Experimental study on flow around an array of four circular cylinders

Experiments were carried out in a towing tank regarding the flow around a stationary array of circular cylinders with low aspect ratio, H/D=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 the columns of the typical multi-column offshore floater system, as semi-submersibles and TLP platforms. The aims are to create a reliable database for CFD studies and to better understand the influence of the relative position of the cylinders on the flow around this type of structure and afterward to use this research in VIM calculations for free multi-columns systems. Two parameters were investigated: distance between column centers, S/D = 2, 3 and 4; and current incidence angle, 0, 22.5 and 45 degrees. The Reynolds number range covers 50,000 up to 250,000. Forces were measured in each column 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.