When a floating structure is located in a current, vortices are separated alternately from its body to cause long-period oscillation in the direction orthogonal to the flow direction. This phenomenon is called Vortex-Induced Motion (VIM) and its prediction model is required to avoid the fatigue failure of mooring lines.

A riser is a linear tubular structure which connects the seabed to the water surface and transports substances, such as natural resources. Similar to VIM, Vortex-Induced Vibration (VIV) occurs for a riser in a current and the analysis method of flexural vibration is developed to avoid the fatigue failure of the riser.