The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
C.e. Nanjundappa - One of the best experts on this subject based on the ideXlab platform.
-
Penetrative ferroconvection in a Porous Layer
Acta Mechanica, 2010Co-Authors: C.e. Nanjundappa, M. Ravisha, Jinho Lee, I. S. ShivakumaraAbstract:Penetrative convection in a horizontal ferrofluid-saturated Porous Layer in the presence of a uniform applied vertical magnetic field has been investigated via the internal heating model using the Brinkman-extended Darcy equation. The rigid-isothermal boundaries of the Porous Layer are considered to be either paramagnetic or ferromagnetic. The eigenvalue problem is solved numerically using the Galerkin method with either thermal or magnetic Rayleigh number as the eigenvalue. The stability of the system is significantly affected by the internal heating in the Porous Layer. It is noted that the paramagnetic boundaries with large magnetic susceptibility delay the onset of penetrative ferroconvection the most when compared to very low magnetic susceptibility as well as ferromagnetic boundaries. An increase in the value of magnetic Rayleigh number (R m ), heat source strength (N S ) and non-linearity of magnetization (M 3) is to hasten the onset of ferroconvection. In addition, the stability of the system when heated from above and also in the absence of thermal buoyancy has been discussed in detail.
-
Effects of quadratic drag and throughflow on double diffusive convection in a Porous Layer
International Communications in Heat and Mass Transfer, 2006Co-Authors: I. S. Shivakumara, C.e. NanjundappaAbstract:The linear stability theory is used to investigate analytically the effects of quadratic drag and vertical throughflow on double diffusive convection in a horizontal Porous Layer using the Forchheimer-extended Darcy equation. The boundaries of the Porous Layer are considered to be either impermeable or Porous, but perfect conductors of heat and solute concentration. Conditions for the occurrence of stationary and oscillatory convection are obtained using the Rayleigh-Ritz method. Stability boundaries are drawn in the Rayleigh numbers plane and the throughflow is found to influence the mode of instability. It is found that, irrespective of the nature of boundaries, a small amount of throughflow in either of its direction destabilizes the system; a result which is in contrast to the single component system.
-
Onset of convection in a sparsely packed Porous Layer with throughflow
Archives of Mechanics, 2001Co-Authors: I. S. Shivakumara, C.e. NanjundappaAbstract:The onset of Rayleigh-Benard convection in a sparsely packed Porous Layer with vertical throughflow is investigated using Brinkman's modification of the Darcy flow model with fluid viscosity different from effective viscosity. The critical Rayleigh numbers are obtained for free-free, rigid-rigid and rigid-free boundaries which are insulated to temperature perturbations. It is noted that an increase in the value of viscosity ratio is to delay the onset of convection. Further, it is observed that the throughflow can be used either to suppress or augment convection, depending on the nature of boundaries and also on the values of physical parameters.
S. Govender - One of the best experts on this subject based on the ideXlab platform.
-
Destabilizing convection using vibration in a rotating Porous Layer with a stabilizing temperature gradient
International Journal of Heat and Mass Transfer, 2019Co-Authors: S. GovenderAbstract:Abstract An analytical investigation in a vertical fluid saturated Porous Layer distant from the axis of rotation is presented when vibration occurs in the presence of a stable temperature gradient. A linear stability analysis is used to determine the convection threshold in terms of the critical Rayleigh number for variation within the Porous Layer and for the offset distance from the axis of rotation. The results indicate that the presence of vibration in a stable system serves to reduce the Rayleigh numbers (both within the Porous Layer and due to offset from the axis of rotation), thus destabilizing the system when a stabilizing temperature gradient exists.
-
Thermal Instability in a Rotating Vertical Porous Layer Saturated by a Nanofluid
Journal of Heat Transfer, 2016Co-Authors: S. GovenderAbstract:An analytical investigation of the onset on convection in a vertical Porous Layer saturated by a nanofluid is presented. The Darcy model is used for the vertical Porous Layer and a linear stability analysis is used to determine the convection threshold in terms of the key parameters for the nanofluid. This study reveals that the Taylor number and gravity effects are passive, and that the most critical mode is roll cells aligned with the vertical axis of rotation. The critical Rayleigh number is presented in terms of the nanofluid parameters for both stationary and oscillatory convection.
-
Coriolis Effect on Convection in a Rotating Porous Layer Subjected to Variable Gravity
Transport in Porous Media, 2013Co-Authors: S. GovenderAbstract:We consider the effects of rotation in a Porous Layer heated from below and subjected to a variable gravity field. The study is presented for large Vadasz numbers where no oscillatory convection is possible. It is demonstrated that the Coriolis acceleration stabilizes the convection in a variable gravity field, whilst the effect of gravity parameter stabilses the convection when reduced and destabilizes the convection when increased.
-
Stability of Convection in a Vibrating Porous Layer
Volume 1, 2004Co-Authors: S. GovenderAbstract:The linear stability theory is used to investigate analytically the effects of vibration on convection in a homogenous Porous Layer heated from below. The gravitational field consists of a constant part and a sinusoidally varying part, which is tantamount to a vertically oscillating Porous Layer subjected to constant gravity. The linear stability results are presented for the specific case of low amplitude vibration for which it is shown that increasing the frequency of vibration stabilizes the convection.Copyright © 2004 by ASME
-
Stability of Convection in a Gravity Modulated Porous Layer Heated from Below
Transport in Porous Media, 2004Co-Authors: S. GovenderAbstract:The linear stability theory is used to investigate analytically the effects of gravity modulation on convection in a homogenous Porous Layer heated from below. The gravitational field consists of a constant part and a sinusoidally varying part, which is tantamount to a vertically oscillating Porous Layer subjected to constant gravity. The linear stability results are presented for the specific case of low amplitude vibration for which it is shown that increasing the frequency of vibration stabilises the convection.
I. S. Shivakumara - One of the best experts on this subject based on the ideXlab platform.
-
Penetrative ferroconvection in a Porous Layer
Acta Mechanica, 2010Co-Authors: C.e. Nanjundappa, M. Ravisha, Jinho Lee, I. S. ShivakumaraAbstract:Penetrative convection in a horizontal ferrofluid-saturated Porous Layer in the presence of a uniform applied vertical magnetic field has been investigated via the internal heating model using the Brinkman-extended Darcy equation. The rigid-isothermal boundaries of the Porous Layer are considered to be either paramagnetic or ferromagnetic. The eigenvalue problem is solved numerically using the Galerkin method with either thermal or magnetic Rayleigh number as the eigenvalue. The stability of the system is significantly affected by the internal heating in the Porous Layer. It is noted that the paramagnetic boundaries with large magnetic susceptibility delay the onset of penetrative ferroconvection the most when compared to very low magnetic susceptibility as well as ferromagnetic boundaries. An increase in the value of magnetic Rayleigh number (R m ), heat source strength (N S ) and non-linearity of magnetization (M 3) is to hasten the onset of ferroconvection. In addition, the stability of the system when heated from above and also in the absence of thermal buoyancy has been discussed in detail.
-
Effects of quadratic drag and throughflow on double diffusive convection in a Porous Layer
International Communications in Heat and Mass Transfer, 2006Co-Authors: I. S. Shivakumara, C.e. NanjundappaAbstract:The linear stability theory is used to investigate analytically the effects of quadratic drag and vertical throughflow on double diffusive convection in a horizontal Porous Layer using the Forchheimer-extended Darcy equation. The boundaries of the Porous Layer are considered to be either impermeable or Porous, but perfect conductors of heat and solute concentration. Conditions for the occurrence of stationary and oscillatory convection are obtained using the Rayleigh-Ritz method. Stability boundaries are drawn in the Rayleigh numbers plane and the throughflow is found to influence the mode of instability. It is found that, irrespective of the nature of boundaries, a small amount of throughflow in either of its direction destabilizes the system; a result which is in contrast to the single component system.
-
On the stability of double diffusive convection in a Porous Layer with throughflow
Acta Mechanica, 2001Co-Authors: I. S. Shivakumara, Arzhang KhaliliAbstract:The effect of throughflow on the stability of double diffusive convection in a Porous Layer is investigated for different types of hydrodynamic boundary conditions. The lower and upper boundaries are assumed to be insulating to temperature and concentration perturbations. The resulting eigenvalue problem is solved by the Galerkin technique. The curvature of the basic temperature as well as solute concentration gradients significantly affects the stability of the system. It is observed that, for a suitable choice of parametric values, Hopf bifurcation occurs always prior to direct bifurcation, and the throughflow alters the nature of bifurcation. In contrast to the single component system, it is found that throughflow is (a) destabilizing even if the lower and upper boundaries are of the same type, and (b) stabilizing as well as destabilizing, irrespective of its direction, when the boundaries are of different types.
-
Onset of convection in a sparsely packed Porous Layer with throughflow
Archives of Mechanics, 2001Co-Authors: I. S. Shivakumara, C.e. NanjundappaAbstract:The onset of Rayleigh-Benard convection in a sparsely packed Porous Layer with vertical throughflow is investigated using Brinkman's modification of the Darcy flow model with fluid viscosity different from effective viscosity. The critical Rayleigh numbers are obtained for free-free, rigid-rigid and rigid-free boundaries which are insulated to temperature perturbations. It is noted that an increase in the value of viscosity ratio is to delay the onset of convection. Further, it is observed that the throughflow can be used either to suppress or augment convection, depending on the nature of boundaries and also on the values of physical parameters.
Brett Paull - One of the best experts on this subject based on the ideXlab platform.
-
Porous Layer open tubular columns in capillary liquid chromatography
Analyst, 2014Co-Authors: David A Collins, Ekaterina P. Nesterenko, Brett PaullAbstract:This review covers the latest developments and applications of Porous Layer open tubular columns in capillary liquid chromatography. Here, the authors provide a concise background on the fundamentals of Porous Layer open tubular columns, their fabrication and application. Over the past two decades, growing interest in the areas of proteomics and hyphenated LC-MS techniques have played a large part in the development of Porous Layer structures within capillary formats due to their high permeability, excellent efficiency and exceptional peak capacity. This review gives a brief overview of open tubular columns in general, however, it focuses predominantly on the applications of covalently bonded Porous Layer open tubular columns in liquid chromatography. Open tubular columns containing non-bonded or electrostatically attached Layers will not be discussed in detail.
David A Collins - One of the best experts on this subject based on the ideXlab platform.
-
Porous Layer open tubular columns in capillary liquid chromatography
Analyst, 2014Co-Authors: David A Collins, Ekaterina P. Nesterenko, Brett PaullAbstract:This review covers the latest developments and applications of Porous Layer open tubular columns in capillary liquid chromatography. Here, the authors provide a concise background on the fundamentals of Porous Layer open tubular columns, their fabrication and application. Over the past two decades, growing interest in the areas of proteomics and hyphenated LC-MS techniques have played a large part in the development of Porous Layer structures within capillary formats due to their high permeability, excellent efficiency and exceptional peak capacity. This review gives a brief overview of open tubular columns in general, however, it focuses predominantly on the applications of covalently bonded Porous Layer open tubular columns in liquid chromatography. Open tubular columns containing non-bonded or electrostatically attached Layers will not be discussed in detail.
