Understanding and Prediction of Ship Motions 



Fig. 7 - Heave damping coefficient for 

 series 60, Cg = 0.60, Model at various 

 Froude numbers, experiments and cal- 

 culations (from Gerritsma, Kerwin, and 

 Newman (1962)) 



SLENDER SHIP THEORY 



A slender body theory, whether for aircraft or for ships, is formulated on 

 the assumption that all dimensions in a cross section of the body are small 

 compared to the length of the body. Also, the rate of change of transverse di- 

 mensions (with respect to the lengthwise coordinate) must be small in a simi- 

 lar sense. Such an approximation appears attractive for ship problems, since 

 ships generally fit such a qualitative description. Nevertheless, the application 

 of slender body theory to ship problems has been long in coming, in spite of the 

 fact that the aerodynamic version of the theory is forty years old. 



57 



