A Study of Vertical Vibration of Ships (2nd report)
1966 Volume 1966 Issue 119 Pages 142-156
Details
1966 Volume 1966 Issue 119 Pages 142-156
Critical frequencies of the vertical vibration were calculated for 2 tankers, 4 high speed cargo liners and an ore-carrier, by means of the digital computation method described in the previous report (1).
The results were compared with the frequencies measured in the sea trials. Although there are some discrepancies between the computed and measured frequencies, the estimation of the frequencies of tankers and bulk carriers can be made with good accuracy by means of the empirical coefficient defined in this report.
Further the authors investigated the effects of the added virtual mass, effective breadth of the plating and the rotational inertia, the results of which showed that the rotational inertia can be neglected up to 67 nodal model. For the ships having no longitudinal bulkheads such as bulk carriers and cargo ships, the effective breadth factor seems to affect the frequencies to some degree, but the detailed study on this subject will be investigated in a subsequent report. For the practical computation, Landweber's two-parametre family with Lewis' correction is fairly applicable to the estimation of virtual added mass.
