Gevassimov y Vevshitz and Rakhmanin 



The terms included in the expressions (3) are determined 

 by the aerodynamic forces acting upon the above-water body in the 

 presence of wind, the anchor chain tension, and the noninertial hydro - 

 dynamic forces generated on the underwater body during its motion. 

 The inertial forces considered in this problem are taken into account 

 in the left-hand side of equations (2). When defining the signs of 

 formulae (3) it was thought that the forces and moments were cal- 

 culated for the positive shifts. 



In equations (2) provision is made for taking account of 

 the constant current in the vicinity of anchorage. For this purpose 

 you need only to represent the CG velocity projections with respect 

 to water in the form of the following obvious expressions (Figure 1. ): 



V t = i + V Cos {a + ), 

 £ o o 



V-n = V - V Sin ( oc + ). (4) 



o o 



In the absence of current V and a Q are equal to zero. 

 Thus three unknown values can be derived directly from equations (2): 

 yaw angle and projections £ and t/ of the CG velocity. In the 

 fixed coordinate systems these projections will have the form 



X = £ Cos - v Sin , Y = £ Sin + 17 Cos (5) 



o o 



By integrating expressions (5) time functions X Q (t) and 

 Y Q (t) can be found which determine the position of CG in space. The 

 position of the hawse-hole can be found from the following obvious 

 relationships : 



X ^ = X - ^uJ 1 " Cos )« Y uu = Y + Uv Sin ( 6 ) 



hh o hh hh o hh 



Along with the relationship for (t) the functions of 

 X (t), Y Q (t), X hh (t) and Yhh(t) g ive rather a full idea of the 

 yawing and drifting of an anchored vessel under the action of wind 

 and current. 



4. Estimation of aerodynamic forces 



Projections of aerodynamic forces on the axis of the body 

 system of coordinates £ Oj rj are defined by expressions 



1084 



