Motor Yacht & Ship Testing

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Background

The Wolfson Unit is a commercial consultancy within the University of Southampton. While it operates alongside the academic department, the consultants are all full time professional engineers. It has been testing models of ships and small craft since its inception in 1967. It has built up considerable experience in test and analysis techniques, not only for towing tank tests on conventional craft but also for innovative testing and unusual configurations. To the designer or builder of powered craft, the Unit offers towing tank tests, wind tunnel tests, radio controlled model tests, special tests to solve particular problems and an opportunity to see the craft moving through the water long before construction has begun. In addition to model testing, the Unit can undertake trials data acquisition on full size craft.

Correct design decisions rely on well executed experiments and the correct interpretation of results. Wolfson Unit engineers conduct all aspects of the test programme; preparation of the model, running the tests, analysis of the results, and writing the report. The benefit of their experience can be brought to bear at every stage. Models can be modified quickly and re-tested if preliminary results indicate that a design change would be beneficial. The towing tank is only one of many research facilities available to the designer. By working within a large successful University the Unit not only carries out test programmes using its own staff, but also acts as a link between the designer and a wide range of academic staff working in such disciplines as electronics, materials and structures, and aerodynamics. The designer thus has access to a multi-disciplinary research team without the burden of project coordination that this would normally entail.

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Towing Tank Tests

The Wolfson Unit uses the towing tank at Southampton Institute for small model testing. For larger or faster models, the tank at QinetiQ Haslar or the number 3 tank at GKN Westland on the Isle of Wight are used.

Tank tests are carried out on models of all types of motor vessel; fast patrol boats, catamarans, SWATH'S, motor yachts, lifeboats, fishing boats, coasters, survey ships, ferries, barges under tow, and hovercraft.

The towing tanks are equipped with computer controlled wave makers that can produce regular waves or a variety of wave spectra and even breaking waves. It is also possible to conduct tests in shallow water and to measure the wave pattern, or wash, produced.

Calm Water Tests
Resistance at a range of speeds, displacements and trims. Optimisation of LCG position and trim control devices. Improvements to spray rails, knuckles and chines. Wash measurement.

Tests in Waves
Measurement of resistance, heave, trim, accelerations and wetness. Statistical quantities of motion in irregular sea spectra. Determination of seasickness incidence and crew performance. Stability and seaworthiness in beam seas or extreme conditions. Effects of bilge keels on roll reduction. RO-RO ferry damage stability assessment.

Flow Visualization
Improvements in appendage design. Bilge keel alignment. Flow into propellers. Flow through tunnels. Improvements in these areas can reduce resistance, increase propeller efficiency and reduce noise and vibration.

Other Tests
Behaviour in breaking waves or wind and waves. Behaviour of barges and barge trains under tow. Wake surveys and self propulsion tests. Coupled roll and yaw instability.

More information can be found on our test facilities page.

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Wind Tunnel Tests

The two large wind tunnels at the University of Southampton are used for a wide range of tests on ship superstructures and fast craft. Also they are often used for flow visualization on towing tank hull models, as the dry environment facilitates visualization and modifications. The moving ground belts ensure accurate representation of the flow beneath planing hulls and hovercraft.

Traditional qualitative methods of flow visualization are now supplemented by Particle Image Velocimetry (PIV). This combines laser, video and computer technology to enable measurement of flow vectors across a section of the flow.

Test programmes include:
Funnel design and determination of smoke plume trajectory. Pollution of ventilation intakes by exhaust emissions. Air flow across passenger and flight decks. Roll forces in beam winds. Wind resistance of superstructures. Forces and passenger comfort on very high speed craft. Suspended lifeboat motions. Hovercraft development.

More information can be found on our test facilities page.

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Radio Controlled Models

Radio controlled models, built and equipped by the Wolfson Unit, and operating in open water or a seakeeping basin, are used for a variety of experiments, including:
Manoeuvring and directional stability trials such as Dieudonne spiral tests and zig-zag manoeuvres. Docking in high winds and use of bow thrusters. Complex or innovative propulsion systems. Seakeeping and motions in irregular seas. Coupled roll and yaw stability at high speed. Broaching.

Recent advances in commercial model water jet drives have enabled affordable and representative testing of vessels with water jet propulsion.

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Open Water Propeller and Propulsion Tests

The Wolfson Unit has a testing device for determining open water characteristic of propellers within a wide range of propeller characteristics, including; diameter, pitch, blade area ratio. The rig measures thrust, torque and revolutions of the propeller in a uniform water inflow.

The open water rig consists of a dynamometer with gearbox and electric engine placed inside of a GRP shroud and the propeller model is mounted on the end of the shaft together with streamlined fairings.

During the tests the rig is immersed and connected to the carriage in such a way, that the propeller is working in undisturbed water flow and its characteristics (J, KT, KQ) may be easily measured. The rig allows the Wolfson Unit to widen our capability of self-propulsion tests in such cases where propulsive coefficients play an important role to predict the required power of ship engines. The device can also be used to test water turbines and predict their performance for a particular condition.

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Trials and Data Acquisition

Wolfson Unit engineers can attend sea trials with portable data acquisition and analysis systems, complete with associated transducers, to carry out a wide range of measurements, including:
Noise, vibration, accelerations, motions and manoeuvring.

More information can be found on our trials page and our onboard systems page.

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Computer Studies

The Wolfson Unit has its own suite of computer programs. A bureau service is operated using these to provide the designer with lines development and fairing, stability data and booklets, ship motions studies, power estimates and propeller designs.

More information can be found on our bureau service page and our software page.

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