Accession Number : ADA262347


Title :   The Free Decay of Coupled Heave and Pitch Motions of a Model Frigate


Descriptive Note : Technical memo,


Corporate Author : DEFENCE RESEARCH AGENCY GOSPORT (UNITED KINGDOM)


Personal Author(s) : Crossland, P ; Wilson, P A ; Bradburn, J C


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a262347.pdf


Report Date : Oct 1992


Pagination or Media Count : 28


Abstract : The PAT-91 ship program has been found to over predict damping especially at resonant frequencies, resulting in there being no significant peak in the transfer function of pitch at resonance. This memorandum presents the results of a series of experiments that measured the decay time histories of a model frigate free to move in the vertical plane, in an attempt to identify where the problems might be occurring. Judgements are made concerning the components in the heave and pitch motions using the terms in the full two dimensional strip theory heave and pitch motion equations to explain the trends shown. The investigation has shown that the sectional damping coefficient appears to be over predicted. This results in a relatively poor prediction of heave decay curves at low speed and over estimates the damping in the pitch decay curves. It appears that the discrepancies seen in the heave and pitch transfer functions could be due to the wave excitation being predicted incorrectly.


Descriptors :   *PITCH(MOTION) , *SHIP MOTION , *FRIGATES , VELOCITY , FREQUENCY , FUNCTIONS , SHIPS , OCEAN WAVES , TRANSFER FUNCTIONS , EQUATIONS OF MOTION , PREDICTIONS , MODELS , TWO DIMENSIONAL , EXCITATION , THEORY , DAMPING , MOTION , ESTIMATES , TIME , RESONANT FREQUENCY , COEFFICIENTS , RESONANCE , TRANSFER , EQUATIONS , AMPLITUDE , SEA STATES , DECAY , STRIPES , HEAVING


Subject Categories : Marine Engineering


Distribution Statement : APPROVED FOR PUBLIC RELEASE