Etude de l’influence de la forme géométrique d’un obstacle cylindrique soumis à un écoulement oscillatoire

Abstract

This work presents a numerical study of a 2D oscillatory flow around different cylinders with elliptical section, under the conditions of three modes of vortex-shedding: regime "A" (Re = 100 and KC = 5) regime "D" (Re = 130 and KC = 6.5) and regime "F" (Re = 170 and KC = 8.5). To study the effect of the ellipticity of the cylinder on the flow field and the hydrodynamic forces, the elliptical ratio (axis ratio) was varied in a wide range (from 1 to 0.1) from the case of a circular cylinder to the case of a cylinder with very slender elliptical section. This investigation is centered mainly on the analysis of the vorticity field and aims to identify the hydrodynamic forces and coefficients for each elliptical report. The results presented in this work were obtained using a numerical code developed in FORTRAN at “Numerical Modeling and Experimental Laboratory of Mechanical Phenomena” (LMNEPM) at the University of Mostaganem. The three-dimensional and non-stationary Navier-Stokes equations were solved by a finite difference method of second order of precision in space and time. The original version of this code was used to simulate the oscillatory flow around circular cylinders where the validation of numerical results was carried out with experimental data from other research. The results of the vortex path, the pressure field, hydrodynamic forces and Morison coefficients will be presented and discussed in the light of their dependence on the elliptical ratio.