THE APPLICATION OF WAVEMAKING 



RESISTANCE THEORY TO THE DESIGN 



OF SHIP HULLS WITH LOW 



TOTAL RESISTANCE 



Pao C. Pien 



David Taylor Model Basin 



Washington, D.C. 



ABSTRACT 



Despite its limitations, the existing wavemaking resistance theory can 

 be applied effectively to the design of better hull forms with practical 

 proportions. Proper application of the theory can produce not only the 

 direct benefit of reducing wave drag but also an indirect gain in viscous 

 drag. Most of the numerical work involved in such application has 

 been programmed into the 7090 IBM high-speed computer. Some nu- 

 merical results obtained by using computing programs are shown. A 

 ship design example to show how we can reduce both wave and viscous 

 drags is also included. 



INTRODUCTION 



The total resistance of a ship consists of two parts, wavemaking resistance 

 and viscous resistance. If wavemaking resistance theory can be used to minimize 

 the wave drag of a ship, we can not only have the direct benefit of low wave drag 

 but also a great possibility of reducing viscous drag. 



It has often been said that the application of this theory to ships currently 

 designed to operate at low Froude numbers holds little promise because wave 

 drag is a very small portion of the total drag. It is true that we cannot reduce 

 the total drag of a ship very much in such cases even if we can eliminate the 

 wave drag entirely. However, if the length of a ship is reduced, the wetted sur- 

 face will be reduced, and as a result, the viscous drag will be decreased. If 

 ship length is decreased, and speed and displacement volume are kept constant, 

 the operating Froude number will be increased. Any experienced ship designer 

 will agree that the increase in wave drag will far exceed the decrease in viscous 

 drag. If the wavemaking resistance can be kept low through the application of 

 the wavemaking resistance theory, then reducing the ship length will achieve a 

 great gain in total resistance as well as a reduction of construction costs. This 



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