The effect of ribs on wind load characteristics of cylindrical structures in streamwise sinusoidal flow: A numerical investigation

This study examines the aerodynamic effects of streamwise sinusoidal flow on circular and ribbed circular cylinders using large-eddy simulation. Six cases with varying oscillation frequencies are analyzed to assess their impact on aerodynamic forces and wake dynamics. The results reveal that increasing the oscillation frequency leads to a rise in both drag and lift coefficients at low frequencies, followed by a sharp decline at higher frequencies. Notably, ribbed cylinders (RC) exhibit higher mean drag and lower root mean square lift fluctuations compared to circular cylinders (CC) at high frequencies. The Strouhal number for RC is also narrower, indicating less efficient aerodynamic characteristics under the same flow conditions. Streamwise sinusoidal flow significantly alters the wake structure, particularly for frequencies fu/fst exceeding 1, with peak wind pressure fluctuations occurring at fu/fst = 2. RC shows complex pressure fluctuations, especially on the windward side, though the trend mirrors CC. For both CC and RC, vortex shedding is suppressed at higher frequencies, with complete cessation observed at fu/fst = 2, corresponding to peak aerodynamic coefficients. Dynamic mode decomposition analysis highlights that low-frequency flow results in more coherent vortex shedding, whereas higher frequencies cause the vortex street to become less organized. RC shows weaker pulsations, contributing to its reduced lift fluctuations and greater aerodynamic stability. Overall, the study demonstrates that streamwise sinusoidal flow and ribbed configurations significantly influence wind load behavior. RC offers superior aerodynamic stability in high-turbulence flows, suggesting its potential for optimizing wind-resistant structural designs.