276 



1 — Model, Nominal Field 



2 - Ship, Nominal Field (Correlation Based 



on Equations (1)-(4I) 



FIGURE 15. Influence of scale effect and propeller 

 operation on harmonic spectrum. 



Model, Effective Field (Titov and Otiesnov, 1975) 

 Model, Effective Field (Proposed Method) 



velocities and results in an increase of the con- 

 stant component of the moment in t±ie vertical plane. 

 The M^q/Kq values calculated from the effective 

 velocity field approximate those observed for full- 

 scale ships of this type under operational condi- 

 tions. This fact confirms the importance of taking 

 into account propeller operation when simulating 

 the velocity field at the propeller. The propeller 

 effect upon the velocity field is dependent on the 

 load, ship hull form and afterbody shape, initial 

 nominal field, and the relationship between pro- 



peller screw size and wake thickness, i.e., on the 

 propeller immersion into the viscous wake. 



The full-scale conditions of effective field 

 formation are likely to differ from the model ones. 

 Hence, the next step in studying the prediction of 

 the flow velocity field in way of the propeller will 

 be the development of procedures which enable simul- 

 taneous consideration of both the scale-effect and 

 the effect of propeller operation on the wake at 

 the s te rn . 



TABLE 2. Variation in the Constant Component of Bending Moment Depending on t±ie 

 Velocity Distribution at the Propeller (Model 1) 



Model . 

 Experiment. 

 Initial Nominal 



Data 



Field 



Model-ship 

 Correlation 

 Using Equa- 



Model. Esti- 



Model. 



mation of Experiment 



Propeller Consideration 



Effect of Propeller 



According to Effect by 



Hoekstra Using Equa- 



tions (l)-(4) (1977) 



Model. 

 Experiment 

 Consideration 

 of Propeller 

 Effect by 

 Using Equa- 



tions (11) -(12) tions (13) -(18) 



\o^\ 



0.04 



-0.07 



-0.08 



-0.35 



-0.25 



