Rudder Type Research Articles

Experimental study of the velocity field induced by a propeller jet in an inland-ship model and the related bed scour

The highly turbulent flow induced by ship propellers has a great potential to scour the alluvial bottom of navigational rivers and canals. Characterization of the complex flow field behind propellers is essential for forecasting the scouring action. In this study the velocity field and scour induced by two standard arrangements of propeller, nozzle and rudder from inland vessels are investigated experimentally with a ship model on a scale of 1:16. There are two objectives: first, to identify the influence of the ship stern on the flow field, and second, to assess induced scour depths in relation to maximum current velocities close to the bottom. It is found that the equilibrium scour depths for the two propeller arrangements are of the same order of magnitude, but that the time development of scour is different. The differences can be explained by the converging trend of the flow velocities at the bottom level for the two situations, when the vertical distance between the propeller and the bottom is high. It is also shown that existing relations for the velocity field require amendment when the propeller is ducted, and for adequately considering the effect of the ship stern and rudder type.

Research on Ducted Propeller and Rudder Interactions in Extreme Conditions

This paper presents the results and analyses of a combined numerical-experimental study into the performance of three types of rudders to quantify the interactions between propeller, nozzle, and rudder at extreme rudder angles. Conventional, flapped and triple rudders are studied numerically as well as experimentally to evaluate the drag, lift, and moment generated by the rudders at moderate-to-extreme rudder angles and at forward propeller shaft speeds and inflow speeds. The experiments were carried out to evaluate the suitability of the three rudder types for a proposed cargo carrier in terms of controllability. The experiments were carried out at the selfpropulsion condition of the model equipped with twin stock ducted propellers along with each of the rudder systems. An extensive numerical study was carried out to evaluate the performance of the three rudders in terms of flow velocity, pressure, and wake fields. Drag and lift for different angles of attack are obtained for complicated propeller-nozzle-rudder arrangements. Investigations are carried out to study the effects of the interaction of the rudder with the propeller-nozzle assembly at extreme rudder angles as high as ±40°. For simplicity, the geometry of the vessel was not modeled in these simulations. The experimental results are presented along with the computational results for all three rudder cases. The lift and drag measurements are in good agreement with the corresponding predictions for each of the rudder arrangements. The mutual interactions between the rudder and the propulsion system were captured in the simulations and were comparable with the corresponding measurements. The research reveals the nature of the velocity and pressure fields due to the complex interactions between the propeller, nozzle, and rudders at extreme rudder angles. It is expected that the current investigation will assist naval architects, at the early design stage, to select the rudder type for their ships such that suitable maneuvering characteristics are obtained and stringent International Maritime Organization maneuvering criteria are met.

Research on Control Scheme of Submarine Hydraulic Rudder

According to the composition of the submarine hydraulic rudder system, the paper analyzed the different advantages and disadvantages of the rudder type, steering agencies and the hydraulic rudder control system as well as the scope of application. System steering bodies of pump control servo, variable pump displacement control system, steering control system and rudder hydrodynamic interference model were modeled. Fuzzy logic hydraulic servo parameter adjustment method is presented, and simulation analysis of the variable pump displacement control system and steering system. As the system parameter uncertainties and load disturbance, the performance impact of parameter variation and load disturbance simulation analysis.

A Novel Fuzzy Logic PID Algorithm for Submarine Hydraulic Rudder Control

According to the composition of the submarine hydraulic rudder system, the paper analyzed the different advantages and disadvantages of the rudder type, steering agencies and the hydraulic rudder control system as well as the scope of application. System steering bodies of pump control servo, variable pump displacement control system, steering control system and rudder hydrodynamic interference model were modeled. Fuzzy logic hydraulic servo parameter adjustment method is presented, and simulation analysis of the variable pump displacement control system and steering system. As the system parameter uncertainties and load disturbance, the performance impact of parameter variation and load disturbance simulation analysis.

A proposal for propulsion performance prediction of a single-propeller twin-rudder ship

The influence of a rudder’s axial force on the prediction of full-scale powering performance of a ship is investigated in this paper. Axial force characteristics of different rudder types were investigated by open water experiments. Viscous scale effects on the rudder’s axial force were investigated by carrying out open water experiments with different sizes of rudder. Experiments were carried out in the towing tank for a model ship fitted with different rudder systems to investigate the influence of rudder’s axial force on full-scale propulsion performance prediction. Based on the experiment results, a new prediction method is proposed for estimating full-scale power that considers scale effect on rudder’s axial force. Good performance of the proposed prediction method is demonstrated by estimating the engine power of a ship installed with a special high lift twin-rudder system from model experiments and comparing it with the values measured on the ship during full-scale experiments.

Comparison of the mariner Schilling rudder and the mariner rudder for VLCCs in strong winds

A simulation model of a very large crude carrier (VLCC) with either a mariner type Schilling rudder or a mariner rudder was developed from captive and free-running model tests. Kijima’s regression formula was used to predict the hydrodynamic hull forces on the VLCC. To simulate full-scale maneuvering at cruising speed, the constant torque operation of the main engine was assumed. Considering the higher normal lift force and maneuverability of the mariner type Schilling rudder as compared to the mariner rudder, the size of mariner type Schilling rudder is kept smaller as compared to mariner rudder. To compare the efficiency of the two types of rudder system, maneuvering simulations at constant engine torque and course-keeping simulations at various gusting wind speeds and encounter angles were carried out. Based on the simulation results, the two rudder types were compared from the viewpoint of maneuvering and fuel efficiency in windy conditions.

Introducing an effective new ship rudder type, Telescopic Rudder

Rudder is the most important controlling device in ship maneuvering. Usually, it is a passive equipment of a ship, which generates the control forces and moments by inflow velocity and loses its performance when the ship speed reduces. Many parameters are involved in rudder design such as rudder's shape, area and span. By increasing rudder span, the aspect ratio, rudder area and rudder forces are increased. In addition, research shows that the increasing of rudder aspect ratio is the best option to receive highest performance of rudder than any other change of rudder parameters. Having known that the rudder dimensions limited by ship stern form, rudder span is limited to the ship overall geometry and the stern geometry. In this research, a new and innovative ship rudder type (Telescopic Rudder) is suggested that allows enlarging the rudder height hence increasing the rudder aspect ratio. This improves the controllability (maneuverability) of vessel by increasing the hydrodynamic coefficients of rudder. The telescopic rudder made by two pieces, which secondary part slides into the main part. A hydraulic system is used to facilitate sliding thus increasing the rudder height, increasing the aspect ratio and area of rudder producing larger forces. A computer code is also developed to investigate the hydrodynamic characteristics of telescopic rudder by boundary element method (3D-panel). The effectiveness of the new rudder type is studied by the said code in comparison with the conventional type.

Model Chinese Junks

A COLLECTION of large-scale models of Chinese junks, which is said to be unique, has been presented to the nation by Sir Frederick Maze, inspector-general of Chinese customs, for exhibition in the Science Museum, South Kensington. The models, ten in number, were built in Hong-Kong or Shanghai by Chinese craftsmen, and are accurate replicas of these sailing craft in every detail, down to the shrines and household gods. They include examples with the magical eye on the prow. These boats, which are now giving place to steam in Chinese waters, and have also suffered many casualties during the present warfare, are of two main types, a northern and a southern. Except for details of rigging, they have not altered in principle over a prolonged period—at least a thousand years, and some authorities would hold for perhaps twice as long before that. Of these types, one has bluff bows and a flat bottom adapted for sailing in shallow waters. The other type has a sharp bow, with sheer lines and a deeper draught. Details of construction and rig in use among Chinese sailors at an early date are shown in these models, which did not appear in Western ships until a very much later period. Such, for example, are the watertight compartment, the battened sail used in yacht racing, lee boards of the keel and rudder types, and multiple sheets for independent handling of the upper and lower parts of the sails.