Offshore and Polar Engineering Conference

3rd Numerical Wave Tank Workshop

Benchmark Test of Diffraction Problem

1. Introduction of NWT Workshop and benchmark test

The Numerical Wave Tank (NWT) group of the International Society of Offshore and Polar Engineers was established at the 5th ISOPE conference in The Hague (1995). This grope is open freely to everybody interested in this topic.

At the 7th conference in Honolulu (1997), it was decided by the member of the group to begin series of informal workshop meeting where computational benchmark cases are defined and their results discussed and commented in a special session during the forthcoming ISOPE conference. A free access data banks are created and enriched with the numerical results of the participants; these data banks are accessible freely and permanently in an web and ftp site via Internet. Then everybody will be able to get data files and to perform his own analysis and comparison with any other participant. The files contain not only numerical results, but also a short text section where the numerical technique is summarized and related bibliographic references are given.

The 1st NWT Workshop was held in ISOPE-98 Montreal Conference.

The 2nd NWT Workshop was held in ISOPE-99 Brest Conference.

The 3rd NWT Workshop was held in ISOPE-2000 Seattle Conference.

The 3rd benchmark results were presented by Katsuji Tanizawa, then openly discussed by all the present participants (contributing or not). (Minutes is here.)

In this web pages, the presented results at the 3rd NWT Workshop session are summarized. You can also access our data bank in this web site.

2. Topic of benchmark test for 3rd NWT Workshop

Wave diffraction by a fixed Lewis form body

Description of benchmark test

• Depth of the body : d = B / 2
• Depth of wave tank : h = 1.25 B
• Lewis form parameter : Ho = 1.0, s = 1.0
• Motion of piston wave maker : Y = A sinwt
• Wave frequencies w and corresponding wave length l

• Amplitude of wave maker : A/B = 0.01875, 0.03125, 0.04375
• Length of effective wave tank between left and right open ends : L ｳ 4l

  For the detail of the 2nd benchmark test, please refer the announcement of 3rd NWT Workshop.　

3. Introduction of contributors and their simulation methods.

Contributor	Simulation Method	Symbol
Hajime Kihara	BEM Fully Nonlinear	BEM-A
Katsuji Tanizawa	BEM Fully Nonlinear	BEM-B
Katsuji Tanizawa	Experiment	Exp.

Submitted test cases by these contributors

4. Simulated free-surface profiles

BEM-A

BEM-B

5. Simulated time histories of hydrodynamic force act on the body

BEM-A

BEM-B

6. Result of Fourier analysis

Hydrodynamic Forces	Sway	Heave	Roll
1st order force
2nd order force
2nd order force (constant)
3rd order force

Wave Ref. & Trans. Coef.

7. Data files of the 3rd NWT Workshop

Zip files

BEM-A 1692MB

BEM-B 2558KB

StuffIt files

BEM-A 1311KB

BEM-B 2013KB

( Data format of these files are prescribed in the announcement of 3nd NWT Workshop. )

　

Data files of the 1st NWT Workshop are available at the ftp site.

ftp://ftp.ec-nantes.fr/NWT/1998/

Data files of the 2nd NWT Workshop are here.

　

The web pages are currently maintained by K.Tanizawa,

Ship Research Institute, 6-38-1, Shinkawa, Mitaka, Tokyo, Japan

E-mail : tanizawa@nmri.go.jp

URL : http://www.nmri.go.jp/safe/skrg/skrg-E.html