Kim and Mevciev 



lag) for co = 0. 



Impulse response functions were obtained as the Fourier trans- 

 forms of the transfer functions in accordance with the theory first in- 

 troduced in ship motions by Fuchs and MacCamy [l4] , and more fully 

 developed by Cummins [15] . Examples, again for Test Run 002, are 

 shown in Figure 5. Tables, such as Table 4 given here, are given in 

 Reference 5 for the twenty-five configurations tested. A comparison 

 of measured and calculated heave and pitch motions for a cruciform 

 model in head seas is given in Figure 6. The computations were carri- 

 ed out by the convolution integrals 



pa 



Z (T) = f k cnfff'-Tjdr 



J z 



and * - (1) 



d(T) =- T - T /k (r)r(F-'7)d7 



V -oo 



where k and k„ are from Table 4. 

 z 8 



DISCUSSION 



Transfer Functions 



A comparison of the results of several test runs indicates the 

 influence of variations in the significant parameters. The transfer 

 functions, particularly the amplitude ratio, afford a convenient graph- 

 ical indication of the performance. 



Heave responses for several cruciform models of Group A 

 (Table 1) are shown in Figure 7. The amplitude ratios ar e plott ed 

 against the non-dimensional frequency parameter, Zo = co \V^/g • An 

 auxiliary chart is arranged beneath the frequency parameter, in which 

 the wave length corresponding to a particular craft displacement (long 

 tons of sea water) and frequency parameter can be read. The displac- 

 ement range covered extends both above and below the usual aircraft 

 range, in case other types of platforms are to be considered. The 

 heave-wave relations shown in Figure 7 all have similar shapes, having 

 virtually no magnification or motion greater than wave elevation, and 

 a sharp fall-off in response above a certain frequency. The damping 

 plate size (which can be considered to be similar to the "footings" fitt- 

 ed to some drill rigs) appears to have the most influence on the heave 

 response for these configurations, but it must be noted that greater 

 variations in geometrical parameters could be adopted. 



800 



