Key words: Boundary layer, laminar flow, heat transfer, Richardson number, diffusion, friction coefficient.

Abstract: The laminar boundary layer is frequently found in nature and in industry. For example: aerodynamic, hydrodynamic, in meteorology and in oceanography. Such as: it causes many problems in aerodynamic such as a jet engine. A numerical study of the boundary layer developing along a horizontal plate is carried out . The aim of this work is to study the effect of Richardson number on thermal and mass behavior of laminar boundary layer, when the flow is subjected to thermal and solutal diffusions.

Key words: Porous medium, heat generation/absorption.

Abstract: The present investigation deals with study of laminar natural convection flow with internal heat generation or absorption in porous enclosure. The numerical simulations were conducted using a numerical approach based on the finite volume method implemented in the code "Nasim". It is interesting to see that the internal heat generation numbers (RaI), Darcy number (Da) and porosity number (?), have a significant role in the heat transfer rate. For all values of the considered Da, the stream function maximum (?max) is found to increase as Da increases. On other hand, at higher value of (?=1), the transfer rate of the heat is so strong which causes a deviation of the heat source maximum temperature corresponding to the absorption case. 

Key words: Rectangular microchannels, pressure drop, friction factor, single-phase flow.

Abstract: This paper focuses on investigating, numerically, the laminar single-phase flow through rectangular microchannels with hydraulic diameters varying from 150μm to 550μm, with aspect ratio changing from 0.3 to 0.97. The numerical model employs the three dimensional Navier-Stokes equations to simulate the flow behavior in microchannels. The numerical solution is obtained by discretizing the governing equations using the finite-element method (FEM). The numerical simulations are done on a range of the Reynolds number (Re) varied from 1 to 400. For the isotherm and laminar single-phase flow model, the liquid water is used as the testing fluid. The viscous dissipation, the pressure work and the gravity are neglected. In this study pressure drop shows an agreement with the theoretical results for rectangular channels. However, for Reynolds number range ≤ 100, the friction factor data were found less than the predicted theoretical data presented by Shah and London in rectangular channels.

Key words: Natural convection, nanoparticles, Nusselt number, Rayleigh number.

Abstract: This work deals with a numerical study on natural convection problem in a rectangular cavity, two-dimensional, differentially heated: the left vertical wall is heated to a constant temperature TH, while the right vertical wall is kept at a cold temperature TC such as (TH ? TC) filled with nanoparticles at different concentrations φ. The fluid is considered incompressible, Newtonian and obeys the Boussinesq approximation. The influence of nanofluid, on the structure of the flow and heat transfer in the cavity was examined for a Rayleigh number Ra varies between 103 ≤ Ra ≤ 106 and concentration of nanoparticles ranging from 0% ≤ φ ≤ 4% in order to examine the best average heat transfer rate through the cavity. The results show, in particular, that the increase of the volume fraction of the nanoparticles (φ) increases the average heat transfer rate. 

Key words: Computational Fluid Dynamics, indoor airflow, standard k-ε, SST k-ω, local mean age.

Abstract: The goal of this work is to investigate the performance of two eddy-viscosity turbulence models, standard k-ε and SST k-ω, in predicting the two-dimensional airflow in a rectangular room and the local mean age of air using an open-source simulation tool, OpenFOAM. Two geometries were analyzed: the room used in the first case (Bartak, 2001), which consists of a lateral air entrance and an outlet on the top of the opposite side, and the experimental room from the second case (Annex 20 room by Nielsen, 1990), which represents a large rectangular room where the air is supplied horizontally on the upper left and is exhausted through the opening on the lower right of the opposite side. The velocity profiles and local mean age of air were analyzed in both cases.