International Shipbuilding Progress - Volume 20, issue 226

Authors: van Manen, J.D.

Article Type: Research Article

Abstract: In this paper the application of non-conventional propulsion devices and the motives thereof with respect to merchant ships are considered. This is done from the viewpoints of efficiency, cavitation, vibrations, stopping, manoeuvring, safety and economics. The propulsion devices considered are: - controllable pitch propellers, - overlapping propellers, - contra-rotating propellers, - ducted propellers, - vertical axis propellers and - high speed propulsion devices, including air propulsion. The main part of this paper has been presented at the 2nd Symposium on Marine Propellers, The Society …of Naval Architects of Japan, Tokyo, 24–25 November, 1971. The illustrations have been compiled from available N.S.M.B.-material; the bibliography is of an international character. controllable pitch propellers, overlapping propellers, contra-rotating propellers, ducted propellers, vertical axis propellers and high speed propulsion devices, including air propulsion. Show more

DOI: 10.3233/ISP-1973-2022601

Citation: International Shipbuilding Progress, vol. 20, no. 226, pp. 173-193, 1973

Authors: Johnsson, C.-A.

Article Type: Research Article

Abstract: A short review is given of the development of the techniques used for cavitation tests with propellers and reference made to the correlation work with full scale carried out lately on merchant ship propellers. The difficulties of making theoretical calculations of the inception and extension of cavitation on propeller blades are discussed with the emphasis on the influence of the leading edge radius on the pressure distribution for the blade profiles. An approximate method for such calculations is outlined and applied to some cases for which results of full scale observations and model tests in cavitation tunnels are available. …The agreement between calculation and experiment is found to be satisfactory. Calculations are made for investigating the influence of leading edge radius, cavitation number, radial circulation distribution and tangential velocities on the extension of cavitation. Finally the results of the calculations are discussed in the view of the desire to predict the danger of erosion and vibration. The conclusions drawn are summarised at the end of the Paper. Show more

DOI: 10.3233/ISP-1973-2022602

Citation: International Shipbuilding Progress, vol. 20, no. 226, pp. 194-210, 1973

Authors: Tanibayashi, H.

Article Type: Research Article

Abstract: Blade stress, vibratory forces and cavitation of marine propellers are treated essentially as unsteady problems arising from non-uniform wake distribution. Since a purely theoretical approach to them requires a complicated calculation based on the unsteady lifting surface theory, a simple and shorter method is more convenient for practical purposes, if applicable with reasonable accuracy. In this regard the applicability of a quasi-steady method has been examined and the result is summarized as follows. 1. Analysis of the numerical data of unsteady lifting surface calculations indicates that a quasi-steady method may be applied to most cases in practice except for …wake variations with very high frequency and extraordinary blade shapes. 2. The theoretical consideration stated above has been supported by measurements of stress at the root of propeller blades in non-uniform flow. It is suggested that the applicability of the quasi-steady method is extended to estimation of thrust and torque fluctuation of propellers working in non-uniform wake distributions. 3. The quasi-steady methods can be applied to prediction of sheet cavitation and bubble cavitation in non-uniform flow on the basis of cavitation pattern in uniform flow. The method fails, however, to predict cloud cavitation and cavity collapse, for which investigation should be made chiefly on the basis of experiment until further development is made in theoretical methods. Show more

DOI: 10.3233/ISP-1973-2022603

Citation: International Shipbuilding Progress, vol. 20, no. 226, pp. 211-222, 1973