Hi! I am trying to compute the natural frequency of a system and I also need to add the added mass term to my equation. The object I have is a torus and is basically in heaving motion. I found a good paper, which gives a formula for 3d added mass and 2d added mass. I would figure that I have to use the 3d added mass formula, correct? But when and why do you need to use the 2D added mass? Thanks!