Scattering of ocean waves by arrays of cylinders with rotational symmetry

Abstract

We consider an approximate method for computing the wave forces on an array of vertical cylinders. We use the plane wave method originated by Simon [(1982), J. Fluid Mech. 120, 1–120] and shown to be a good approximation for regular arrays of 2, 3, and 5 cylinders by McIver and Evans [(1984), Appl. Ocean Res. 6, 101–107]. In the case of a single cylinder, it has recently been shown that the well-known theory of MacCamy and Fuchs [(1954), Tech. Memo. No. 69, U.S. Army Corps of Engineers, Beach Erosion Board] can be derived from this approach. We compute the forces parallel and orthogonal to waves incident along reflection axes of regular triangular arrays of 3 and 7 cylinders. A simplication in computation of the scattered waves under the plane wave approximation is found to result from the rotational symmetry of the array. Situations are discussed where wave forces are significant orthogonal to the direction of propagation of the incident wave and interaction effects are computed.