International Shipbuilding Progress - Volume 28, issue 321

Authors: Wereldsma, R.

Article Type: Research Article

Abstract: High installed power and increased R.P.M. of today’s ships are the very cause of an increased vibration excitation, an excitation larger than that of regular ships designed some ten years ago. Also the larger dimensions of today’s ships result in an increased vibration amplitude. At this very moment an international evaluation of ship vibrations is being prepared by the I.S.O. and a proposal for international adaptation has been issued recently (Figure 1). In this proposal the acceptable maximum vibration levels are indicated, and for ships to be built this proposed norm is already nowadays a basis for the contracts between …the shipbuhder and shipowner. Under these conditions it is necessary to have a reliable prediction technique available in order to analyze the expected ship vibration level in the design stage. A state of the art [1] of vibration prediction techniques shows that a reliable method for the vibration analysis is not yet well possible. In the various checkpoints, available for the ship designer, to check his design against vibration acceptance, the mass-elastic response of the hull girder is not incorporated (Figure 2). Show more

DOI: 10.3233/ISP-1981-2832101

Citation: International Shipbuilding Progress, vol. 28, no. 321, pp. 96-101, 1981

Authors: Zhu, D.M.

Article Type: Research Article

Abstract: A theoretical computational method to evaluate the performance characteristics of cycloidal propellers is presented. Starting from Taniguchi’s method, improvements have been derived to make it applicable for various eccentricities in the whole advance coefficient region. First the effect of the curved orbit of the blades and the blade rotation is taken into account, that influences camber and zero lift angle. Then the effect of low Reynolds number on drag coefficient and the effect of stalling on lift coefficient are analysed and discussed in detail. Some linearizations are given up to improve the computation accuracy. The improved method is described. …Using this improved method to compute the performance of a DTNSRDC model and comparing the results with systematic experiment results (see DTNSRDC Report 2983), it is shown that the agreement between them is quite good for a larger range of advance ratios and eccentricities. Show more

DOI: 10.3233/ISP-1981-2832102

Citation: International Shipbuilding Progress, vol. 28, no. 321, pp. 102-111, 1981

Authors: Inoue, S. | Hirano, M. | Kijima, K.

Article Type: Research Article

Abstract: Model experiments have been carried out to investigate the hydrodynamic forces acting on ship in even keel and trimmed conditions. The relations between this force and load condition of ship were proved, and the linear and non-linear derivatives in manoeuvring mathematical models for fitting the measured results to describe the forces were also examined semi-empirically by using the model tests of various kinds of ships and applying a theoretical approach. Finally, the approximate formulae for practical application in estimation the lateral force and moment on ship in manoeuvring motion.

DOI: 10.3233/ISP-1981-2832103

Citation: International Shipbuilding Progress, vol. 28, no. 321, pp. 112-125, 1981