Prediction of Aeroelastic Vibration of Rectangular Cylinders by k -ε Model

Abstract

The applicability of the k-ε model in the prediction of aerodynamic force and instability is investigated herein. To show that two-dimensional analysis by the k-ε model is different from ordinary two-dimensional analyses that simply neglect the spanwise velocity, an analysis of the aeroelastic vibration of a cross section with B/D = 2.0 is performed first using the latter method. In this case, motion-induced vortex oscillation was successfully simulated; however, galloping, in which the flapping motion of the separated shear layer plays an important role, could not be simulated. The result shows that physically reasonable flows can not be obtained by ordinary two-dimensional analyses, unless the spanwise momentum diffusion is incorporated correctly. On the other hand, the k-ε model, which incorporates this diffusion process by an eddy viscosity, enables two-dimensional analyses even in the high Reynolds number region. In this paper, applicability of the model is examined for rectangular cross sections with a wide range of B/D ratio, i.e., 0.6 ≤ B/D ≤ 8.0. Various typical aerodynamic features calculated using this model were found to be in good agreement with those obtained experimentally, particularly including discontinuities in Strouhal number at the critical cross sections of B/D = 2.8 and 6.0. Based on this result, an elastically supported B/D = 2.0 cylinder was analyzed. The motion-induced vortex oscillation and a coupling of the vortex-induced oscillation and galloping were successfully simulated, and their values were in good agreement with those measured in experiments conducted earlier.