VORTEX-INDUCED VIBRATIONS OF A RISER WITH DESIGN VARIATIONS

摘要

As meta-stable motions transverse to fluid flow in slender bluff-bodied structures, Vortex-Induced Vibrations (VIV) are mostly determined by three-dimensional (3D) geometric and relativistic changes that evolve in the structure. Simplistic models of the structure ignore these key physical principles. In a 2014 OMAE paper, we introduced the key physical concepts for simulating VIV in a horizontal-oriented slender structure (pipeline). In a 2015 OMAE paper, we re-oriented the same structure vertically to simulate VIV in a vertical riser. In this paper, one or more of the following variations in the vertically-oriented riser will be made, in order to judge the physical effect each variation has on the character and distribution of VIV along the riser: 1. Cyclically move the upper end of the vertical riser 2. Change into an S-shaped riser by adding weight/buoyancy 3. Disconnect the lower end of the S-shaped riser The simulations help show and reinforce the following mechanical concepts of VIV: 1. How gravity and fluid drag evolves a 3D shape in the riser 2. How this shape creates specific structural flexibilities 3. How these flexibilities set the stage for specific VIV 4. How tension and end conditions are vital to VIV behavior.