Showing papers on "Combined forced and natural convection published in 2018"
TL;DR: In this paper, the steady laminar MHD mixed convection boundary layer flow of a SiO2-Al2O3/water hybrid nanofluid near the stagnation point on a vertical permeable flat plate is analyzed.
184 citations
TL;DR: In this article, mixed convection on MHD flow of casson nanofluid over a nonlinearly permeable stretching sheet has been investigated and analyzed numerically, and the effects of thermal radiation, chemical reaction, heat generation/absorption, viscous dissipation, suction and Joule heating are considered.
162 citations
TL;DR: In this paper, the potential use of kerosene-Al2O3 nano-liquid for thrust chamber regenerative cooling in semi-cryogenic rocket engine due to its enhanced thermal properties is explored.
146 citations
TL;DR: In this article, the mixed convection stationary point flow of an incompressible viscous nano fluid into a vertical permeable circular cylinder along with electric conductivity is analyzed, and the strong nonlinear systems calculations are presented using the Numerical Method after non-dimensionalization.
Abstract: In this research, the mixed convection stationary point flow of an incompressible viscous Nano fluid into a vertical permeable circular cylinder along with electric conductivity is analyzed. Ethylene glycol is used as an ordinary liquid, while nanoparticles include copper and silver. The problem has been calculated without the presence of an inductive and electrical magnetic field while taking into account homogeneous and heterogeneous reactions. The strong nonlinear systems calculations are presented using the Numerical Method after non-dimensionalization. Graphical analysis of the effective parameters such as Prandtl number ( Pr ) , permeability parameter ( V w ) , Schmidt number ( Sc ) , magnetic parameter ( M ) , mixed convection parameter ( λ ) and curvature parameter ( γ ) is precisely investigated on the profiles of velocity, concentration and temperature for different nanoparticles. Conclusions indicate that: The thickness of the thermal boundary layer changes more than the thickness of the hydro-dynamic boundary layer for injection and suction. Also, due to the higher thermal conductivity of silver nanoparticles, the temperature increase in these nanoparticles is more than that of copper. In fact, this paper shows that the heat transfer rate increases with the addition of nanoparticles. In addition, the role of the curvature parameter ( γ ) on the concentration profile shows that the concentration profile decreases with the gradual increase of γ .
139 citations
TL;DR: In this article, a coupled transient representative particle and fix-bed model was developed to describe the entire fixed-bed in the flow direction of primary air, and a three-region approach has been incorporated into the model, which divided the reactor into three regions in terms of different fluid velocity profiles.
137 citations
TL;DR: In this article, the authors present knowledge of double-diffusive convection at low Prandtl number obtained using direct numerical simulations, in both the fingering regime and the oscillatory regime.
Abstract: This work reviews present knowledge of double-diffusive convection at low Prandtl number obtained using direct numerical simulations, in both the fingering regime and the oscillatory regime. Particular emphasis is given to modeling the induced turbulent mixing and its impact in various astrophysical applications. The nonlinear saturation of fingering convection at low Prandtl number usually drives small-scale turbulent motions whose transport properties can be predicted reasonably accurately using a simple semi-analytical model. In some instances, large-scale internal gravity waves can be excited by a collective instability and eventually cause layering. The nonlinear saturation of oscillatory double-diffusive convection exhibits much more complex behavior. Weakly stratified systems always spontaneously transition into layered convection associated with very efficient mixing. More strongly stratified systems remain dominated by weak wave turbulence unless they are initialized into a layered state. The eff...
134 citations
TL;DR: In this paper, Tangent hyperbolic nanomaterial model is used to describe the important slip mechanism, namely Brownian and thermophoresis diffusions, and an optimization of entropy generation is performed through thermodynamics second law.
132 citations
TL;DR: In this article, the authors investigated steady conjugate mixed convection in a double lid-driven square cavity including a solid inner body, where the annulus is filled with water-Al2O3 nanofluid based on Buongiorno's two-phase model.
120 citations
TL;DR: A systematic review procedure on the effects of Grashof number and mixed convection parameter on the flow of various fluids is presented in this article, where 30 relevant articles were screened and reviewed for the study.
120 citations
TL;DR: In this paper, mixed convection of nanofluids in a three dimensional cavity with two inner adiabatic rotating circular cylinders were analyzed by using finite element method, and a correlation for the average Nusselt number in polynomial form was developed which is a function of Rayleigh number and angular rotational speed of the cylinders.
120 citations
TL;DR: In this article, a lattice Boltzmann model was developed to predict the fluid flow and heat transfer of air through the inclined lid driven 2D cavity while a large heat source is considered inside it.
Abstract: Nano scale method of lattice Boltzmann is developed to predict the fluid flow and heat transfer of air through the inclined lid driven 2-D cavity while a large heat source is considered inside it. Two case studies are supposed: first one is a pure natural convection at Grashof number from 400 to 4000 000 and second one is a mixed convection at Richardson number from 0.1 to 10 at various cavity inclination angles. Using LBM to simulate the constant heat flux boundary condition along the obstacle, is presented for the first time while the buoyancy forces affect the velocity components at each inclination angle; hence the collision operator of LBM and also a way to estimate the macroscopic velocities should be modified. Results are shown in the terms of streamlines and isotherms, beside the profiles of velocity, temperature and Nusselt number. It is observed that the present model of LBM is appropriately able to simulate the supposed domain. Moreover, the effects of inclination angle are more important at higher values of Richardson number.
TL;DR: In this paper, three dimensional numerical simulations have been performed on a cubical cavity using finite volume method and the results of mixed convection and entropy generation are illustrated with particle trajectories, isotherms, Nusselt number and Bejan number.
TL;DR: In this paper, the mixed convection in a lid-driven cavity containing a hot elliptical centric cylinder was studied by using of Water-Aluminum oxide (Al2O3) nanofluid.
TL;DR: In this article, a lid driven trapezoidal cavity filled with Al2O3-water nanofluid under the effect of an inclined magnetic field was numerically investigated for various electrical conductivity models.
TL;DR: In this article, the authors improved the lattice Boltzmann method ability to simulate the mixed convection of Water / FMWCNT nanofluid inside a two dimensional microchannel.
Abstract: Lattice Boltzmann method ability is improved to simulate the mixed convection of Water / FMWCNT nanofluid inside a two dimensional microchannel. The influences of gravity on hydrodynamic and thermal domains are studied while the microchannel walls are imposed by a constant thermal heat flux at three different case studies as no-gravity, R i = 1 and R i = 10 . The flow Reynolds number is chosen as one and the liquid micro flow conditions are involved by B = 0.005, B = 0.01 and B = 0.02. The mass fraction of carbon nanotubes in water are selected as ϕ = 0 , ϕ = 0 .1% and ϕ = 0 .2%. Double population distribution functions of “f” and “g” are used in lattice Boltzmann method. To the best of author’s knowledge, there is no article concerned the way of heat flux boundary condition simulation by LBM considering the buoyancy forces effects on nanofluid slip velocity. Generate a rotational cell due to gravity in entrance region which leads to observe the negative slip velocity phenomenon can be presented as the several interesting achievements of this work.
TL;DR: In this article, an analysis of entropy generation and magnetohydrodynamics impacts in unsteady viscous nanoliquid flow is elaborated, and the rate of total entropy generation is evaluated for distinct arising variables such as skin-friction and Nusselt and Sherwood numbers in addition to velocity, temperature and nanoparticles concentration.
TL;DR: In this article, the authors investigated the novel characteristics of entropy generation in nonlinear mixed convective flow of nanofluid between two stretchable rotating disks and showed that entropy generation rate and Bejan number have inverse behavior for higher estimation of Hartman number.
TL;DR: In this article, the analysis of a typical system is demonstrated considering bottom-heating, porous medium and Cu-water nanofluid, and the results reveal that the heat transport of base liquid is greatly influenced by these parameters.
TL;DR: This study mainly focuses on gold nanoparticles; however, for the sake of comparison, four other types of nanoparticles namely silver, copper, alumina and magnetite are analyzed for the heat transfer rate and the obtained results show that metals have higher rate of heat transfer than metal oxides.
Abstract: Impacts of gold nanoparticles on MHD Poiseuille flow of nanofluid in a porous medium are studied. Mixed convection is induced due to external pressure gradient and buoyancy force. Additional effects of thermal radiation, chemical reaction and thermal diffusion are also considered. Gold nanoparticles of cylindrical shape are considered in kerosene oil taken as conventional base fluid. However, for comparison, four other types of nanoparticles (silver, copper, alumina and magnetite) are also considered. The problem is modeled in terms of partial differential equations with suitable boundary conditions and then computed by perturbation technique. Exact expressions for velocity and temperature are obtained. Graphical results are mapped in order to tackle the physics of the embedded parameters. This study mainly focuses on gold nanoparticles; however, for the sake of comparison, four other types of nanoparticles namely silver, copper, alumina and magnetite are analyzed for the heat transfer rate. The obtained results show that metals have higher rate of heat transfer than metal oxides. Gold nanoparticles have the highest rate of heat transfer followed by alumina and magnetite. Porosity and magnetic field have opposite effects on velocity.
TL;DR: The main physical implication of the results is that both momentum and temperature layers are thinned with strong magnetic fields, and upper branch solutions are more cooled leading to higher heat transfer rates as compared to the lower branches.
TL;DR: In this article, the effect of two porous layers on the bottom wall of a lid-driven cavity is numerically studied and it has been found that in the natural convection regime an addition of nanoparticles leads to heat transfer enhancement, while for mixed convection and forced convection regimes an increase in nanoparticles volume fraction leads to the heat transfer reduction.
TL;DR: In this paper, the authors used the computational method to investigate the flow and heat transfer characteristics of turbulent sCO2 in a large horizontal tube with the buoyancy effects taken into account, RNG and three selected low-Reynolds number k - e turbulence models have been validated against experiments published in literatures.
TL;DR: In this article, the authors focused on time-dependent flow of non-Newtonian Williamson fluid driven by a radially stretching geometry with nanoparticles, and the analysis is subject to the effects of variable magnetic field, mixed convection and newly proposed zero nanoparticles mass flux condition.
TL;DR: In this paper, a realistic three dimensional magnetohydrodynamic flow of an Oldroyd-B fluid is studied after developing a convergent analytic scheme. And the resulting problems are computed by homotopy analysis method (HAM).
Abstract: In this article, a realistic three dimensional magnetohydrodynamic flow of an Oldroyd-B fluid is studied after developing a convergent analytic scheme. Soret and Dufour effects with mixed convection are taken into account. The governing highly non-linear partial differential equations are transformed into the system of ordinary differential equations using similarity transformations. The resulting problems are computed by homotopy analysis method (HAM). Profiles of dimensionless velocities, temperature and concentration are plotted and discussed for various emerging physical parameters. Numerical values of physical quantities of interest such as local Nusselt number and local Sherwood number are tabulated. A comparative study with existing literature are found in an excellent agreement.
TL;DR: In this paper, the authors present a brief review on the buoyancy criteria for supercritical fluids (mainly water, carbon dioxide and hydrocarbon fuels) and compare the most reliable buoyancy criterion for vertical and horizontal tubes.
TL;DR: In this paper, the authors investigated the heat transfer characteristics of developing and fully developed flow in smooth horizontal tubes in the transitional flow regime at a constant heat flux, and found that the Reynolds number at which transition started was independent of axial position, and transition occurred at the same moment in time along the whole tube length.
TL;DR: In this paper, the role of fluid-structure interaction (FSI) in the mixed convection inside a square cavity having two inlet and outlet openings was investigated, where a flexible elastic fin was attached to the bottom wall of the cavity.
TL;DR: In this paper, a computational analysis has been performed on mixed convection in a double sided lid-driven cavity in the presence of volumetric heat generation or absorption, and the effects of inclined magnetic field are also studied.
TL;DR: This numerical study considers the mixed convection and the inherent entropy generated in Al2O3–water nanofluid filling a cavity containing a rotating conductive cylinder and shows that the rotation of the cylinder boosts the rate of heat exchange when the Rayleigh number is less than 5×105.
Abstract: This numerical study considers the mixed convection and the inherent entropy generated in Al 2 O 3 –water nanofluid filling a cavity containing a rotating conductive cylinder The vertical walls of the cavity are wavy and are cooled isothermally The horizontal walls are thermally insulated, except for a heat source segment located at the bottom wall The dimensionless governing equations subject to the selected boundary conditions are solved numerically using the Galerkin finite-element method The study is accomplished by inspecting different ranges of the physical and geometrical parameters, namely, the Rayleigh number ( 10 3 ≤ R a ≤ 10 6 ), angular rotational velocity ( 0 ≤ Ω ≤ 750 ), number of undulations ( 0 ≤ N ≤ 4 ), volume fraction of Al 2 O 3 nanoparticles ( 0 ≤ ϕ ≤ 004 ), and the length of the heat source ( 02 ≤ H ≤ 08 ) The results show that the rotation of the cylinder boosts the rate of heat exchange when the Rayleigh number is less than 5 × 10 5 The number of undulations affects the average Nusselt number for a still cylinder The rate of heat exchange increases with the volume fraction of the Al 2 O 3 nanoparticles and the length of the heater segment