Added mass is the inertia added to a system due to the fact that an accelerating or decelerating body must move some volume of surrounding fluid with it as it moves. The added mass force opposes the motion, and acts as a kind of drag force.

Not to be confused with relativistic mass increase.

Applications

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The added mass can be incorporated into most physics equations by considering an effective mass as the sum of the mass and added mass.

That is, F = m * a becomes F = (m + added mass) * a.

Added mass for a sphere = :$\backslash frac\{\backslash rho\; 4\; \backslash pi\; r^3\}\{6\}$

r = radius of the sphere

Added mass for a cylinder = Density of liquid * Volume of Cylinder

Added mass for any object = Added mass constant for object * Density of fluid * Volume of displaced fluid

References

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MIT OpenCourse Ware

Fluid dynamics