the most important in the history of events sponsored by ABCM. For this year, no figures will be presented. The 1988 ENCIT had no particula[r]

154 Ler mais

Tbe ftrst author was sponsored by lhe Fundação de Amparo à Pesquisa do Estado de Sao Paulo (Brasil). "Void Fraction Mea~wements in Vertical Siug Flow: Applicatioos to[r]

171 Ler mais

A numerical solution has been presented for the flow of an incompressible fluid and contaminant transport in an isotropic **porous** **medium** using the finite element method. The domain of solution was a scale model of a Landfill which was integrated into Finite Element analysis software COMSOL Multi3physics. By comparing real3life results obtained at the Bukit Tagar sanitary landfill shown in Figure 4.5 with the results generated using this model, as shown in Figs. 235, this work produced results that are very close to what obtains in reality.

13 Ler mais