{'fraction_non_alphanumeric': 0.0232, 'fraction_numerical': 0.0, 'mean_word_length': 5.38265306122449, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Calculating Riser Dynamic Effects on Spar Motions in Waves

Riser and mooring that are hanging off from offshore platforms move with and constrain the platform motions in waves. In some industrial practice, effects of mooring line dynamics and riser dynamics may be neglected, i.e., with an uncoupled analysis model, resulting in conservative predictions of the platform motion responses. Riser and mooring dynamic effects are actually important factors for accurately calculating the platform motions in waves. As for a case study, associated with a sample spar platform, risers are modeled as BernoulliEuler beams and the dynamic effects are thus accounted for. The spar motions are simulated using this so-called “coupled” analysis, comparing to the “uncoupled” quasi-static analysis. Observations were made that riser’s dynamics shows different magnitudes in various wave conditions. The uncoupled analysis typically results in very conservative motion responses in medium and low seastates, potentially leading to difficult challenges and high costs for riser fatigue design, in particular, near riser hang-off and seafloor touch-down regions. The coupled analysis thus becomes necessary for a feasible and cost effective solution for the riser.