A numerical simulation method for separated flow around a large horizontal cylinder with sharp edges in waves is newly developed based on the combined diffraction theory and discrete vortex method. A damping vortex model is proposed semi-empirically and used in order to simulate the steady-state vortex flow pattern, which is observed in the real wavy flow. Vortex patterns around a vertical thin-walled barrier, i.e. a curtain-walled breakwater, in waves are observed experimentally and compared wi th the numerical simulation results. Wave transmission and reflection characteristics, and wave induced forces are also measured in order to examine the resultant effects of flow separations. It is confirmed that the proposed numerical method is very useful for predicting the steady-state vortex flow pattern around the curtain-walled breakwater as well as the vortex-induced forces on it.
In the last decade, knowledge of flow separation phenomena around a small body in wavy and oscillatory flows and these resultant effects, such as vortex induced forces, has been extensively accumulated (Sarpkaya and Isaacson 1981). It has also become known that, in the so-called "diffraction regime", the body with rounded corners experiences no distinctive flow separation because the Keulegan Carpenter number remains small. However, when the body contains sharp corners or edges, e.g. a thin walled wave barrier, flow separation inevitably occurs and viscous effects such as a vortex formation and shedding may not be neglected. And flow separation phenomena may play an important role for the wave transformation and the flow field around the body. In the previous studies, Iittle is known about flow separation phenomena around a large and angular body, which belongs to the "diffraction regime". This situation may be partly responsible for the lack of adequate analytical procedures.
