MHD transient flows and heat transfer of dusty fluid in a channel with variable physical properties and Navier slip condition

AbstractIn this paper, we study the unsteady flow and heat transfer of a dusty fluid between two parallel plates with variable viscosity and electric conductivity. The fluid is driven by a constant pressure gradient and an external uniform magnetic field is applied perpendicular to the plates with a Navier slip boundary condition. The governing non-linear partial differential equations are solved numerically using a semi-implicit finite difference scheme. The effect of the wall slip parameter, viscosity and electric conductivity variation and the uniform magnetic field on the velocity and temperature fields for both the fluid and dust particles is discussed

Effects of Chemical Reaction and Radiation Absorption on MHD Flow of Dusty Viscoelastic Fluid

This investigation is undertaken to study the effects of heat source and radiation absorption on unsteady hydro-magnetic heat and mass transfer flow of a dusty viscous incompressible, electrically conducting fluid between two vertical heated, porous, parallel plates in the presence of chemical reaction under the influence of a transverse applied magnetic field. Initially, the channel walls as well as the dusty fluid are assumed to be at the same temperature and the mass is assumed to be present at low level concentration so that it is constant everywhere. It is also assumed that the dusty particles are non-conducting, solid, spherical and equal in sizes, these are uniformly and symmetrically distributed in the flow field. The governing equations are solved analytically using the perturbation technique. Non-dimensional velocity, temperature, concentration and skin-friction are discussed through graphs for various physical parameters entering into the problem. It is found that velocity of the dusty particles is less than that of the dusty fluid and the skin-friction of the dusty particles is greater than that of the dusty fluid. It is observed that the temperature is minimal at the centre of the channel and decreases towards the plates whereas the concentration is minimal at the center of the channel but increases towards the plates

Investigation of Transient MHD Couette flow and Heat Transfer of Dusty Fluid with Temperature-Dependent Oroperties

In the present study, transient MHD Couette flow and heat transfer of dusty fluid between two parallel plates and the effect of the temperature dependent properties has been investigated. The thermal conductivity and viscosity of the fluid are assumed as linear and exponential functions of temperature, respectively. A constant pressure gradient and an external uniform magnetic field are considered in the main flow direction and perpendicular to the plates, respectively. A hybrid treatment based on finite difference method (FDM) and differential transform method (DTM) is used to solve the coupled flow and heat transfer equations. The effects of the variable properties, Hartman number, Hall current, Reynolds number and suction velocity on the Nusselt number and skin friction factor have been discussed. It is found that when Hartman number increases, skin friction of the upper and lower plates increases

ANALYSIS OF ENTROPY GENERATION DUE TO MAGNETOHYDRODYNAMIC COUPLE STRESS FLUID

We demonstrate the first reconfigurable photonic metamaterial controlled by electrical currents and magnetic fields, providing first practically useful solutions for sub-megahertz and high contrast modulation of metamaterial optical properties

MAGNETOHİDRODİNAMİK KANAL AKIŞLARININ KARŞILIKLI SINIR ELEMANLARI METODU İLE ÇÖZÜMÜ

In the thesis, four different MHD duct flow problems are solved by using the Dual Reciprocity Boundary Element Method (DRBEM) with the suitable boundary conditions according to the physics of the problem. The two-dimensional, steady or unsteady, fully-developed MHD flow of a viscous, incompressible and electrically conducting fluid is considered in a long pipe of rectangular cross-section (duct) under the effect of an externally applied magnetic field which is either uniform or time-dependent or axially changing. The inductionless MHD flow with temperature dependent viscosity and heat transfer is the first considered problem. In this problem, the induced magnetic field is neglected due to the small magnetic Reynolds number assumption. Secondly, the MHD duct flow under a time-varied external magnetic field is studied. Then, we turn our concern to MHD flow problems under an axial-dependent magnetic field varying in the streamwise direction (pipe-axis direction) in the third and the fourth problems. Specifically, the inductionless MHD flow with electric potential is considered under the effect of the axially-changing magnetic field as the third problem. Adding the induced magnetic field to the velocity and electric potential equations as a triple is the last MHD flow problem considered in the thesis. The parametrix BEM implementation is also presented for the solution of the variable coefficient convection-diffusion type equations. The influence of the magnetic fields on the MHD flows is investigated and simulated in terms of the velocity, temperature, induced magnetic field and electric potential contours for several values of physical parameters.Bu tezde, dört farklı Magnetohidrodinamik (MHD) kanal akış problemi, problemin fiziğine göre uygun sınır koşulları ile birlikte karşılıklı sınır elemanları metodu (DRBEM) kullanılarak çözülmüştür. Viskoz, sıkıştırılamaz ve elektrik ileten sıvının dikdörtgen kesitli bir kanal içerisindeki iki boyutlu, zamana bağlı veya zamandan bağımsız tam gelişmiş akışı dışarıdan uygulanan bir manyetik alan etkisinde incelenmiştir. Akışı etkileyen manyetik alan ya tek düzedir ya zamana bağlıdır ya da eksenel olarak değişmektedir. Ele alınan ilk problem, sıcaklığa bağlı viskoziteye ve ısı transferine sahip indüksiyonsuz MHD akışıdır. Bu problemde, indüklenen manyetik alan küçük manyetik Reynolds sayısı varsayımından dolayı ihmal edilmiştir. İkinci problem olarak, dışarıdan uygulanan ve zamana bağlı manyetik alan etkisindeki MHD akış çalışılmıştır. Daha sonra ise, üçüncü ve dördüncü problem olarak akım yönündeki eksen boyunca değişen bir manyetik alan etkisindeki MHD akış problemleri çözülmüştür. Üçüncü problemdeki MHD akışı elektrik potansiyeline sahip fakat indüksiyonsuz bir akıştır. Dördüncü problemde ise üçüncü problemdeki MHD akışa indüklenen manyetik alan eklenerek problem denklemleri hız, elektrik potansiyel ve indüklenen manyetik alan olarak üçlü çözülmüştür. Değişken katsayılı konveksiyon-difüzyon tipi denklemlerin çözümü için parametre sınır elemanı metodu (parametrix BEM) da kullanılmıştır. Uygulanan manyetik alanların MHD akışlarına etkisi, çeşitli fiziksel problem parametre değerleri için hız, sıcaklık, indüklenen manyetik alan ve elektrik potansiyeli açısından incelenmiş ve simülasyonları yapılmıştır.Ph.D. - Doctoral Progra

Study of Various Fluid Flow and Heat Transfer Problems in the Slip Regime

Microdevices such as microelectromechanical system(MEMS) have been used in many science and technology applications. These devices and systems often involve fluid flow and heat transfer processes in microchannels. Hence, the study of fluid flow in microchannels and the associated heat transfer process is important for the design and application of microdevices and systems. This project will focus on the study of various microflow and heat transfer problems in the slip regime

Unsteady squeezing flow of a magnetized nano-lubricant between parallel disks with Robin boundary conditions

The aim of the present work is to examine the impact of magnetized nanoparticles (NPs) in enhancement of heat transport in a tribological system subjected to convective type heating (Robin) boundary conditions. The regime examined comprises the squeezing transition of a magnetic (smart) Newtonian nanolubricant between two analogous disks under an axial magnetism. The lower disk is permeable whereas the upper disk is solid. The mechanisms of haphazard motion of NPs and thermophoresis are simulated. The non-dimensional problem is solved numerically using a finite difference method in the MATLAB bvp4c solver based on Lobotto quadrature, to scrutinize the significance of thermophoresis parameter, squeezing number, Hartmann number, Prandtl number and Brownian motion parameter on velocity, temperature, nanoparticle concentration, Nusselt number, factor of friction and Sherwood number distributions. The obtained results for the friction factor are validated against previously published results. It is found that friction factor at the disk increases with intensity in applied magnetic field. The haphazard (Brownian) motion of nanoparticles causes an enhancement in thermal field. Suction and injection are found to induce different effects on transport characteristics depending on the specification of equal or unequal Biot numbers at the disks. The main quantitative outcome is that, unequal Biot numbers produce significant cooling of the regime for both cases of disk suction or injection, indicating that Robin boundary conditions yield substantial deviation from conventional thermal boundary conditions. Higher thermophoretic parameter also elevates temperatures in the regime. The nanoparticles concentration at the disk is boosted with higher values of Brownian motion parameter. The response of temperature is similar in both suction and injection cases; however, this tendency is quite opposite for nanoparticle concentrations. In the core zone, the resistive magnetic body force dominates and this manifests in a significant reduction in velocity i.e. damping. The heat buildup in squeeze films (which can lead to corrosion and degradation of surfaces) can be successfully removed with magnetic nanoparticles leading to prolonged serviceability of lubrication systems and the need for less maintenance

Unsteady Fluid Flow and Heat Transfer Through a Porous Medium in a Horizontal Channel with an Inclined Magnetic Field

This paper investigates the unsteady flow and heat transfer of a viscous, incompressible, and electrically conducting fluid through a porous medium in a horizontal channel. The basic physical properties of the fluid and the porous medium are constant. The fluids considered are those with the Prandtl number less than 1. The channel walls are made of horizontal permeable plates, which are at constant but different temperatures. Fluid suction/injection through the plates occurs at a velocity perpendicular to the plates, whose intensity is a cosine function of time. The applied external magnetic field is homogeneous and inclined in relation to the transverse plane of the channel. The problem is dealt with through an inductionless approximation. Fluid flow is instigated by constant pressure drops along the channel. The equations used to describe the problem are transformed to dimensionless forms and solved analytically using the perturbation method. Approximate analytical expressions for dimensionless fluid flow velocity and dimensionless temperature are determined as functions of the following physical parameters: Prandtl number, Hartmann number, porosity factor, frequency, amplitude, and magnetic field inclination angle. Numerical results are presented as diagrams and tables and are used to analyse the influence of physical parameters on the fluid flow velocity and temperature

Unsteady MHD free convection flow of Jeffrey fluid and Jeffrey nanofluid along a vertical plate with radiation effect

Fluid is a substance that continuously deform under the influence of shear stress. Basically, fluid can be classified into two categories which are Newtonian and non-Newtonian. In reality, most fluids belong to the class of non-Newtonian fluids and one of them is Jeffrey fluid. Jeffrey fluid is also known as viscoelastic fluid that exhibits both viscous and elastic characteristics. Recently, this type of fluid have received considerable attention due to their numerous applications in industries especially in polymer industries. Due to this reason, many investigations have been made to study the Jeffrey fluid in various aspects from both analytical and numerical methods. Therefore, in this thesis, the effect of thermal radiation on unsteady magnetohydrodynamics (MHD) free convection flow of Jeffrey fluid with and without nanoparticles past an infinite vertical plate are studied. The fluid is taken electrically conducting in the presence of uniform transverse magnetic field applied in a direction perpendicular to the flow. Specifically, focused of this study is to obtain an exact solution for velocity and temperature distributions under conditions of ramped wall temperature and isothermal plate. Using the constitutive relation of Jeffrey fluid and some assumptions of physical conditions, five specific problems are modelled as partial differential equations. For the first three problems, the fluid is considered as non-rotating fluid, while in the fourth and fifth problems the rotating fluid is analyzed. An appropriate dimensionless variables are employed to the dimensional governing equations and solved analytically with the help of Laplace transform technique. The effect of pertinent parameters such as Jeffrey fluid parameter, rotation parameter, phase angle, Hartmann number, permeability parameter, nanoparticles volume fraction, Grashof number, Prandtl number, radiation parameter and time on velocity and temperature are plotted graphically and discussed in details. Numerical results of Nusselt number and skin friction for various emerging parameters are calculated and presented in tabular forms. In order to authenticate the present results, the limiting cases are provided, where an excellent agreement are found. Results obtained show that, increasing of Hartmann number tends to retard the fluid flow due to the Lorentz force effect. Increasing the values of radiation parameter led to an increase in velocity and temperature fields. Further, in the case of rotating fluid, large values of rotation parameter reduces the primary velocity but enhance in the secondary velocity. On the other hand, increasing nanoparticles volume fraction causes the velocity of non-rotating fluid increases but decreases for rotating fluid. It also found that, the fluid motion for ramped wall temperature is always slower compared to an isothermal plate. Interestingly, Jeffrey fluid can be reduced to a Second grade fluid in the absence of material parameter

Unsteady Unidirectional MHD Flow of Voigt Fluids Moving between Two Parallel Surfaces for Variable Volume Flow Rates

The velocity profile and pressure gradient of an unsteady state unidirectional MHD flow of Voigt fluids moving between two parallel surfaces under magnetic field effects are solved by the Laplace transform method. The flow motion between parallel surfaces is induced by a prescribed inlet volume flow rate that varies with time. Four cases of different inlet volume flow rates are considered in this study including (1) constant acceleration piston motion, (2) suddenly started flow, (3) linear acceleration piston motion, and (4) oscillatory piston motion. The solution for each case is elaborately derived, and the results of associated velocity profile and pressure gradients are presented in analytical forms