# NA4 Ships Vibrations Test Model

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.

## Description

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.

## Features & Benefits

• 3 Oscillator mounting points along the hull
• Provides an analogue comparison to software model behaviour

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
• Apparatus designed to enable students to investigate a simple model hull form for resonance phenomena
• The apparatus comprises an experimental model hull, a rigid supporting frame, a vibrator (complete with signal generator and power amplifier) and an optional Flotation Tank (order code NA4-11)
• The experimental model is flat bottomed, wall-sided and open topped. It has an elliptical plan form.

-Length to Beam ratio 8:1

-Length to Depth ratio 12:1

• Used to demonstrate the principle phenomena associated with ship resonant vibration
• Can be used to investigate resonance phenomena in both air & water

Flotation tank (NA4-11) for NA4-10

Electrical supply:
NA4-10-A: 220V-240V/1ph/50Hz, 2A
NA4-10-B: 120V/1ph/60Hz, 4A

Free water surface, if NA4-11 Flotation Tank not ordered

## Packed and crated shipping specifications

• Volume: 1.0 m3
• Gross weight: 75 kg

Length: 1.44 m
Width: 2.66 m
Height: 1.44 m

• NA4-10 Ships Vibrations Test Model
• NA4-11 Floatation Tank for NA4-10