My seakeeping
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UTMUTMUNIVERSITI TEKNOLOGI MALAYSIA
SML 5922 MARINE TECH LAB IISML 5922 MARINE TECH LAB II
SELF PROPULSIONSELF PROPULSION TESTTEST
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� Mohd Rahim Amran
� Mohd Asrol Abu Bakar
� Mohd Amirul Affendy Ahmad� Mohd Firdaus Rusli
� Mohd Aiful Amir Awang Noh
� Mohd Izdihar Saleh
� Mohd Hisyamudin Hamid
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To obtain heave, pitch and roll Response Amplitude
Operator (RAO).
To obtain significant acceleration at forward
perpendicular in sea state 5
Theoretical study of seakeeping to understanding of
Simple Harmonic Motion. Familiarize with techniques that can predict natural
periods of ship motions.
SEAKEEPING TEST
Objective
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SEAKEEPING TEST
The seakeeping experiment done to obtain the motion
characteristic of ship. The excessive motion which are
undesirable since they may impair discomfort to the
crew and passengers.
The significant acceleration at forward speed isimportant for some ship such as warship because
they want to put the missile onboard.
Background
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Towing tank and Carriage
I
Apparatus
Function
To run model at
required speed.
Hold instrumentation
equipment.
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SEAKEEPI EST
Wave generator
Apparatus
Function
To generate wave at
required wavelength
and wave height.
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SEAKEEPI TEST
Wave probe
Apparatus
Function
To measure the
wavelength and wave
height at location in
front of model.
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SEAKEEPI TEST
Resistance dynamometer and potentiometer
Apparatus
Function
To measure the
pitching angle of
model.
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SEAKEEPI TEST
Accelerometer
Apparatus
Function
To measure the
vertical acceleration of
model at forward and
aft.
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SEAKEEPI TEST
Dewetron data processing system
Apparatus
Function
To collect output data
from transducers and
process it into
required output
measurement in
computer screen using Dewisoft.
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SEAKEEPING TEST
Theory
1.Surge
2.Sway
3.Heave
4.Roll
5.Pitch
6.Yaw
- Only heaving rolling and pitching are pure oscillatory motions.
- For surging, swaying and yawing, the ship does not return to its
original equilibrium.
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TheoryEquation of motion
SEAKEEPING TEST
InertialForce
Dampingforce
Restoringforce
Excitingforce
m = mass of the shipaz = added mass (Have no physical meaning but represents additional
inertia force due to body oscillating in a fluid)b = damping force coefficient c = restoring force coefficient Fo= Amplitude of wave force (exciting force)we= Encounter Frequency, (Where w = we for stationary bodies)
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3 TYPE OF OSCILLATORY MOTION
1. Free, Undamped Heaving Motion
When Fo = 0, b = 0
2 2
1 z 2 z
1 2
1 2
( + a ) + cz = 0
and,z = A = sin t + A cos t
where,
A = A
= tan A
z m z
A
A
[ [
F
&&
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3 TYPE OF OSCILLATORY MOTION
2. Free Damped Heaving Motion
Where, F = 0( ) 0z m a z bz cz @ !&& &
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3 TYPE OF OSCILLATORY MOTION
3. Force Heaving Motion
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SEAKEEPING TEST
Heaving Motion Happen when a ship moving oscillates
vertically upward and downward in seaway
will continue oscillated vertical up and
down until the equilibrium position isreached .
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Pitching Motion Occur when the bow and stem
of ship will moving trimming
oscillates at Y axis.
SEAKEEPING TEST
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SEAKEEPING TEST
The experiment must covers:i. Model run at least 10 times for each speed.
ii. Covering wavelength from 0.5LBP 2.0LBP
iii. Wave height / wavelength ratio about 1:40iv. Covers sea state 5(wave height 2.5 to 4 m)v. Experiment covers for rolling, pitching, and rolling.
Experiment Protocol
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SEAKEEPING TEST
(m) T (s) H (m)
Wave
Height
(m)
Wave
Amp.
(m)
Heave
(m)
Pitch
(deg) 3/A
wave
slope
(rad) 5/A
0.5 0.0462 0.3163 0.3338
0.6 0.0479 0.5637 0.5167
0.7 0.0510 0.7471 0.7072
0.8 0.0555 0.7225 0.7295
0.9 0.0579 0.7876 0.8407
1.0 0.0588 0.7908 0.8737
0.0628 0.7627 0.8979
0.0679 0.7187 0.8787
0.0727 0.6768 0.8962
0.0784 0.7041 0.8818
0.0901 0.7070 0.8608
Experiment Protocol
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SEAKEEPING TEST
Particulars Unit Ship Model
Length Between Perpendicular, LBP
Breadth, BDepth, D
Draft, T
Displacement (volume)
Displacement (weight)
LCB and LCG
KGTrial Sp d
Block Coefficient, CB
Waterplane Coefficient, Cw
Scal
m
mm
m
m3
tonnes
m
MKnot
-
-
-
138.0
21.812.5
8.7
22171
21635
7 from AP
8.214
2.76
.436.25
.174
.177
.16886
1.4 from AP
.1641. 19(m/s)
.8 6
.9 9
1:5
Preparation
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SEAKEEPING TEST
Preparation1. Calculate the total amount of the ballast to be loaded
for the various conditions to be tested.
2. Release the oscillation table of the apparatus for themeasuring ship model inertia moment .3. Adjusted the level of the oscillation table to the
required height .4. Measure height of a specific point at one end of the
model above a certain reference (e.g floor).5. Push one side of the empty oscillation table down and
release it to let it oscillate freely
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SEAKEEPING TEST
6. Determine the time for one complete oscillation(natural oscillation period).
7. Calculate the natural oscillation time.8. Position the model on the table & ballast 9. Determine the time for one complete oscillation by
measuring the lime passing for 10 oscillations dividedby 10.
10. Check whether the oscillation time agrees with thecalculated oscillation time
11. Remove the model and fixate the ballast weights. Themodel is now as far as its mass distribution inconcerned ready for the testing in the basin.
Preparation
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Attached model to the towing carriage by air struck at LCG
of the model.
When the model is well balanced, it is put on the carriage
The model will towed by towing carriage
The vertical motion will measure by potentiometer
The data is then being analysis and plotted by theprogram in the carriage
SEAKEEPING TEST
Experiment Setup