Skin-friction prediction

[Leo Lazauskas]

Here's something from the July 2007 newletter of the ITTC that might be of interest to those who write resistance prediction software...

Specialist Committee on Powering Performance Prediction

The committee has continued the work on scale effect of form factor, using results of several geosim model series. The work has been extended to look at the effect of choice of friction line on the form factor scale effect.

It turns out that using Grigson’s friction line rather than ITTC’57 correlation line when using Prohaska’s method to determine the form factors gives significantly less scale effect on the form factor. Although it is a bit early to draw final conclusions, this indicates that the slope of Grigson’s friction line is more suitable for a three-dimensional extrapolation line than ITTC’57, something that might have been expected, since ITTC’57 correlation line was
originally designed for two-dimensional extrapolation.

To broaden the base for making firm conclusions and to extend the geosim test series to full ship forms, the committee is trying to make a new geosim test series based on the KRISO tanker previously used for the Gothenburg 2000 workshop on ship CFD.

The full text can be found at:
http://ittc.sname.org/ITTC-News%2056.pdf

Regards,
Leo.