PART I. HYDRAULIC SCALE MODEL STUDY 

 by 

 C. L. Liu, Ph.D. 



INTRODUCTION 



There has been an increasing need for locating tactical and strate- 

 gic bases in various parts of the world. A potential solution to this 

 problem is huge ocean-borne platforms which could provide the area for 

 such bases. One concept for a large platform is the Mobile Ocean Basing 

 System (MOBS) which consists of floating platform modules connected to- 

 gether. This concept is similar to the concept of the FLoating AIRport 

 (FLAIR) recently developed by Mr. Paul Weid linger . ■'- MOBS, however will 

 be positioned in much deeper water and farther from shore than FLAIR. 



One of the necessary requirements for MOBS is the capability to 

 maintain position within a selected region of the ocean. Conventional 

 spread moorings, deep taut line moorings, and dynamic positioning are 

 examples of methods for controlling surface position of platforms. The 

 large size of the proposed ocean-based structures requires large mooring 

 lines, huge anchors and/or large propulsion power. All of these are 

 difficult to realize. However, if the wave drag can be reduced or even 

 utilized to provide resistance to wind and current drag, the mooring re- 

 quirements will be reduced, hopefully, eliminating the need for special 

 mooring gears and expensive propulsion power. 



This report presents and evaluates a hypothesis which states that 

 wave energy can be extracted by properly orienting vertical non-symmetric 

 cylinders in regular waves. Net wave forces along and against the dir- 

 ection of wave propagation may be produced due to the difference in drag 

 coefficients at the front and the rear of a non-symmetric cylinder. The 

 report contains the results of a free drift experiment and a wave force 

 model study for the verification of the hypothesis. 



BACKGROUND 



Hydrodynamic drag force on an object is generally expressed in terms 

 of fluid kinetic pressure, cross-sectional area normal to the flow, and 

 a drag coefficient. The drag formula can be written as'^ 



F = Cp 



P\P_ (1) 



2 



