On behalf of the Victorian Regional Channels Authority (VRCA), Victoria, Australia, DHI contracted us to simulate whether it is possible to sail Suezmax tankers into the Port of Geelong along the 14 Nm long approach channel. 

The objective was to assess the current and potential future channel capacity for Suezmax tanker traffic from a navigational point of view taking phenomena as bank effect, blockage and squat into consideration.

Making the cut

When performing the study special emphasis was paid on an area of the channel called ‘The cut’. This particular area is very narrow and the area outside the dredged channel has shallow water, which can create bank effects.
We performed full-mission simulations using the channel as it is today as well as a dredged version of the channel. 

The existing channel

Sailing a typically vessel at the usual speed during a high wind caused a large drift angle especially through ‘the cut’.

The bank effects affected the vessel and made it necessary to use more engine and rudder power to compensate. This did not leave much engine power or steering capacity in case of unforeseen situations.

Even when reducing the wind speed, bank effects were still observed.  A wind limit of 15 knots with gusts up to 20 knots was found to be the limit for safe handling of vessels of this size in ‘the cut’.

We also found that an escort tug in centre lead aft was an advantage as it brought down the speed, while the tanker’s engine could run ahead providing a larger water flow to the rudder and thereby increasing the steering ability.

The dredged layout

The simulations in the dredged layout proved less challenging. By keeping the speed below 6 knots, the bank effects were reduced. With a wind speed limit of 15 knots with gusts up to 20 knots keeping the vessel on track in the centre of the channel was no problem. On top of this rudder and engine was used in a smaller scale.

In this scenario, the escort tug was also beneficial when it came to keeping the speed of the vessel low.

The conclusion was that the speed had to be restricted-especially at ‘the cut’ and that the use of escort tugs was beneficial in maintaining low speed.