Dern 



1,3- Buoy motion on waves - 



For waves defined as above (1,2), let us put : 

 <P (t) Roll angle 



9 (t) Pitch angle 



^ (t) Yaw angle 



The pitching motion (respectively rolling motion) is 



defined as the motion about an axis parallel to O y 



o o 



(resp. Ox). Thus pitching occurs in a vertical plane 



parallel to the direction of wave propagation , rolling 

 occurs in a vertical plane parallel to the wave - crest 

 lines . 



X (t) Surge of buoy . The surge is a motion parallel to O x , 



direction of wave propagation 



Y (t) Sway of buoy 



Z (t) Heave of buoy 



s (t) Vertical distance between point O (i. e . the point being 



in O in calm water) and the instantaneous water surface, 

 s (t) defines the relative motion of the buoy with respect 

 to the water . 



The index A represents the half - amplitude : e. g. Z is 

 the half -amplitude of heaving (Z (t) = Z cos a t) . 



II - PRINCIPLE OF THE EXPERIMENTAL METHOD - 



2,1 - Models - 



Scale : 1 / 4. 2672 



The models were adjusted in weight , position of center 

 of gravity and in transversal moment of inertia . In order to adjust 

 the values of these 3 parameters , three weights could be moved 

 along a threaded rod inside the models . 



2,2- Measurements performed - 



In general four quantities were measured . However in 

 some experiments only two or three of these quantities were actually 

 measured . 



2, 21 - The wave height £" (t) was measured with a capa - 

 citance probe , made of a coated wire , and the capacitance between 

 the water and the wire , proportional to the length of wetted wire , 



1012 



