ABSTRACT 



This report concerns the realistic simulation of irregular long-crested 

 seas in the Harold E. Saunders Maneuvering and Seakeeping Facility. Random 

 Gaussian seaways which approximated the Neumann spectral shape were pro- 

 duced for model testing by use of an electrohydraulic control system for wave 

 generation. Techniques and difficulties associated with the use of an analog 

 computer for wavemaker control are discussed. Plans for further development 

 and extension to directional sea simulation are presented. 



INTRODUCTION 



In recent years the seaworthiness characteristics of ship designs have become 

 increasingly important. The unsolved scientific problem of explaining the behavior of a 

 ship in a heavy seaway is exceedingly complex and involves the interaction of a body free 

 to move in six degrees of freedom with a randomly disturbed water surface. The associated 

 problem of designing a hull form with specified seakeeping qualities .is even further from 

 complete solution. 



Testing of scale models in waves has provided a fruitful means for investigating 

 these problems. Essentially two paths have been followed: 



1. The ship is characterized as a linear system responding to the various sinusoidal 

 increments in the wave pattern, often through motion response tests in regular or pure sinus- 

 soidal waves. 



2. The ship model is operated in a controlled wave environment which is structured to 

 simulate conditions found at sea, and the linear approximation is evaluated along with 

 various nonlinear phenomena such as slamming, shipping water over the deck, and extreme 

 motions. 



This report is concerned with the second type of seaworthiness testing as conducted 

 at the David Taylor Model Basin, utilizing the new Harold E. Saunders Maneuvering and 

 Seakeeping Facility (MASK) to simulate a random seaway. More specifically, the report 

 presents the results obtained in an exploratory program of wave generation together with 

 plans for future development. 



DESCRIPTION OF THE WAVEMAKING FACILITIES 



A complete description of MASK has recently been presented by Brownell. ^ Basically, 

 the test basin is 360 ft long, 240 ft wide, and 20 ft deep; it has an array of pneumatic wave- 

 makers along two adjacent sides and two wave-absorbing beaches along the other sides. 



References are listed on page 19. 



