Numerical investigation of added mass coefficient of a subsea manifold in the accelerating flow and oscillating flow

The hydrodynamic forces and dynamic responses of subsea equipment, like manifolds, are significantly affected by the motions of the mothership or the unexpected incoming underwater flows like current or internal wave. In this paper, the hydrodynamic coefficients of a simplified subsea manifold, a submerged 3D prism are predicted through the constant acceleration method and forced oscillating method, which are both implemented by the CFD simulation approach. The three directional added mass coefficients of the prism in accelerating flow with different accelerations are obtained. But the value of constant acceleration is found not significantly influencing the added mass coefficient of the rectangular prism. The added mass coefficient of the rectangular prism studied in the paper is 0.233, 0.395, and 2.191 in X, Y and Z direction, respectively. In order to predict the added mass coefficient of the 3D rectangular prism in oscillating flow, the forced oscillating method is used to simulate the rectangular prism oscillating in three directions (X, Y, Z) under different oscillating amplitude and frequency.