Project

Dynamic keel clearance (DKS) second opinion 5 marginal voyages Sloehaven and risk assessment maneuvering margin

Code
174F09120
Duration
01 June 2020 → 01 November 2021
Funding
Regional and community funding: various
Research disciplines
  • Engineering and technology
    • Hydrodynamics
    • Hydrostatics
    • Marine engineering not elsewehere classified
Keywords
keel clearance ship hydrodynamics
 
Project description

Within the DKS[1] project, theGemeenschappelijke Nautische Autoriteit (GNA) implements a probabilistic calculation method for the calculation of the accessibility to the Scheldt ports in the GNA area. In a probabilistic calculation method, the acceptability of a voyage is assessed based on the probability of bottom contact, supplemented by a minimum value for the manoeuvre margin [2]. This DKS method is to replace the current deterministic criteria based on gross keel clearance [3]. For the calculation of tidal windows for tide-dependent vessels, a tender was issued in 2014 to adapt the software tool WESP[4] to the new calculation method. This contract was awarded to CGI and Charta. The latter integrated its probabilistic calculation tool ProTide into the new version of WESP (WESP 4).

In order to validate the prediction of vertical ship movements, as provided by the DKS calculations, true size measurements were carried out on normative ships heading for the Scheldt ports. These projects were carried out by WL/UGent in close cooperation with the Dutch Pilotage and DAB Pilotage. For example, measuring voyages were performed on seven bulk carriers to Vlissingen-Sloehaven (Verwilligen et al., 2017) and nine measuring voyages on container ships from and to Antwerp (Verwilligen et al., 2019).

The vertical ship motions measured during the seven calls of bulk carriers to Vlissingen-Sloehaven (Verwilligen et al., 2017) showed good similarities with the calculations carried out using ProTide. These calculations were indeed performed using the same calculation engine (ProTide) as implemented in WESP, but not using the WESP tool itself. The reason for this is that at the time of the measuring voyages to Sloehaven, WESP 4 was not yet operational.

The acceptable agreement between ProTide calculations and Sloehaven voyages led to a next phase, the shadow running, in the roll-out of DKS. For the bulk carriers sailing to Sloehaven, both a deterministic and a probabilistic time gate have been issued since August 2018. Until now, the deterministic time gate is normative and the probabilistic time gate is only communicated informatively to the pilots.

In order to validate the WESP4 probabilistic time gates for inland bulk shipping to Sloehaven, WL/UGent performs post calculation at the request of GNA of five DKS calculations.

Additionally, a risk assessment is performed on the manoeuvre margin criterion that is part of the DKS calculation. Based on exploratory calculations it is made clear at which manoeuvres this criterion is normative for the accessibility of ports.

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1] DKS: Dynamic keel clearance

2] Manoeuvring margin: keel clearance obtained by reducing the water depth by the amidships draught and the squat

3] Gross keel clearance: The difference between the bottom depth and the hydrostatic maximum draught (in salt or fresh water) of the ship

4] WESP: WESterschelde Planner