ERDC/CHL CHETN-IX-14
March 2004
In general, the measured squat in the Charleston Harbor study was consistent with PIANC (1997)
empirical predictions. The Golden Farmer had the largest block coefficient (Cb = 0.78) and exhibited
greater squat at the bow, in agreement with PIANC. Greater squat was observed in the stern for nine
out of the other 10 ships in the study, also in agreement with PIANC for ships with smaller Cb
values. The only measured squat inconsistent with the PIANC findings was for the MSC Sabrina.
Although it was a container ship with low Cb, it had greater squat at the bow.
Comparisons between the observed and predicted squat values were varied. The Barrass and Huuska
equations overestimated measured squat, but this is good since the predictions are conservative. The
Romisch equations for bow and stern squat provided good estimates of the observed squat, with the
Romisch stern providing the best predictions of all four predictor equations. This finding is
consistent with PIANC (1997). The success of the Romisch equations may be due in part to Romisch
being the only one of the three equations directly including the depth/draft (h/T) ratio in the
prediction equation. This is probably an important parameter in the unrestricted shallow-water sites
used in the Charleston Harbor analysis.
POINTS OF CONTACT: For additional information, contact Dr. Michael J. Briggs (Voice: (601)
634-2005, e-mail: ) or Dr. Stephen T. Maynord (Voice: (601)
634-3284, e-mail: ).
REFERENCES
Barrass, C. B. (1979). "A unified approach to squat calculations for ships," PIANC Bulletin , 3-10.
__________. (1981). "Ship squat- a reply," The Naval Architect,268-272.
Eryuzlu, N. E., Cao, Y. L., and D'Agnolo, F. (1994). "Underkeel requirements for large vessels in shallow vessels in
shallow waterways," 28th International Navigation Congress, PIANC, Paper S II-2, Sevilla 1994, 17-25.
Guliev, U. M. (1971). "On squat calculations for vessels going in shallow water and through channels," PIANC Bulletin
1(7), 17-20.
Huuska, O. (1976). "On the evaluation of underkeel clearances in Finnish Waterways," Helsinki University of
Technology, Ship Hydrodynamics Laboratory, Otaniemi, Report No. 9.
ICORELS (International Commission for the Reception of Large Ships). (1980). "Report of working group IV," PIANC
Bulletin 35, Supplement.
Permanent International Association of Navigation Congresses (PIANC). (1997). "Approach channels, a guide for
design," Supplement to Bulletin No. 95, Brussels, Belgium.
Romisch, K. (1989). "Empfehlungen zur Bemessung von Hafeneinfahrten," Wasserbauliche Mitteilungen der
Technischen Universitat Dresden, Heft 1, 39-63.
NOTE: The contents of this technical note are not to be used for advertising, publication,
or promotional purposes. Citation of trade names does not constitute an official endorsement
or approval of the use of such products.
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