Ship whipping is the rapid flexing of the hull girder as a consequence of a wave impact in either the flat bottom or the bow flare. It is a dynamic effect and usually results in high-frequency cyclic oscillations of the hull girder, which result in increased vertical wave-induced bending moments and shear forces compared to linear theory.
The whipping effect is a hull vibration with a fundamental two-noded frequency. It can produce stresses similar in magnitude to the quasi-static wave-bending stresses.
In rough seas, the ship’s bow and stern may occasionally emerge from a wave and re-enter the wave with a heavy impact or slam, as the hull structure comes in contact with the water. A ship with such excessive motions is subject to very rapidly developed hydrodynamic loads. The ship will experience impulse loads with high-pressure peaks during the impact between the ship hull and water. Of interest are the impact loads such as bow flare slamming, bottom slamming, stern slamming, green water, and bow impact loads. These impact loads are of a transient nature and can cause severe structural damages.
They can also induce hull girder vibration mainly in the fundamental 2-node mode. This hull girder vibration is referred to as “whipping”.
The appraisal of this kind of dynamic effect needs sophisticated analysis procedures and software, as well as deep expertise in impact simulations.
RINA has the necessary knowledge to build up and complete the necessary simulations used as tools to study this phenomenon.
Alessandro Pescetto Sector Manager Marine Innovation
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