Seakeeping Test Lab Report

TABLE OF CONTENTSContentsPages1. Table of Contents...12. Spar Platform..23. Introduction. 54. Objectives65. Equipment76. Design..77. Procedure88. Result and Discussion...99. Conclusion..2710. Appendix28

SPAR PLATFORMAs the research for oil and other natural resources have progressed into deeper waters, the traditional fixed type of offshore structures have become unsuitable and new technologies had to be resorted to. Spar is a type of deepwater floating type of platform used in ultra deepwaters of depth more than 1500 m.The spar platform has been modeled as a rigid body connected to the sea floor by multi-component catenary mooring lines. Unidirectional regular wave and random wave model spectra are used for computing the incident wave kinematics The response analysis has been performed in time domain to solve the dynamic behavior of the moored spar platform as an integrated system.

A spar, named for logs used as buoys in shipping and moored in place vertically, is a type of floating oil platform typically used in very deep waters. Spar production platforms have been developed as an alternative to conventional platforms.A spar platform consists of a large-diameter, single vertical cylinder supporting a deck. The cylinder is weighted at the bottom by a chamber filled with a material that is denser than water to lower the center of gravity of the platform and provide stability. Spars are anchored to the seabed by way of a spread mooring system with either a chain-wire-chain or chain-polyester-chain composition.There are three primary types of spars; the classic spar, truss spar, and cell spar. The classic spar consists of the cylindrical hull noted above, with the heavy ballast at the bottom of the cylinder.A truss spar has a shorter cylindrical "hard tank" than a classic spar and has a truss structure connected to the bottom of hard tank. At the bottom of the truss structure, there is a relatively small, square shaped "soft tank" that houses the heavy ballasting material. The majority of spars are of this type. A cell spar has a large central cylinder surrounded by smaller cylinders of alternating lengths. At the bottom of the longer cylinders is the soft tank housing the heavy ballasting material, similar to a truss spar. There is currently only one cell spar in operation

Characteristics Applicable in 1,500 ft. to 10,000 ft. water depths Cost relatively insensitive to water depth, most competitive in very deep water Hull cost is relatively insensitive to deck payload Platform motions are mostly lateral (minimal heave) Uses standard shipyard and offshore deck construction Hull is initially transported by towing in a horizontal, self-floating position Wells can be pre-drilled or drilled from the platform Production risers are steel pipe with surface trees Hull can be configured for significant liquids storage if this is advantageous Particularly applicable in remote locations which lack infrastructure Economical to relocate to other sites, in both deeper and shallower water.

Type of Spar Platform based on depth:

INTRODUCTIONA Seakeeping Test on a spar platform will be carried out in Universiti Teknolgi Petronas Wave Tank. The general purpose of this test and lab activities is to present the procedures and result of the seakeeping test using the spar platform model. The test will be carried out in test condition as shown in table 1 below:Table 1:Seakeeping test ConditionTest NoWave Characteristics

Lw/LMLw (m)Hw (m)TW (s) (rad/s)

Semisubmersible at trimmed condition at static condition (V=0 m/s)10.50.50.0310.56611.104

20.60.60.0380.62010.136

30.70.70.0440.6709.384

40.80.80.0500.7168.778

5110.0630.8007.851

61.11.10.0690.8397.486

71.21.20.0750.8777.167

81.31.30.0810.9136.886

91.41.40.0880.9476.636

101.51.50.0940.9806.411

In accordance, this report contains a brief explanation about the theory for seakeeping, equipment used for the test, procedures on carry out the seakeeping test, data analysis in order to get the result, result of the test, observation during test is carried out, discussion on the result, conclusion for the test and the references.

OBJECTIVE To show the procedure on conducting a regular wave seakeeping tests for a spar platform To present the result of RAO (response amplitude operator) value at versus the wave frequency. To present the result of the RAO for the spar platform for head seas for both heaving and pitching motions.

EQUIPMENT:Equipments used in this test are:1. Spar model2. Wave tank3. Data Acquisition and Analysis System (DAAS)4. Potentiometer5. Wave Generator System

DESIGN OF SPAR MODEL:

PROCEDURE:1. The model was ballasted until reaches its design waterline (models displacement).2. The centre of gravity of model is the being determined by using swing frame.3. Check the heeling of the model by placing the model into basin. If there was heeling, the weights were then moved sideways(port or starboard) until the model at even keel.4. The model was then attached to wire for restraining purpose.5. After the wave generator system created the wave, the vertical motion will measure by potentiometer inside the model. The potentiometer is connected to the DAAS and the signals are simultaneously digitize and record on paper chart or computer.6. The data is then being analysis and plotted by the program in the acquisition system.7. Step 5 to 7 was repeated for other nine tests running with different wave characteristics as in table 1.

RESULTS:1. Obtained the results from D.A.A.S.2. For example for test no 10, Hw = 0.094m, plot the graph of heave (Za), pitch a and wave height Hw in time domain were plotted. Plot for every test.

Heave at all run:Test 1:

Test 2:

Test 3:

Test 4:

Test 5:

Test 6:

Test 7:

Test 8:

Test 9:

Test 10:

Pitching at all run

Test 1:

Test 2:

Test 3:

Test 4:

Test 5:

Test 6:

Test 7:

Test 8:

Test 9:

Test 10:

Wave heights at all run Test 1

Test 2

Test 3

Test 4

Test 5

Test 6

Test 7

Test 8

Test 9

Test 10

3. Heave, pitch and roll value need to be consider is the average value (or mean)

Average value (mean) 4. The value for wave height, Hw, and wave period, Tw , will follow the same step as in step number 3. Therefore, fill in the table 3 given below.Table 3:CalculationAverage Value

Heave vs TimeZa 0.000380.000550.000390.001060.003460.003080.002380.000940.001770.00095

Pitch vs Timea 0.415660.498130.486820.662480.522730.563100.481030.502690.558830.65602

HW vs TimeHW 0.138360.1833050.086940.385900.364370.249370.582610.425750.232510.22857

5. Repeat step 1-4 for every test (Lw/LM) and fill in the table 4 given belowLw/LmLwWave period,TwEncountering FrequencyeWave HeightHwWave amplitudeWave slopeAverage Pitch AmplitudeAverage Heave AmplitudePitch RAOHeave RAO

0.50.1650.56611.1040.0250.01250.4760.415660.000380.873230.000798

0.60.3350.62010.1360.0350.01750.3280.498130.000551.518680.001676

0.70.3550.6709.3840.0450.02250.3980.486820.000391.223160.000979

0.80.4030.7168.7780.0490.02450.3820.662480.001061.734240.002774

10.470.8007.8510.0550.02750.3680.522730.003461.420460.009402

1.10.4950.8397.4860.0600.030.3810.563100.003081.477950.008083

1.20.5620.8777.1670.0680.0340.3800.481030.002381.265860.006263

1.30.690.9136.8860.0850.04250.3870.502690.000941.298940.002428

1.40.780.9476.6360.0870.04350.3500.558830.001771.596650.005057

1.50.880.9806.4110.0880.0440.3140.656020.000952.089230.003025

6. Plot the graph of Heave RAO against encountering frequency

7. Plot the graph of Heave RAO against Lw/Lm

8. Plot the graph of Pitch RAO against encountering frequency.

9. Plot the graph of Pitch RAO against Lw/Lm

10. Discuss the results.

The results of The Pitch RAO and Heave RAO are the average of Heave or Pitch divide by wave slope. Graphs above represent Heave RAO and Pitch RAO against Encountering Frequency and Lw/Lm. From the test run, it can be seen that the graph not drawn as been expected. The reason of this matter may be happen due to some errors which happen during the test run.

11. It is given that :

, where A = 0.0081.g2 and B = 0.74(g/V)4;Wave Frequency, A/5B/4S()

11.1044.61770056963144E-062.51504709471954E-064.61771E-06

10.1367.28601438355825E-063.62240935416009E-067.28604E-06

9.3840.00001071230768166334.93073812806316E-061.07124E-05

8.7780.00001495702264203850.00000643993713810381.49571E-05

7.8510.00002613353424838040.00001006384697951492.61338E-05

7.4860.00003315690002104660.00001217487870194593.31573E-05

7.1670.00004122265990086970.00001449153253748444.12233E-05

6.8860.00005034866292661990.00001700575275734295.03495E-05

6.6360.00006057468255581750.00001971689050927656.05759E-05

6.4110.00007197706760450870.00002263397472699287.19787E-05

12. Plot the wave spectrum and motion response for heaving, and pitching.

Heave RAO vs Wave Spectrum

Pitch RAO vs Wave Spectrum

CONCLUSION:1. What can you conclude from this experimental calculation?As the conclusion, the wave height and wave amplitude affects the heaving and pitching of the spar. Besides, the spar is in stable condition in the experiment. For the present analysis, peak to peak method is used. In this method, the peak and trough values are searched and analyzed to get the amplitude and frequency of a measured signal. Using peak-to-peak method, the wave amplitude, heave and pitch amplitudes and wave encounter frequency and period can be obtained2. What is the physical relationship between wave length and wave frequency to the heave and pitch response of the spar?

From the result, the effects of wave frequencies to heave pitch and roll is response to the spar. So, the higher the wave frequencies, the higher the effect on the heaving and pitching response occurs. When we are properly scaled the vessel, constructed, balanced, instrumented, and tested, physical models can be used to predict ship response from monochromatic waves. Monochromatic waves are series of waves generated in a laboratory, each of which has the same length and period. The movement of the spar under the static water surface may caused by waves that will affect its motion. It will respond to waves by the vertical motions of pitch, heave, and roll in the wave tank.

3. Discuss any error you observed during the experiment or the experiment data itself.The measurement of the wave height is measured by manual which using the ruler and marking point may not precise and accurate. As the observation is conducted by human, the value may have parallex error and error by human. Besides,The potentiometers used for the measurement of heave and pitch amplitudes are zero-order instruments in which there are no errors in the output due to the dynamic response. However, the characteristic of the servo needle type wave probe(in the potentiometer) is not clearly known. This error is considered to be asymmetric error because the measured values of wave amplitudes are alwayssmaller than the true values.

4. Using graphical integration, find the average of the one-third highest wave amplitude and the one-third highest, and one-tenth of heave and pitch amplitude in Pierson-Moskowitz spectrum.Heaving:Wave Frequency, WS (w)S (we)Heave RAORAO^2 HeaveSz (we)SMf (Sz)

11.1044.62E-064.62E-060.0007986.36804E-072.94058E-1212.94058E-12

10.1367.29E-067.29E-060.0016762.80898E-062.04663E-1136.13989E-11

9.3841.07E-051.07E-050.0009799.58441E-071.02672E-1133.08016E-11

8.7781.50E-051.50E-050.0027747.69508E-061.15096E-1022.30192E-10

7.8512.61E-052.61E-050.0094028.83976E-052.31017E-0936.9305E-09

7.4863.32E-053.32E-050.0080836.53349E-052.16633E-0936.49899E-09

7.1674.12E-054.12E-050.0062633.92252E-051.61699E-0923.23398E-09

6.8865.03E-055.03E-050.0024285.89518E-062.9682E-1038.90459E-10

6.6366.06E-056.06E-050.0050572.55732E-051.54912E-0934.64737E-09

6.4117.20E-057.20E-050.0030259.15063E-066.5865E-1016.5865E-10

f(Sz)2.31853E-08

mo=x C.I. x f(Sz)

= x 0.52 x (2.31852 x 10-8)

=4.52114 x 10-9

=4.00

=2.00

=2.00(4.52114 x 10-9)=1.34478 x 10-4 mPitching:

Wave Frequency, WS (w)S (we)Pitch RAOPitch RAO^2 S (we)SMf (S)

11.1044.62E-064.62E-060.873230.7625313.52115E-0613.52115E-06

10.1367.29E-067.29E-061.518682.3063891.68044E-0535.04133E-05

9.3841.07E-051.07E-051.223161.496121.6027E-0534.80811E-05

8.7781.50E-051.50E-051.734243.0075884.49848E-0528.99696E-05

7.8512.61E-052.61E-051.420462.0177075.27303E-0530.000158191

7.4863.32E-053.32E-051.477952.1843367.24267E-0530.00021728

7.1674.12E-054.12E-051.265861.6024026.60563E-0520.000132113

6.8865.03E-055.03E-051.298941.6872458.49519E-0530.000254856

6.6366.06E-056.06E-051.596652.5492910.00015442630.000463277

6.4117.20E-057.20E-052.089234.3648820.00031417910.000314179

f(S)0.00173188

mo=x C.I. x f(S)

= x 0.52 x 0.00173188

=3.377166 x 10-4

=4.00

=2.00

=2.00(3.377166 x 10-4)=0.0367 m

5. Is this submersible/spar platform is seaworthy in sea state 7. Please give your comment.

Yes, this spar platform is seaworthy in sea state 7 as the design of the spar platform can provide stability in the deep sea and irregular wave. There are many type of spar platform can withstand with the high wave and current based on the depth of seawater. Since the laboratory experiment is testing the spar model, the result can be obtained as the spar is in stable condition with the wave of different height and amplitude. So, the the actual spar platform is seaworthy in the deep sea state 7.

APPENDIXESOverview of UTP Wave Tank:

Wave Generator at UTP Wave Tank:

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