THE EFFECT OF LEEWAY ANGLE ON THE PROPELLER PERFORMANCE

2019 ◽  
Author(s):  
J. J. A. Schot ◽  
R Eggers
Keyword(s):  
Prediction Method ◽  
Model Tests ◽  
Design Stage ◽  
Propulsive Efficiency ◽  
Single Screw ◽  
Captive Model Tests ◽  
Twin Screw ◽  
Propeller Performance ◽  
Thrust And Torque ◽  
Ship Speed

One of the aspects influencing the performance of wind assisted vessels is the effect of leeway (drift) angle on the propeller performance. It is known that due to leeway the delivered propeller power and propulsive efficiency can vary significantly from the straight sailing condition. This effect of leeway angle is studied using a combination of viscous flow calculations and captive model tests for one twin screw and three single screw vessels. It is observed that the changes in mean axial velocity and pre-swirl rotation in the wakefield due to a combination of leeway angle and propeller suction are sufficient to describe the trends observed in captive model tests. This knowledge is used in a proposed prediction method to model the changes in propeller thrust and torque due to leeway angle at the design stage. The prediction model combined with a fit of the average wake parameters for the studied vessel types is finally used the show the trends in propulsive efficiency and delivered propeller power at constant propeller rotation rate and ship speed for small leeway angles.

scholarly journals Numerical Estimation of Hull Hydrodynamic Derivatives in Ship Maneuvering Prediction

2021 ◽  
Vol 28 (2) ◽  
pp. 46-53
Author(s):  
Radosław Kołodziej ◽  
Paweł Hoffmann
Keyword(s):  
Model Tests ◽  
Circular Motion ◽  
Computational Method ◽  
Design Stage ◽  
Hydrodynamic Characteristics ◽  
Ship Maneuvering ◽  
Hydrodynamic Derivatives ◽  
Captive Model Tests ◽  
Ship Maneuverability ◽  
Free Running

Abstract Prediction of the maneuvering characteristics of a ship at the design stage can be done by means of model tests, computational simulations or a combination of both. The model tests can be realized as a direct simulation of the standard maneuvers with the free running model, which gives the most accurate results but is also the least affordable, as it requires a very large tank or natural lake, as well as the complex equipment of the model. Alternatively, a captive model test can be used to identify the hydrodynamic characteristics of the hull, which can be used to simulate the standard maneuvers with the use of dedicated software. Two types of captive model tests are distinguished: circular motion tests (CMT) and planar motion mechanism tests (PMM). The paper presents an attempt to develop a computational method for ship maneuverability prediction in which the hydrodynamic characteristics of the hull are identified by means of computational fluid dynamics (CFD). The CFD analyses presented here directly simulate the circular motion test. The resulting hull characteristics are verified against the available literature data, and the results of the simulations are verified against the results of free running model tests. Reasonable agreement shows the large potential of the proposed method.

Numerical Prediction of Propeller Characteristics

1973 ◽  
Vol 17 (01) ◽  
pp. 12-18
Author(s):  
Damon E. Cummings
Keyword(s):  
Open Water ◽  
Model Tests ◽  
Numerical Prediction ◽  
Water Model ◽  
Variable Pitch ◽  
Cavitation Inception ◽  
Fraction Distribution ◽  
Thrust And Torque ◽  
Ship Speed

A procedure is described for predicting the performance of a propeller numerically to within the accuracy of tunnel and open-water model tests. Given the geometry of the propeller, ship speed, wake fraction distribution and rpm, the thrust and torque characteristics are calculated. The procedure gives good results not only for "normal" propellers but also for such abnormal cases as a variable-pitch propeller operating at off-design pitches. The possibility exists of extension of the method for calculation of spindle torques, stresses, and cavitation inception.

Numerical Calculation of Added Mass for Ship Dynamic Stability by High Order Panel Method

2011 ◽  
Vol 97-98 ◽  
pp. 802-805
Author(s):  
Hua Ming Wang ◽  
Han Xing Zhao ◽  
Yu Long Yang ◽  
Xiao Song Rui
Keyword(s):  
Dynamic Stability ◽  
Three Dimensional ◽  
Added Mass ◽  
Model Tests ◽  
Panel Method ◽  
Design Stage ◽  
Captive Model Tests ◽  
Ship Maneuverability ◽  
Wigley Hull ◽  
Free Running

IMO Standards for ship maneuverability require prediction of ship’s maneuvering performance at the design stage. For this purpose, various methods such as those based on free running model tests, captive model tests or numerical simulation using mathematical models can be used. While this paper describes a numerical method for estimating ship’s dynamic stability by computing the linear sway and yaw added mass coefficients using a higher-order panel method based on Non-Uniform Rational B-Spline. Three dimensional forward-speed radiation problems are formulated and solved in frequency domain. The linear hydrodynamic coefficients are calculated and preliminary results are presented for a modified Wigley hull.

Evaluation of Linear and Nonlinear Hydrodynamic Coefficients of Underwater Vehicles Using CFD

2009 ◽  
Author(s):  
Amit Ray ◽  
S. N. Singh ◽  
V. Seshadri
Keyword(s):  
Underwater Vehicles ◽  
General Purpose ◽  
Model Tests ◽  
The Body ◽  
Design Stage ◽  
Hydrodynamic Coefficients ◽  
Concept Design ◽  
Straight Line ◽  
Captive Model Tests ◽  
Linear And Nonlinear

Hydrodynamic coefficients (HDCs) in the equations of motion for trajectory simulation of any underwater vehicle are inherent characteristics of the body geometry. At the concept design stage of underwater vehicles, there is a requirement for affordable and efficient use of general-purpose CFD tools to get a first estimate of the HDCs, with greater accuracy than empirical methods, but at lesser cost and time than model testing. This paper reports the prediction of values of straight-line and rotary HDCs for a submerged axisymmetric body of revolution using a general-purpose RANSE solver and with modest, readily available computational facilities. Various alternatives for grid generation and grid size have been compared and a solution strategy evolved to optimize requirements of accuracy, time and computational resources. Linear and nonlinear HDCs for straight-line and rotary motions were obtained by curve-fitting of the forces and moments plotted against angle of attack and angular velocity. To compute rotary HDCs, an approach was evolved to define a circular domain and effectively simulate the motion of a model in Rotating Arm captive model tests. Results were compared with experimental results from Planar Motion Mechanism tests of the same body. The trends in variation of forces and moments are captured well by computations. Accuracy obtained for yaw moment HDCs is comparable to the uncertainty levels from model tests. It is shown that CFD techniques offer flexibility for computing nonlinear coefficients as well, by simulating combinations of linear and angular velocities.

Ship-Model Correlation of Powering Performance on USS Oliver Hazard Perry, FFG-7 Class

1983 ◽  
Vol 20 (01) ◽  
pp. 35-52
Author(s):  
Everett L. Woo ◽  
Gabor Karafiath ◽  
Gary Borda
Keyword(s):  
Performance Prediction ◽  
Prediction Method ◽  
Model Tests ◽  
Trial Data ◽  
Full Scale ◽  
Ship Model ◽  
Single Screw ◽  
Post Trial ◽  
Model Correlation

Standardization trials were conducted on USS Oliver Hazard Perry (FFG-7) in May 1978. From the results of the trial data and the post-trial model correlation experiments which simulated the trial conditions, the powering correlation allowance of 0.00045 was obtained for the FFG-7. It should be noted that the pretrial model tests used the design correlation allowance of 0.0005 to predict full-scale powering performance. In addition, the powering performance was predicted using the "1978 ITTC Performance Prediction Method for Single Screw Ships."

Experimental Performance of a Trochoidal Propeller with High-Aspect-Ratio Blades

1989 ◽  
Vol 26 (03) ◽  
pp. 192-201 ◽  
Author(s):  
Neil Bose ◽  
Peter S. K. Lai
Keyword(s):  
Aspect Ratio ◽  
High Efficiency ◽  
Open Water ◽  
Finite Amplitude ◽  
Dynamic Stall ◽  
Frictional Drag ◽  
Overall Performance ◽  
Small Ship ◽  
Propeller Performance ◽  
Thrust And Torque

Open-water experiments were done on a model of a cycloidal-type propeller with a trochoidal blade motion. This propeller had three blades with an aspect ratio of 10. These experiments included the measurement of thrust and torque of the propeller over a range of advance ratios. Tests were done for forward and reverse operation, and at zero speed (the bollard pull condition). Results from these tests are presented and compared with: a multiple stream-tube theoretical prediction of the performance of the propeller; and a prediction of the performance of a single blade of the propeller, oscillating in heave and pitch, using unsteady small-amplitude hydrofoil theory with corrections for finite amplitude motion, finite span, and frictional drag. At present, neither of these theories gives a completely accurate prediction of propeller performance over the whole range of advance ratios, but a combination of these approaches, with an allowance for dynamic stall of the blades, should lead to a reliable simple theory for overall performance prediction. Application of a propeller of this type to a small ship is discussed. The aim of the design is to produce a lightly loaded propeller with a high efficiency of propulsion.

Model Tests for the Validation of Extreme Roll Motion Predictions

2002 ◽  
Author(s):  
Walter L. Kuehnlein ◽  
K.-E. Brink
Keyword(s):  
Practical Knowledge ◽  
Rapid Development ◽  
Model Tests ◽  
Design Stage ◽  
Roll Motion ◽  
Ministry Of Education ◽  
Following Seas ◽  
Early Design Stage ◽  
Shaped Container ◽  
Motion Characteristics

At present common stability criteria are based on practical knowledge gained from the operation of ships. Therewith the assessment of ship safety against capsizing is partly determined by long-term statistics of accidents. Regulations like the IMO-Resolution A 167 do not rate the typical seakeeping characteristics of different hull form geometries. Therefore strictly speaking, these criteria are just applicable for ships of similar types as included in statistics. Rapid development in ship design calls for the determination of ship and cargo safety in regard of extreme roll motions or capsizing during early design stage. Within the ROLL-S project, which was founded by the German Federal Ministry of Education and Research, dynamic stability tests with a box shaped Container Ship and a RO-RO vessel have been performed. The performance of model tests, which are intended to serve for the validation of numerical simulation methods, put high demands on test and data acquisition techniques. The data of the waves encountered, course and position, as well as the response of the model had to be determined by model tests in order to use these data for the validation of numerical ship motion simulations. During the tests extreme roll motions of the two considered vessels could be observed in head seas and in following seas. Besides critical motion characteristics in following seas, like broaching, parametric induced roll motion effects were investigated in head sea condition. Remark: This paper should be read in conjunction with paper OMAE 2002-28297 which describes generation and transformation of the used waves.

Performing captive model tests with a hexapod

2019 ◽  
Vol 171 ◽  
pp. 49-58 ◽  
Author(s):  
Haiwen Tu ◽  
Lei Song ◽  
De Xie ◽  
Zeng Liu ◽  
Zhengyi Zhang ◽  
...  
Keyword(s):  
Model Tests ◽  
Captive Model Tests
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