16:00
Hydrodynamics in Ocean V
Chair: Bo Wu
16:00
30 mins
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CHALLENGES WITH SHALLOW WATER WAVES FOR SEAKEEPING AND MANOEUVRING TESTS
Manases Tello Ruiz, Marc Vantorre, Thibaut van Zwijnsvoorde, Guillaume Delefortrie
Abstract: The new Energy Efficiency Design Index (EEDI) regulations issued by IMO consider among others ship manoeuvrability in adverse weather conditions. This has boosted research on ship manoeuvring in waves, which is being studied by different consortia in the world, e.g. SHOPERA [1] in Europe.
At the Towing Tank for Manoeuvres in Shallow Water [2] (co-operation Flanders Hydraulics Research – Ghent University) both captive and free running manoeuvring model tests in regular waves have been conducted in shallow water conditions. During the tests, different challenges were experienced, related to the ship motions, the wave behaviour in finite water depths, and the propagation of waves along the tank. In addition, challenges due to interaction between the ship, the waves, and the tank’s sidewalls have also been encountered. In shallow water, such interaction is rather inevitable mainly due to the lower ship speeds attained. For this reason, tests with (regular) waves needed to be optimized according to several criteria. The publication provides an overview of these issues encountered and how these have been coped with in model testing.
REFERENCES
[1] www.shopera.org
[2] Delefortrie, G.; Geerts, S.; Vantorre, M. (2016). The Towing Tank for Manoeuvres in Shallow Water. MASHCON 2016, Hamburg, Germany.
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16:30
30 mins
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DYNAMIC PRESSURES AND RUN-UP ON VERTICAL AND CURVED SEAWALL UNDER RANDOM WAVES
Anand Vaideeswaran, Sundar Vallam
Abstract: Apart from the coastal erosion and rise in sea level natural coastal hazards like storm surge and tsunami are affecting particularly, the densely populated areas resulting in loss of life and property. It is evident that a seawall as a coastal protection measure should be effective with an optimum use of the coastal space, with less or no wave overtopping by maintaining a lower crest elevation. Seawall depending on the shape of its surface facing the ocean waves can further be classified as vertical, sloping, curved or stepped. The hydrodynamic characteristic of curved front sea wall that is expected to guide the wave along its surface and finally enable it to return back into the sea, by the process of which, significant amount of energy is believed to be dissipated. Three such curved configurations have been chosen for the study. The experimental investigation on dynamic pressure variation along the surface and run-up over the seawall models placed over a bed slope of 1 in 30 and subjected to the action of random waves following the PM spectrum were conducted.
The details of the models considered for the study are, vertical wall (model–VW), The seaside front face of curved front seawall (model–GS) is a combination of two radii of curvature as suggested in (Coastal Engineering Manual, 2006) by US Army Corps of Engineers that was adopted at Galveston, Texas, USA, during 1905. The model (model–FSS) is a modified version of the model proposed by (Kamikub et al., 2000). The cross section of the seawall model proposed by him was formed with the deepest point from its base and from the vertical joining its toe and the crest of the wall is around 50% of its height respectively. The pressure experienced by such a wall is reported as some 3 to 4 times more than that on a vertical wall, and hence for the present study a modified section with the deepest point from the vertical joining its toe and the crest of the wall as 40% of its height was considered. The other model (model–CPS) considered is a curved front seawall from the concepts of (Weber, 1934), which consists of a parabolic curve at the bottom with a quarter circle at the re-curved portion which was connected smoothly at the intersection.
The results on the variations of dynamic pressures and the run-up on the curved seawall models compared with for a vertical wall are analysed and discussed in detail.
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