Comparisons of CFD and PIV data for the flow around a rectangular cylinder

Computing power has increased substantially over the last several years. Along with developments in processing speed, the reliability of commercially available computational fluid dynamics (CFD) packages has also increased. The wind engineering community has long recognized the importance and difficulties of using CFD as a design tool [1]. The need has also been recognized to validate the results of these numerical simulations with both full scale and wind tunnel test data [2]. One of the simplest forms of a bluff body is the rectangular cylinder. Although the geometry is simple, the flow around such a body proves to be quite complicated and difficult to predict because of the separation at the leading edge, subsequent reattachment, and separation again at the trailing edge. Compounding this difficulty are possible interactions between vortices shed from the leading edge interacting with vortices shed from the trailing edge. Thus, this flow has many of the characteristics which make computation difficult in bluff body aerodynamics. There has been some work done to understand this flow [3,4]; however, there remains a need for research in order to develop algorithms for the numerical prediction of long-span bridge aerodynamics. In the current study an elongated rectangular cylinder with a chord to thickness (c:t) ratio of 7:1 in a flow of Re = 3x10 has been evaluated with a commercial CFD code. Experiments were also performed on the cylinder using Particle Image Velocimetry (PIV) and surface pressure measurements. The data presented reveals that there are important differences between the results of the CFD simulations and the experimental data.