Oscillatory tests were performed on several geometric shapes in the vicinity of' the free surface of an undisturbed fluid. The tests, together with an accompanying literature review, were conducted to determine the influence of geometry, depth, amplitude of motion, and frequency on the fluid added mass and damping coefficients.
The results, which are in broad agreement with the theoretical calculations, are used to generate empirical expressions for a range of frequencies, depths, and geometries.
In this paper we are addressing the problem of determining the added mass and the damping coefficients for submerged bodies oscillating near the surface. Why are these parameters of interest. Because they influence the motions and loads of all bodies subjected to the dynamic forces of the sea.
The expansion of' offshore and undersea operations has resulted in many new technological problems, among them the design of structures to withstand and operate in ocean waves. Typical areas of interest include:
Motions of drilling ships
Motions and loads in semi-submersibles
Dynamics and loads of' mooring systems
Dynamics and loads of towing systems
wads in stationary offshore structures
Dynamics and loads of submerged systems
The following sections discuss added mass and damping, and review some of the techniques for using these coefficients for analyzing dynamic motions. In addition, we discuss values of added mass and damping calculated in the literature and, finally, present the results of tests conducted on simple geometric shapes.
For spherical, cylindrical, ellipsoidal, other simple configurations a number of authors (See Refs. 1-6) have obtained mathematical solutions for the fluid pressures resulting from harmonic motions of the structure. Few, however, - this paper included have obtained fluid pressures for harmonic motions of the fluid, such as that produced by waves. In this paper we shall refer to the former as "hydrodynamic" pressures and the latter as "virtual" pressures.