1st Workshop of ISOPE Numerical Wave Tank group

The 8th Annual ISOPE Conference: May 24-29 1998, Montréal, Canada

First NWT Benchmark series : Numerical Wave Absorption

The Numerical Wave Tank Group (NWTG) of the International Society for Offshore and Polar Engineering was initiated by Prof. C.H. Kim (Texas A&M Univ. USA) at the 5th ISOPE conference in The Hague (1995). This group is informal and is open freely to everybody interested in this topic. The aim of the group is to promote the concept of Numerical Wave Tank, and to exchange related experiences and data among participants freely from any competition and mercantile spirit. The final goal of these computer codes is to simulate physical wave basins as closely as possible.

At the 7th Conference in Honolulu (1997), it was decided by the members of the group to begin a series of informal workshop meetings where computational benchmark cases will be defined and their results discussed and commented in a yearly special session during forthcoming ISOPE conferences. A free access data bank has been created after this first benchmark series and will be enriched with the numerical results of the participants; this data bank is accessible freely and permanently by anonymous ftp connection at (ftp://ftp.ec-nantes.fr/NWT/1998). These data will soon be mirrored on the present ISOPE web site also.

The topic of the first workshop was : numerical absorption of outgoing waves in numerical wave tanks. Four 2D and two 3D test cases were proposed. In these numerical time-domain simulations, one or several boundaries of the computational domain should behave as if they were transparent to the water waves generated in the domain and propagating outwards, in order to avoid wave reflection from these closing boundaries as perfectly as possible.

Five researchers from Denmark, France, Japan and USA contributed to these benchmark test cases. Potential and viscous flows approaches were represented. The absorption methods were: numerical beach, active piston absorber, mesh stretching. Unfortunately, no contribution based on Orlanski’s method was proposed. The results were analysed by the NWT leader and presented to the forty participants to the NWT workshop session of the ISOPE98 Conference in Montréal. A printed report of this workshop is included in the proceeding of the forthcoming (ISOPE99-Brest) Conference.

After an open discussion of this topic by the participants, several subjects were proposed for the 1999 Benchmark series. My successor, Dr. K. Tanizawa, elected during this 1998 Workshop session, finally chose to investigate radiation forces as the next benchmark topic. I would like to thank all the former, present and future participants to the Numerical Wave Tank group for their active participation and their contributions. I wish this group will grow and prosper in the same open spirit, and all the best to my successor(s) at the head of the group.

Dr. Alain H. CLEMENT, the leader of ISOPE Numerical Wave Tank Group (1996-1998)

Laboratoire de Mécanique des Fluides Division Hydrodynamique Navale ECN, 1 Rue de la Noe 44300 Nantes, FRANCE

tel: (33) 240 37 25 26; fax: (33) 240 37 25 23

http://www.ec-nantes.fr/DHN/ E-mail: Alain.Clement@ec-nantes.fr