Numerical Simulation of Stochastic Characteristics of Fluctuating Lift on a Fixed Circular Cylinder

In order to investigate the applicability of large eddy simulation (LES) in wind engineering research, numerical simulation was carried out for flow field around a circular cylinder at Re=4.11104. The obtained mean and root mean square (RMS) component of fluctuating pressure and the vortex shedding Strouhal number are in good agreement with the results from available reports. An equation, based on the correlation coefficients between 90 and 270 position and RMS of the fluctuating pressure at those two points, was presented to estimate the sectional fluctuating lift on the cylinder. Coherent analysis was carried out between fluctuating pressures on circular surface, and the flow mechanism of aerodynamic forces was discussed in view of the coherence function of the fluctuating pressures on cylinder surface. It is found that the vortex shedding is not in-phases along the span-wise direction, and the vortex shedding frequency varies with the flow time. In particular, the vortex shedding energy is concentrated on a narrow band of frequency, while the pressure fluctuating energy is concentrated on the vortex shedding frequency; the fluctuating pressure time series at 90 and 270 on the opposite shoulder of the circular share the same statistical features.