Numerical Simulation of Three Dimensional Flow Past a Cylinder Oscillating at the Strouhal Frequency

Abstract

The paper presents computational results of 3D flow past a cylinder forced to oscillate: (a) transversely with respect to a uniform stream and (b) both transversely and inline with respect to a uniform stream, following a figureeight trajectory. For a flow from left to right the figureeight is traversed counterclockwise in the upper halfplane. Direct numerical simulation (DNS) of the Navier–Stokes equations for 3D flow is performed using a spectral element code. Computations are carried out for a Reynolds number equal to 400, at a transverse oscillation frequency equal to the natural frequency of the Kأ،rmأ،n vortex street. For both oscillation modes, the transverse oscillation amplitude is varied from 0 to 0.60 cylinder diameters. The forces on the cylinder are calculated and related to flow structure in the wake. The results indicate that, in general, the presence of inline oscillation increases the magnitude of forces acting on the cylinder, as well as the power transfer from the flow to the structure. Flow visualizations indicate that, for the figureeight mode, lowamplitude forcing tends to reduce the wake threedimensionality. However, at high oscillation amplitudes, the wake structure is found to become more complex at increasing amplitude.