Added mass

Summary

Added mass is the extra inertia that a body appears to have when it accelerates through a fluid. To speed up the body, one must also speed up the surrounding fluid, and this costs force. In ideal potential flow the effect is a symmetric matrix, the added mass tensor. It depends only on the shape of the body and the density of the fluid. It matters for ships, submarines, bubbles and anything that moves quickly back and forth in water.