Soheil Soleimani

A study of natural convection heat transfer in a nanofluid filled enclosure with elliptic inner cylinder

– The purpose of this paper is to study the effects of natural convection heat transfer in a cold outer circular enclosure containing a hot inner elliptic circular cylinder. The fluid in the enclosure is Cu-water nanofluid. The main emphasis is to find the numerical treatment for the said mathematical model. The effects of Rayleigh number, inclined angle of elliptic inner cylinder, effective of thermal conductivity and viscosity of nanofluid, volume fraction of nanoparticles on the flow and heat transfer characteristics have been examined. , – A very effective and higher order numerical scheme Control Volume-based Finite Element Method (CVFEM) is used to solve the resulting coupled equations. The numerical investigation is carried out for different governing parameters namely; the Rayleigh number, nanoparticle volume fraction and inclined angle of elliptic inner cylinder. The effective thermal conductivity and viscosity of nanofluid are calculated using the Maxwell-Garnetts (MG) and Brinkman models, respectively. , – The results reveal that Nusselt number increases with an increase of nanoparticle volume fraction, Rayleigh numbers and inclination angle. Also it can be found that increasing Rayleigh number leads to a decrease in heat transfer enhancement. For high Rayleigh number the minimum heat transfer enhancement ratio occurs at. , – To the best of the authors’ knowledge, no such analysis is available in the literature which can describe the natural convection heat transfer in a nanofluid filled enclosure with elliptic inner cylinder by means of CVFEM.

Numerical Investigation of the Effect of Magnetic Field on Natural Convection in a Curved-Shape Enclosure

This investigation reports the magnetic field effect on natural convection heat transfer in a curved-shape enclosure. The numerical investigation is carried out using the control volume-based-finite element method (CVFEM). The numerical investigations are performed for various values of Hartmann number and Rayleigh number. The obtained results are depicted in terms of streamlines and isotherms which show the significant effects of Hartmann number on the fluid flow and temperature distribution inside the enclosure. Also, it was found that the Nusselt number decreases with an increase in the Hartmann number.

Homotopy perturbation method for motion of a spherical solid particle in plane couette fluid flow

Hes homotopy perturbation method is applied to obtain exact analytical solutions for the motion of a spherical particle in a plane couette flow. It is demonstrated that the applied analytical method is very straightforward in comparison with existing techniques. Furthermore, it is decidedly effectual in terms of accuracy and rapid convergence. The formulation of the problem is presented in the text as well as the analytical and numerical procedures. The current results can be used in different areas of particulate flows.

Investigation of heat and mass transfer of rotating MHD viscous flow between a stretching sheet and a porous surface

Purpose – The purpose of this paper is to analyze hydromagnetic flow between two horizontal plates in a rotating system. The bottom plate is a stretching sheet and the top one is a solid porous plate. Heat transfer in an electrically conducting fluid bounded by two parallel plates is also studied in the presence of viscous dissipation.Design/methodology/approach – Differential Transformation Method (DTM) is used to obtain a complete analytic solution for the velocity and temperature fields and the effects of different governing parameters on these fields are discussed through the graphs.Findings – The obtained results showed that by adding a magnetic field to this system, transverse velocity component reduces between the two plates. Also as the Prandtl number increases, in presence of viscous dissipation, the temperature between the two plates enhances while an opposite behavior is observed when the viscous dissipation is negligible.Originality/value – The equations of conservation of mass, momentum and e...

The Influence of Uniform Suction/Injection on Heat Transfer of MHD Hiemenz Flow in Porous Media

The steady two-dimensional laminar forced magneto-hydrodynamic (MHD) Hiemenz flow against a flat plate with variable wall temperature in a porous medium is analyzed. The transformed nonlinear boundary-layer equations are solved analytically by homotopy analysis method (HAM). Results for the velocity and temperature profiles are presented for various values of Prandtl number Pr , the Hartmann number ( M ), exponent of wall temperature ( λ ), the permeability parameter ( Ω ), and suction and injection parameter ( fw ). Increments in fw , M , and Ω increase the velocities profiles but decrease the temperature profiles. Contrarily, the increment in the Pr decreases the velocity profiles and increases the temperature profiles. The convergence of the obtained series solutions is explicitly studied and a proper discussion is given for the obtained results. Comparison between the HAM and numerical solutions showed excellent agreement.

Approximate solutions to Van der Pol damped nonlinear oscillators by means of He's energy balance method

In this article, Hes energy balance method (EBM) is applied to solve Van der Pol damped nonlinear oscillators. Three examples of Van der Pol oscillators are presented and solved by this method to illustrate the effectiveness and convenience of the EBM. In this method, only one iteration leads to high accuracy of the solution. Comparisons are made between EBM results and exact solutions of the problems. The results show that the method can be easily extended to other nonlinear systems and can therefore be found widely applicable in engineering and other science.

Analysis of blood flow through a viscoelastic artery using the Cosserat continuum with the large-amplitude oscillatory shear deformation model

In this investigation, semiempirical and numerical studies of blood flow in a viscoelastic artery were performed using the Cosserat continuum model. The large-amplitude oscillatory shear deformation model was used to quantify the nonlinear viscoelastic response of blood flow. The finite difference method was used to solve the governing equations, and the particle swarm optimization algorithm was utilized to identify the non-Newtonian coefficients (k(υ) and γ(υ)). The numerical results agreed well with previous experimental results.

The Effect of Different Injection Strategies and Intake Conditions on the Emissions Characteristics in a Diesel Engine

Choosing various injection strategies and intake conditions are potentially effective techniques to reduce exhaust emission from diesel engines. The purpose of this study is to investigate the effect of different spray incoming angles, different spray cone angles, different injection timing, and different intake temperatures together with emission characteristics on a heavy duty diesel engine via three dimensional computational fluid dynamics (CFD) procedures. Furthermore the effect of multiple injector combustion chamber and its benefits in pollutant reduction is studied. The principal results show the significant differences in soot and 𝑁𝑂 generation during combustion between above different strategies.

Steady State Simulation of Gaseous Combustor Using Local Extiction Eddy Dissipation Concept

Non-premixed turbulent reacting flow in a methane-fuelled coaxial jet combustor has been studied numerically employing Reynolds Averaged Navier-Stokes (RANS) models. A Local Extinction approach for treating chemical reaction kinetics within the Eddy Dissipation Concept (EDC) has been examined. It applies a database of pre-calculated chemical time scales, which contains the influence of chemical kinetics that is otherwise timeconsuming to calculate. Simulations were carried out using RNG k-epsilon turbulence models by open-source CFD-toolbox OpenFOAM. The results were compared to available numerical results and experimental data for velocity, and temperature fields. All simulations were conducted with a reasonable number of mesh to demonstrate the accuracy of turbulent RANS models in OpenFOAM solver, which has a wide range of engineering applications in such type of flows.

Secondary reactions of turbulent reacting flows over a film-cooled surface using OpenFOAM

Demand for greater engine efficiency and thrust-to-weight ratio has driven the production of aircraft engines with higher core temperatures and pressures. Such engines operate at higher fuel-air ratios, resulting in the potential for significant heat release and chemical reactions on a film-cooled surface. Currently, there is little basis for understanding the effects on aero-performance and durability due to such secondary reactions. In this paper, the chemically turbulent reactive film cooling over a surface with an inclined coolant hole is investigated by a Reynolds-averaged Navier–Stokes approach with the shear-stress transport (SST) turbulence model using OpenFoam. To take into account the secondary combustion resulting from the unburned fuels in the crossflow, a two-step reaction scheme was used for the combustion of propane. The relative increase in surface heat flux due to near wall reactions was investigated for film cooling with N2 and air injections. An eddydissipation concept fast chemistry approach was used to account for the turbulence– chemistry interaction. Results demonstrate that reactions in the turbine cooling film can result in increased heat transferred to the surface. Failure to design for this effect could result in augmented heat transfer caused by the cooling scheme, and turbine life could be degraded substantially. The analysis suggests that high fuel-air ratio designs may have to consider changes to cooling strategies to accommodate secondary combustion.