Dr Md. Mamun Molla | North South University (original) (raw)

Papers by Dr Md. Mamun Molla

International Journal of Ambient Energy

Axiom, 2023

This study aims to consider lattice Boltzmann method (LBM)–magnetohydrodynamics (MHD) data to dev... more This study aims to consider lattice Boltzmann method (LBM)–magnetohydrodynamics (MHD) data to develop equations to predict the average rate of heat transfer quantitatively. Thepresent approach considers a 2D rectangular cavity with adiabatic side walls, and the bottom wall is heated while the top wall is kept cold. Rayleigh–Bénard (RB) convection was considered a heattransfer phenomenon within the cavity. The Hartmann (Ha) number, by varying the inclination angle
(q), was considered in developing the equations by considering the input parameters, namely, the Rayleigh (Ra) numbers, Darcy (Da) numbers, and porosity (e) of the cavity in different segments. Each
segment considers a data-driven approach to calibrate the Levenberg–Marquardt (LM) algorithm, which is highly linked with the artificial neural network (ANN) machine learning method. Separate
validations have been conducted in corresponding sections to showcase the accuracy of the equations. Overall, coefficients of determination (R2) were found to be within 0.85 to 0.99. The significant findings of this study present mathematical equations to predict the average Nusselt number (Nu). The equations can be used to quantitatively predict the heat transfer without directly simulating LBM. In other words, the equations can be considered validations methods for any LBM-MHD model, which considers RB convection within the range of the parameters in each equation.

International Journal of Engineering Science, Aug 1, 2006

Natural convection laminar boundary layer flow from a horizontal circular cylinder with a uniform... more Natural convection laminar boundary layer flow from a horizontal circular cylinder with a uniform surface temperature at presence of heat generation has been investigated. The governing boundary layer equations are transformed into a non-dimensional form and the resulting nonlinear systems of partial differential equations are solved numerically applying two distinct methods namely (i) Implicit finite difference method together with the Keller box scheme and (ii) Series solution technique. The results of the surface shear stress in terms of the local skin friction and the surface rate of heat transfer in terms of the local Nusselt number for a selection of the heat generation parameter γ (= 0.0, 0.2 0.5, 0.8, 1.0) are obtained and presented in both tabular and graphical formats. Without effect of the internal heat generation inside the fluid domain for which we take γ = 0.0, the present numerical results show an excellent agreement with those of Merkin [1]. The effects of γ on the fluid velocity, temperature distribution, streamlines and isotherms are examined.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, May 12, 2023

The wind flow around the buildings with different rooftops is studied numerically using large-edd... more The wind flow around the buildings with different rooftops is studied numerically using large-eddy simulation (LES). The filtered Navier-Stokes equations in LES are used to compute the large eddies, whereas the dynamic Smagorinsky subgrid-scale (SGS) model calculates the small eddies. A turbulent spot method is applied for the synthesis of artificial turbulent fields at the inlet. In this separated and reattached flow, our aim is to analyze the wakes’ vortical structure along with the buildings of different heights and shapes. A large number of engineering applications involve precise predictions of the airflow around buildings to ensure performance and safety. To validate the numerical solver, a comparison is performed with the earlier reported numerical and experimental data. The turbulent flow characteristics are discussed in terms of instantaneous flow structure and time-averaged statistical flow quantities. All the cases are simulated for a Reynolds number [Formula: see text] to understand the turbulent airflow patterns. The flow shows a separable bubble at the leading edge of the rooftop of the building that leads to recirculation at the lee side of the first row of buildings. Due to the recirculation, the suction arises near the leading edge of the building to assure a continuous flow of air around the obstacles. Further, Reynold stresses show high momentum fluxes in the frontal region of the buildings.

Nucleation and Atmospheric Aerosols, 2018

The laminar flow of viscoplastic fluids inside a lid-driven skewed cavity has been investigated u... more The laminar flow of viscoplastic fluids inside a lid-driven skewed cavity has been investigated using a numerical scheme based on finite volume method considering Bingham model. Viscoplasticity is characterized by a yield stress, below which the materials behave as solids, and above which they deform and flow according to different constitutive relations. The governing two dimensional unsteady incompressible Navier-Stokes equations were initially non-dimensionalized using appropriate transformation. Then the dimensionless form of these equations is transformed to curvilinear coordinates to simulate complex geometry. The transformed equations are then discretized with appropriate boundary conditions to deal with the non-orthogonal grids. The code is first validated against the existing benchmark results for two-dimensional lid driven square cavity problem considering both Newtonian and non-Newtonian fluids. Then the code is applied to the skewed cavity problem involving non-Newtonian fluid which can be described by the Bingham model. The constitutive equation is regularized as proposed by Papanastasiou [1]. Moreover, grid independence test has been performed for a skewed cavity for different values of Bingham numbers. Reynolds number and Bingham number are two important parameters which can describe the flow behavior of Bingham fluid in the skewed cavity. In this research, the skewness of the geometry has been changed by changing the skew angle. The consequent numerical results are presented in terms of the velocity and streamlines for the different values of Bingham numbers having a different angle of a skewed cavity.The laminar flow of viscoplastic fluids inside a lid-driven skewed cavity has been investigated using a numerical scheme based on finite volume method considering Bingham model. Viscoplasticity is characterized by a yield stress, below which the materials behave as solids, and above which they deform and flow according to different constitutive relations. The governing two dimensional unsteady incompressible Navier-Stokes equations were initially non-dimensionalized using appropriate transformation. Then the dimensionless form of these equations is transformed to curvilinear coordinates to simulate complex geometry. The transformed equations are then discretized with appropriate boundary conditions to deal with the non-orthogonal grids. The code is first validated against the existing benchmark results for two-dimensional lid driven square cavity problem considering both Newtonian and non-Newtonian fluids. Then the code is applied to the skewed cavity problem involving non-Newtonian fluid which can be des...

International Journal of Mechanical Sciences, May 1, 2021

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  MHD convection and entropy generation in a cavity with a heated plate is studied.  The finite volume method is used to solve the dimensionless governing equations.  Magnetic field suppresses the convective flow, heat transfer and entropy generation.  Magnetic field inclination angle is a very good control parameter for heat transfer.

Journal of Applied Fluid Mechanics, Apr 1, 2012

Laminar magnetohydrodynamic (MHD) natural convection flow from an isothermal sphere immersed in a... more Laminar magnetohydrodynamic (MHD) natural convection flow from an isothermal sphere immersed in a fluid with viscosity proportional to linear function of temperature has been studied. The governing boundary layer equations are transformed into a non-dimensional form and the resulting nonlinear system of partial differential equations are reduced to convenient form which are solved numerically by two very efficient methods, namely, (i) Implicit finite difference method together with Keller box scheme and (ii) Direct numerical scheme. Numerical results are presented by velocity and temperature distribution, streamlines and isotherms of the fluid as well as heat transfer characteristics, namely the local skin-friction coefficients and the local heat transfer rate for a wide range of magnetohydrodynamic paramagnet and viscosity-variation parameter.

Mathematical and Computer Modelling, Mar 1, 2011

The effect of thermal radiation on a steady two-dimensional natural convection laminar flow of vi... more The effect of thermal radiation on a steady two-dimensional natural convection laminar flow of viscous incompressible optically thick fluid along a vertical flat plate with streamwise sinusoidal surface temperature has been investigated in this study. Using the appropriate variables, the basic governing equations are transformed to convenient form and then solved numerically employing two efficient methods, namely, the Implicit Finite Difference method (IFD) together with the Keller box scheme and Straight Forward Finite Difference (SFFD) method. The effects of the variation of the physical parameters, for example, conduction-radiation parameter (Planck number), surface temperature parameter, and the amplitude of the surface temperature, are shown on the skin-friction. Heat transfer rate is shown quantitatively and numerically. Velocity and temperature profiles as well as streamlines and isotherms are also presented and discussed for the variation of the conduction-radiation parameter. It is found that both skin-friction and rate of heat transfer are enhanced considerably by increasing the values of conduction radiation parameter, R d .

Numerical Heat Transfer Part A-applications, Jan 9, 2023

Heat Transfer - Japanese Research, May 24, 2021

This research aims to conduct a numerical simulation of mixed (combined) convective non-Newtonian... more This research aims to conduct a numerical simulation of mixed (combined) convective non-Newtonian fluid flow inside a two-dimensional cavity (skewed) having a moving lid. The upper and bottom extremities of the cavity with different temperatures and two insulated side walls cause natural convection. Moreover, the forced convection is maintained by the motion of the lid with constant velocity. The governing equations are non-dimensionalized with appropriate transformations and then transformed to curvilinear coordinate. A finite volume numerical procedure with a collocated grid arrangement is used to solve these equations. Comparisons with previously reported results are carried out, which shows an excellent agreement. Non-Newtonian behaviors such as pseudo-plastic (shear-thinning) and dilatant (shear-thickening) are considered using the power-law model, and thus power-law index is chosen accordingly. A wide range of the governing dimensionless parameters which affect the mixed convection flow inside the skewed cavity, including Grashof number (10 2 ≤ Gr ≤ 5 × 10 4), Richardson number (0.000625 ≤ Ri ≤ 5), Reynolds number (Re = 100 and 400) and power-law index (0.7 ≤ n ≤ 1.3). The Prandtl number (P r =10) is fixed and the skew angles (ϕ = 45 • , 90 • and 135 •) are considered for acute, right-angle and obtuse angles. The obtained numerical outcomes of the study are shown graphically and also in tabular form for vertical and horizontal velocities, streamlines, isotherms, temperature distributions, and the rate of heat transfer and insight physics of the flow features, are discussed thereafter. It can be concluded that the rate of heat transfer in the present case is sensitive to the skew-angle as well as power-law index, and maximum heat transfer occurs in the case of dilatant (shear-thickening) fluid.

Nucleation and Atmospheric Aerosols, 2018

The present paper aims to study of non-Newtonian fluid flow behaviors in a two-dimensional bifurc... more The present paper aims to study of non-Newtonian fluid flow behaviors in a two-dimensional bifurcated channel using lattice-Boltzmann method (LBM). In this LBM, well known D2Q9 model, and the single-relaxation-time (SRT) called the Lattice-BGK (Bhatnagar-Gross-Krook) approach has been adopted. In a bifurcated channel, the flow patterns are analogous to blood flows in branched arteries. Firstly, the code is validated by comparing the available published results for the Newtonian fluid flows in a channel with T-junction. The numerical results are simulated for the Reynolds number Re = 300, power-law index n = 0.5, 1.0 and 1.5, and the outlet flow rate ratio β. The effects of this relevant parameter on the streamlines, velocity distribution, recirculation zones as well as wall shear stress will be discussed to analyze the hemodynamic of blood flows near arterial bifurcations.

Faculty of Built Environment and Engineering, Nov 1, 2011

Scaling analysis of the unsteady natural convection boundary layer adjacent to an inclined plate ... more Scaling analysis of the unsteady natural convection boundary layer adjacent to an inclined plate for Pr > 1 following instantaneous heating.

Case Studies in Thermal Engineering, Feb 1, 2022

The objective of this paper is to study the entropy generation and natural convection of water-Al... more The objective of this paper is to study the entropy generation and natural convection of water-Al2O3 nanofluid in an inclined cavity which consists of two connected inclined triangular enclosures under a horizontal magnetic field. The horizontal diameter of the cavity is small in thickness and has the temperature Tc. Half of the bottom wall and also the right wall are at the temperature Th. The rest of the walls are adiabatic. The governing equations of the nanofluid flow are algebrized and solved using the FVFEM method. The effective parameters are 103 < Ra < 105, 0 < Ha < 40, 0°< γ < 90°, and 0.00 < φ < 0.06. The results indicate that the rate of heat transfer increases by 12% and the entropy generation enhances by 13% through enhancing the Raleigh number. As the Hartmann number increases, the rate of heat transfer and the entropy generation decrease by 6.5% and 8%, respectively. The Bejan number also decreases for a higher Raleigh number and a lower Hartmann number. For a higher angle of the cavity, the average Nusselt number calculated on the right wall always reduces. Entropy generation decreases and Bejan number increases for a higher inclined angle.

Heat Transfer - Japanese Research, Feb 23, 2020

This study is aimed to investigate the natural convection heat transfer from discrete heat source... more This study is aimed to investigate the natural convection heat transfer from discrete heat sources (similar to heated microchips) using Bhatnagar‐Gross‐Krook lattice Boltzmann method via graphics process unit computing. The simulation is carried out separately for three and six heated blocks model for different Rayleigh numbers and fixed Prandtl number, (air). The uniformly heated blocks are placed at the bottom wall inside a rectangular enclosure. The enclosure is maintained by the cold temperature at its left and right walls. The top and bottom surface is maintained by adiabatic conditions apart from the regions where blocks are attached to the bottom wall. The numerical code is validated with the benchmark heat transfer problem of side‐heated square cavity as well as with an experimental study for one discrete heat source. The rate of heat transfer is presented in terms of the local Nusselt and average Nusselt number for each block. It is found that the heat transfer rate becomes maximized in the leftmost and rightmost blocks due to the adjacent cold walls. It is found that the number of blocks and their positions play a substantial role in determining their collective performance on the heat transfer rate.

Procedia Engineering, 2014

A steady natural convection along a vertical cone with uniform surface heat flux for temperature ... more A steady natural convection along a vertical cone with uniform surface heat flux for temperature dependent thermal conductivity k (T) has been investigated numerically. Using the appropriate variables the basic equations are transformed to non-dimensional boundary layer equations and then solved employing marching order implicit finite difference method. In this paper, attention is mainly focused to the evolution of the surface shear stress in terms of local skin-friction and the rate of heat transfer in terms of local Nusselt number, velocity and temperature profiles, velocity vector field, streamlines and isotherms for a wide range of values of thermal conductivity variation parameter. The present numerical results are compared with the available published results which show a good agreement indeed.

Heat Transfer

This study conducts a numerical simulation of mixed (combined) convective non‐Newtonian fluid flo... more This study conducts a numerical simulation of mixed (combined) convective non‐Newtonian fluid flow inside a two‐dimensional cavity (skewed) having a moving lid. The upper and bottom extremities of the cavity with different temperatures and two insulated side walls cause natural convection. Moreover, the forced convection is maintained by the motion of the lid with constant velocity. The governing equations are nondimensionalized with appropriate transformations and then transformed into curvilinear coordinates. A finite volume numerical procedure with a collocated grid arrangement is used to solve these equations. Comparisons with previously reported results are carried out, which shows an excellent agreement. Non‐Newtonian behaviors such as pseudo‐plastic (shear‐thinning) and dilatant (shear‐thickening) are considered using the power‐law model, and thus the power‐law index is chosen accordingly. A wide range of the governing dimensionless parameters which affect the mixed convectio...

International Journal of Thermal Sciences, 2022

Building Simulation, 2021

This work aims to find the origin and connection of the surface, near-wake, and far-wake structur... more This work aims to find the origin and connection of the surface, near-wake, and far-wake structures in the flow encompassing a high-rise building for a high Reynolds number. The origin and interconnection of the stream-wise tip vortices, with the other components of the wake, is analysed in this study for the current scenario. The Unsteady Reynolds Averaged Navier-Stokes equations (URANS) together with the realizable k-ϵ turbulence model have been used in this investigation to study the turbulent wake flow following a ground-surface-attached square shape building. A moderately big obstacle aspect ratio of 4, a Reynolds number of 12,000, and a thin evolving boundary layer thickness have been used in the flow modeling. The designed flow addresses the reversed-flows at the outlet during computation to improve the accuracy of the realizable k-ϵ model. The Reynolds stress components are retrieved using the Boussinesq approach. The wake’s principal compositions, including span-wise-side eddies and area of high stream-wise vorticity in the uppermost portion of the wake, are illustrated by both three-dimensional (3D) representations and planner projections of the mean flow distributions. A braided vortex formation, composed of asymmetric hairpin vortexes, is witnessed in the far-wake area. The association of the near-wake vortex structures with the far-wake and near-wall flow, which is associated with the flow strengths, is also discussed. In this investigation, few areas of large stream-wise vorticity magnitude, like tip vortexes, are correlated to the 3D curving of the fluid motion, and tip vortices did not continuously reach to the free end part of the building. The 3D fluid motion interpretation, which combined several measurements of the flow distribution encompassing the cylinder, shows that the time-averaged near-wake structures are formed of two segments of distinct source and section of dominance. Furthermore, addressing reversed-flow during computation shows notable improvement in the results.

International Journal of Ambient Energy

Axiom, 2023

International Journal of Engineering Science, Aug 1, 2006

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, May 12, 2023

Nucleation and Atmospheric Aerosols, 2018

International Journal of Mechanical Sciences, May 1, 2021

Journal of Applied Fluid Mechanics, Apr 1, 2012

Mathematical and Computer Modelling, Mar 1, 2011

Numerical Heat Transfer Part A-applications, Jan 9, 2023

Heat Transfer - Japanese Research, May 24, 2021

Nucleation and Atmospheric Aerosols, 2018

Faculty of Built Environment and Engineering, Nov 1, 2011

Case Studies in Thermal Engineering, Feb 1, 2022

Heat Transfer - Japanese Research, Feb 23, 2020

Procedia Engineering, 2014

Heat Transfer

International Journal of Thermal Sciences, 2022

Building Simulation, 2021

Unsteady natural convection flow in a two dimensional fluid saturated porous enclosure with local... more Unsteady natural convection flow in a two dimensional fluid saturated porous enclosure with localized heating form below with heat flux, symmetrical cooling from the sides and the insulated top wall has been investigated numerically. The governing equations are the Darcy's law for the porous media and the energy equation for the temperature field has been considered. The non-dimensional Darcy's law in terms of the stream function is solved by finite difference method using the successive over-relaxation (SOR) scheme and the energy equation is solved by Alternative Direction Alternative (ADI) scheme. The uniform heat flux source is located centrally at the bottom wall. The numerical results are presented in terms of the streamlines and isotherms, as well as the local and average rate of heat transfer for the wide range of the Darcy's Rayleigh number and the length of the heat flux source at the bottom wall.

A numerical study on natural convection flow of Cu-Water nanofluid along a vertical wavy surface ... more A numerical study on natural convection flow of Cu-Water nanofluid along a vertical wavy surface with uniform heat flux has been carried out. The governing boundary layer equations are transformed into parabolic partial differential equations by applying a suitable set of variables. The resulting nonlinear system of equations are then mapped into a regular rectangular computational domain and solved numerically by using an implicit finite difference method. Numerical results are thoroughly discussed in terms of velocity and temperature distributions, surface temperature distribution, skin friction coefficient and Nusselt number coefficient for selected key parameters such as solid volume fraction of nanofluid () and amplitude (a) of surface waviness. In addition, velocity vectors, streamlines and isotherms are plotted to visualize momentum and thermal flow pattern within the boundary layer region.

In this research, heat transfer efficiency of nanofluids, through natural convection, ... more In this research, heat transfer efficiency of nanofluids, through natural convection, inside a sealed wavy cavity has been
examined numerically. Copper has been used as nanoparticles for primary investigation, with water as the base fluid. The
governing Navier-Stokes and energy equations have been transformed into Cartesian curvilinear coordinates and then
solved numerically using the finite volume method imposing several boundary conditions. Numerical code written in
FORTRAN programming language is used to simulate the dimensionless, discretized governing equations. The study has
been conducted for a range of Rayleigh numbers (10
3
< Ra < 10
6
) and different volume fractions (0 < ϕ < 0.2). The code is
validated with previous published results and found to be in good agreement. The obtained results are illustrated in terms of
the isotherm s, streamlines, velocity and temperature profiles as well as the rate of heat transfer. It is observed that volume
fraction of nanoparticles and the Rayleigh number affect the flow and heat transfer characteristics of nanofluids within the
cavity.

In this research, the improved thermal features of nanofluids are studied by investigating the la... more In this research, the improved thermal features of nanofluids are studied by investigating the laminar fluid flow over a two dimensional sinusoidal wall channel whose top and bottom wavy sections are heated. The nanofluid used is composed of copper (Cu) nanoparticles suspended in water (H2O) which acts as the basefluid. The flow is characterized by a range of Reynold numbers (Re) with varying volume fractions for a particular Grashof Number (Gr). In addition, the effect of mixed convection, which takes both natural and forced convection of the fluid into account, is examined by altering the Richardson number (Ri = Gr/Re2). The governing equations which include the continuity, Navier-Stokes and energy equations are in Cartesian coordinates which are non-dimensionalised and then transformed into curvilinear coordinates. The transformed equations are then discretized using finite volume method, applying the appropriate boundary conditions. The consequent numerical results are represented in the form of local Nusselt number graphs, isotherms, streamlines, temperature and velocity profiles.

The effects of conduction and convection on magneto hydrodynamic (MHD) boundary layer flow with v... more The effects of conduction and convection on magneto hydrodynamic (MHD) boundary layer flow with viscous dissipation from a vertical flat plate of thickness 'b' have been investigated. The governing equations are made dimensionless by using suitable transformations. The dimensionless equations are then solved numerically in the entire region starting from the lower part of the plate to the down stream by means of implicit finite difference method known as Keller box scheme. The dimensionless skin friction co-efficient, the surface temperature distribution, the velocity distribution and the temperature profile over the whole boundary layer are shown graphically for different values of the magnetic parameter M, the viscous dissipation parameter N and the Prandtl number Pr.

The effects of conduction and convection on magneto hydrodynamic (MHD) boundary layer flow from a... more The effects of conduction and convection on magneto hydrodynamic (MHD) boundary layer flow from a vertical flat plate of thickness 'b' have been investigated. The governing equations are made dimensionless by using suitable transformations. The dimensionless equations are then solved numerically in the entire region starting from the lower part of the plate to the down stream by means of implicit finite difference method known as Keller box scheme. The dimensionless skin friction co-efficient, the surface temperature distribution, the velocity distribution and the temperature profile over the whole boundary layer are shown graphically for different values of the magnetic parameter M and the Prandtl number Pr.

In this paper, direct numerical simulation (DNS) is used to simulate the physiological pulsatile ... more In this paper, direct numerical simulation (DNS) is used to simulate the physiological pulsatile flow in a constricted channel to gain insight into the transition-to-turbulent flow in an artificial arterial stenosis. An in-house code has been developed using OpenMP and DNS was performed based on available high performance shared memory parallel computing facilities. The Womersley number tested was fixed to 10.5 and the Reynolds number was varied from 800 to 1800 in the simulation. The physical characteristics of the flow field have been thoroughly analyzed in terms of the mean streamwise velocity, the root mean square (RMS) velocities, turbulence kinetic energy (TKE), viscous wall shear stresses and wall pressure.

The effect of thermal radiation on a steady two-dimensional natural convection laminar flow of vi... more The effect of thermal radiation on a steady two-dimensional natural convection laminar flow of viscous incompressible optically thick fluid along a vertical wavy surface has been investigated. Using the appropriate variables; the basic equations are transformed into the local non-similarity boundary layer form and then solved employing the Keller-box scheme of finite difference method. Numerical results are presented by streamline, isotherms, velocity and temperature distribution of the fluid as well as the local heat transfer rate in terms of local Nusselt number and average rate of heat transfer for a wide range of Planck number R d and the surface heating parameter θ w . The present numerical result shows excellent agreement with the published results when the effect of thermal radiation was passed over.

The effects of temperature dependent viscosity on natural convection flow from a vertical permeab... more The effects of temperature dependent viscosity on natural convection flow from a vertical permeable circular cone with uniform heat flux is studied. The viscosity is a linear function of temperature which is valid for small Prandtl numberPr. The governing boundary layer equations are transformed into a non-dimensional form and the resulting nonlinear system of partial differential equations are reduced to local non-similarity equations which are solved numerically by three distinct solution methodologies; namely (i) perturbation solution for small transpiration parameter (ii) asymptotic solution for large  and (iii) the implicit finite difference method together with Keller box scheme for all . Numerical results of velocity and viscosity profiles of the fluid are displayed graphically as well as heat transfer characteristics, namely the shearing stress in terms of the local skin-friction coefficient and the rate of heat transfer in terms of the local Nusselt number are given in tabular form for the viscosity parameter  and the Prandtl number Pr.

The effect of temperature dependent viscosity μ(T), on steady two dimensional natural convection ... more The effect of temperature dependent viscosity μ(T), on steady two dimensional natural convection flow along a vertical wavy cone with uniform surface heat flux has been investigated. Viscosity is considered to be a linear function of temperature. Using the appropriate variables, basic equations are transformed to non-dimensional boundary layer equations and then solved numerically employing implicit SFFD method. The effects of viscosity variation parameter on the velocity profile, temperature profile, skin friction, average Nusselt number and isotherm have been discussed.

The effect of temperature dependent viscosity μ(T), on steady two dimensional natural convection ... more The effect of temperature dependent viscosity μ(T), on steady two dimensional natural convection flow along a vertical wavy cone with uniform surface heat flux has been investigated. Viscosity is considered to be inversely proportional to temperature. Using the appropriate variables the basic equations are transformed to non-dimensional boundary layer equations and then solved numerically employing implicit finite difference method. The effects viscosity variation parameter on the velocity profile, temperature profile, velocity vector field, skin friction, average Nusselt number, streamlines and isotherm have been discussed. The results have been shown graphically by utilizing the visualizing software Techplot. The present numerical result shows excellent agreement with the published results when the effect of temperature dependent viscosity was passed over.

Unsteady natural convection laminar flows in a square cavity formed by insulated bottom and top w... more Unsteady natural convection laminar flows in a square cavity formed by insulated bottom and top walls, uniformly heated left wall and the cooled right wall has been investigated numerically. The governing equations are transformed into non-dimensional form and the resulting partial differential equations are solved applying upwind finite difference method together with Successive Over-Relaxation (SOR) scheme. The effect of the heat generation and the Rayleigh number on streamlines and isotherms as well as on the rate of heat transfer from the heated wall of the cavity are presented.

A steady two-dimensional natural convection boundary layer flow on a sphere with heat generation ... more A steady two-dimensional natural convection boundary layer flow on a sphere with heat generation in a viscous incompressible fluid is investigated in the present paper. Using the appropriate transformation, the basic equations for mass continuity, momentum and energy are transformed into nondimensional boundary layer equations. These non-dimensional equations are solved numerically by using a very efficient finite difference method known as the Keller box scheme. Numerical results presented include velocity and temperature profiles as well as heat transfer characteristics, namely the local skin friction and local rate of heat transfer for a wide range of non-dimensional heat generation parameter Q and the Prandtl number Pr

order of magnitude as the hydrodynamical and inertial forces. Thus in the equations of motion, we... more order of magnitude as the hydrodynamical and inertial forces. Thus in the equations of motion, we This paper describes the problem of natural convection flow on a sphere in a steady two dimensional viscous incompressible fluid in presence of magnetic field. Using the appropriate transformation, the governing boundary layer equations are transformed into a non dimensional form, which are solved numerically using a very efficient finite difference method together with Keller box method. Numerical results are presented including the surface shear stress in terms of local skin friction and the rate of heat transfer in terms of local Nusselt number as well as velocity and temperature distribution for a wide range of MHD parameter having Prandtl number 0.7 to 7.0

Large Eddy Simulation (LES) is performed to study the physiological pulsatile transition to turbu... more Large Eddy Simulation (LES) is performed to study the physiological pulsatile transition to turbulent non-Newtonian blood flow through a 3D model of arterial stenosis using the different non-Newtonian blood viscosity models. The computational domain has been chosen is a simple channel with a biological type stenosis formed eccentrically on the top wall. The physiological pulsation is generated at the inlet of the model using the fourth harmonic of the Fourier series of the physiological pressure pulse (Womersley [1]). The computational results are presented in terms of the post-stenotic re-circulation zone, shear stress, mean and turbulent kinetic energy.

Natural convection thermal boundary layer adjacent to an instantaneous heated inclined flat plate... more Natural convection thermal boundary layer adjacent to an instantaneous heated inclined flat plate is investigated through a scaling analysis and verified by direct numerical simulations. It is revealed from the analysis that the development of the boundary layer may be characterized by three distinct stages, i.e. a start-up stage, a transitional stage and a steady state stage. These three stages can be clearly identified from the numerical simulations. Major scales including the flow velocity, flow development time, and the thermal and viscous boundary layer thicknesses are established to quantify the flow development at different stages and over a wide range of flow parameters. Details of the scaling analysis are described in this paper.

Pulsatile laminar-turbulent transitional flow in a threedimensional (3D) constricted channel repr... more Pulsatile laminar-turbulent transitional flow in a threedimensional (3D) constricted channel represents a challenging topic and has many important applications in bio-medical engineering. In this research, we numerically investigate the physics of a physiological pulsatile flow confined within a 3D channel with an idealized stenosis formed eccentrically on the top wall using the method of large-eddy simulation (LES). The advanced dynamic nonlinear subgrid-scale stress (SGS) model of Wang and Bergstrom was implemented in the current LES approach to properly resolve the unrealistic SGS dissipation effects and numerical instabilities that are intrinsic to the Smagorinsky type dynamic models (DM). The Reynolds numbers tested in the simulation are 1700 and 2000, which are characteristic of human blood flows in large arteries. An in-house 3-D LES code has been modified to conduct our unsteady numerical simulations, and the results obtained have been validated using two different grid arrangements and the experimental results of Ahmed and Giddens . The numerical results have been examined in terms of the resolved mean velocity, turbulence kinetic energy, viscous wall shear stress, resolved and subgrid-scale Reynolds stresses, as well as the local kinetic energy fluxes between the filtered and subgrid scales.