CressHelp - Jets - Propeller jets - Main propeller

Cress Help - Jets - Propeller jets - Main propeller - A20.2

Pushbarge

Various types of propeller jet are generated by moving ships but for the design of a bank or bottom protection those of a manoeuvring ship are normative. In some cases it is also desirable to know the propeller jet load that occurs in a sailing ship, for example for the design of a bottom protections over which only sailing ships pass and thus no manoeuvring takes place. As an indication here :

equation 1

and

equation 2

in which is:

uhs, b, v: flow velocity along bottom caused by a sailing ship [m/s]
uhs, o, v: flow velocity along the bank caused by a sailing ship [m/s]

equation 3

and

equation 4

in which is:

AM = underwater/wet cross sectional area of ship [m2]

Bs = beam of ship [m]

CF = friction coefficient [-]

Cp = pressure coefficient [-]

Ls = length of ship [m]

S1 = underwater area of ship hull [m2]

Ts = draught of ship [m]

Dh = average lowering of water level [m]

v = dynamic viscosity of water (= 10-6) [m2/s]

rw = density of water [kg/m3]

The following values are taken for Cp :

Cp = 0.1 for push barge convoys in the formations 2x2, 2x1 and 2x3
Cp = 0.3 for push barge convoys in the formations 3x2