Turning Circle Maneuver Research Articles

Design of a Bio-inspired Hull Shape for an AUV from Hydrodynamic Stability Point of View through Experiment and Numerical Analysis

The hydrodynamic characteristics and body shape of catfish, Hypostomus, are used to design and develop an Autonomous Underwater Vehicle (AUV) named ZRAUV for subsea pipeline and cable inspection. Among the hydrodynamic characteristics, stability of this bio-inspired AUV, which may be adversely affected by disturbances such as marine currents during inspection process, is taken into consideration and evaluated both numerically and experimentally. Concerning numerical investigation, computational fluid dynamics based on Reynolds Averaged Navier-Stokes equations are applied to compute the hydrodynamic damping derivatives needed for stability analysis. In order to verify the numerical predictions, computations are also performed for the well-known submarine body with a typical axisymmetric hull shape, SUBOFF. Experiments are also carried out for both proposed AUV and a conventional axisymmetric one using self-propulsion tests. Measurements of turning rate in turning circle maneuver are in reasonably good agreement with those of numerical estimations and indicate that the turning rate of conventional bodies like SUBOFF is approximately 3.8 times as great as that of bio-inspired AUV. In other words, the findings reveal that in comparison with common axisymmetric bodies, the proposed AUV with biological hull shape is more stable by about 99%, thus, it is highly suitable for subsea pipeline and cable inspection.

Obtaining First and Second Order Nomoto Models of a Fluvial Support Patrol using Identification Techniques

In this paper we present a method for obtaining a second order Nomoto model that describes the yaw dynamic of a Patrol River Boat. This model is obtained from experimental input and output data gathered from the turning circle maneuver. System identifications techniques and a gray box model are employed to find the coefficients of the Nomoto model. The results of the identification process as well as the results of validation process are presented

CFD analysis of the sensitivity of propeller bearing loads to stern appendages and propulsive configurations

The present investigation focuses on the effects of the stern appendages and the propulsion system on the hydro-loads generated by the propeller during off-design conditions, with particular emphasis on the in-plane components. Recent experimental investigations carried out by free running model tests [7,8] and CFD analysis [5] for a modern twin screw model, highlighted that maneuvers at small drift angles and yaw rates might be as critical as the tighter ones due to complex propeller-wake interactions. Therefore, design criteria should take into account also these operative conditions, in order to reduce the effects of propeller-wake interaction phenomena that degrade the overall propulsive efficiency, induce shaft/hull structural vibration and increase noise emission. In the present study we analyze the effects of geometric and propulsive modifications with respect to the twin screw configuration studied in [5]. In particular, the effect of the centreline skeg, propeller direction of rotation and control strategies of the propulsion plant on the propeller bearing loads have been investigated from the analysis of the nominal wake in maneuvring conditions, computed by unsteady RANSE simulations coupled with a propeller model based on Blade Element Theory. The considered test cases were turning circle maneuvers with different rudder angles at FN=0.265.

Analysis of propeller bearing loads by CFD. Part II: Transient maneuvers

The numerical study presented in Part I (Dubbioso et al., 2017) on the bearing loads developed by the propellers of a twin screw model during quasi–steady conditions is extended to transient maneuvers. In the previous study, numerical simulations highlighted that the hydrodynamic loads might experience significant peak at moderate turning rates due to complex interaction of the propeller with the wake. In the present paper, the complete turning circle maneuver at δ=35∘ at Fr=0.265 is numerically simulated in order to analyze the character of the blade loads during the transient phases after the actuation of the rudder (start and pull–out). The analysis shows that the overall degradation of the propeller performance may occur also at kinematic conditions weaker than those usually considered as the most critical ones (in general, tight maneuvers); therefore, these conditions should be accounted for also in the early design phases.

Analysis of the asymmetric behavior of propeller–rudder system of twin screw ships by CFD

The interference between the hull, propeller and rudder remarkably affects the control and maneuvering capabilities of marine vehicles. In case of twin screw/twin rudder ships, the asymmetric evolution of the wake past the hull causes the asymmetric functioning of the propeller–rudder system. Systematic investigations on this aspect for twin screw ships are limited. Available experimental data carried out on simplified hull–propeller–rudder system and captive model tests do not allow to completely understand the fluid mechanism at the basis of the hydrodynamic interaction that should be taken into account in simplified maneuvering mathematical models for preliminary predictions. In this paper the hull–propeller–rudder interactions phenomena for a twin screw/twin rudder model are investigated by URANS simulations, with a particular focus on the asymmetry of the propeller–rudder system. To this aim, captive model tests consisting of pure rudder and coupled drift–yaw motions corresponding to the steady phases of turning circle maneuvers at different rudder angles (δ=15°÷35°) are performed at the speed correspondent to Fr=0.265. Moreover, a free running maneuvering simulation is also performed to gain more insight on the transient phase of the maneuver. An identity rudder lift methodology is applied to synthesize the hull–propeller–rudder interactions by means of a flow straightening coefficient; the analysis highlights that these effects are weak and invariant with respect to the rudder angle on the windward shaft, whereas on the leeward side these effects are extremely sensitive to the evolution of the hull and propeller wake.

Evaluation of planing craft maneuverability using mathematical modeling under the action of the rudder

In the recent years, different mathematical models are suggested for maneuvering of displacement vessels which are capable to estimate the vessel maneuver with acceptable precision. But simulation of planing craft maneuverability through mathematical model is not developed yet. In this paper a mathematical model is developed for planing craft maneuvering by including the rudder forces and moments. Different maneuvers are executed through the mathematical model such as straight-line stability, course keeping and turning circle maneuver. Simulation results were validated with the published experimental results and they are in good agreement. Finally, the influence of rudder angle on maneuverability of planing craft was studied and also the effect of aspect ratio has been investigated. The mathematical model and hydrodynamic coefficients were presented in this paper can be applied for the optimization of planing craft maneuvering and the course control purposes.

Adaptive Fuzzy Autopilot for a Scale Ship Model

This paper discusses the implementation of an adaptive fuzzy autopilot for a scale ship model using a Fuzzy Model Reference Learning Controller (FMRLC). Initially, a fuzzy singleton model of the scale ship model is obtained from experimental input and output data gathered from the turning circle manoeuvre. After that, the paper describes how to design a Fuzzy Model Reference Learning Controller (FMRLC) for controlling the directional heading of the scale ship model. At the end, results of the implementation of the adaptive ship autopilot are showed.

Sensitivity analysis of the hydrodynamic coefficients in 4 degrees of freedom ship manoeuvring mathematical model

The S-type test is simulated based on a ship manoeuvring mathematical model of 4 degrees of freedom (4-DOF); simultaneously, sensitivity analysis of the hydrodynamic coefficients in the mathematical model is implemented by using an indirect method. The mathematical model is simplified by omitting the coefficients of smaller sensitivity according to the results of sensitivity analysis. The 10° /10° zigzag test and 35° turning circle manoeuvre are simulated with the original and the simplified mathematical models. The comparison of the simulation results shows the effectiveness of the sensitivity analysis and the validity of the simplified model.

System identification modelling of ship manoeuvring motion based on support vector regression

Based on the ɛ – support vector regression, three modelling methods for the ship manoeuvring motion, i.e., the white-box modelling, the grey-box modelling and the black-box modelling, are investigated. The 10°/10°, 20°/20° zigzag tests and the 35° turning circle manoeuvre are simulated. Part of the simulation data for the 20°/20° zigzag test are used to train the support vectors, and the trained support vector machine is used to predict the whole 20°/20° zigzag test. Comparison between the simulated and predicted 20°/20° zigzag test shows a good predictive ability of the three modelling methods. Then all mathematical models obtained by the modelling methods are used to predict the 10°/10° zigzag test and 35° turning circle manoeuvre, and the predicted results are compared with those of simulation tests to demonstrate the good generalization performance of the mathematical models. Finally, the modelling methods are analyzed and compared with each other in terms of the application conditions, the prediction accuracy and the computation speed. An appropriate modelling method can be chosen according to the intended use of the mathematical models and the available data for the system identification.

Turning ability analysis of a fully appended twin screw vessel by CFD. Part I: Single rudder configuration

The turning circle manoeuvre of a naval supply vessel (characterized by a block coefficient CB~0.60) is simulated by the integration of the unsteady Reynolds-Averaged Navier Stokes equations coupled with the equations of rigid body motion with six degrees of freedom. The model is equipped with all the appendages, and it is characterised by an unusual single rudder/twin screws configuration. This arrangement causes poor directional stability qualities, which makes the prediction of the trajectory a challenging problem. As already shown in previous works, the treatment of the in-plane loads exerted by the propellers is of paramount importance; to this aim each propeller is simulated by an actuator disk model, properly modified to account for oblique flow effects. The main goal of the present paper is to assess the capability of the CFD tool to accurately predict the trajectory of the ship and to analyse the complex flow field around a vessel performing a turning manoeuvre. Distribution of forces and moments on the main hull, stern appendages and rudder are analysed in order to gain a deeper insight into the dynamic behaviour of the vessel. Validation is provided by the comparison with experimental data from free running tests.

System identification modeling of ship manoeuvring motion in 4 degrees of freedom based on support vector machines

Based on support vector machines, three modeling methods, i.e., white-box modeling, grey-box modeling and black-box modeling of ship manoeuvring motion in 4 degrees of freedom are investigated. With the whole-ship mathematical model for ship manoeuvring motion, in which the hydrodynamic coefficients are obtained from roll planar motion mechanism test, some zigzag tests and turning circle manoeuvres are simulated. In the white-box modeling and grey-box modeling, the training data taken every 5 s from the simulated 20°/20° zigzag test are used, while in the black-box modeling, the training data taken every 5 s from the simulated 15°/15°, 20°/20° zigzag tests and 15°, 25° turning manoeuvres are used; and the trained support vector machines are used to predict the whole 20°/20° zigzag test. Comparisons between the simulated and predicted 20?/20° zigzag tests show good predictive ability of the proposed methods. Besides, all mathematical models obtained by the proposed modeling methods are used to predict the 10°/10° zigzag test and 35° turning circle manoeuvre, and the predicted results are compared with those of simulation tests to demonstrate the good generalization performance of the mathematical models. Finally, the proposed modeling methods are analyzed and compared with each other in aspects of application conditions, prediction accuracy and computation speed. The appropriate modeling method can be chosen according to the intended use of the mathematical models and the available data needed for system identification.

A time-domain strip theory approach to maneuvering in a seaway

A time-domain body exact strip theory is developed to predict maneuvering of a vessel in a seaway. A frame following the instantaneous position of the ship, by translating and rotating in the horizontal plane, is used to set up the boundary value problem (BVP) for the perturbation potentials. A boundary integral technique is used for solving the Laplace equation. Linearized free surface boundary conditions are used for stability and computational efficiency, and exact body boundary conditions are used to capture nonlinear effects. A nonlinear rigid body equation of motion solver is coupled to the hydrodynamic model to predict ship responses. Results are presented for the turning circle maneuver of the containership S-175 in calm water and in the presence of regular waves. The results are compared with available experimental results. The simulations are able to capture general qualitative aspects and overall physics of the problem.

Design of a Fuel-Cell-Powered Catamaran-Type Unmanned Surface Vehicle

The goal of this study is to verify the applicability of fuel cells for powering surface vessels by developing a small catamaran-type unmanned surface vehicle (USV) powered by a hydrogen fuel cell. This study encompasses the entire process of designing a fuel-cell-powered USV, as well as sea trial tests with a 1.487-m full-scale prototype. To improve the performance and system efficiency of the USV, a simulation-based hull form design and integrated control systems were implemented during the design process. First, the optimum hull form of the catamaran, with the optimum separation, was determined based on hydrodynamic optimization using parametric models to achieve good fuel economy. Second, an automatic control system integrated with the global positioning and inertial navigation systems was implemented in the designed catamaran so that it had the ability to perform waypoint, departure, station keeping, and turning circle maneuvers. Next, the gain parameters of the fuzzy proportional-integral-derivative (PID) controller were adjusted to assure reliable tracking control. Automatically controlled trial tests were then conducted to validate the performance of the autonomous surface vehicle with respect to the fuel cell power requirements and its dynamic motion. Based on the results of the trial tests and the transient response of the fuel cell, a hybrid power control algorithm for the fuel cell and the batteries was implemented for more efficient power utilization. This catamaran-type unmanned surface vehicle powered with a fuel cell can be utilized for ocean environment monitoring and multifunctional missions.

Investigation of the radial bearing force developed during actual ship operations. Part 1: Straight ahead sailing and turning maneuvers

The quantification of the radial force exerted by the propeller is of paramount importance for the improvement of the design procedures as well as for enhancing the prediction of the controllability and maneuvering qualities of oceangoing vessels. In this work the radial load experienced by the bearing strut of a twin screw configuration is experimentally investigated by free running model tests carried out at the CNR-INSEAN outdoor maneuvering basin. To this purpose the model has been equipped with a novel, in-house developed, two-component transducer. Results obtained for the straight ahead motion for a large range of speeds (0.05<FN<0.425) and turning circle maneuvers at different rudder angles (15°–35°) and three different speeds (FN=0.218, 0.32 and 0.35) are presented and discussed in this paper. The main task is also to identify, from a phenomenological perspective, the nature of this load, in particular during tight maneuvers, characterized by critical overloading of the propellers. The use of the free running, self-propelled model, is the best way to gain a deeper insight on the loads generated by the propeller during quasi-steady and, especially, transient motions that are difficult to reproduce in a towing tank via captive model tests.

Sensitivity analysis and parametric identification for ship manoeuvring in 4 degrees of freedom

The spiral test is simulated by using a ship manoeuvring mathematical model of 4 degrees of freedom. Based on the simulation data, sensitivity analysis using the direct method is implemented for the hydrodynamic coefficients in the mathematical model, and the mathematical model is simplified by omitting the coefficients of smaller sensitivity according to the sensitivity analysis results. 10°/10°, 20°/20° zigzag tests and 35° turning circle manoeuvre are simulated with the original and the simplified mathematical models. The comparison of simulation results obtained by the original and the simplified models shows the effectiveness of the sensitivity analysis and the validity of the simplified model. The hydrodynamic coefficients in the simplified model are then identified by using the least square support vector machines, with the training samples taken from the simulation data of 20°/20° zigzag test. 20°/20°, 10°/10° zigzag tests and 35° turning circle manoeuvre are predicted by using the identified hydrodynamic coefficients, and the predicted results are compared with the simulation results to demonstrate the validity and generalization performance of the identification method.

Manoeuvring simulation of catamaran by using implicit models based on support vector machines

Manoeuvring models based on support vector machines (SVMs) are proposed for the manoeuvring simulation of a catamaran. Implicit models of manoeuvring motion are derived from the SVM regression instead of using the traditional methods for identification of the hydrodynamic coefficients. Data obtained from full-scale trials are used for regression analysis. Disturbances induced by current and wind are estimated. At the training stage, the inputs to the SVMs are the surge speed, sway speed, yaw rate and rudder angle, while the outputs are the derivatives of the surge speed, sway speed and yaw rate, respectively. At the simulation stage a predictive model is constructed with the obtained support vectors, Lagrangian factors and a constant. The Gauss function kernel is employed in the SVMs to guarantee the performance of the approximation and the robustness of the SVM regressor. The turning circle manoeuvre is simulated based on the regression manoeuvring models. Comparisons between the trials and the simulated results are conducted to demonstrate the validity of the proposed modelling method.

Influence of propulsion system configuration on the manoeuvring performances of a surface twin-screw ship

Propulsion system can experience large power absorption fluctuations during tight maneuvers. In the case of a turning circle manoeuvre for a twin-screw ship, the power required by the two shaft lines can be completely different; in case of non conventional propulsion system, like cross-connect configurations, a compromise must be met in order to design a safe control system without affecting dramatically the vessel's manoeuvring performance. In this work, a series of free running model tests on a unmanned surface twin screw ship model have been carried out in order to investigate the influence of different propulsion system operation settings on the vessel's manoeuvring characteristics.

Simulation of turning circle by CFD: Analysis of different propeller models and their effect on manoeuvring prediction

Propeller modelling in CFD simulations is a key issue for the correct prediction of hull-propeller interactions, manoeuvring characteristics and the flow field in the stern region of a marine vehicle. From this point of view, actuator disk approaches have proved their reliability and computational efficiency; for these reasons, they are commonly used for the analysis of propulsive performance of a ship. Nevertheless, these models often neglect peculiar physical phenomena which characterise the operating propeller in off-design condition, namely the in-plane loads that are of paramount importance when considering non-standard or unusual propeller/rudder arrangements. In order to emphasize the importance of these components (in particular the propeller lateral force) and the need of a detailed propeller model for the correct prediction of the manoeuvring qualities of a ship, the turning circle manoeuvre of a self-propelled fully appended twin screw tanker-like ship model with a single rudder is simulated by the unsteady RANS solver χnavis developed at CNR-INSEAN; several propeller models able to include the effect of the strong oblique flow component encountered during a manoeuvre have been considered and compared. It is emphasized that, despite these models account for very complex and fundamental physical effects, which would be lost by a traditional actuator disk approach, the increase in computational resources is almost negligible. The accuracy of these models is assessed by comparison with experimental data from free running tests. The main features of the flow field, with particular attention to the vortical structures detached from the hull are presented as well.

Manoeuvre test simulation of a teleoperated robot designed for flow measurement in natural water bodies

This article describes the simulation results of manoeuvring operations used in ships, but applied to an SA-1 teleoperated aquatic robot. The SA-1 is a type of robot designed for flow measurement in natural water bodies (rivers, lakes). A robot's dynamic stability and course stability must be guaranteed due to the different tasks assigned to it. These features can be demonstrated through the pull-out manoeuvre, the Dieudonné spiral manoeuvre, modified Kempf manoeuvre and turning circle manoeuvre. System behaviour when using such manoeuvres can be used to propose a better control system for improving robot performance or modify system design.

Influence of propulsion system configuration on the manoeuvring performance by free running model tests

Propulsion system can experience large power absorption fluctuations during tight maneuvers. In the case of a turning circle maneuver for a twin-screw ship, the power required by the two shaft lines can be completely different; in case of non conventional propulsion system, like cross-connect configurations, a compromise must be met in order to design a safe control system without affecting dramatically the vessel's maneuvering performance. In this work, a series of free running model tests have been carried out in order to investigate the influence of different propulsion system operation settings on the vessel's maneuvering characteristics.