Unclassified 



DOCUMENT CONTROL DATA - R 8. D 



Naval Civil Engineering Laboratory 

 Port Hueneme, California 93041 



Unclassified 



Wave Energy Extraction By Crescent Shaped Columns For Station 

 Keeping Of Floating Ocean Platforms - Hydraulic Model And 

 Feasibility Study 



HOBISI fflr«ln«m«, middle Inlllml, 



C. L. Liu 



R. H. Fashbaugh 



March 1971 



59 



11 



ZF 38.512.001.017 

 03-001 



TN-1156 



Approved for public release; distribution unlimited. 



Office of Naval Research and 

 Director of Navy Laboratories 



Fixed or floating column-supported platforms in the ocean exper 

 ience direct and reverse wave drag caused by the oscillating water 

 particle velocity. The drag coefficient for the direct flow can be 

 different from that for the reverse flow if the cross-sectional area 

 of the supporting column is not symmetric about the column axis. 

 Therefore, a net wave drag force theoretically can be produced. The 

 purpose of this study was to determine whether this concept can be 

 utilized to reduce the power requirements for positioning large 

 floating platforms such as the proposed Mobile Ocean Basing System 

 (MOBS ) . 



Two support column cross sections were chosen for evaluation; a 

 semi-circle and a crescent shape which is formed by two intersecting 

 circles (the larger circle having a radius 1-1/2 times that of the 

 smaller circle). A circular cross section was included to provide a 

 reference. Free drift velocity tests of three small scale tri-column 

 platforms with the three different cross sections were made in a 

 small wave tank as a preliminary experiment. Based on the results of 

 this drift experiment wave drag measurements were made with larger 



DD,ire,1473 



S/N 0101-807-68 



Unclassified 



"ConTTnued 



