Vortex Shedding and Wake Merging Behind Clusters of Square Cylinders

Inam, Saad; Nguyen, Cung; Wang, Changchang; Lasagna, Davide; Xie, Zheng-Tong

Abstract

The study examines the cluster effect of arrays of square cylinders in smooth and turbulent inflows, focusing on vortex shedding and wake dynamics. Several clusters in varying arrangements (2 × 2, 3 × 3 and 4 × 4 ) and spacings were investigated using high-fidelity large-eddy simulations. The analysed key parameters include the location at which individual wakes merge, and the Strouhal number of the dominant vortex of the entire cluster. The obtained data reveal that the shedding frequency of the dominant vortex is primarily influenced by the solid portion of the cluster’s cross-section. From this observation, an effective cluster size, which mainly consists of the solid potion with a minor adjustment for the cluster porosity, is proposed in the study. The Strouhal number based on the effective cluster size closely resembles that of an isolated square cylinder, suggesting the characteristic length is the effective cluster width, but not the geometric cluster size. For turbulent inflows with an integral length scale exceeding the cluster size, the Strouhal number decreases markedly compared to smooth inflow cases, indicating a significant influence of large-scale turbulence on cluster dynamics. Further analysis reveals that the free-stream turbulence weakens the vortex shedding and reduces the turbulent kinetic energy generated by the cluster, resulting in weaker turbulent entrainment in the near wake and an extended recirculation region.

• Presentation Conference Type: Conference Paper (published)
• Conference Name: 14th UK Conference on Wind Engineering
• Start Date: Sep 4, 2025
• End Date: Sep 6, 2025
• Acceptance Date: May 31, 2024
• Online Publication Date: Sep 16, 2024
• Publication Date: Sep 16, 2024
• Deposit Date: Jun 15, 2025
• Peer Reviewed: Not Peer Reviewed
• Book Title: Proceedings of the 14th UK Conference on Wind Engineering: University of Southampton, 4-6 September 2024
• DOI: https://doi.org/10.2139/ssrn.5131754
• Publisher URL: http://eprints.soton.ac.uk/id/eprint/493853