A MODEL TESTING TECHNIQUE AND 



METHOD OF ANALYSIS FOR THE 



PREDICTION OF STEERING AND 



MANOEUVRING QUALITIES 



OF SURFACE SHIPS 



J. Strf^m-Tejsen and M. S. Chislett 

 Hydro- and Aerodynamics Laboratory 

 -Lyngby, Denmark 



ABSTRACT 



A semitheoretical method of investigating steering and manoeuvring 

 qualities of surface vessels is described. A general mathematical 

 model, consisting of nonlinear equations of motion for a body free to 

 move in the horizontal plane, is used as a basis. The hydrodynamic 

 coefficients of the equations are obtained by carrying out captive -model 

 experiments for each particular vessel, after which any desired ma- 

 noeuvre can be predicted with the aid of a computer. 



The hydrodynamic coefficients are determined using a planar-motion 

 mechanism system to test 6-m (20-ft) wax models in a conventional 

 towing tank. Details of the design, construction, and use of this mech- 

 anism are given, together with a description of the methods used to 

 analyse the measured forces. The convenient manner in which non- 

 linear and cros scoupling coefficients, necessary for the accurate pre- 

 diction of radical manoeuvres, can be obtained with a planar-motion 

 mechanism technique is described. 



Short mention is made of the influence of frequency and tank- 

 interference effects on the measured hydrodynamic forces, and it is 

 shown that troublesome resonant standing-wave conditions can be 

 avoided. 



INTRODUCTION 



There is no completely analytical method available at this time for predict- 

 ing the steering and manoeuvring characteristics of ships. Due to this lack of 

 theoretical methods, experimental techniques using free-running models have 

 been employed by model basins for many years. Of more recent development is 



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