Giddings and Wermter 



WITHOUT TANKS 

 WITH TANKS 



— e 



^O 2.0 



ii 



5i- 1.01- 



< 



WlTHOyT TANKS 

 WITH TANKS 



= 0.3 



0.5 



1.0 



1.5 



— e 



Figure 1 



Then the equation of motion will be written as Eq. 1 in Fig. 1. It is noted that 

 the excitation is modulated by a function which becomes zero when co^ - yjg/h^. 

 It means that tank water does not move at all at this frequency regardless of 

 amount of heave. Therefore, this frequency will be called as zero response fre- 

 quency. 



From this it can be seen that h^ should be chosen so that m^ does not coin- 

 cide with the natural frequency of pitching. Considering the average pitching 

 period, it can be easily seen that h^ should not be too large. 



On the other hand, the resonant frequency of the tank water level is also 



Vhyg which is the same as the zero-response frequency. Therefore, in this 

 case of wall sided tanks, the response of tank water is very small and will not 

 be effective. 



804 



