UFC 4-159-03
3 October 2005
1
ρw Vc2 S Cxca cos(θc )
FxFRICTION =
(17)
EQUATION:
2
where
ρw = mass density of water, from Table 4-1
Vc = current speed (m/s)
S = wetted surface area (m2); estimated using
D
EQUATION:
(18)
S = 1.7 T L
Tγ
wL +
w
average vessel draft (m)
T=
waterline length of vessel (m)
LwL =
ship displacement (newtons)
D=
γ =
weight density of water, from Table 4-1
w
longitudinal skin friction
C xca =
coefficient, estimated using:
2
EQUATION:
(19)
Cxca
0.075
log R
2
/
-
=
10
N
R N = Reynolds Number
Vc LwL cos(θc )
RN =
(20)
EQUATION:
ν
ν = kinematic viscosity of water, from Table 4-1
θ c = current angle (degrees)
FxPROP =
longitudinal current load due to fixed propeller drag
1
= ρw Vc A p CPROP cos(θC )
EQUATION:
(21)
2
FxPROP
2
where
90
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