Str^m-Tejsen and Chislett 



,2 



Hence, the hydrodynamic coefficients 



X*, X^^, X^s, Xg5 



Y*. Y^, Yy^^, Y^5g, Yg, Yggg, Yg^^ 



N*, N,, N,,,, N^gg. Ng, Nggg, Ng,, 



are simply the coefficients of these expressions, when they are used as approx- 

 imating functions in fairing the experimental measurements. 



Figure 23 and Table 3 further illustrate the principle of the analysis. The 

 figure shows results from a "static drift-angle" test carried out for the Mariner 

 hull-form. The test was executed at 15 knots, and forces and moments were 

 measured over the complete range of drift angles (/3 = -9.5, -7.5, -4.5, -2.0, -1.0, 

 -0.5, 0.0, 0.5, 1.0, 2.0, 4.5, 7.0, 9.5 degrees) and of rudder angles (s = to ±40 

 degrees in steps of 10 degrees). The experimental points are plotted in the fig- 

 ure as circles, whereas the solid curves show the expressions obtained from 

 fairing the data. 



Table 3 presents the corresponding output from the computer program used 

 in the analysis. The experimental and faired values are indicated bye and f, 

 and the fairing polynomials are given at the bottom of the table. 



Similar principles are applied in the analysis of results from tests made 

 in the dynamic mode of operation. Figure 24 and Table 4 show, for example, the 

 analysis of forces measured in the "pure yaw" test. 



The out-of -phase forces are in this case faired by the expressions 



X = (Xrr-mxQ) r^ 



Y. (Y,-mu) r + |Y,„r^ 



N = (N^-mx^u) r + fw^^^r^ 



and the in-phase forces by expressions of the form 



Y = (Y._.-mxQ)f 



N = (N- -I,) r . 



The hydrodynamic coefficients are determined after corrections for differences 

 in mass and moment of inertia for model and ship. 



352 



