Model Test Techniques to Quantify the Hydrodynamic Added Mass and Damping Associated with Longitudinal Flexural Response

Dynamic loading problems such as springing, propeller-induced vibration or continuous breaking of level ice cover, all involve hydrodynamic phenomena associated with hull responses and fluid reactions. The usual convention, which dates back to Lewis (1929), is to express the coupling between the fluid forces and hull responses in terms of the hydrodynamic added mass and damping effects. These effects are usually quantified by the so called coefficients which are expressed as functions of hull geometry, fluid density, frequency of oscillation and modal response shape. In principle, all modes of vibration participate in the response of a ship's hull to excitation. However, it is generally observed that response to shock or impact loading is dominated by the first few lower modes, while response to cyclic disturbances such as rotating machinery and wave induced loads, is influenced by higher modes with frequencies which couple with the frequencies of excitation. The contents of this paper deals with a special series of preliminary tests carried out to investigate the feasibility of using a segmented flexible model for determining the hydrodynamic added mass and damping.