Norrbin 



Results for Force and Moment Coefficients 



Figs. 29 - 32 show plot of force and moment coefficients 

 from tests in deep (free) and shallow water, and the analytical 

 approximation obtained by stepwise regression analysis. Results 

 from the near-to-wall experiments have been given in Fig. 23. 



In the evaluation it was consistently assumed that the changes 

 of first and second order derivatives due to finite depth could be 

 approximated by terms proportional to t,. As the tests did include 

 two values of t, only, one of which very small, this does not effect 

 the derivatives derived for these two depth conditions, nor the "true- 

 deep-water" values. 



Further, because of the scatter of experimental data it proved 

 suitable to perform the analysis with an assumed value for the deep- 

 water cross -flow resistance corresponding to Cq = 0.7; cf. Section VI. 



In agreement with earlier findings the test results indicate a 

 very marked Influence of shallow water on the non-linear force contri- 

 butions, and on the latereuL force due to yaw in particular. It shall be 

 observed that the analysis involves a change of sign in the first-order 

 rotary force derivative as water depth is reduced. 



The force and moment derivatives derived from shallow water 

 and canal tests will be presented in next Section. 



Fig. 29. 98 000 tdw tanker - Force coefficient Y"(P)/u"^ in deep 

 and shallow water. 



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