Offshore and Polar Engineering Conference

2nd Numerical Wave Tank Workshop

Benchmark Test of Radiation 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 first special NWT Workshop session was held in ISOPE-98 Montreal Conference and the second NWT Workshop session was held in ISOPE-99 Brest Conference. The second benchmark results were presented by the NWT grope leader (currently Katsuji Tanizawa) at the NWT workshop, then openly discussed by all the present participants (contributing or not). (Minutes is here.)

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

2. Topic of benchmark test for 2nd NWT Workshop

Wave radiation by sinusoidal heave motion of a wedge

Description of benchmark test

• Ratio between half breadth and depth of the wedge : a/d=0.4
• Depth of wave tank : h=3d
• Heave motion of the wedge : Y = A sinwt
• Heave frequencies w, periods T and corresponding wave length l

• Heave amplitude : A/a = 0.2,0.4,0.6
• Left end (x=0) is the axis of symmetry
• Right end (x=L) is supposed to be open
• Length of wave tank : L ｳ 4l

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

3. Introduction of contributors and their simulation methods.

Contributor	Simulation Method	Symbol
Katsuji Tanizawa	BEM Fully Nonlinear	BEM-A
Masashi Kashiwagi	BEM Fully Nonlinear	BEM-B
Hajime Kihara	BEM Fully Nonlinear	BEM-C
Alain Clement	BEM Fully Nonlinear	BEM-D
Christoophe Maisondieu	BEM 2nd order	BEM-E
R. Otto & J.H. Westhuis	FEM Fully Nonlinear	FEM
Nobuyuki Hirata	FVM Fully Nonlinear	FVM

Submitted test cases by these contributors

4. Simulated radiation wave by heave motion of the wedge

BEM-A

BEM-B

BEM-C

BEM-D

BEM-E

FEM

FVM

　

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

w2 a / g	0.2	0.4	0.6	0.8	1.0	1.2
A / a = 0.2	Case 1	Case10	Case 2	Case11	Case 3	Case12
A / a = 0.4	Case 4	Case13	Case 5	Case14	Case 6	Case15
A / a = 0.6	Case 7	Case16	Case 8	Case17	Case 9	Case18

6. Result of Fourier analysis

Added mass

A / a

0.2

0.4

0.6

Damping coefficient

A / a

0.2

0.4

0.6

Second order hydrodynamic force

A / a

0.2

0.4

0.6

Second order hydrodynamic force (Constant component)

A / a

0.2

0.4

0.6

Third order hydrodynamic force

A / a

0.2

0.4

0.6

7. Data files of the 2nd NWT Workshop

Zip files

BEM-A 1578MB

BEM-B 84KB

BEM-C 864KB

BEM-D 1168KB

BEM-E 4759KB

FEM 1749MB

FVM 296KB

StuffIt files

BEM-A 1635KB

BEM-B 92KB

BEM-C 892KB

BEM-D 1207KB

BEM-E 4973KB

FEM 1795KB

FVM 308KB

( Data format of these files are prescribed in the announcement of 2nd NWT Workshop. )

　

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

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

8. Next benchmark test for 3rd NWT Workshop at ISOPE-2000

Wave diffraction problem with wave maker & absorber

Down load the announcement of 3rd NWT Workshop.

benchmark2000.ps (PS file)

benchmark2000.pdf (PDF file)

benchmark2000.doc (Word file)

　

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