Comparison of Formulations for the Hydrostatic Stiffness of Flexible Structures

The formulation for the hydrostatic stiffness (restoring force) for linear rigid body hydrodynamics is well known, whereas there are several formulations in literature for the corresponding stiffness of flexible structures. Which of these formulations to use is not immediately obvious. This paper clarifies the relationship and the differences between the formulations and the selection of the appropriate one. In addition, it will be shown that a general formulation of the hydrostatic stiffness for flexible structures involves the internal stress distribution under gravity loads, just as it does the corresponding hydrostatic pressure distribution.