Nonlinear Three Dimensional Dynamic Analysis of Titanium Drilling Riser

Rizwan A. Khan; Abhishek Khandelwal; Suhail Ahmad

Abstract

Titanium alloys are selected for a high-pressure drilling riser’s application due to its high specific strength, corrosion resistance, and favorable elastic properties. The qualification of this titanium alloy requires assessing its resistance to hydrogen embrittlement and stress corrosion cracking due to seawater with/without cathodic protection, evaluating its dynamic response under long crested random sea. The response analysis is based on a simulation technique which duly considers the various nonlinear effects such as relative velocity squared drag force, variable added mass due to variable submergence and nonlinearity due to large excursions. It also accounts for variable tension in riser due to variable submergence, variable buoyancy and wave forces. Results are presented which illustrate the effects of nonlinearities, long term drift oscillations and instantaneous motion due to current velocity on the bending stress in the marine risers. The response time histories are obtained and presented in terms of bending stress envelopes and spectra showing contribution of various harmonics which is significant because of a nonlinear system. Keywords: Titanium, drilling riser, alloysCite this Article Khan Rizwan A, Khandelwal Abhishek, Ahmad Suhail. Nonlinear three dimensional dynamic analysis of titanium drilling riser. Journal of Offshore Structure and Technology. 2015; 2(2): 27–40p.