In the frequency domain, the total fluid pressure at the point 
on the hull surface can be expressed as
 | (13–62) |
where 
are the incident wave, diffraction wave, radiation wave pressure, and
hydrostatic components respectively.
In the time domain analysis, the incident wave pressure and hydrostatic pressure are defined in Extended Wheeler Stretching Method and Second Order Correction of Linear Irregular Waves.
In the regular wave case, based on the incident wave definition in Equation 13–37 the diffraction pressure is expressed as
 | (13–63) |
In the irregular wave case, based on the irregular incident wave definition in Equation 13–43 the diffraction pressure is linearly expressed as
 | (13–64) |
In the multiple structure hydrodynamic interaction case, the total degrees of rigid body motions are 6xM where M is the number of structures in a hydrodynamic interaction group. The radiation wave pressure is usually expressed as
 | (13–65) |
where pjm is the radiation pressure due to the unit j-th motion of the m-th structure whilst other structures remain stationary, and xjm is the motion RAO.
The inverse Fourier transform of the radiation pressure in frequency domain is
 | (13–66) |
where 
is the acceleration RAO, 
, 
is the acceleration in time domain, and the impulse function of the
acceleration related is
 | (13–67) |
and
 | (13–68) |
The wave elevation components due to radiation wave and diffraction wave in the time domain can be estimated by
 | (13–69) |