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The NA4-10 Ships Vibrations Test Model is designed to enable students to investigate a simple model hull form for resonance phenomena. It may be used in conjunction with the optional Armfield Flotation Tank or any suitable customer supplied tank. Many of the principal phenomena associated with ship resonant vibration are clearly demonstrated.

At a more advanced level the distribution of mass and second moment of area may be calculated and using a Young’s Modulus value for the material of the ship shaped beam, the natural frequencies may be estimated by a simple tabular method or other means and compared with the measured value.

In air to:

Investigate modal characteristics of a simple suspended ship shaped box girder

Produce a resonance curve

Produce the amplitude curve of a 2-node and 3-node flexural model

Illustrate the influence of mass and its distribution upon natural flexural frequencies

In water to:

Measure the influence of added virtual mass on natural frequency

Illustrate the effect of the addition and distribution of sand ballast on the natural frequency

Calculate the added virtual mass by different methods and compare with experimentally measured influence using a Schlick-type formula