Twin-rudder Ship Research Articles

Trajectory Optimization for Autonomous Berthing of a Twin-Propeller Twin-Rudder Ship

Autonomous berthing is a crucial technology for autonomous ships, requiring optimal trajectory planning to prevent collisions and minimize time and control efforts. This paper presents a two-phase, two-point boundary value problem (TPBVP) strategy for creating an optimal berthing trajectory for a twin-propeller, twin-rudder ship with autonomous berthing capabilities. The process is divided into two phases: the approach and the terminal. Tunnel thruster use is limited during the approach but fully employed during the terminal phase. This strategy permits concurrent optimization of the total trajectory duration, individual phase trajectories, and phase transition time. The efficacy of the proposed method is validated through two simulations. The first explores a scenario with phase transition, and the second generates a trajectory relying solely on the approach phase. The results affirm our algorithm's effectiveness in deciding transition necessity, identifying optimal transition timing, and optimizing the trajectory accordingly. The proposed two-phase TPBVP approach holds significant implications for advancements in autonomous ship navigation, enhancing safety and efficiency in berthing operations.

Maneuvering simulations of twin-propeller and twin-rudder ship in shallow water using equivalent single rudder model

Maneuvering simulations of twin-propeller and twin-rudder ship in shallow water using equivalent single rudder model

The effect of uncoupled propulsion and steering on the manoeuvring behaviour in coastal waters

The present paper introduces a mathematical model capable of simulating the behaviour of a twin propeller, twin rudder ship in uncoupled conditions, meaning that the portside and starboard propeller and/or rudder work at different rates, respectively angles. Such conditions are typically applied while manoeuvring in harbour conditions. The mathematical model coefficients are determined based on a captive manoeuvring test program which covers these uncoupled conditions. After implementation in the ship manoeuvring simulator, fast-time simulations have been carried out, which were successfully compared with free running tests in uncoupled conditions as well.

Investigation the effect of canted rudder on the roll damping of a twin-rudder ship

Reducing ship's roll motion has always been a major concern in ship design. In the present study, the effect of the angle of a canted rudder system on roll damping of a twin-screw naval vessel has been investigated by using a RANS solver. Moreover, the influence of forward speeds, initial inclination angle, as well as viscosity are also taken into account. For this purpose, free roll decay test is simulated. Besides, numerical validation and verification are performed based on the procedures proposed by the ITTC. The simulation results are then compared with experimental data with regard to an acceptable agreement between them. Based on the results an approximate relation was extracted for calculating roll damping ratio as a function of rudder vertical angle and Froude number. It can be concluded that the roll damping increases, especially for higher forward speeds, as the angle of the canted rudder system increases.

System-based prediction of maneuvering performance of twin-propeller and twin-rudder ship using a modular mathematical model

The turning circle and zigzag maneuvering performance of surface combatant, DTMB 5415 have been investigated by using system-based method. Unsteady Reynolds averaged Navier Stokes (URANS) approach is utilized to estimate hydrodynamic derivatives and hull-propeller-rudder interactions. DTMB 5415 is a twin-propeller / twin-rudder ship and there are some studies on the derivation of maneuvering coefficients in the literature but none of them took into account the propeller and rudder forces. In this study, static drift, pure yaw, combined yaw and drift, self-propulsion and rudder tests of DTMB 5415 hull have been simulated in calm and deep water condition. Bare hull PMM simulations were carried out for a fixed Froude number of Fr=0.28, while the simulations related to rudder and propeller were performed at Fr=0.25. Computational results were used by MMG (Maneuvering Modeling Group) model to estimate the maneuvering performance of the ship. Hydrodynamic derivatives from numerically generated forces and moment data were obtained by single-run and multiple-run methods. The results from both methods were tested in an in-house maneuvering simulation code (MANSIM) that solves for ship motions and they were compared with computed turning circle and zigzag maneuvering performances. Although it is known a priori that the multiple-run method would give better solution in overall, it was found that the single-run method can be a good alternative in some specific cases. For the zigzag and turning circle tests, the results from single-run method were found satisfactory when correct PMM test conditions were adopted.

Broaching probability for a ship in irregular stern-quartering waves: theoretical prediction and experimental validation

To avoid stability failure due to the broaching associated with surf riding, the International Maritime Organization (IMO) has begun to develop multilayered intact stability criteria. A theoretical model using deterministic ship dynamics and stochastic wave theory is a candidate for the highest layer of this scheme. To complete the project, experimental validation of the theoretical method for estimating broaching probability in irregular waves is indispensable. We therefore conducted free-running model experiments using a typical twin-propeller and twin-rudder ship in irregular waves. A simulation model of coupled surge–sway–yaw–roll motion was simultaneously refined. The broaching probability calculated by the theoretical method was within the 95 % confidence interval of that obtained from the experimental data. This could be an example of experimental validation of the theoretical method for estimating the broaching probability when a ship meets a wave.

Bifurcation analysis of a high-speed twin-propeller twin-rudder ship maneuvering model in roll-coupling motion

In this paper, bifurcation analysis of a high-speed twin-propeller twin-rudder ship maneuvering mathematical model has been carried out. Surge, sway, yaw, and roll are the degrees of freedom considered in the model. Coupling of roll with sway and yaw motion during zigzag and turning maneuvers is shown. Hopf, fold, and period-doubling-type bifurcations are identified by allowing one-parameter numerical continuation of equilibrium. The vertical center of gravity is considered as the bifurcation parameter. Physical behavior of roll motion and capsize during the bifurcations are discussed. The bifurcation analysis is carried out using MATCONT. MATCONT is an MATLAB-based program that computes curves of equilibrium and its bifurcation points for any dynamical system. Influence of the wind on roll angle during turning maneuver is shown.

Manoeuvring characteristics of twin-rudder systems: rudder-hull interaction effect on the manoeuvrability of twin-rudder ships

With a recent increase in ship capacity and propulsion performance, a wide-beam ship fitted with a twin-rudder system has been adopted in many cases. However, to improve ship manoeuvring, it is still necessary to have a better understanding of rudder-hull interactions in twin-rudder ships. Captive model tests (oblique towing and circular motion test) as well as free-running tests with a single-propeller twin-rudder ship and a twin-propeller twin-rudder ship are carried out. The effect of drift angle on the rudder forces and some peculiar phenomena concerning rudder normal force for twin-rudder ships are evaluated. A method for estimating the hull-rudder interaction coefficients based on free-running experimental results is proposed.

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.

Mathematical model of single-propeller twin-rudder ship

A mathematical model of a single-propeller twin-rudder ship has been developed from captive and free running model experiments. An open water rudder experiment was carried out to figure out the characteristics of the rudder. Captive experiments in a towing tank were carried out to figure out the performance of a single-propeller twin-rudder system on a large vessel. Interactions between the hull, propeller and twin rudders, including mutual interactions between the twin rudders, were expressed with several coefficients that were calculated from the experimental results at various ship speeds. In the analysis, the unique characteristics of a single-propeller twin-rudder ship, which affects rudder forces, were explained and formulated in the mathematical model. The captive model tests were conducted with zero ship’s yaw rate, so the interaction coefficients, which are influenced by the yaw rate, are determined from free running model experiments. Validation of the mathematical model of a single-propeller twin-rudder system for a blunt body ship is carried out with an independent set of free running experiments, which were not used for determining the interaction coefficients. The validated numerical model is used for carrying out simulations. Based on simulation results, some recommendations have been proposed for installing a single-propeller twin-rudder system.

二軸二舵船の操縦運動数学モデルに関する研究 : 通常航行時から極低速時の操縦運動について

二軸二舵船の操縦運動数学モデルに関する研究 : 通常航行時から極低速時の操縦運動について

二軸二舵船の船体・プロペラ・舵の相互干渉について

二軸二舵船の船体・プロペラ・舵の相互干渉について

二軸二舵船の操縦性能に関する研究

二軸二舵船の操縦性能に関する研究

A Study on the Manoeuvring Mathematical Model for a Twin-Propeller Twin-Rudder Ship

The so-called M.M.G. mathematical model, a modular type of hydrodynamic model, has proven useful in studying various aspects of ship maneuvering motion. The model was originally developed for a single-propeller, single-rudder ship. Relatively little is known about the maneuvering performance of multipropeller, multirudder ships, though many are in use. The purpose of this paper is to contribute knowledge in this area by clarifying the maneuvering performance of one vessel of this type, the twin-propeller, twin- rudder ship. It is shown that the M.M.G. model can be applied for this type of ship as well, except for the mathematical expression of the propeller wake. This mathematical model of the wake is then modified to well describe the wake. Finally, the predicted maneuvering performance of the twin-propeller, twin-rudder ship is compared with the results of free-sailing model tests to examine the validity of the newly-proposed mathematical model.