Dynamic behavior of a deepwater hard suspension riser under emergency evacuation conditions

A model is developed to investigate the dynamic behavior of a deepwater drilling platform riser system under emergency evacuation conditions. In the model, the riser in the ocean environment is modeled as a beam with coupled transverse and axial motions, and its upper and lower ends are respectively connected to the platform and to the lower marine riser package with hard joints. The fluid forces and the added mass and drag forces are modeled using a semi-empirical Morison equation, so the equations of the model are nonlinear, coupled, and multibody. The model is discretized in a finite element approach and solved using Newmark's method. Its validity is verified using ANSYS. Using the model, the influences of platform motion, riser suspension length, ocean load, and platform evacuation speed on the dynamic behavior of the riser are determined, and the results can provide theoretical support for the design and practical operation of hard suspension pipe strings.