Free Sailing Manoeuvring Tests & SIMMAN Workshop
Flanders Hydraulics Research with the scientific support of Ghent University has been developing since 1992 ship manoeuvring mathematical models based on captive model tests executed in the towing tank. The execution of captive model tests where the ship model follows a prescribed track gives the advantage of being able to measure the hydrodynamic forces acting on the ship model.
The model tests have especially been used for predicting the manoeuvring behaviour of a ship in both deep and shallow water. According to PIANC shallow water is detected once the underkeel clearance (UKC) is smaller than 50% of the ship's draft. These low UKC's are more the rule than the exception in Flanders so that the influence of shallow water on the turning characteristics of ships has always been of interest. As these characteristics like advance, transfer and tactical diameter are for most ships increasing with decreasing UKC the validation of the predicted characteristics using the developed mathematical models must be realised.
Therefore FHR has ordered two new developments:
- The implementation of a free-sailing device in the existing towing tank attached to the main carriage so that free-sailing tests can be executed in the 7 m wide towing tank. Nevertheless, due to the small width of the tank only some standard manoeuvres can be executed (acceleration, deceleration, crash stop, zigzag tests)
- The construction of new ship models of different ship types so the ship model database represents all ship types coming to the ports of Flanders and the execution of free-sailing model tests in both deep (100% UKC) and (very) shallow water (35% to 10% UKC) in the manoeuvring basin of a foreign company.
These free-sailing model tests (crash stop, turning circles and zigzag manoeuvres) are actually being performed and the first results have been reported. These results will be published in future and are directly linked to the objectives of the SIMMAN workshop organised in 2008.
The 2008 SIMMAN workshop was held to benchmark the capabilities of different ship manoeuvring simulation methods including systems and CFD based methods through comparisons with results for tanker (KVLCC2), container ship (KCS) and surface combatant hull form test cases. Systems based methods were compared with free-model test data using provided PMM and CMT (circular motion mechanism/rotating-arm) data, whereas CFD based methods were compared with both PMM/CMT and free-model test data.
The next workshop is scheduled for 2012 and will particularly deal with the shallow water manoeuvring behaviour of the tanker KVLCC2 and container ship KCS. For that reason the SIMMAN organizers contacted Flanders Hydraulics Research to cooperate on the execution of:
- captive model tests with the KCS
- free running tests with the KCS
- captive model tests with the KVLCC2
- free running tests with the KVLCC2
- captive model tests with the KVLCC2, bare hull
The above mentioned tests are being executed (September-November 2010) in the shallow water towing tank of Flanders Hydraulics Research.
A call is launched to everyone who wants to participate in this study by offering all valuable information for reproducing a real ship at model scale.