Bow Thruster Calculation

CALCULATION & SELECTION OF BOW THRUSTER 1. Wind Resistance The wind resistance can be calculated by this following formula: RA : Ka x Aa x Va2 Where:

Ka : Wind's coefficient

=

Aa : Projected area of ship above the waterline Va : Wind's relative speed to the ship movement

= =

So, the result of wind resistance's calculation is: RA : 0,735 x 643,76 x 102 : 68135.5584 N : 68.1355584 kN 2. Frictional Resistance The frictional resistance can be calculated by this following formula: RW : Kw x Aw x (( Vw + Vs )2 + 0,33 x ( Vw + Vs )) Where:

Kw : Coefficient of frictional resistance

=

Aw : Wet Surface Area ( WSA ) Vw : Wave's speed Vs : Ship's speed at operation of bow thruster

= = =

So, the result of frictional resistance's calculation is: RW : 1,212 x 2802,997 x (( 1,03 + 0,514 )2 + 0,33 x ( 1,03 + 0,514 )) : 23752.089796 N : 23.752089796 kN 3. Form Resistance The form resistance can be calculated by this following formula: RV : Kv x As x Vs2 Where:

Kv : Form's Coefficient

=

As : Projected area of ship under the waterline Vs : Ship's speed at operation of bow thruster

= =

So, the result of form resistance's calculation is: RV : 73,2 x 233,153 x 0,514 : 4439.074576 N : 4.439074576 kN 4. Resistance Caused by Equipments The resistance caused by equipments can be calculated by this following formula: RP : Kp x Ds2 x ( Vw + Vs )2 Where:

Kp Ds Vw Vs

: : : :

Coefficient of resistance caused by equipments Tunnel thruster's diameter Wave's speed Ship's speed at operation of bow thruster

= = =

To define the thruster's diameter, have to know the specification of bow thruster. Therefore, calculating the initial power of bow thruster with using the graphic of lateral thruster.

From the graphic above, it can be conclude that: f : 0.078 kN/m2 So, the value of initial power is: Yo : f x Lpp x T : 0,078 x 72 x 4,24 : 23.8 kN Po : Yo / Co : 23,8 / 0,15 : 158.75 kW : 212.88 HP With the requirement specification above, select the bow thruster: Merk : Tunnel Thruster Type : Hydraulic Pod Motor Driven Power : 200 - 250 HP Tunnel Diameter : 36 inch : 914.4 mm : 0.9144 m

So, the value of resistance caused by equipments is: RP : 52.35 N : 0.05235 kN 5. Total Resistance So, the value of total resistance is : RT : RA + RW + RV + RP : 96.38 kN

CALCULATION OF BOW THRUSTER MANOEUVERING 1. Define the Value of Thrust Power ( f ) The value of thrust power ( f ) is can be calculated by following formula: f : Yo / ( Lpp x T ) [N/m2] Where: Yo : Effective force T : Draught of ship Lpp : Length of perpendicular So, the value of thrust power is: f :

= = =

70.2 N/m2

2. Define the Value of Angular Velocity ( ѱ ) The value of angular velocity ( f ) is can be calculated by following formula: ѱ : (k/Lpp) x (f/p)0,5 [o/s] Where:

k : Degree

=

f : Thrust power Lpp : Length of perpendicular p : Density So, the value of angular velocity is: ѱ :

= = =

0.62 o/s

From the calculation above, it means that to make one full rotation (360 o), time's needed is 580,645 seconds or 9,677 minutes.

From the calculation above, it means that to make one full rotation (360 o), time's needed is 580,645 seconds or 9,677 minutes.

CALCULATION OF BOW THRUSTER MANOEUVERING 1. Define the Value of Thrust Power ( f ) The value of thrust power ( f ) is can be calculated by following formula: f : Yo / ( Lpp x T ) [N/m2] Where: Yo : Effective force T : Draught of ship Lpp : Length of perpendicular So, the value of thrust power is: f :

= = =

78 N/m2

2. Define the Value of Angular Velocity ( ѱ ) The value of angular velocity ( f ) is can be calculated by following formula: [o/s] ѱ : (k/Lpp) x (f/p)0,5 Where:

k : Degree

=

f : Thrust power Lpp : Length of perpendicular p : Density So, the value of angular velocity is: ѱ :

= = =

0.78 o/s

From the calculation above, it means that to make one full rotation (360 o), time's needed is 679,2453 seconds or 11,3 minutes.

USTER

0.735 kgm/m4 643.76 m2 12 m/s

1.212 kgm/m4 2802.997 m2 1.03 m/s 0.51 m/s

73.2 kgm/m4 233.153 m2 0.51 m/s

26.4 kgm/m4 1.03 m/s 0.51 m/s

e, calculating the initial power of bow

VERING

23811.84 N 4.24 m 80 m

190 o 70.2 N/m2 80 m 1025 kg/m3

's needed is 580,645 seconds or 9,677

VERING

23811.84 N 4.24 m 72 m

190 o 90 N/m2 72 m 1025 kg/m3

s needed is 679,2453 seconds or 11,32

2.76

643.494