Experimental Study on Flow Around an Array of Four Cylinders With Different Section Geometries

Experiments were carried out in a towing tank regarding the flow around a stationary array of four cylinders with low aspect ratio, H/L = 1.5, piercing the water free surface. One isolated cylinder and one array of 4 cylinders were tested; this number of cylinders corresponds to the number of columns of a typical multi-column offshore floater system, such as semi-submersibles and TLP platforms. Three different geometries of cylinder sections were studied: circular, square and diamond. The aims are to better understand the influence of the relative position of the cylinders on the flow around this type of structure; to create a reliable database for CFD studies and afterward to use this research in VIM calculations for free multi-columns systems. Two parameters were investigated for a distance between column centers S/L = 3: current incidence angles 0, 22.5 and 45 degrees and column section geometries. The Reynolds number range covers from 50,000 up to 250,000. Forces were measured in each column by using a three degree-of-freedom load cell. Results of lift and drag forces are presented for each column separately and for the whole system. This paper is a piece of an extensive experimental study on flow around an array of multi-cylinders.