Towing Tank

Figure 1 - AMC Ship Hydrodynamics Centre Towing Tank

Overview

A major upgrade of the AMC Towing Tank has recently been completed. Among the many improvements, the test section of the tank has been doubled from approximately 40 to 80 metres in length (the overall length has increased from 60m to 100m). The primary benefits from this augmented length are to increase both the maximum attainable carriage speed and the time available at constant speed for data acquisition. In addition to the increase in length of the tank, the upgrade has resulted in numerous improvements to the capabilities and operation of the facility.

The "new" tank has a length of 100m, is 3.55m wide and the water depth can be varied from empty up to 1.6m deep (the standard depth is 1.5m). The bottom of the tank is very flat providing the ability to conduct experiments in very shallow water depths if required. The facility has a powered carriage to tow models up to a maximum speed of approximately 4.6m/s and can accommodate at least 6 passengers for viewing purposes. The carriage can maintain a constant speed within +/- 0.01m/s in either the forward or reverse directions allowing both head and following sea tests to be conducted.

Waves can be produced by a hydraulically driven wavemaker positioned at one end of the tank. The computer software that controls the wavemaker paddle provides the ability to produce a wide variety of wave forms, including: regular waves, most commonly available irregular wave spectra and user defined wave spectra or sequences. A large wave energy dissipation device (beach) is fitted to the opposite end of the tank and a removable wave dissipation device is fitted to one side of the tank.

A variety of test rigs can be installed upon the Towing Tank carriage to measure the forces, moments and motions experienced by a model. A conventional two-post dynamometer is generally used for the majority of the models of powered craft. In 2002, two new 6-component force balances were designed, built and commissioned by AMC. The first of these, a large 6-DOF force balance, is specially designed for the conduct of high performance yacht model tests and other specialised applications. The second, a small 6-DOF force balance, is designed to undertake force measurements of lifting foils on high-speed vessels.

Figure 2 - Schematic Diagram of Towing Tank

The Centre's involvement of several America's Cup campaigns over the past 15 years has assisted in the development of very strict procedures for assuring test accuracy. Figure 3 shows a model of a high-speed catamaran during a typical calm water resistance test.

Figure 3 - Model of a high-speed catamaran during a typical calm water resistance test.

Experimentation on over 300 ship models has allowed the Centre to develop an extensive ship resistance database that allows the calm water performance of new hull designs to be compared against existing hull forms.

As with most of AMC's facilities, the Towing Tank is a National facility, making it available to researchers from many Australian research institutions. The Towing Tank has been widely utilised by researchers, academic staff and postgraduate and undergraduate students to undertake a wide variety of physical experiments. For example, over the past few years the University of NSW, University of Western Australia, Curtin University of Technology and the Department of Defence have made use of this facility.

There are only two academic institutions within Australia that offer a degree in Naval Architecture – AMC and UNSW. AMC students gain exposure to the Towing Tank (and other AMC facilities) throughout their four year degree, however, UNSW does not possess any such facilities. Each year, AMC hosts the third year Naval Architecture students from UNSW for up to two days during which they receive brief exposure to most of AMC’s facilities.

The first commercial consultancy project was conducted in the Towing Tank in 1985. Since then, the SHC has conducted approximately 300 commercial consultancy projects for Australian and international clients through the business arm of AMC, AMC Search Ltd. These projects have involved experiments on many varied types of vessels and maritime operations, including: patrol and police boats, catamaran, frigates, bulk carriers, container ships, motor yachts, fishing boats, high performance racing yachts, landing craft, barges, stern landing vessels, trimarans, submarines, wave energy structures, SWATH's, pontoons, sonar equipment and semi-submersibles.

Examples of the type of services offered are given below:

(a) Calm Water Resistance / Powering Prediction / Hull Form Optimisation

• Resistance measured over a range of speeds to give effective power curves
• Resistance variation with displacement and LCG position
• Optimisation of running trim and wedge/trim tab/interceptor design
• Measurement of lift and drag for high-performance yachts
• Flow visualisation for appendage alignment and design (such as bilge keels, propulsion equipment, bow thruster tunnels etc.)

(b) Tests in waterways of restricted depth and/or width

• Resistance
• Ship squat
• Ship - bank interaction

(c) Seakeeping Tests

• Motion measurement (pitch, heave, roll, vertical acceleration)
• Added resistance in waves
• Variation of motions with wave length and wave height
• Statistical qualities of motion in irregular sea spectra.

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Specifications

General

Length 100 metres

Width 3.55 metres

Depth 0 to 1.6 metres (standard = 1.5m)

Carriage speed 0 to 4.6 metres/second

Ship model length 1.0 to 2.5 metres

PC based data acquisition and processing

Wave Generation

Hydraulically driven single flap type paddle

Regular and irregular waves

Maximum wave height 0.4 metres (approximately)

Instrumentation

Multiple force balances, load cells, displacement transducers, wave probes, accelerometers etc.

Digital PC Computer

In-house Data Acquisition and Analysis Software

Typical Sampling Rates : 1 - 500Hz

Multi-Video System

Digital Photography

Contact

For further information contact:

Australian Maritime College
Ship Hydrodynamics Centre
PO Box 986
Launceston Tasmania 7250
Australia

Phone: +61 (0)3 6335 4880
Fax: +61 (0)3 6335 4720

Email: G.Macfarlane@amc.edu.au

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