Numerical Simulation of Pulsating Slurry Flow in a Jumper for Subsea Mining

Abstract For the design and operation of a subsea mining system, it is important to predict pressure loss due to the hydraulic transport of solid particles in the lifting system. The lifting system has a short flexible jumper to connect the seafloor mining tool to the lifting pump and a vertical riser pipe connecting this pump to the production support vessel. The configuration of the flexible jumper shall have an inclined part so that the mining tool can move freely on the seafloor. In the actual mining system, the slurry flow in the pipe system is expected to be unsteady. Then, the time-domain simulation is required for safe and reliable ore lifting. In the present paper, we develop the numerical model for the time-domain simulation for pulsating slurry flow in a jumper. The model is validated by comparison with the experimental results we carried out in the previous work using alumina beads, of which densities are almost the same as those of seafloor polymetallic sulphides ore, as solid particles. Next, we investigate the slurry flow in a jumper with steep wave configuration using the model developed. We assume the 100 m long flexible jumper of which outer and inner diameters are 0.254 m and 0.200 m, respectively. Seafloor polymetallic sulphides ore, whose density and diameter are 3,440 kg/m3 and 0.03 m respectively, are assumed as the solid particles. We vary the pulsating conditions of slurry flow and jumper configuration, and discuss the effects of slurry parameters, such as slurry flow pulsation on water velocity, solid velocity, solid concentration and pressure loss in the jumper system. As a result, the total time-averaged pressure loss increases as the top end of jumper is away from the neutral position. The amplitude of pressure loss pulsation is almost uniformly distributed along the jumper although the amplitude of solid concentration pulsation is ununiformly distributed. The slurry parameters should not be estimated using straight pipe simulation results for the neutral or near position of the jumper system.