Loading on rounded square foundation elements of offshore structures with marine growth at incidence

A systematic wind tunnel study is performed to identify the mean and fluctuating loads experienced by a 2D square prism with non-dimensional rounded edges of r/D = 0.16 and covered with hard marine fouling for Reynolds numbers between 70,000 and 8 million. The incidence angle is varied from α=−45◦ to 3.25◦ with increments of 3.25◦ and 6.5◦. The critical angle of incidence, at which a reattachment of the free shear layer takes place on the lateral windward directed side surface, is found at αcr =−6.5◦. For α<αcr two opposite trends – governed by the Reynolds number – of the mean drag coefficient, the r.m.s. of the lift fluctuations, and the Strouhal number are obtained. On the contrary, all aerodynamic parameters are relatively Reynolds-number independent for α > αcr. For the latter angles of incidence, a decrease towards −45◦ induces higher values of CD and the r.m.s. of the lift fluctuations, as well as lower Strouhal numbers and mean lift forces.