GerassimoVj Pershitz and Rakhnanin 



? hh 



C°, C° Cos jS + C° Sin/3 L Sin tg S^l 



a£ a£ o a 77 o o o hh 



AlC . C ' ^ ' L J 



LC 



o o o 



0O *« "o 



+ -^— + > tf + 6 



(25) 



2tt 



o s 



where AX Q is the non-dimensional shifting of the hawse-hole in 

 relation to the anchorage depth H^ as the ship passes from the 

 state of rest in the absence of wind to an equilibrium position with 

 the wind having the velocity of V. 



It can practically be assumed that —r — = 0. 5. In this 

 case angle /3 is equal to zero, which can easily be verified by 

 using formula (23), and the criterion (25) is simplified taking the 

 form 



Taking into account the curves of Figure 3 it can easily be shown 

 that for the conventional arrangement of the forward hawse-hole 

 condition (26) is not met, i. e. in the absence of current the anchor- 

 ed vessel subjected to wind will not be stable to angular deflections 

 from the course. 



Instability of equilibrium of a vessel held in place by the 

 anchor is the main cause of drifting and yawing, which in the absence 

 of current and with constant wind have the nature of auto-oscillations 

 which are symmetrical with respect to the wind directions. Fig. 5 

 shows the curves obtained by computer simulation of the set of 

 equations (18), which characterize the auto-oscillations of the an- 

 chored vessel (_|±- = 5; J 1 * 1 =0.5; 6 = 0.07) subjected 



B Z». 



to constant wind ( V = 12 m/sec) in the absence of current 



(V = 0). 



Under the simultaneous action of the wind and current the 

 yawing becomes asymmetric with respect to the wind provided that 

 the direction of the wind differs from that of the current. The average 

 angle Q and average shifting of the hawse-hole Y^q increase 



1090 



