The characteristics of drag and lift forces on a circular cylinder model near a wavy boundary have been experimentally investigated in a water tunnel. In the range of the Reynolds numbers, based on the diameter of cylinder model, from 104 to 1.9 X 104, the drag, lift force on the cylinder and lift force frequencies have been measured at the wave crest and trough and various distances from the wavy boundary. Flow visualization experiments revealed the wake structure varying as gap-to-diameter ratios (G / D) and mechanism Interacting between the cylinder and the boundary.
In the offshore engineering, pipelines are used to convey oil and gas for power generation, sea-water for desalination, sewage for disposal at sea, and for the protection of communication cables. There are numerous problems associated with the design and installation of pipeline in deep-water offshore. The submerged pipelines are often fixed by concrete saddles and buried by dredging and trenching the sand at a seabed. It has been known from the practice that pipeline spans can occur due to local scour of the bed sediment The proximity of a pipeline near a seabed boundary gives rise to hydrodynamic and environmental problems m offshore engineering. Research on flow field and forces on the cylinder at various distances from the seabed boundary are of a great interest to many. There are many investigations (see Davis,1976) on forces on submerged pipelines In flow or wave. A lot of research works also have been carried out about wave forces on a cylinder near a plane boundary (see Sarpkaya,1981, Shankar et al.,1988). However, researches of hydrodynamic forces on a cylinder near a plane boundary in steady flows are relatively scarce. Second, the plane boundary changes the symmetry of flow about the cylinder nearby.
