Influence of the group positioning of cylinders on the wind pressure distribution in the post-critical regime

In order to estimate the wind loads on circular cylindrical shell structures, the pressure coefficient as a function of the Reynolds number is given for an isolated cylinder in Eurocode 1 - Part 2-4: Actions on structures - Wind actions. As cylinders are often placed in groups and the configuration of these groups largely influences the pressure distribution around the cylinders, a computation of the wind flow provides a more realistic estimation of the pressure coefficients. First, the transient 2D turbulent air flow around a single cylinder at a Reynolds number of 12.4 millions is computed using the SST turbulence model and the results are compared with the pressure coefficients in Eurocode 1 and with experimental data. The minimum pressure coefficient is underestimated, while the base pressure coefficient is slightly overestimated. Unsteady simulations are performed for the flow around a group of 2 by 2 and of 8 by 5 cylinders. Vortex shedding occurs both from the group as a whole, and from individual cylinders. The group configuration drastically changes the time-averaged pressure distribution around the cylinders. High values of suction are present at the location of the small gaps between the cylinders and upstream of the separation points of the cylinders on the side corners of the groups. The cylinders at the borders of the groups experience high drag or lift forces, while these forces are considerably lower in the middle of the group.