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TECHNISCHE HOGESCHOOL DELFT
AFDELING DER MARITIEME TECHNIEK
LABORATORIUM VOOR SCHEEPSHYDROMECHANICA
ON SWAY DAMPING AND ADDED MASS IN
SHALLOW WATER
W. Beukelman
17th International Towing Tank Conference
Proceedings Volume 2, 8-15 September 1984
Gótenborg, Sweden.
Report No. 603-P
Ship Hydromechanics Laboratory - Delft
Delft University of Technology Ship Hydromechanics Laboratory Mekelweg 2
2628 CD DELFT The Netherlands Phone 015 -786882
17TH INTERNATIONAL
TOWING
CON FERENCE
SSPA
8520 202.01.27PROCEEDINGS
VOLUME 2
8-15 SEPTEMBER 1984
GOTEBORG, SWEDEN
6789O12345C79u
W. BEUKELMAN - Ship Hydromechanics Laboratory, Deift University of Technology, Delft, The Netherlands.
ON SWAY DAMPING AND ADDED MASS IN SHALLOW WATER
I agree with the Recommendation of the Committee to continue the development of theoretical and empirical methods for the determination of hydrodynamic and aerodynamic forces acting on a
ship.
A suggestion would be to add and to stress the importance of the shallow
water case.
Recent work in this field has been carried out by the towing tank of the Delft University of Technology.
Forced oscillation tests with a segmented model have been performed
188 8520c 202.0127 o 0.26 Experiment f A w - 0.50 0 w 0.75 w 0.26 - - - Calculation ( £ u 0.50 w 0.75 + - Static 8 50
Fig. 1 Measured and calculated
distribu-tion of Y" for h/T = 2.4, 1.5
v and 1.15
to obtain added mass and damping distributions in shallow water ranging from 2.4 to 1.15 T. The experiment covered a low frequency range to be of interest for
manoeuvring including static tests.
Fig. 1 shows the distribution of sway damping forces for three
waterdepth ratios. The dynamic test results agree satisfactorily with the static values as well as with the results of a calculation based on a two-dimensional multipole
approxi-Experiment o = 0.26 A w = 0.50 o = 0.75 w 0.26
- - - caicuiationf £ w
0.50 = 0.75Fig. 2 Measured and calculated
distribu-tion of Y for h/T = 2.4, 1.5 V
and 1.15
mation. It should be remarked that no viscosity effects are included in
the calculation. The comparison
indicated a rather important influence of viscosity in the aft part of the
model.
Fig. 2 compares the sway added mass as
found in the experiment with
corres-ponding calculated values.
Except for the smallest waterdepth ratio (1.15) the agreement of the distributions is satisfactory.
In general the agreement is better for larger waterdepth ratios and
higher frequencies of oscillation and further investigations are
required with respect to the
distribution of the damping
coeffi-cient in shallow water.
Reference
[11 Beukelman, W. and Gerritsma, J.,
"The longitudinal distribution of low frequency hydrodynamic deriva-tives for lateral motions in
shallow water",
Ship Hydromechanics Laboratory, Delft University of Technology, Report no. 562 A and no. 603 P,