Effect of the inclination angle of finned cylinder over a BFS on the MHD behavior in the presence of a nanofluid

The present numerical study is based on the forced magnetohydrodynamic (MHD) convection of a ferrofluid through a backward facing step (BFS). A cylinder with two fixed fins and fixed dimensions is implanted inside fluid. The dimensionless governing equations have been solved using the multigrid finite element method. Several parameters were considered, such as the Hartmann number 0≤ Ha ≤100, the magnetic field inclination angle 0°≤ ɣ ≤90°, the Reynolds number 10≤ Re ≤200, the nanoparticle volume fraction 0%≤ φ ≤10%, and the fins inclination angle 0°≤ a ≤180°. The results have shown that the presence of the fins improves the heat transfer, especially at the position a = 90° where the Nuave number increases with a ratio of 113% for Re = 200.

Numerical investigation of the nanoparticles nature effect on the MHD behavior in a square cavity with a metallic obstacle

In this paper, a study is conducted to determine numerically the effect of the nanoparticles nature (Al2O3, CuO, and Fe3O4) on the thermo-magnetohydrodynamic behavior of a nanofluid in a square cavity with a circular obstacle. The left wall of this cavity is movable and provided with a cold temperature (Tc) and the right wall is exposed to a hot temperature (Th). However, the upper and lower walls are considered adiabatic. The purpose of this paper is to highlight the effect of aluminum dioxide, copper oxide, and iron trioxide nanoparticles on the thermal and hydrodynamic behavior under the influence of different volume fractions(0 ≤ φ ≤ 0.1), different Hartmann numbers (0 ≤ Ha ≤ 75) and Richardson number (0 ≤ Ri ≤5). The system of governing équations was solved by the finite element method adopting the Galerkine discretization. The obtained results showed that the CuO nanoparticles improve the heat transfer at the fluid and obstacle, in addition, the increase of Hartmann number reduces the heat capacity, especially with the use of Fe3O4 nanoparticles. This study falls within the context of improving the cooling rate of industrial equipment.

The Effects of Aiding and Opposing Thermal Buoyancy on Downward Flow around a Confined Circular Cylinder

In this paper, two-dimensional simulations are carried out to understand the effects of aiding and opposing thermal buoyancy on the downward flow and heat transfer characteristics around a heated/cold circular cylinder confined in vertical channel. The numerical results have been presented and discussed for the range of conditions as: Re = 5 to 40, Ri = -1 to 1 at fixed Pr = 1 and blockage ratio β = 0.2. The steady simulations are performed with a finite volume method based on ANSYS-CFX code. The main results are presented in terms of streamlines and isotherm contours to interpret the obtained phenomena. In addition, the average Nusselt number is computed to determine the role of Reynolds and Richardson numbers on heat transfer rate. It is found that increase in the effect of aiding buoyancy reduces the heat transfer rate but increase in the effect of opposing buoyancy enhances the heat transfer rate. Moreover, for aiding buoyancy condition creates some counter rotating regions in upstream region

A numerical analysis of pollutant dispersion in street canyon: influence of the turbulent Schmidt number

Realizing the growing importance and availability of motor vehicles, we observe that the main source of pollution in the street canyons comes from the dispersion of automobile engine exhaust gas. It represents a substantial effect on the micro-climate conditions in urban areas. Seven idealized-2D building configurations are investigated by numerical simulations. The turbulent Schmidt number is introduced in the pollutant transport equation in order the take into account the proportion between the rate of momentum turbulent transport and the mass turbulent transport by diffusion. In the present paper, we attempt to approach the experimental test results by adjusting the values of turbulent Schmidt number to its corresponding application. It was with interest that we established this link for achieving our objectives, since the numerical results agree well with the experimental ones. The CFD code ANSYS CFX, the k, e and the RNGk-e models of turbulence have been adopted for the resolutions. From the simulation results, the turbulent Schmidt number is a range of 0.1 to 1.3 that has some effect on the prediction of pollutant dispersion in the street canyons. In the case of a flat roof canyon configuration (case: runa000), appropriate turbulent Schmidt number of 0.6 is estimated using the k-epsilon model and of 0.5 using the RNG k-e model

Modélisation numérique des écoulements générés dans une cuve mécaniquement agitée par une turbine de Rushton.

Cet article concerne une simulation numérique de l'écoulement des fluides pseudoplastiques dans une cuve mécaniquement agitée par une turbine de Rushton. La présence des chicanes dans la cuve a une influence importante sur la taille des vortex. La largeur de ces chicanes doit être optimisée, et c'est l'objet de cette étude. La détermination de la taille de ces vortex est mise en évidence et l'influence des paramètres rhéologiques et hydrodynamiques des fluides est étudiée

Structure of the out- flows behind buildings and Influence of the geometry of the streets on the out-flows

This paper intends to study the latest results from the research methods available with special intentions given to the architectural effects of the street valley and wind speed. Extensive research has been carried out through several research approaches to understand the effect of wind flow formation in the streets and the current wind condition on the structure of the wind current. The main goal of this paper is to study the structure of out- flows of buildings and the effect of street engineering on external flows. The numerical modeling is to simulate the effect of the wind flow and the layer limit on different building structures using the ANSYS Fluent package. The program was based on the K-ε model to incorporate the potential of differential equations forming the mathematical model. Three cases were considered; the first case is the height-to-width ratio of the valley (h/w), the second is the width of the dome (b3/b) and the third case the ratio of the height of the valley (h3/h) to see the effect of street valley engineering and wind speed effect

Caractérisation de L'Ecoulement de Fluides Oswaldiens dans un Faisceau à Cylindres Rotatifs (S17)

La caractérisation des écoulements entre deux cylindres a été entreprise par voie de simulation numérique. Le cylindre interne tourne avec une vitesse de rotation constante, tandis que l'externe reste fixe. Le fluide mis en procédé présente un comportement pseudoplastique, modélisé par la loi d'Oswald De Waele. L'influence de la vitesse d'entrée d'écoulement et la rhéologie évolutive du fluide sur la structure hydrodynamique a été étudiée. Le processus est supposé isotherme dans un régime laminaire

3D simulation of incompressible Poiseuille flow through 180° curved duct of square cross-section under effect of thermal buoyancy

CITATION: Mokeddem, M., et al. 2019. 3D Simulation of Incompressible Poiseuille Flow through 180° Curved Duct of Square Cross-section under Effect of Thermal Buoyancy. Periodica Polytechnica Mechanical Engineering, 63(4):257–269. doi:10.3311/PPme.12773The original publication is available at https://pp.bme.hu/me/indexIn this paper, three-dimensional numerical simulations are carried out to investigate and analyze the gradual effects of thermal buoyancy strength on laminar flow of an incompressible viscous fluid and heat transfer rate inside a 180° curved channel of square cross-section. The governing equations of continuity, momentum and energy balance are obtained and solved numerically using finite volume method. The effect of Dean number, De, and Richardson number, Ri, on dimensionless velocity profiles and Nusselt number are examined for the conditions: De = 125 to 150, Ri = 0 to 2 at Pr = 1. The mean results are illustrated in terms of streamline and isotherm contours to interpret the flow behaviors and its effect on heat transfer rate. Dimensionless velocity profiles and the local Nusselt number at the angle 0° and 90° are presented and discussed. Also, the average Nusselt number on surfaces of curved duct is computed. The obtained results showed that by adding thermal buoyancy to computed domain, some early Dean vortices are observed at the angle 0° and new sort are observed at 90°. Furthermore, increase in Dean number increases the heat transfer rate. In other hand, increase in Richardson number decreases the average Nusselt number of 180° curved duct.https://pp.bme.hu/me/article/view/12773Publisher’s versio

MHD forced convection using ferrofluid over a backward facing step containing a finned cylinder

In this paper, a numerical study of forced convection on a backward facing step containing a single-finned fixed cylinder has been performed, using a ferrofluid and external magnetic field with different inclinations. The partial differential equations, which determine the conservation equations for mass, momentum and energy, were solved using the finite element scheme based on Galerkin’s method. The analysis of heat transfer characteristics by forced convection was made by taking different values of the Reynolds number (Re between 10 and 100), Hartmann number (Ha between 0 and 100), nanoparticles concentration (φ between 0 and 0.1) and magnetic field inclination (γ between 0° and 90°); also, several fin positions α [0°–180°] were taken in the counter clockwise direction by a step of 5. After analysing the results, we concluded that Hartmann number, nanoparticles concentration, Reynolds number and magnetic field angles have an influence on the heat transfer rate. However, the fin position on the cylinder has a big impact on the Nusselt number and therefore on heat transfer quality. The best position of the fin is at (α = 150°), which gives the best Nusselt number and therefore the best heat trans-fer, but the fin position at (α = 0°) remains an unfavourable case that gives the lowest Nusselt values

Vpliv kota ukrivljenosti v kanalu z adiabatnim valjem nad nazaj obrnjeno stopnico na magnetohidrodinamično obnašanje ob prisotnosti nanofluida

A backward facing duct are present in various industrial applications especially those focused on heat transfer. The flow through a curved backward facing duct especially in the presence of nanofluid presents complexities compared to a straight backward facing step (BFS) duct. Therefore, the present numerical study deals a nanofluid flow (Fe3O4-H2O) forced convection in a curved backward facing duct. The objective of this investigation is to visualize at different curvature angles g (0°, 30°, 45°, 60°, 90°) imposed on the top wall of the duct, the effect of Hartmann number Ha (0, 50, 100), magnetic field inclination angle γ (0°, 60°, 90°), Reynolds number Re (10, 100, 200) and nanoparticle volume fraction φ (0 %, 0.05 %, 0.1 %). The dimensionless governing equations are solved using the multigrid finite element method. The results showed that the heat transfer was enhanced at the curved angle g = 90° for large Hartman numbers, thus, the average Nusselt number increased with a ratio of 240.74 % in the case of Hartmann number (Ha = 100)