4-5

current forces and moments on stationary moored vessels in the surge and sway

directions and yaw moment are presented in this section. These planar directions are

of primary importance in many mooring designs.

4-5.1

defined as that component of force perpendicular to the vessel centerline. If a ship has

a large underkeel clearance, then water can freely flow under the keel, as shown in

Figure 4-8(a). If the underkeel clearance is small, as shown in Figure 4-8(b), then the

ship more effectively blocks current flow, and the transverse current force on the ship

increases. These effects are considered and the transverse current force is determined

from the equation:

(10)

EQUATION:

where

= transverse current force (newtons)

ρw

= mass density of water (from Table 4-1)

= current velocity (m/s)

Vc

= vessel waterline length (m)

L wL

= average vessel draft (m)

T

= transverse current force drag coefficient

C yc

θc

= current angle (degrees)

The transverse current force drag coefficient as formulated in *Broadside*

coefficient can be determined from:

82