Breslin, Savitsky, and Tsakonas 



frequency- of- encounter. On the other hand, the w without subscript e will be 

 retained for those equations involving the function 



g(^,^, O = e ^ 

 as given in Eq. (14). 



Without this correction, the wave-height information as seen by the body is 

 implied to be the same as that picked up by the stationary probe. This is tanta- 

 mount to a wave excitation on a body essentially hove-to or a body running in 

 cross-seas. If we assume the latter to be the case, then the significance of this 

 error implies the loss of a cross-product term Ucp^^ in the linearized pressure 

 integral. This can be shown by examining the Bernoulli equation. For the case 

 of a body advancing with forward speed u, the pressure terms after lineariza- 

 tion can be written 



Subscripts i and 2 are used here to denote quantities related to calm-water 

 and wave respectively. Then cpj^^ is the longitudinal perturbation velocity in 

 calm water, ^p^x (o^ -Pwx) is the corresponding contribution in waves, cp^^ and 

 cpjt are the unsteady contributions to the pressure in calm-water and waves 

 respectively. 



On the other hand, the linearized pressure due to the body running with 

 forward speed U in calm water conditions is 



~y ^ UcPi^ + g? + CPjt • 



Adding this to the contribution due to the seaway but with the body held fixed. 



Ap 



gives 



Apj + Ap2 



Ucpjx + gC + CPit + 0^21 



Comparing the above pressure equation to that of the previous case where 

 the total pressure was obtained with body translating with speed in waves shows 

 a loss of the U(P2^ contribution. 



The second issue is the age-old question of the extent of the validity of the 

 somewhat heuristic development of the mathematical model adopted. These re- 

 fer to the forcing functions employed in Eqs. (11) and (12). Basically, it as- 

 sumes a lumped mass, dashpof, spring system. It utilizes the wave information 

 at the wave probe station and transfers the fluid particle effects to the center of 



502 



