DISCUSSION

by Dr. J.Ando and Dr. K.Nakatake

Kyushu Univ., Japan.

We would like to congratulate the authors for developing SSTH by concerted applications of several numerical techniques. We are interested in the flow field in the stern region where the propeller is operating. According to our experience, the free surface effect on the stern flow becomes large at high speeds. A comparison between Fig. 18 with Fig. 16 in your paper indicates the strong effect of the free surface on the vorticity field. You showed the calculated flow field near the stern region without free surface. If the free surface is considered, however, we believe that the flow field will be fairly different. Would you comment on this point?

Author's Reply

As the discussors suggest, the interaction of the free-surface with the viscous motion is most important at the stern. This is especially true for high-speed vessels and has been one of the major objectives of the researches at the author's laboratory. However, we have not yet reached the satisfactory results due partly to the nonlinearity of the free-surface motion and partly to the inadequacy of the turbulence modelling.

DISCUSSION

by Dr. Raven

MARIN

According to your presentation, you used two (2) criteria to select the best hull form from the wave-resistance point of view:

  • the peak wave heights in between the demi-hulls;

  • the integrated wave energy in the entire domain.

The former is not necessarily related to the wave resistance. Could you clarify the second criterion?

Is this a wave pattern analysis approach, or anything else representative of radiated wave energy?

Author's Reply

One of the shortcomings of such CFD simulation of waves in a restricted region is that the dispersive spread of wave system is not well realized. Therefore, the estimation of the relative magnitude of wave resistance must be made by either integration of wave energy in the computational domain or integration of the surface pressure distribution. For local modification of the hull form the use of the former is useful and the letter for other cases if pressure integration is carefully performed.

DISCUSSION

by Dr. Marshall P.Tulin

Ocean Engineering Laboratory, UCSB

The authors do not provide section plans for the hulls, which are the subject of the paper. It is therefore difficult to analyze their results. Could they provide a sketch showing section plans?

Author's Reply

The purpose of our paper is to demonstrate the extent the CFD techniques can be applied to very practical problems. Unfortunately we cannot show details of the lines, because it is really practical.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement