Figure 1. Dimensionless damping coefficient in heave, C33 = 



, as a function of the 



TTp B' V gL 

 frequency parameter co*. (From Haskind, Reference 25.) 



There are some experimental findings for submerged bodies where a definite 

 speed dependence of damping at a constant frequency was established. 



Thus the problem of dependency upon the Froude number is not yet settled, 

 although recent experimental results by Golovato indicate that one is entitled to accept 

 Haskind's result as a useful working hypothesis within the most important speed range. 

 Conditions may be different in the case of roll. Japanese writers [29] have indicated 

 an increase of wave damping with increasing Froude number. Further, effects due to 

 viscosity become important. 



3.4. Simplified Theory of Heave and Pitch 



We shall classify all investigations based on the Froude-Krylov hypothesis as 

 simplified and, when in addition coupling terms are neglected, as simple. It is quite 

 significant that investigations of such a character still appear today. 



A consequent work of this character has been published recently by Gerritsma 

 [39] on heave and pitch in longitudinal waves. Coupling terms following Korvin- 

 Kroukovsky have been considered separately; but their contribution is not large in 

 the present case. 



Regarding the importance of Smith effect and relative-motion corrections to the 

 simplified theory, I take note of recent research on diffraction and do not quite agree 

 with a remark made by Cartwright and Rydill [40], that it may not pay to consider 

 anything else beyond the simplest theory for interpreting full-scale experiments in an 

 actual seaway. 



3.5. Investigations on Exciting Forces 



The classical theory of motion of bodies in an unbounded fluid, with approxi- 

 mations introduced to deal with a non-uniform and non-steady flow, showed that the 



U 

 heaving force depends upon such factors as K 33 -K u and — . 



71 



