The 'colliding participating mass': a novel technique to quantify riser collisions

摘要

In a close array of top-tensioned risers, storms may induce interference among adjacent risers. Numerical simulation shows that during the interference the risers experience an impact within its first milliseconds, and with impact energy spreading along their lengths they continue to have contact for a longer duration. The impact process contains the peak collision force and is the main focus of this paper. However, only small lengths of risers can respond to the first millisecond impact, so this paper further introduces the concept of Collision Participating Mass. The corresponding impact peak force or energy can be calculated assuming energy and momentum conservations. The possible damages caused by the riser collision can be estimated. Finally, an example demonstrates that the risers can tolerate moderate collisions, and it is unnecessary to have riser spacing large enough to avoid riser interference completely.