In this paper, a computational model is developed to simulate the dynamics of a riser system in the process of deployment. From the beginning of deployment process, the riser is considered to be vertically suspended to a deploying frame which is located at the support vessel, and gradually pulled into the sea water by mining tool. Considering the variable length of the immersed riser, a numerical model is presented to capture the dynamics of the riser with a lumped mass approximation. Discretization scheme for riser and pipe geometry and methodology for calculating the internal and external force acting on riser are presented. The riser and the pipe are discretisized into an assembly of N linear elements. The mass of the riser and pipe are lumped at the N+1 node points. A 4th order Runge-Kutta approach with proper step size is employed to achieve numerical implementation. Four ocean conditions which are proper for deployment are considered, and the effect of deploying velocity is also researched. The results indicate that the ocean condition and the deploying velocity are playing an important role to determine the kinematic and dynamic condition of the deployment process of deep sea mining systems, and the research results can provide basic information for the design of the heave compensation system and reduction of dynamics effects of riser system on seafloor mining tool during the deploying process.
Deep sea mining is a field of mining which attracts more and more attention from all over the world, it is considered as an important means to meet the challenge of the gradually exhaustion of land mineral resources. The discussed deep sea mining system typically consists of a mining support vessel, riser and lifting system (including flexible riser, lifting pump and pipe), intermediate station and seafloor mining tool.
