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This study deals with convective heat transfer in a square cavity with a localized heat source at its center. The form factor of this configuration is (h/H=0.6) which is the ratio between the height of the source and the height of the cavity. The Rayleigh number is Ra=106 that indicated a laminar flow in this cavity. The numerical simulation gives a good result compared to the experimental data, which justifies the choice of our models used in this study. The objective is to make this natural convection a forced convection by the mobility of the upper wall. This made it possible to change the concentration of the state parameters in this cavity. This result can be used to make an orientation of the heat in this cavity. We note the use of four (4) speeds of the mobile wall in order to see the influence of the speed of this north wall on the convection phenomenon.

In this paper, we focus on the effect of the inner diameter and Reynolds number on the recirculation zone in an annular jet flow with numerical simulation by resolving the Reynolds-averaged Navier-Stokes equations with the first closed model of turbulence k-epsilon. The annular jet plays an essential role in stabilizing the flame in the burner which is used in many industrial applications. The annular jet is characterized by the inner and outer diameter. In this study, three different inner diameters are adopted with constant width of the annular jet. We adopted also three different values of the Reynolds number show the effect of the Reynolds number on the recirculation zone. The simulation is realized by a CFD code which uses the finite element method. The results obtained from this study are in good agreement with the experimental data. Two recirculation zones are shown; a large recirculation zone at the outlet of the flow and a small recirculation zone just near the injection generated by the annular flow and the inner diameter Di ; it is observed that the size of the recirculation zone increases when the inner diameter increases and the length of the recirculation zone depends only on the inner diameter. This recirculation zone is also affected by the Reynolds number with a very low variation of the recirculation length.

In this work we present a numerical study on the aerodynamic behavior of a vertical axis wind turbine of the Savonius type for different axial positions between the blades (overlap rates a/D). The study focuses on predicting the effect of the axial position of the blades to the torque coefficient and also to determine the dynamic field of the flow around the wind turbine for three cases overlap rates (a/D=0, a/D=0.16 and a/D=0.32). The study of the numerical simulation is carried out using a CFD calculation code with use of the finite volume method for the discretization of the differential equations. The equations governing the flow are solved by the SIMPLE algorithm using the K-epsilon model as the closure model.