UFC 4-159-03
3 October 2005
Static Longitudinal Wind Force. The static longitudinal wind force on a
4-4.2
vessel is defined as that component of wind force parallel to the centerline of the vessel.
This is the force in the "X" or surge direction in Figure 4-2. Figure 4-1 shows the
definition of winds areas.
The longitudinal force is determined from NCEL, TN-1628 using the
equation:
Fxw = 0.5 ρa Vw 2A x Cxw fxw (θw )
(5)
EQUATION:
where
longitudinal wind force (newtons)
Fxw =
ρa =
mass density of air (from Table 4-1)
wind speed (m/s)
Vw =
transverse wind area of the ship (m2)
Ax =
longitudinal wind force drag coefficient
Cxw =
fxw (θw ) =
shape function for longitudinal force
θw =
wind angle (degrees)
The longitudinal wind force drag coefficient, Cxw , depends on specific
characteristics of the vessel. Additionally, the wind force drag coefficient varies
depending on bow ( CxwB ) or stern ( CxwS ) wind loading. Types of vessels are given in
three classes: hull dominated, normal, and excessive superstructure. Recommended
values of longitudinal wind force drag coefficients are given in Table 4-3.
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