The real and imaginary parts of the incident, diffracted, radiated and hydrostatic-varying pressure components calculated in the Hydrodynamic Diffraction analysis are used to evaluate the total hydrodynamic pressure at each structure node for the specified incident wave amplitude and phase angle:

(8–1)

Where P_θ is the total hydrodynamic pressure at the required phase angle θ, with θ=0° when the incident wave crest passes the center of gravity of the structure; is the specified incident wave amplitude; and P_r and P_i are the real and imaginary parts, respectively, of the summed hydrodynamic (incident, diffracted, radiated and hydrostatic-varying) pressure components.

Where hydrostatic pressure is also included, the total pressure P is the summation of the hydrodynamic and hydrostatic parts:

(8–2)

Where the hydrostatic pressure P_s is calculated as:

(8–3)

In which ρ and g are the water density and acceleration due to gravity, respectively, as specified in the Hydrodynamic Diffraction analysis; and z is the depth of the structure node below the waterline in the Static Structural axis system (after any Axis Transformation has been applied).

Distributed loads on submerged Line Bodies are calculated using the Morison equation:

(8–4)

Where:

F is the total Morison force per unit length;

D is the Line Body diameter (which should take into account any marine growth);

C_d is the viscous drag coefficient;

u_f is the flow velocity normal to the Line Body (comprising the diffracted wave particle velocity and any defined current);

u_s is the structure velocity normal to the Line Body;

and are the flow and structure accelerations, respectively, normal to the Line Body;

A is the cross-sectional area of the Line Body;

is the added mass coefficient, from which:

(8–5)

Where C_m is the inertia coefficient. Setting C_m =0.0 turns off loading due to the diffracted wave and added mass effects (second and third terms of Equation 8–4); otherwise the valid range of values are C_m ≥1.0. Similarly, viscous drag (first term of Equation 8–4) can be ignored by setting C_d =0.0. For non-cylindrical cross sections, the Morison equation is applied separately in each direction normal to the Line Body.

The Hydrodynamic Pressure Mapping Add-on determines whether the ends of each beam element are above or below the local water surface and loads the Line Body accordingly. For elements that cut the water surface the loading is applied over the wetted length only.