Analysis of the natural frequency of transverse vibration of a deep water riser based on a nonlinear model
HAO Yi, WANG Wenming, LI Haoran, GONG Pu, XIONG Minghao, GU Jijun
1 College of Mechanical Engineering, China University of Petroleum-Beijing, Beijing 102249, China; 2 Nanjing Chenguang Group Corporation Ltd., Nanjing 210006, China
Inthispaper,thetransversevibrationcontrolequationofa riserisestablishedbyusingtheelementmethod. Assuming the axial force changes linearly, a nonlinear riser model can be obtained. The model is solved by the method of finite difference. Then, the influence of various factors on the natural frequency of the riser is analyzed. The results show-: When the length of the riser increases, its natural frequency decreases; As the riser’s wall thickness increases, the natural frequency increases; and that the greater the top tension is, the higher the natural frequency of the riser is, so changing the tension ratio can effectively avoid the resonance frequency; Drilling fluid should be considered in calculations, but its density has little effect on the natural frequency; The effect of additional mass on the natural frequency cannot be ignored. The research content provides an important theoretical basis for assessing risks of deep water riser operation.
