Direct Simulations of Turning Circle Maneuver in Waves Using RANS-Overset Method

2018 ◽  
Author(s):  
Jianhua Wang ◽  
Decheng Wan
Keyword(s):  
Open Source ◽  
Rotational Speed ◽  
Computational Domain ◽  
Overset Grids ◽  
Ship Model ◽  
Wave Effects ◽  
Twin Screw ◽  
Free Running ◽  
Flow Visualizations ◽  
Onr Tumblehome

In the present work, a RANS-overset method is used to numerically investigate turning circle maneuver in waves for a twin-screw ship. CFD solver naoe-FOAM-SJTU is used for the numerical computations of the fully appended ONR Tumblehome ship model. Overset grids are used to fully discretize the ship hull, twin propellers and rudders. The simulation of turning circle maneuver is carried out at constant propeller rotational speed with 35° rudder deflection. Open source toolbox waves2Foam is utilized to generate desired waves for the moving computational domain. Predicted ship trajectory and 6DoF motions, hydrodynamic forces and moments acting on the ship and the moving components are presented. The main parameters of the turning circle maneuver, such as the advance, the transfer, the tactical diameter, and the turning diameter, are presented and compared with the available experiment. Wave effects on the free running turning circle maneuver are discussed through detailed flow visualizations. The trajectory and main parameters agree well with the experiment, which show that the present RANS-overset method is a reliable approach to directly simulate turning circle maneuver in waves.

scholarly journals Effect of the Intensive Plasticizing Zone Design on the Effectiveness of Corotating Twin-Screw Extrusion

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Emil Sasimowski ◽  
Łukasz Majewski
Keyword(s):  
Experimental Design ◽  
Rotational Speed ◽  
Extrusion Process ◽  
Empirical Models ◽  
Filling Ratio ◽  
Mixing Zone ◽  
Twin Screw Extrusion ◽  
Screw Extruder ◽  
Screw Extrusion ◽  
Twin Screw

The aim of this study was to investigate the effect of a new intensive plasticizing and mixing screw zone design on the effectiveness of the corotating twin-screw extrusion process for talc-filled polypropylene. The study determined the effect of the angle between the trilobe kneading elements forming the intensive plasticizing and mixing zone of the screws, the screw rotational speed, and the polypropylene/talc filling ratio on the characteristics of the extrusion process in a corotating twin-screw extruder EHP-2x20. The paper describes the experimental design and obtained results as well as the developed empirical models for selected variables of the extrusion process.

Uncertainty Analysis of Free Running Manoeuvring Model Test on a Modern Ferry, With Emphasis on Heel Angles

2019 ◽  
Author(s):  
Anton Kisjes ◽  
Frans Quadvlieg ◽  
Victor Ferrari
Keyword(s):  
Uncertainty Analysis ◽  
Model Test ◽  
Initial Conditions ◽  
Test Series ◽  
Confidence Bounds ◽  
Approach Speed ◽  
Twin Screw ◽  
Free Running ◽  
The Mean ◽  
The Stability

Abstract This paper presents an uncertainty study on the manoeuvring behaviour of a twin screw ferry. In particular, we are interested in heel angles that this ship achieves while manoeuvring. Earlier published uncertainty analysis has focused on the uncertainty of overshoot angles and tactical diameters see [1] and [2]. The heel angles of these ships are not large. However, there is a class of ships that may encounter large heel angles due to steering. Ferries are such ships. The present paper quantifies also the uncertainty of the measured heel angles due to manoeuvres. During the model test series, results are obtained for various values of the stability (GM), where large heel angles are observed. This provides a unique insight in the relation between the GM, approach speed, directional stability and the achieved heel angles. Because of the demonstrated large heel angles, it was important to make an uncertainty analysis of these tests. More publications have been written on the uncertainty of overshoot angles and dimensions of turning circle manoeuvres. However, the uncertainty of heel angles during manoeuvres hasn’t been published yet, which makes this a unique paper. The uncertainty analysis will be based on repeat tests for the zigzag 10°/10° and 35° turning circle manoeuvres. Repeat tests are carried out for these manoeuvres to verify the mean and the uncertainty of the experimentally obtained values. The methodology for estimating the uncertainty with 95% confidence bounds are derived by accounting for 1) uncertainty from measurement, 2) repeat tests and 3) the uncertainty from propagation of initial conditions and the error in check angle and rudder. The uncertainty results are compared with a previous study of uncertainty of manoeuvring characteristics of model tests with the KVLCC2 [1] and [2].

KAJIAN SEAKEEPING KAPAL FERRY RO-RO 750 GT BERBASIS PENGUJIAN HIDRODINAMIKA

ROTOR ◽  
2018 ◽  
Vol 11 (2) ◽  
pp. 8
Author(s):  
Mujahid Syaiful Ahmad
Keyword(s):  
Test Procedure ◽  
Test Methods ◽  
Ocean Basin ◽  
Test Results ◽  
M Wave ◽  
Ship Model ◽  
Measurement Results ◽  
Free Running ◽  
Ship Behavior ◽  
Large Investment

The Ferry Ro-Ro is a ship that functions to crossing inter island and to transport vehicles, passengers and goods. Building a ship requires a very large investment value so that the design of the ship is a very important consideration by conduct the intens study to determine the performance of a ship, one of them is the performance of the ship motion, endurance, and reliability while sailing which can be seen by conducting a hydrodynamic test in the form of a seakeeping test on the Ferry Ro-Ro Ship Model. This study conduct the seakeeping testing due to Ferry Ro-Ro 750 GT Ship Model which aims to predict the pattern of ship behavior by using the seakeeping test methods at Manoeuvering and Ocean Basin at Laboratorium Hidrodinamika Indonesia at Balai Teknologi Hirdoinamika - BPPT with th parameter Wave Height Hs = 2.50 m, Wave Period Tp = 9.00 s by heading 180 deg and 135 deg, and model scale is 1 : 21.19. The seakeeping test procedure for the Ferry Ro-Ro 750 GT Ship Model is based on ITTC No 7.5-02-07-02 standards. Testing of the ship model is conducted by using the method of free running where ship moving at a speed of 12 knots (actual scale). Analysis of measurement results is displayed in the form of Response Amplitude Operator (RAO) and statical analysis. The hydrodynamic test results in the form of a seakeeping test of Ferry Ro-Ro 750 GT Ship Model shows the value of Root Mean Square (RMS) of each direction of the ship relative to the direction of arrival of the wave (heading) 180 deg with roll value = 0.825 deg and pitch value = 2.231 deg. And heading 135 deg with roll value = 2.410 deg and pitch value = 1.797 deg, where NORDFORSK 1987 criteria standard for RMS roll value is 6 deg, and RMS pitch value is 1.5 deg. Keywords: Seakeeping, Ferry Ro-Ro, Hydrodynamics

A New Methodology for the Evaluation of the Maneuvering Characteristics of Surface Ship Models

2008 ◽  
Author(s):  
Joel T. Park ◽  
David D. Hayden ◽  
Joseph H. Kim ◽  
Mark P. Melendez
Keyword(s):  
Calibration Data ◽  
Number Range ◽  
Ship Model ◽  
Surface Ship ◽  
Straight Line ◽  
Free Running ◽  
Quantitative Results ◽  
Turn Radius ◽  
Approach Velocity ◽  
Velocity Calibration

An Arc Second Indoor Global Positioning System (IGPS) has been applied in the evaluation of the maneuvering characteristics of surface ships. The system consists of a series of laser transmitters located around the Maneuvering and Seakeeping (MASK) Basin at the David Taylor Model Basin (DTMB) in West Bethesda, Maryland. Receivers for the location of the model within the MASK are installed on a free-running surface ship model. Since the system provides position of the model within the basin as a function of time, velocity is also computed from finite differences of position and time. The system has been effective in providing velocity calibration data versus propeller shaft speed in straight-line runs. The characteristics of circle maneuvers have also been determined from the system such as the steady turn radius as a function of approach velocity and rudder angle, velocity in a turn, and the drift angle. Quantitative results are provided for a surface ship model in circle maneuvers and velocity calibration from straight-line runs. The typical Froude number range for a test is typically 0.1 < Fr < 0.4 with an uncertainty of ±0.0048 at the 95% confidence level.

scholarly journals Propulsion simulation on fully appended ship model

2021 ◽  
Vol 44 ◽  
pp. 95-100
Author(s):  
Andreea Mandru ◽  
Liliana Rusu ◽  
Florin Pacuraru
Keyword(s):  
Volume Fraction ◽  
Physical Modelling ◽  
Open Water ◽  
Close Attention ◽  
Ship Model ◽  
Multi Phase Flow ◽  
Numerical Discretization ◽  
Multi Phase ◽  
Onr Tumblehome ◽  
Disk Method

This study presents the numerical investigation for the flow around the propeller of the ONR Tumblehome combatant in open water and for the flow around the same ship in the case of self-propulsion with actuator disk method. Computational Fluid Dynamics based on RANS-VOF solver have been used in order to analyse the flow. The free surface treatment is multi-phase flow approach, incompressible and nonmiscible flow phases are modelled through the use of conservation equations for each volume fraction of phase. Accuracy involves close attention to the physical modelling, particularly the effects of turbulence, as well as the numerical discretization.

Validation of Numerical Motion Simulations by Direct Comparison With Time Series From Ship Model Tests in Deterministic Wave Sequences

2005 ◽  
Author(s):  
Gu¨nther F. Clauss ◽  
Janou Hennig ◽  
Heike Cramer ◽  
Kay-Enno Brink
Keyword(s):  
Time Series ◽  
Wave Train ◽  
Test Procedure ◽  
Weather Conditions ◽  
Ship Design ◽  
Ship Motions ◽  
Validation Data ◽  
Ship Model ◽  
Validity Range ◽  
Free Running

Ship safety under normal and severe weather conditions is determined by ship design, approval, and operation. Numerical simulation of ship motions has proven to be a valuable tool for ship design evaluation — not only for accident investigations and studies addressing fundamental stability related phenomena, but also during the design process. A sufficient number of simulations provide a data basis for polar plots to judge the ship’s situation in a sea state — defined by significant wave height and characteristic period — with respect to load case, encounter angle and ship speed. Application of data provided by numerical tools has to take into account the validity range of the model and has to be validated sufficiently by model test data. For providing useful validation data, the exact correlation of wave excitation and ship motion in model testing is indispensable. In the framework of the German research project SINSEE, this is achieved by a fully automated test procedure with a free running ship model in combination with deterministic generation of tailored realistic wave sequences and their transformation to the moving reference frame of the cruising ship. The resultant wave train can be directly correlated with time series of motions — registered by an optical system — and forces. In this paper, these methods are applied to investigate pre-simulated seakeeping scenarios in the model basin and compare the results directly to the simulation results.

Wave Drift Forces Affecting on Maneuverability Derivatives

2011 ◽  
Author(s):  
Yongze Xu ◽  
Takeshi Kinoshita ◽  
Weiguang Bao ◽  
Hiroshi Itakura
Keyword(s):  
Low Frequency ◽  
Hydrodynamic Forces ◽  
Hydrodynamic Coefficients ◽  
Frequency Oscillation ◽  
Low Frequency Oscillation ◽  
Ship Model ◽  
Marine Vehicles ◽  
Small Constant ◽  
Wave Effects ◽  
Wave Drift Forces

Maneuverability in waves is important for the safety of ships and other marine vehicles. Conventionally, the maneuvering experiments are performed in still water at a constant forward velocity. In order to investigate the wave effects on ships steering, a series of towing tests with a Planer Motion Mechanism System (PMM) are carried out in waves in the present work. The ship model is forced to oscillate in horizontal plane at a low frequency when being towed forward at a small constant speed. As an extension of the previous work, the low-frequency oscillation of yaw motion is also considered. Hydrodynamic forces and the displacements of the ship model are measured throughout the tests. Then, the measured data are analyzed by the Fourier analysis to obtain components at different frequencies. By comparing the hydrodynamic forces measured in still water and that in waves, the wave effects on the maneuverability of ships are estimated. The variation of these nonlinear hydrodynamic coefficients against the wave amplitude and wavelength is examined.

scholarly journals Real-Time Parameter Estimation of a Nonlinear Vessel Steering Model Using a Support Vector Machine

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Haitong Xu ◽  
M. A. Hinostroza ◽  
Vahid Hassani ◽  
C. Guedes Soares
Keyword(s):  
Support Vector Machine ◽  
Real Time ◽  
Time Parameter ◽  
Least Square ◽  
Training Data ◽  
Support Vector ◽  
Dynamic Parameters ◽  
Ship Model ◽  
Free Running ◽  
Marine Vessels

The least-square support vector machine (LS-SVM) is used to estimate the dynamic parameters of a nonlinear marine vessel steering model in real-time. First, maneuvering tests are carried out based on a scaled free-running ship model. The parameters are estimated using standard LS-SVM and compared with the theoretical solutions. Then, an online version, a sequential least-square support vector machine, is derived and used to estimate the parameters of vessel steering in real-time. The results are compared with the values estimated by standard LS-SVM with batched training data. By comparison, a sequential least-square support vector machine can dynamically estimate the parameters successfully, and it can be used for designing a dynamic model-based controller of marine vessels.

Estimation of Hydrodynamic Coefficients of a Nonlinear Manoeuvring Mathematical Model With Free-Running Ship Model Tests

2018 ◽  
Vol Vol 160 (A3) ◽  
Author(s):  
Haitong Xu ◽  
M A Hinostroza ◽  
C Guedes Soares
Keyword(s):  
Mathematical Model ◽  
System Identification ◽  
Model Tests ◽  
Loss Functions ◽  
Identification Algorithm ◽  
Hydrodynamic Coefficients ◽  
Global Optimization Algorithm ◽  
Identification Process ◽  
Ship Model ◽  
Free Running

Free-running model tests have been carried out based on a scaled chemical tanker ship model, having a guidance, control and navigation system developed and implemented in LabVIEW. In order to make the modelling more flexible and physically more realistic, a modified version of Abkowitz model was introduced. During the identification process, the model’s structure is fixed and its parameters have been obtained using system identification. A global optimization algorithm has been used to search the optimum values and minimize the loss functions. In order to reduce the effect of noise in the variables, different loss functions considering the empirical errors and generalization performance have been defined and implemented in the system identification program. The hydrodynamic coefficients have been identified based on the manoeuvring test data of free-running ship model. Validations of the system identification algorithm were also carried out and the comparisons with experiments demonstrated the effectiveness of the proposed system identification method.

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