International Shipbuilding Progress - Volume 28, issue 320

Authors: Yücel Odabaşi, A.

Article Type: Research Article

Abstract: In this paper an attempt is made to evaluate the possibility of extending the ad hoc lateral ship motions theory to the large amplitude rolling motion analysis. To gain a better insight, the problem is first posed within small amplitude restrictions (i.e. linear) with viscosity included and it is shown that the assumption on the separability of different contributions is not correct and the concept of added mass and damping in a viscous fluid are not well-understood. Contributions from the bilge keels are treated separately in a similar manner to the wing-body problems in aeronautics as opposed to the very …low aspect ratio approach proposed by Schmitke [5]. Next the features of the large amplitude rolling motion of a ship as a non-linear system is discussed and the essential differences between this and the linear systems are high-lighted. Some suggestions on the possible method of approach are also discussed. Having completed the examination of analytical methods, attention is paid to the experimental procedures and data in the light of the scaling laws and dimensional analysis and it is shown that almost all of the reported experiments do not comply with the scaling laws since no attempt has been reported to derive them for the non-zero forward speed case. Some suggestions are made on possible future work on both the analytical and the experimental sides. Show more

DOI: 10.3233/ISP-1981-2832001

Citation: International Shipbuilding Progress, vol. 28, no. 320, pp. 74-82, 1981

Authors: van Amerongen, J. | de Goeij, W.F. | Moraal, J.M. | Ort, J.W. | Postuma, A.

Article Type: Research Article

Abstract: During the last few years several papers have been published about adaptive autopilots, where the parameters of the controller are automatically tuned. To show the ‘optimality’ of the design, in most cases a simple quadratic criterion is used to measure the savings which may be expected. Full scale measurements which clearly show fuel-savings, are difficult and time consuming to carry out and until now they are hardly reported. This paper gives some results of a series of full-scale trials. Another solution is to measure the difference in performance of various steering algorithms with the aid of a scale model …in a sea-keeping basin, where the conditions during the measurements can be well controlled. A series of model tests has been carried out at the Netherlands Ship Model Basin (NSMB) to compare the performance of the adaptive autopilot of Delft University of Technology with a conventional PID controller. A description is given of the set-up of these measurements and the results which are obtained are discussed. Show more

DOI: 10.3233/ISP-1981-2832002

Citation: International Shipbuilding Progress, vol. 28, no. 320, pp. 83-89, 1981

Authors: Inglis, R.B. | Mikelis, N.E. | Price, W.G. | Waite, J.B.

Article Type: Research Article

Abstract: Computations of the hydrodynamic coefficients of sway added mass and yaw added moment of inertia associated with manoeuvring rectangular barges floating in various depths of open water are obtained by three dimensional fluid finite element and boundary integral methods. The barges are of ship like proportions and the numerical solutions are compared with experim.ental data from ship model tests [1]. A discussion of the convergence of the solutions is included.

DOI: 10.3233/ISP-1981-2832003

Citation: International Shipbuilding Progress, vol. 28, no. 320, pp. 90-93, 1981