SOME HYDRODYNAMIC ASPECTS 

 OF SHIP MANEUVERABILITY 



J. N. Newman 



David Taylor Model Basin 



Washington, D.C. 



ABSTRACT 



Recent developments are discussed which further the understanding of 

 the hydrodynamic force and moment acting on surface vessels during 

 maneuvers. Photographs are shown of the flow past a model of a Mar- 

 iner class hull with several drift angles, to support the validity of sim- 

 plified mathematical models for the hydrodynamic force and nnoment 

 analyses. It is shown that memory effects due to separation and free- 

 surface wave motions, together with the non-analytic dependence of the 

 nonlinear viscous forces on drift angle, require a more complicated 

 mathematical model for the force and moment than the usual Taylor 

 series expansion in powers of the velocity and acceleration. Methods 

 for analyzing the added mass, circulation, free surface, viscous, and 

 propeller influences are reviewed and discussed. Experimental and 

 theoretical evidence of the existence of memory or frequency effects is 

 noted. Several recommendations are made for detailed problems which 

 could profit fronn further investigation. 



INTRODUCTION 



The study of maneuverability and control of surface ships had its genesis 

 when man first set forth with raft and paddle. In the ensuing millennium this 

 field has become progressively more refined and scientific. Nevertheless much 

 work remains to be done in order to advance our understanding of the hydrody- 

 namic phenomena which are involved when a ship undergoes a maneuver. The 

 purpose of this paper is to review recent accomplishments and also to indicate 

 possible directions for future research and progress. 



The history of ship maneuverability and control can be traced back at least 

 as far as Euler (1749). Two centuries later, the paper of Davidson and Schiff 

 (1946) organized the subject of ship dynamics within a modern engineering 

 framework and served as a stimulus and basis for most of the subsequent re- 

 search in this field. Six years ago the David Taylor Model Basin was host to a 

 Symposium on Ship Maneuverability which included a broad survey of the field 

 by Norrbin (1960). 



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