Examination of the intact stability and the seakeeping behaviour

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2 Theory ˆ △R, the added resistance due to waves ˆ v 0 , the ship's mean speed ˆ m ∗ , the ship's mass with a part of hydrodynamic mass 2.1.3 Conclusion The described method has been evaluated and approved in the scope of various research projects at the TUHH including extensive model test at the HSVA. In addition the accident examination reports [1][2][3] prove, that it was possible to anticipate exactly the seakeeping behavior of the vessels in the respective accident situations. Due to the application of Grim's [10] equivalent wave, the method computes reasonably fast. Therefore it is possible to obtain realistic results for the seakeeping behavior of ships in various seaways within short calculation time. For the same reasons, the method has the named limitations of simulating the seakeeping behavior in beam seas and of describing the broaching in following seas. Considering these limitations, it is a very suitable method to calculate head and following seas. 2.2 Environmental conditions The seakeeping method of E4 is able to simulate various types of seaways with or without wind. 2.2.1 Sea condition The most elementary seaway, which may be generated, is a seaway of regular waves. The waves in this seaway have just one direction and a constant wave period. Such seaways do not exist in nature and can only be generated in a model tank. Natural seaways are usually represented by superposed regular waves of dierent frequencies and encounter directions. A frequency distribution appearing in nature is respected by applying a wind sea spectrum like the Pierson- Moskowitz 1 or the Jonswap 2 spectrum. These spectra are based on extensive measurements of real seaways. The encounter directions are calculated randomly according to a manually chosen number of directions. This leads to a more realistic, random seaway with either short-crested or long-crested waves, depending on a small or large number of encounter directions. Another problem may be, that real seaways mostly consist of a wind sea part, generated by the actual wind and a swell part, remaining from former wind conditions. Hence for examinations in seaways containing a high swell part, it may be reasonable to generate a seaway based on a so called multi-peak spectrum. Such a spectrum has two peaks in the frequency distribution. One wide-band peak for the wind sea part and one narrow-band peak for the swell part of the seaway. But the following calculations are based on heavy seaways, where the wind sea part is essential. Therefore it is decided to use a Jonswap-spectrum in combination with short-crested waves. With a given signicant wave height H 1/3 and a signicant wave period T s a seaway is generated, which is considered being matching best a natural wind sea seaway. The wave height H 1/3 is the average wave height (trough to crest) of the one-third largest waves, while the signicant wave period T s is the associated average wave period of the one-third largest waves. A typical Jonswap spectrum for a constant signicant wave height of H 1/3 = 7.5 m and a constant peak 1 A spectral form for fully developed wind seas proposed by Pierson and Moskowitz (1964) 2 A corrected Pierson Moskowitz spectrum with data from the JOint North Sea WAve Project by Hasselmann et al. (1973) 10
2.2 Environmental conditions period of T p = 11 s is shown in gure 2.3, where the energy density spectrum S (ω) is shown against the wave circular frequency ω. Figure 2.3: Jonswap spectrum for H 1/3 = 7, 5 m and T p = 11 s 2.2.2 Wind condition It is possible to consider the inuence of incoming wind on the seakeeping behavior. The governing factor for the wind induced rolling moments is the size of the lateral areas facing the wind. The lateral area of a container vessel in the ballast arrival loading condition is relatively small, because no containers are stowed on deck. The wave induced rolling moments are signicant compared to the wind induced moments and the wind inuence can be neglected. Therefore it is decided to determine the seakeeping behavior without wind in the scope of the thesis. 11
Page 1: Dezember 2010 SCHRIFTENREIHE SCHIFF
Page 5: 1st Examiner: Prof. Dr.-Ing. Stefan
Page 9 and 10: Contents List of Figures List of Ta
Page 11 and 12: Contents A.14 Vessel No. 14 . . . .
Page 13 and 14: List of Figures 2.1 Calculation mod
Page 15 and 16: List of Tables 3.1 Accident situati
Page 17 and 18: Nomenclature Symbol Unit Meaning A
Page 19 and 20: 1 Introduction In the years 2008/20
Page 21 and 22: 1.2 Following objectives for the di
Page 23 and 24: 2 Theory 2.1 Description of the uti
Page 25 and 26: 2.1 Description of the utilised sea
Page 27: 2.1 Description of the utilised sea
Page 31 and 32: 3 Data input The thesis is written
Page 33 and 34: 3.6 Free surface correction 3.6 Fre
Page 35 and 36: 3.10 Bridge height 3.10 Bridge heig
Page 37 and 38: 4 Examination For each vessel the s
Page 39 and 40: 4.2 Vessel No. 02 4.2 Vessel No. 02
Page 41 and 42: 4.3 Vessel No. 03 ˆ The documented
Page 43 and 44: 4.5 Vessel No. 05 accident situatio
Page 45 and 46: 4.6 Vessel No. 06 4.6 Vessel No. 06
Page 47 and 48: 4.7 Vessel No. 07 ˆ The stability
Page 49 and 50: 4.9 Vessel No. 09 Figure 4.16: Tran
Page 51 and 52: 4.10 Vessel No. 10 4.10 Vessel No.
Page 53 and 54: 4.11 Vessel No. 11 ˆ The limiting
Page 55 and 56: 4.13 Vessel No. 13 Figure 4.24: Tra
Page 61 and 62: 5 Evaluation Based on the determina
Page 63 and 64: 5.3 Recommendations accelerations s
Page 65 and 66: 6 Detailed examination The evaluati
Page 67 and 68: 6.1 Variation of the GM values acce
Page 69 and 70: 6.2 Rolling behavior of the large v
Page 75 and 76: 7 Conclusions Summing up the result
Page 77 and 78: A Vessel data A.1 Vessel No. 01 Tab
Page 79 and 80:
A.3 Vessel No. 03 A.3 Vessel No. 03
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
A.11 Vessel No. 11 A.11 Vessel No.
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
B Variation of the bilge keel area
Page 95 and 96:
C Variation of the ship's speed 16
Page 97:
Bibliography [1] BSU; Federal Burea
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Examination of the intact stability and the seakeeping behaviour

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