Numerical simulation of the flow induced by a transversely oscillating inclined elliptic cylinder

The unsteady flow past an inclined elliptic cylinder which starts translating and oscillating impulsively from rest in a viscous fluid is numerically investigated for large Reynolds number. The flow is incompressible and two-dimensional, and the oscillations are harmonic. These oscillations are allowed in a direction perpendicular to the uniform oncoming flow having a magnitude which is less than or equal to the constant translational velocity. The investigation is based on an implicit finite difference/spectral scheme for integrating the unsteady Navier-Stokes equations expressed in a stream function/vorticity formulation. Present calculations are performed at a sufficiently large oscillation amplitude to induce separation. The effect of the maximum oscillatory-to-translational velocity ratio and of the angle of inclination on the laminar asymmetric wake evolution has been studied for a Reynolds number R = 10(3). The object of this study is to examine the effect of increase of velocity ratio on the near-wake structure as well as the hydrodynamic forces acting on the cylinder. Vortex dynamics close behind the cylinder are affected by the changing acceleration of the cylinder. An interesting phenomenon has been observed in the flow patterns depending upon the velocity ratio and the angle of inclination. A switch over in the nature of the fluctuations of the drag coefficients has been also observed with the increase of angle of inclination. (C) 2001 Academic Press.