OCIMF_Mooring_Equipment_Guidelines_(Second_Edition)

Where:

Lateral current

force

Current yaw

moment.

F J C e ye ( --D, ) V,TL^1 op

7600

e.", non-dimensional longitudinal wind force coefficient

non-dimensional transverse wind force coefficienJ

non-dirnc.nsional wind yaw momem coefficient

density of air = 1.223 Kg/m! at 20°C

eyw

e""

j)",

v .. veJocity of wind at IOm elevation in knots

(5)

(6)

AT

AL

Lop

lransverse (head-on) above water area in metre" (for condition invest.igated)

10ngitudJnal (broadside) above water area in metre! (for condit.ion invest.igated)

length between perpendiculars in metres

F", longitudinal wind force in kN

FY>" lateral wind force in kN

M",-.. = wind yaw moment in kN metres

C ,c noo-dimensional longitudinal cunent force coefficient

C>, non-dimensjonal transverse current force coefficient

C.rc non·dimensional curre nt yaw moment coefficient

p, density of sea water = 1025 Kg/mJ at woe

V, average current veloci,ty acting over the draft of ship in knots

T ship draft in metres (for eondit ion investigated)

f" longitudinal current force in k N

F ye lateral currenl force in k N

M,ye current yaw moment in kN melres

For the eonventi.on using lat\:ral forces and coefficients at the perpendiculars. the formulae (2) and

(5) above apply with the substitlllion of F y with either P yf or F ,,, and C y with ei ther eyr or erA.

The shape of the bow may have some inOuence on the wind and current c.oefficients. Reference 3
sbows two separate. values where the coefficients are different. A "conventional" bow represents a
bulbous bow. and "cylindrical" bow represents a bow without a bulb and rounded wa!erline.~ in tbe
stem area .. The different bow shapes are shown in Figure 2.2.

Figures 2.3 through 2.8 are provided for use with hand calculations. Figures 2.6 through 2.8, and

Figure 2.2 are taken directly from Reference 3.

Figure 2.3 provides tbe Lateral wind coefficients at the forward and afl perpendicular (C, ... and

C,r",) for loaded and balLasted oil [ankers. Figure 2.4 provides lhe longitudinal wind force coefficient for

loaded and ballasted oil tankers. Figures 2.3 and 2.4 provide these coefficients for various wind

attack angles. Figure 2.5 provides the lateral current force coefficients (CyAC and C wd and Figure 2.6

the longitudinal current force coefficient.s (C,,) for water depth to draught ratios of 1.1 in full load

condition and various current attack angles. Figure 2.7 provides the lateral current force coefficients

(C'A< and CYh.) in the ballast condition with a water depth to draught ratio of 1.5. Coefficients for

the standard ratio of 3.0 are nOI available.