Elastic One-Dimensional Oscillations of an Elongated Body in Fluid: Reduction Coefficients

In this section we discuss a way to describe elastic oscillations of an elongated body (say, a hull) in a fluid along the long axis of the body. Assuming that the shape of cross-sections of the body remains unchanged under oscillations (i.e., the oscillation is identical to the oscillations of an elastic rod), one can introduce the notion of a so-called reduction coefficient. The reduction coefficients describe three-dimensional effects: a reduction coefficient is given by the ratio of an added mass of an elongated body oscillating in one direction (vertical, horizontal of torsional) to the added mass computed by the method of planar sections.