More than 450 ship model test conditions have undergone calm water resistance tests within the AMC Towing Tank since 1985. The resistance results from all these ship models have been collated within a database to provide a powerful tool for providing preliminary powering estimates and comparing against the performance of a specific hull form.

A typical example of the output available from the AMC Ship Resistance Database

As can be seen in the figure above, the model test data contained within the database can be scaled to match the desired waterline length and vessel speed. The resulting drag on displacement ratios can be used as a measure of the hydrodynamic efficiency of a hull. Put simply, those vessels with a lower drag on displacement ratio are more efficient than those with higher values - at this combination of length, speed and displacement.

Such plots can be generated rapidly which can assist designers/operators to get a feel for how well their vessel is performing even while it is still undergoing tests in the tank. This can also be very useful to quantify the effectiveness of a particular modification to a hull form.

Every project undertaken by the SHC that involves an assessment of calm water resistance performance includes a comparison using the ship resistance database. Ship model test results are continually being added to the database.

Please note that, in general, the details of all vessels within the ship resistance database remain anonymous to protect their commercial-in-confidence status.

A few of examples of AMC research recently utilising the Towing Tank are briefly described below:

An investigation into the effect ship interaction has on the manoeuvring characteristics of an ANZAC Frigate and a tanker during a replenishment at sea (RAS) evolution has been studied. The model tests measured the side force and yawing moment experienced by the ANZAC Frigate at various lateral separations and with variable longitudinal separation simulating a vessel moving through the phases of a RAS. The results obtained were used to define the coefficients required to model the RAS manoeuvre within both the AMC's and the Royal Australian Navy's ship handling simulators.

In order to investigate the limits of applicability of linear theory for predicting vessel motions in an irregular head sea, tests have been carried out on two ship models: (a) a small high speed patrol craft and (b) a high speed displacement hull form. The model test program included a comprehensive series of experiments in both regular and irregular waves over a range of vessel speeds. The results obtained in irregular waves were compared with those calculated using standard linear strip theory, and with those obtained from linear superposition theory combined with the experimental results in regular waves. This has enabled the limits of both linear strip theory and linear superposition theory to be obtained when applied to vessels of this type. Further study of a similar nature is planned for a high-speed multihull vessel.

Roll motions on vessels can be uncomfortable and lead to motion sickness. The simplest form of roll stabilisation is to fit bilge keels, which can offer a significant reduction in roll motion and work especially well at low speeds. They also have the advantage of having no moving parts and require no more maintenance than is given to the hull surface.

The Ship Hydrodynamics Centre at the Australian Maritime College offers a service to design, position and evaluate the effectiveness of bilge keels to suit your vessels requirements.

To minimise the resistance of bilge keels they must be aligned with the flow streamlines. This can be achieved using flow visualisation tests to determine the shape of the streamlines. The photograph to the left shows the resulting streamlines on the model of a 35m fishing vessel following the conduct of some 'paint smear' flow visualisation tests. As can be seen, paint smear flow visualisation gives a clear guide for bilge keel alignment. Flow visualisation tests are usually only conducted at a single speed, which would normally be the design speed.

Once the bilge keels have been designed and positioned, model tests in beam seas can be undertaken to evaluate their effectiveness. Testing is conducted with the model having both a barehull and the new bilge keels attached. Such tests provide quantitative information of the vessel's roll and heave motions, similar to the graph shown below. Video footage of all tests can also be readily obtained.

The Ship Hydrodynamics Centre has previously performed bilge keel design, positioning and evaluation on a variety of hullforms, including defence, fishing, passenger and cruising vessels.