Wave Induced Forces and Motions of Tubular Structures 



VI. CONCLUSIONS 



In the previous section, a comparison is shown of experi- 

 mental measurements and theoretical predictions of platform motions 

 and mooring leg tensions, using the procedure developed here» The 

 theoretical results were obtained by the simplest form of the pro- 

 cedure in which constant infinite fluid values were assumed for added 

 mass coefficients. Constant linear drag coefficients were used, and 

 no attempt was made to account for the hydrodynamic interference 

 between members of the structure. The first two groups of experi- 

 mental results show that the observed performance of single members 

 cind assemblages does, indeed, follow a nearly linear pattern in 

 regular waves, ajid this pattern is well predicted by the present pro- 

 cedure. The last group of experimental results show nearly equally 

 good results in both regular and irregular waves. There is, however, 

 some consistent nonlinear amplitude variation in longer waves, as 

 may be seeti in Fig. 9. 



It is probable that the good agreement Is obtained because 

 tlie structures tested consisted of assemblages which satisfied the 

 Initial assumption reasonably well, l,e,, 



(1) All members were long, slender cylinders relatively 

 sparsely distributed throughout the structure. 



(2) The bulk of the members were submierged sufficiently 

 deeply below the free surface, 



(3) The cross sectional dimensions of all members were 

 small compared to the waves used In the experiments. 



(4) The motions of the models were small compared to the 

 model dimensions and to the wave lengths. 



The aforementioned nonlinear behavior probably Illustrates 

 the failure of a single value of the linear drag coefficient to ade- 

 quately represent this component of the hydrodynamic force over the 

 entire range of frequencies. 



ACKNOWLEDGMENTS 



This work was conducted under the sponsorship of Deep Oil 

 Technology, Inc. and the author expresses his appreciation for 

 their permission to publish the foregoing resiolts. The assistance 

 of a numiber of Individuals in conducting experiments and performing 

 Ccilculatlons Is also acknowledged. Special thanks In this respect are 

 due to Mr, O. J. Slbul, and graduate students Kwang June Bal and 

 Nabll Daoud of the University of California, Department of Archi- 

 tecture, and Mr, Paul Glllon of Deep Oil Technology. 



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