Marneni Narahari

Free Convection Flow of a Nanofluid Past an Isothermal Inclined Plate

In this paper, the natural convective boundary-layer flow of a nanofluid over an isothermal inclined plate is investigated numerically with the effects of Brownian motion and thermophoresis in the nanofluid model. The equations governing the flow are expressed in the form of coupled non-linear ordinary differential equations using the similarity analysis. These equations are then solved numerically by an implicit finite-difference method known as the Keller-box method. The effect of inclination angle on the dimensionless velocity, temperature, nanofluid volume fraction and Nusselt number has been analyzed through graphs. Brownian motion and thermophoresis effects on the Nusselt number at an inclined plate are also discussed.

Transient two-dimensional natural convection flow of a nanofluid past an isothermal vertical plate using Buongiorno’s model

Purpose The purpose of this paper is to present a numerical investigation of the transient two-dimensional natural convective boundary-layer flow of a nanofluid past an isothermal vertical plate by incorporating the effects of Brownian motion and thermophoresis in the mathematical model. Design/methodology/approach The problem is formulated using the Oberbeck–Boussinesq and the standard boundary-layer approximations. The governing coupled non-linear partial differential equations for conservation of mass, momentum, thermal energy and nanoparticle volume fraction have been solved by using an efficient implicit finite-difference scheme of the Crank–Nicolson type, which is stable and convergent. Numerical computations are performed and the results for velocity, temperature and nanoparticle volume fraction are presented in graphs at different values of system parameters such as Brownian motion parameter, thermophoresis parameter, buoyancy ratio parameter, Prandtl number, Lewis number and dimensionless time. The results for local and average skin-friction and Nusselt number are also presented graphically and discussed thoroughly. Findings It is found that the velocity, temperature and nanoparticle volume fraction profiles enhance with respect to time and attain steady-state values as time progresses. The local Nusselt number is found to decrease with increasing thermophoresis parameter, while it increases slightly with increasing Brownian motion parameter. To validate the present numerical results, the steady-state local Nusselt number results for the limiting case of a regular fluid have been compared with the existing well-known results at different Prandtl numbers, and the results are found to be in an excellent agreement. Research limitations/implications The present analysis is limited to the transient laminar natural convection flow of a nanofluid past an isothermal semi-infinite vertical plate in the absence of viscous dissipation and thermal radiation. The unsteady natural convection flow of a nanofluid will be investigated for various physical conditions in a future work. Practical implications Unsteady flow devices offer potential performance improvements as compared with their steady-state counterparts, and the flow fields in the unsteady flow devices are typically transient in nature. The present study provides very useful information for heat transfer engineers to understand the heat transfer enhancement with the nanofluid flows. The present results have immediate relevance in cooling technologies. Originality/value The present research work is relatively original and illustrates the transient nature of the natural convective nanofluid boundary-layer flow in the presence of Brownian motion and thermophoresis.

MHD natural convection flow past an impulsively started infinite vertical porous plate with Newtonian heating in the presence of radiation

Purpose – The purpose of this paper is to investigate the effects of thermal radiation and viscous dissipation on steady natural convection flow of a viscous incompressible fluid along a uniformly moving infinite vertical porous plate with Newtonian heating in the presence of transverse magnetic field. The governing non-linear boundary layer equations are solved by using homotopy analysis method (HAM). The effects of various system parameters on velocity and temperature fields are discussed graphically, and the numerical values for skin friction and Nusselt number are presented in tabular form. Design/methodology/approach – The problem is formulated using the Boussinesq approximation under the effects of thermal radiation and transverse magnetic field. The resulting coupled system of non-linear differential equations is solved using HAM with appropriate boundary conditions for Newtonian heating of the plate. HAM is a powerful method which provides rapidly converging series solution for the velocity and te...

Natural Convective Coutte Flow in a Vertical Parallel Plate Microchannel

In the present paper, the exact analysis of steady state fully developed natural convective Couette flow in a vertical parallel plate microchannel is performed. Exact solutions are derived for the dimensionless velocity, temperature, volume flow rate, vertical heat flux and Nusselt number. The effects of Grashof number, wall-ambient temperature difference ratio and Knudsen number on the velocity, volume flow rate and Nusselt number have been discussed through graphs. The study revealed that the fluid velocity and volume flow rate increases with increasing Grashof number whereas the Nusselt number decreases with increasing Grashof number.

Effects of Time Dependent Temperature and Thermal Radiation on Free Convection Flow in Unsteady Couette Motion

The effect of thermal radiation on free convection flow in unsteady Couette motion between vertical parallel plates has been investigated subject to a time dependent temperature boundary condition at the moving plate. Rosseland diffusion approximation is used to describe the radiative heat flux in the energy equation. Analytical solutions of the dimensionless governing equations are derived using the Laplace transform technique. The velocity and temperature profiles are shown on graphs, the variation of skin-friction, Nusselt number, volume flow rate and vertical heat flux are presented in tabular form. The effects of system parameters such as Grashof number, radiation parameter and time on the flow fields have been discussed in detail.

Joule heating effects on unsteady natural convection flow near a moving semi-infinite vertical plate with variable heat flux and mass transfer

The unsteady MHD free convective boundary-layer flow along an impulsively started semi-infinite vertical plate with variable heat flux and mass transfer have been investigated numerically. The effects of chemical reaction, thermal radiation and Joule heating are incorporated in the governing equations. Crank-Nicolson finite-difference method is used to solve the governing coupled non-linear partial differential equations. The influence of thermal radiation, chemical reaction and Joule heating on flow characteristics are presented graphically and discussed in detailed. To validate the present numerical results, a comparison study has been performed with the previously published results and found that the results are in excellent agreement. It is found that the local Nusselt and Sherwood numbers decreases with the intensification of magnetic field and the local Sherwood number slightly decreases with the increase of radiation parameter.

Unsteady natural convection flow of nanofluids past a semi-infinite isothermal vertical plate

Numerical analysis is performed to investigate the unsteady natural convection flow of a nanofluid past a semi-infinite isothermal vertical plate. Five different types of water based nanofluids are considered in this investigation where Silver (Ag), Copper (Cu), Copper Oxide (CuO), Alumina (Al2O3) and Titanium Oxide (TiO2) are the nanoparticles. The governing non-dimensional partial differential equations are solved by employing an implicit finite-difference method of Crank–Nicolson type. Numerical results are computed for different values of pertinent parameters. The results for nanofluid temperature, velocity, local Skin friction and Nusselt number, average Skin friction and Nusselt number are discussed through graphs. The present numerical results for local Nusselt number have been compared with the well-established pure fluid correlation results for the limiting case and the comparison shows that the results are in excellent agreement.

Mathematical modelling of unsteady MHD natural convection flow past a vertical plate with variable surface temperature and mass flux in the presence of radiation and chemical reaction

In the present study, a numerical analysis is made for unsteady magnetohydrodynamic (MHD) natural convective boundary-layer flow past an impulsively started semi-infinite vertical plate with variable surface temperature and mass flux in the presence of thermal radiation and chemical reaction. The Crank-Nicolson implicit finite difference technique is implemented to solve the system of governing equations. Numerical results are obtained for different values of system parameters and analyzed through graphs. The velocity profiles of the present study have been compared with the available results for the limiting case and a good agreement is found between the results.

Forward Modeling of Seabed Logging by Finite Integration and Finite Element Methods

Seabed electromagnetic (EM) modeling for detection of deep target hydrocarbon reservoirs has been a challenge for oil and gas industry. More precise and accurate electromagnetic (EM) methods are required for better detection of hydrocarbon (HC) reservoirs. To overcome this problem, Finite integration method (FIM) and Finite element method (FEM) were chosen for 3D modeling of seabed logging to produce more precise EM response from the hydrocarbon reservoir. EM modelling is used to investigate the total electric and magnetic fields instead of scattered electric and magnetic fields, because it shows accurate and precise resistivity contrast at the target depth of up to 3000 m below seafloor. The FIM and the FEM were applied to our proposed seabed model having an area of 20 × 20 km. It was observed that the FIM showed 6.52 % resistivity contrast at a target depth of 1000 m whereas the FEM showed 16.78 % resistivity contrast at the same target depth for the normalised E-field. It was also found that normalised E-field response decreased as the target depth increased gradually by 500 m from 1000 to 3000 m at constant frequency of 0.125 Hz and current of 1250 A. It was also observed that at frequency of 0.125 Hz, phase versus offset (PVO) showed 3.8 % for FIM whereas 6.58 % for FEM better delineation of hydrocarbon at 3000 m target depth. PVO of electric field gives better delineation of HC presence compared to magnitude of E and H fields.

Unsteady Magnetohydrodynamic Free Convection Flow of a Radiative Fluid Past an Infinite Vertical Plate with Constant Heat and Mass Flux

Theoretical analysis of unsteady magnetohydrodynamic free convection flow of a viscous incompressible radiative fluid past an infinite vertical plate with constant heat and mass flux is presented. The dimensionless governing linear partial differential equations have been solved using the Laplace transform technique. The exact solutions for the velocity, temperature and concentration fields are derived. The effects of radiation, magnetic field and buoyancy ratio parameters on the velocity and temperature fields are discussed through graphs. It is found that the velocity increases with increasing radiation parameter whereas it decreases with increasing magnetic field parameter for buoyancy assisted flows.