Abstract

This paper deals with investigations performed at the Netherlands Ship Model Basin on thrusters which are able to improve the maneuverability and position-keeping ability of vessels and other floating objects. The characteristics of these thrusters (thrust and power at different angles of attack, transverse forces and moments) are discussed.

Introduction

In the last few years, there has been a growing demand for improving the maneuverability and position-keeping capability of research vessels, drilling vessels, drilling platforms, submersibles and other vessels which may be of use for ocean exploration. This paper deals with investigations performed at the Netherlands Ship Model Basin (NSMB) on thrusters which are able to improve the maneuverability and position-keeping abilities of these vessels. Considered thruster systems are:

  1. right-angle drive propellers in nozzles,

  2. tunnel thrusters with screw propellers,

  3. thrusters driven by an ejector.

Investigations have already been performed at the NSMB to determine the propeller thrust and torque characteristics of conventional and ducted propellers over the entire operation region (see Ref. 1, 2 and 3). With these results it was possible to calculate the characteristics of these systems at different angles of attack. A comparison between these results and the results of recently performed experiments has been made. Based on the results of open-water tests with ducted propellers and momentum theory the characteristics of bow thrusters have been determined. Also, tunnel thrusters driven by an ejector have been considered.

Characteristics Of Open- And Ducted Screw Propellers

Among the well-known screw series as developed by Schifrin, Taylor, Gown and others, the Wakening B-screw series of haplite NSMB (1) take an important place. The B-series screw type is frequently used in practice. It possesses satisfactory efficiency as well as reasonable cavitations properties. The dimensions of the B-screw series are given in Table 1 whereas the general plans of the four bladed screws are given in Fig. 1.

Open-water tests with the B-screw series have been carried out. The results are given in the conventional way with the coefficients:

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