Ahmed Kaffel

Eigenspectra and mode coalescence of temporal instability in two-phase channel flow

The stability of two immiscible fluids with different densities and viscosities is examined for channel flow. A multi-domain Chebyshev collocation spectral method is used for solving the coupled Orr-Sommerfeld stability equations for the entire spectrum of eigenvalues and associated eigenfunctions. Numerical solution of the eigenvalue problem is obtained with the QZ eigenvalue solver and is validated with analytical results derived in the long and short wave limits. A parametric study is carried out to investigate the spectral characteristics and eigenfunction structures related to the shear and interfacial modes of instability. The interactions and mode switching between the two instability modes are investigated. Under certain conditions, the two modes are found to become unstable simultaneously. Mode coalescence can occur in either the stable or the unstable part of the spectrum. In general, the eigenfunction of the most dangerous mode is observed to vary sharply in the neighborhood of the interface and the critical points.

Experimental Characterization of a NACA2415 Airfoil Wind Turbine

In this paper, an experimental characterization of a horizontal axis NACA2415 airfoil type wind turbine has been developed. Particularly, a detailed description of the used wind tunnel and the various manipulations performed are presented to study the aerodynamic characteristics of the wind turbine. The experimental setup is developed to estimate the velocity profiles and the torque meter variation for different Reynolds numbers and wedging angles of the blade. The main objective is to develop results to validate the numerical results established with Computational Fluid Dynamics (CFD) codes.

Numerical and Experimental Investigations on the Meshing Model Choice of a NACA2415 Airfoil Wind Turbine Placed in an Open Wind Tunnel

In this work, we are interested on the numerical and experimental investigations of a NACA2415 airfoil wind turbine placed in an open wind tunnel. The study of the meshing effect on the numerical results was developed using a commercial CFD code based on the resolution of the Navier-Stokes equations in conjunction with the standard k-e turbulence model. These equations were solved by a finite volume discretization method. The developed numerical results are compared with experimental results to choose the adequate meshing.