About the Oscillatory Flow Phenomenon within 3D Cylindrical Annulus: Critical Buoyancy and Annulus’ Aspect Ratio for Oscillation Stability

The main purpose of our investigation is to providethe impact of some pertinent parameters,asthe thermal buoyancy and the geometryratio,on the oscillatory flow’stability of a Newtonian fluid which occurs within an annulus, found between a cold outer circular cylinder and a hot inner one, to come out at the end with critical conditions that couldpredict this phenomenon intosuch an industrial geometry. To do so, aphysical model is developed using the Lattice-Boltzmann approachside by side with the finite difference one. The validity of the latter is ascertained after comparison between our primary predictionsand various experimental & theoretical ones. By usinganunsteady-state regime, both Isotherms and velocity profiles of ourconvective fluidare widely inspected. Going far with its value, the use of a critical aspect ratio could die-out the impact of any investigated parameter on the oscillatoryflow. Then, only a conductive regime will take control intothe annulus. It is tonote that athree dimensions D3Q19model was adopted based on a cubical Lattice

Pore-scale modeling on supercritical CO2 invasion in 3D micromodel with randomly arranged spherical cross-sections

International audienc

About the Oscillatory Flow Phenomenon within 3D Cylindrical Annulus: Critical Buoyancy and Annulus’ Aspect Ratio for Oscillation Stability

The main purpose of our investigation is to providethe impact of some pertinent parameters,asthe thermal buoyancy and the geometryratio,on the oscillatory flow’stability of a Newtonian fluid which occurs within an annulus, found between a cold outer circular cylinder and a hot inner one, to come out at the end with critical conditions that couldpredict this phenomenon intosuch an industrial geometry. To do so, aphysical model is developed using the Lattice-Boltzmann approachside by side with the finite difference one. The validity of the latter is ascertained after comparison between our primary predictionsand various experimental & theoretical ones. By usinganunsteady-state regime, both Isotherms and velocity profiles of ourconvective fluidare widely inspected. Going far with its value, the use of a critical aspect ratio could die-out the impact of any investigated parameter on the oscillatoryflow. Then, only a conductive regime will take control intothe annulus. It is tonote that athree dimensions D3Q19model was adopted based on a cubical Lattice

Numerical study of mixed convection heat transfer in a lid-driven cavity filled with a nanofluid

This paper reports a numerical study of mixed convection in a square enclosure, filled with a mixture of water and different types of nanoparticles. The upper and the bottom walls of the cavity are thermally insulated, while the remaining walls are mobile and differentially heated. In order to solve the general coupled equations, a computer code based on the finite volume method is used and it has been validated after a comparison between the present results and those of the literature. To make clear the effects of the governing parameters on the fluid flow and heat transfer inside the square, a wide range of the Richardson number, taken as 0.01 to 100, and the nanoparticles volume fraction, taken from 0 to 10%, is investigated. The phenomenon is analyzed through streamlines and isotherm plots with a special attention to the Nusselt number. The obtained results show that the mean Nusselt number is an increasing function of the decrease Richardson number, and increases with increasing values of the nanoparticles volume fraction, and far from the natural convection mode, higher heat transfer is noted with Ag-water nanofluid. At the end, useful correlations predicting heat transfer rate as a function of the solid volume fraction are proposed for each value of the Richardson number, which predict the numerical results within ±0.02%

Oscillatory flow of Koo–Kleinstreuer and aggregate nanofluids in cylindrical annuli: Toward an innovative solution to deal with nanofluids instability

International audienceThis paper exhibits the oscillatory characteristics of a free convective flow of nanofluids in horizontal concentric annuli of pilot dimensions to provide a mechanical solution against their particles settling which occurs by aggregation. These nanofluids are generated according to each class of particles that may exist with four types of industrial base liquids. Koo–Kleinstreuer semi-empirical models are used to generate databases of ideal suspended particles with Brownian motion. Meanwhile, Maxwell–Bruggeman and Kreiger–Dougherty semi-empirical models are used to incorporate the aggregation mechanism. A hybrid lattice Boltzmann/finite-difference approach is adopted to provide the space-time solutions. The accuracy of this numerical tool is inspected by providing over nine validations based on literature data. Hence, an improved flow pattern chart is accomplished to expand the open literature, depending on the flow nature of the base liquids in the annuli. Next, the oscillatory nature is fully revealed for each nanofluid processed. Following the frontiers toward the non-settling of aggregates, three main regimes are identified depending on the annulus size and the combination between ideal and aggregate mechanisms. Owing to this, a new settling chart is established to emerge the sheer limit of the annulus size for a non-settling process

On the validity of a numerical model predicting heat and mass transfer in porous square cavities with a bottom thermal and solute source: case of pollutants spreading and fuel leaks

The present work refers to the study of natural convection into a confined porous medium, driven by cooperating thermal and solutal buoyancy forces. The side walls are maintained at a uniform temperature and concentration, lower than that of a heat and solute source, which located at the center of the bottom wall, the rest of the horizontal walls are kept insulated. The physical model for the momentum conservation equation makes use of the Brinkman extension of the classical Darcy equation, the set of coupled equations is solved using the finite volume method and the SIMPLER algorithm. To account for the effects of the main parameters such the buoyancy ratio, the Lewis and porous thermal Rayleigh numbers, as well as the source length, heat and mass transfer characteristics are widely inspected and then, new powerful correlations are proposed, which predict within ±1% the numerical results. Note that the validity of the used code was ascertained by comparing our results with experimental data and numerical ones already available in the literature

Progress on numerical simulation of yield stress fluid flows (Part I): Correlating thermosolutal coefficients of Bingham plastics within a porous annulus of a circular shape

International audienc

Three-dimensional fluid flow simulation into a rectangular channel with partitions using the lattice-Boltzmann method

In this paper, we investigate numerically the 3D dimensional laminar flow of an incompressible Newtonian fluid into a rectangular channel, including several blocks mounted on the lower and upper walls. To do so, a numerical code based on the lattice Boltzmann method is utilized and it has been validated after comparison between the present results and those of the literature. The adiabatic partitions are arranged in three different manners: in the first one; and by using two blocks, these latter are mounted the one against the other. In the second, the bottom block is disposed next to the flow entry. Whereas, in the third; three parallel (or alternative) blocks are taking place the one close to the other at an equal distance. Regarding the Reynolds number and the partitions’ distance effects on the fluid flow inside the channel, our phenomenon is widely analyzed throughout streamlines and velocity profiles, with special attention to the partitions’ arrangement and the global drop pressure. It is to denote that the three dimensions D3Q19 model is adopted in this work, based on a cubic lattice, where each pattern of the latter is characterized by nineteen discrete speeds

Lid-Driven and Inclined Square Cavity Filled With a Nanofluid: Optimum Heat Transfer

This paper reports a numerical study on mixed convection within a square enclosure, filled with a mixture of water and Cu (or Ag) nanoparticles. It is assumed that the temperature difference driving the convection comes from the side moving walls, when both horizontal walls are kept insulated. In order to solve the general coupled equations, a code based on the finite volume method is used and it has been validated after comparison between the present results and those of the literature. To make clear the effect of the main parameters on fluid flow and heat transfer inside the enclosure, a wide range of the Richardson number, taken from 0.01 to 100, the nanoparticles volume fraction (0% to 10%), and the cavity inclination angle (0º to 180º) are investigated. The phenomenon is analyzed through streamlines and isotherm plots, with special attention to the Nusselt number