Simulating the Role of Axial Flow in Stay Cable Vibrations via a Perforated Wake Splitter Plate

摘要

The inclined and/or yawed orientation of bridge stay cables results in the formation of secondary axial flow on the leeward side of cable surface, which is believed to be one of the contributing factors exciting some unique wind-induced cable vibration phenomena. To clarify the role of axial flow in triggering aerodynamic instability of stay cables, a numerical study has been conducted to indirectly examine the axial flow effect via a perforated splitter plate placed along the central line of a circular cylinder wake. By manipulating the perforation ratio of the perforated plate at four different levels, the variation of von Karman vortex shedding strength, which reflects the axial flow intensity, can be simulated. The impact of the splitter plate perforation ratio on the flow structure around a circular cylinder, in terms of the instantaneous vortex structure, the surface pressure distribution and the aerodynamic forces are discussed in detail by exploiting the numerical data obtained from the large eddy simulation. Results show that the presence of a perforated wake splitter plate would play a similar role as the axial flow in affecting the strength of von Kdrmdn vortex shedding. A more solid wake splitter plate is found to cause a stronger interruption on the interaction between the shear layers formed on the two sides of the cylinder and consequently lead to a more symmetric surface pressure distribution pattern and weaker von Kdrmdn vortex shedding strength. Reductions on the fluctuating amplitude of the instantaneous lift and drag as well as the mean drag are also observed, which would ultimately affect the aerodynamic response of the studied cylinder.