Fluid-Induced Motion and Loads of Offshore Platforms

Offshore oil exploration and production platforms experience a unique set of design problems all their own.  When subjected to ocean currents these bluff body platforms shed unsteady vortex wakes.  This introduces a periodic loading that induces vibration, and can affect drill strings, the entire platform, or both.   Any vibrations that become excessive present potential design hazards.  Drill string vibration can cause structural fatigue; contact banging of adjacent risers; or onboard machinery vibrations.  Platform motion amplitudes of even a small fraction of platform diameter result in large onboard accelerations and mooring system stresses.  Both types of motion occasionally become so intense that work is difficult or dangerous. 

Predicting the conditions under which Vortex-Induced Motion (VIM) occurs is essential for ranking potential design candidates.  But the physics involved are complex and require unsteady, fluid/structures coupled RANS solutions.  Marine fouling introduces additional complications, and necessitates advanced turbulence models able to account for extreme roughness.  AFT’s codes are capable and validated in all these areas, and have been used for VIM applications to directly affect a company’s bottom line.  They have also been applied for the design of VIM mitigation devices aimed at maximizing a platform’s total production time. 

Click on a menu item at left to see how AFT helps oil companies study VIM, rank their designs, and develop VIM mitigation devices.