TOTAL HYDRODYNAMIC FORCE AND MOMENT 
The total normal hydrodynamic force acting on the body is obtained by integrating the 
stripwise, 2-D, hydrodynamic force given by Equations (2) and (6) over the wetted length 2 
of the body. A body coordinate system (£,¢) with its origin at CG and the & axis pointing 
forward parallel to the baseline of the body is defined in Figure | to facilitate this integration. 
The hydrodynamic force acting in the vertical or z direction of the fixed integral coordinate 
system is given by 
-Ncos@) = FU(t) = / f cos @dé +f igat 
Q Q 
= | ftraeoveo + m, (,t) V(E, t) 
Q 
a0} 
dg 
+Cy Deb EN VE,D} cos dé 
+apsade] (7) 
where the integration is taken over the instantaneous wetted length. Similarly the force 1 
acting in the horizontal or x direction is given by 
F, = [tin oat 
= — [ {mge.0 ven + m,(é,t) V(t) 
- UE) = [m,(E.0 VED) 
+ Cp .é.teb,0V7(E,b} sin 0 dé (8) 
Wave forces are obtained by neglecting diffraction and assuming that the wave excitation 
is caused both by the geometrical properties of the wave, altering the wetted length and 
draft of the craft, and by the vertical component of the wave orbital velocity at the surface 
w,, altering the normal velocity V. The horizontal component of orbital velocity is neglected, 
