The effect of multiple Rushton impellers configurations on hydrodynamics and mixing performance in a stirred tank has been investigated. Three configurations defined by one, two and three Rushton impellers are compared. Results issued from our computational fluid dynamics (CFD) code are presented here concerning fields of velocity components and viscous dissipation rate. These results confirm that the multi-impellers systems are necessary to decrease the weaken zones in each stirred tanks. The experimental results developed in this work are compared with our numerical results. The good agreement validates the numerical method.

In this paper, the mixing performance of double helical ribbons and double helical screw ribbons impellers mounted on stirred tanks is numerical investigated. The computer simulations are conducted within a specific computational fluid dynamic (CFD) code, based on resolution of the Naviers-Stokes equations in the laminar flow with a finite volume discretization. The field velocity and the viscous dissipation rate are presented in different vessel planes. The global characteristics and the power consumption of these impellers are also studied. The numerical results showed that the velocity field is more active with the double helical screw ribbons impeller. In this case, the effectiveness of the viscous dissipation and the pumping flow has been obviously noted. Also, the pumping and the energy efficiency reach the highest values at the same Reynolds number. The good agreement between the numerical results and the experimental data quietly confirmed the analysed method.

Experimental investigations are carried out to study the influence of the internal recovery on the performance of a Savonius rotor at different Reynolds number. Four different internal recoveries equal to r pi =0, r pi =0.1, r pi =0.2 and r pi =0.3 are attempted in this study. Results conclude that the internal recovery value has an effect on the presentation of the global characteristics. Particularly, we have observed that the power and the torque coefficients reach the most important values for the internal recovery value equal to r pi =0. With the increase of the internal recovery values, a progressive decrease of the power values is observed at the same specific speed λ.

A coupling algorithm is used to compute the equilibrium of a flexible anchor impeller in a stirred vessel. This coupling algorithm is based on a partitioned approach, which consists of three relatively independent modules: the computational fluid dynamics (CFD), the computational structure dynamics (CSD) and the interface. In the CFD module, the Euler formulation was used to account for the moving boundary. In the CSD module, the updated Lagrangian formulation for solving the motion of non-linear structure was used and a static study was adopted. In the interface module, an exchange of the forces and displacements was allowed. The numerical results, such as the velocity field, the turbulent kinetic energy, its dissipation rate, the turbulent viscosity and the mechanical deformation, have been presented. Particularly, we are interested in the study of the static behavior of the anchor impeller and the evolution of the displacement field of the arms during various iterations of our coupling algorithm. Accordingly, if the anchor impeller undergoes a deformation due to the flexion of the arms of the anchor impeller, the numerical results changes slightly from iteration to another. At the end of certain iteration, the anchor impeller becomes deformed and the velocity field is preserved. These results confirm that the fluid has a significant effect on the deformation of the arms of the anchor impeller during mixing depending on the velocity of the anchor impeller and the fluid flow. The numerical results were validated by a comparison with literature data.

In this paper, a study of the effect of Reynolds number on the aerodynamic characteristics of a horizontal axis wind turbine equipped by three adjustable blades of the Göttingen 188 airfoil has been developed. Particularly, different aerodynamic regimes defined by Reynolds numbers were investigated. To achieve this, an open wind tunnel has been used to determine the global characteristics of the wind turbine. The obtained results consist of the recovered power, the exerted torque on the rotor in static and in dynamic modes as well as power coefficient and torque coefficient. This work has been developed at Laboratory of Electro-Mechanic Systems (LASEM) of the National School of Engineers of Sfax (ENIS).