UFC 4-159-03
3 October 2005
Static Current Yaw Moment. The current yaw moment is defined as that
4-5.4
component of moment acting about the vessel's vertical "Z"-axis. This moment is
determined from the equation:
ec
M xyc = Fyc (
(24)
EQUATION:
)L
LwL wL
where
= current yaw moment (newton*m)
M xyc
= transverse current force (newton)
Fyc
ec
= ratio of eccentricity to vessel waterline length
LwL
= eccentricity of Fyc
(m)
ec
= vessel waterline length (m)
LwL
ec
The dimensionless moment arm
is calculated by choosing the slope and y-intercept
LwL
variables from Table 4-10 which are a function of the vessel hull. The dimensionless
moment arm is dependent upon the current angle to the vessel, as shown in Equation
25:
e
= a + b *θc
θc=0 to 180
(25)
EQUATION:
LwL
e
= a + (b * (360 deg- θc )) θc=180 to 360
(25a)
LwL
where
ec
= ratio of eccentricity to vessel waterline length
LwL
= y-intercept (refer to Table 4-10) (dimensionless)
a
= slope per degree (refer to Table 4-10)
b
θc
= current angle (degrees)
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