RESULTS OF TESTS IN REGULA.R WAVES 



Results of the tests in regular waves indicated that the model response 

 to a given wave length was nonlinear with respect to wave height. Test 

 results for the displacement conditions showed that the general trend was 

 for the linearity to improve with increase in displacement. 



Regular wave data were obtained for Conditions 1 and 4 in the linear 

 range. Figure 2 shows the results of the tests for the two conditions, 

 and Figures 3 and 4 show the frequency response curves for these conditions. 

 Most of these results cannot be utilized as valid estimators of the platform 

 motions in seas greater than States 3 and 4. They do, however, provide 

 some insight into the behavior of the platform in waves. 



It is readily apparent that the motions are reduced considerably 

 with the platform in the deep draft condition. The heave amplitude is 

 large for wave periods of 10 to 14 sec in displacement Condition 1 

 (light draft). Fortunately, the natural period in heave is 5.3 sec. These 

 curves may be considered indicative of the maximum vertical motions to be 

 expected. This unusual peaking of these curves near the natural periods 

 of pitch and roll suggest strong coupling between these motions and heave. 

 The heave amplitude curve is quite smooth for displacement Condition 4. 

 However s the curve is not complete in the low- frequency range because of 

 physical limitations of the wavemaker system. It is not expected that a 

 peaking or resonance condition will occur in this low- frequency range 

 because of the natural heave frequency of the platform is very low compared 

 to the frequencies of waves normally encountered in a seaway. 



The pitch and roll motions show similar characteristics with respect 

 to frequency content. The peaking of these curves for displacement Condition 1 

 occurs in the vicinity of the natural periods of pitch and roll. The natural 

 frequencies for pitch and roll for displacement Condition 4 arte much lower 

 than will be found in a given seaway and should have no effect on peaking 

 the response curve. This is shown in Figure 4. 



