SHAFT LOADS ON AZIMUTH PROPULSORS IN OBLIQUE FLOW AND WAVES

2021 ◽  
Vol 153 (A1) ◽  
Author(s):  
H Amini ◽  
S Steen
Keyword(s):  
Mechanical Design ◽  
Bending Moment ◽  
Ship Hull ◽  
Propeller Shaft ◽  
Towing Tank ◽  
Oblique Flow ◽  
Straight Line ◽  
Calm Water ◽  
Bending Loads ◽  
Marine Technology

A range of model experiments have been carried out in calm water and waves for an oil spill vessel model with twin tractor azimuth thrusters at different heading angles and advance coefficients in the large towing tank at the Marine Technology Centre in Trondheim, Norway. Propeller shaft bending loads have been measured using a shaft dynamometer capable of measuring all shaft side force and bending moment components as well as propeller torque and thrust. The results include the loads on the propeller shaft with and without the presence of a ship hull model at the same heading angles and advance velocities in order to study the wake influence from the ship hull on the hydrodynamic loads. Results show that the ship hull wake has a much stronger effect on the propeller loads when the propeller is azimuthed outward from the ship hull centreline than inward. Measurements from the experiments in waves are also presented for the same thruster model in a straight-line course for both the head and following sea states under different wave conditions. Larger bending loads are found in head sea conditions compared with the following sea conditions. Generally it is found that the shaft bending loads and lateral forces are quite large, which is important to consider in the mechanical design layout and for dimensioning of components.

Experimental and Theoretical Analysis of Propeller Shaft Loads in Oblique Inflow

2011 ◽  
Vol 55 (04) ◽  
pp. 268-288 ◽  
Author(s):  
Hamid Amini ◽  
Sverre Steen
Keyword(s):  
Bending Moment ◽  
Lateral Force ◽  
Propeller Shaft ◽  
Oblique Flow ◽  
Bending Loads ◽  
Inflow Conditions ◽  
Straight Ahead ◽  
Pushing And Pulling ◽  
Good Agreement ◽  
Blade Element

A series of model tests on an azimuth thruster model in oblique inflow conditions were performed for different heading angles and at different advance coefficients in pushing and pulling modes. Tests were performed in ventilating and non-ventilating conditions. A novel shaft dynamometer was used to measure all six component forces and moments on the propeller shaft. It was found that the propeller shaft lateral force and bending moment were quite large, and thus, the load at the shaft-bearing positions was about three times larger than when only the propeller weight was considered. The results also showed that oblique inflow due to steering gives higher bending loads than when the propeller is subject to ventilation in the straight-ahead condition. A basic blade element momentum method (BEMT) was used to predict the forces and moments on the propeller shaft in oblique flow conditions. Fairly good agreement was found between the BEMT results and the experimental results.

Experimental Study of a Tanker Ship Squat in Shallow Water

2014 ◽  
Vol 66 (2) ◽  
Author(s):  
Mohammadreza Fathi Kazerooni ◽  
Mohammad Saeed Seif
Keyword(s):  
Experimental Study ◽  
Shallow Water ◽  
Experimental Approach ◽  
Model Tests ◽  
Ship Hull ◽  
Experimental Results ◽  
Shallow Waters ◽  
Towing Tank ◽  
Ship Model

One of the phenomena restricting the tanker navigation in shallow waters is reduction of under keel clearance in the terms of sinkage and dynamic trim that is called squatting. According to the complexity of flow around ship hull, one of the best methods to predict the ship squat is experimental approach based on model tests in the towing tank. In this study model tests for tanker ship model had been held in the towing tank and squat of the model are measured and analyzed. Based on experimental results suitable formulae for prediction of these types of ship squat in fairways are obtained.

Vibration and sound radiation analysis of the final drive assembly considering the gear-shaft coupling dynamics

2016 ◽  
Vol 230 (7-8) ◽  
pp. 1258-1275 ◽  
Author(s):  
Yawen Wang ◽  
Junyi Yang ◽  
Dong Guo ◽  
Teik C Lim
Keyword(s):  
Dynamic Models ◽  
Acoustic Analysis ◽  
Bending Moment ◽  
Moment Of Inertia ◽  
System Dynamic ◽  
Dynamic Responses ◽  
Propeller Shaft ◽  
Hypoid Gear ◽  
Gyroscopic Effect ◽  
Gear Mesh

A generalized dynamic model of driveline system is formulated that includes the coupling effect and gyroscopic moments of the propeller shaft and hypoid gear rotor assembly. Firstly, the dynamic models with only gear-shaft coupling, with only gyroscopic effect, and with both gear-shaft coupling and gyroscopic effect are analyzed and compared. The results show that the combined effects of the gear-shaft interaction and gyroscopic behavior have considerable influence on the system dynamic responses surrounding gear bending resonances, especially for the bearing responses. However, the gear out-of-phase torsional modes still dominate the gear mesh frequency response. Secondly, the influence of pinion bending moment of inertia, propeller shaft stiffness and bearing stiffness on the system dynamic responses are examined. The system responses are then applied to perform further vibration and acoustic analysis for an axle housing structure. Computational results reveal that NVH (noise, vibration, and harshness) refinement can be achieved by tuning the pinion bearing rotational stiffness and pinion bending moment of inertia for the example considered. This study provides an understanding of the interaction between hypoid gear pair and propeller shaft, and can be employed to enhance driveline system design.

An Evaluation of Planing Boat Trim Measurements

2017 ◽  
Author(s):  
Carolyn Judge ◽  
Bill Beaver ◽  
John Zseleczk
Keyword(s):  
Performance Prediction ◽  
Measurement Methods ◽  
The Other ◽  
Test Program ◽  
Towing Tank ◽  
Calm Water

The resistance of a planing hull is known to be highly dependent on trim angle. For several reasons, trim is difficult to measure to the level of accuracy normally attained with other towing tank measurements such as resistance or speed. In a recent study intended to validate CFD methods for planing hulls, 4’ and 8’ long geosim models of the Generic Prismatic Planing Hull (GPPH) were built and tested at USNA. Significant differences were found between the trim of the two models so a separate test program was conducted which focused specifically on the trim measurement of these two models in calm water. Five different trim measurement methods were used simultaneously on one model and then used again on the other model. Trim angles were compared between measurement methods and between models. Trim measurements with the same model agreed well and are the basis for an evaluation of measurement methods. The trim measured on the two different size models did not agree well even though the same instruments were used in most cases. The paper discusses reasons for the confirmed differences in calm water running trim of the two models and suggests ways to take advantage of this knowledge to make the best use of towing tank tests for planing boat performance prediction.

The Stresses Developed in Sections Subjected to Bending Moment

1942 ◽  
Vol 46 (379) ◽  
pp. 161-180 ◽  
Author(s):  
J. L. Beilschmidt
Keyword(s):  
Bending Moment ◽  
Stress Strain ◽  
Strain Characteristic ◽  
Fibre Stress ◽  
Straight Line ◽  
The Law

It is a well known fact that the (simple) Engineers’ Theory of Bending is based on the assumption of the Law of Proportionality, that is to say that the stress-strain characteristic of the material concerned is a straight line, and it accordingly follows that stress values determined by the formulæ: , for the stress at any station on the section, and M/Z for the maximum fibre stress can be correct only when the M/Z value lies within the limit of proportionality of the material.

A Comparison of Some Multivariate Weibull Distributions

2010 ◽  
Author(s):  
Bernt J. Leira
Keyword(s):  
Probability Density ◽  
Density Function ◽  
Statistical Models ◽  
Mechanical Design ◽  
Bending Moment ◽  
Probability Density Functions ◽  
Density Functions ◽  
Weibull Distributions ◽  
Linear Combinations ◽  
Simplified Procedure

Three different possible choices of statistical models for multivariate Weibull distributions are considered and compared. The concept of “a correlation field” is introduced and is subsequently applied for the purpose of comparing the different models. Linear combinations of Weibull distributed random variables are considered, and expressions for the corresponding probability density functions are established. Furthermore, a simplified procedure for approximating the resulting density function is described. Comparison is made between the statistical moments of increasing order for the specific case of two Weibull components. This example of application arises e.g. in connection with mechanical design of a column which is subjected to a bi-axial bending moment.

Investigation of Hydrodynamic Loads and Flow Patterns Near an Escort Tug in Oblique Flows

2015 ◽  
Author(s):  
Fatima Jahra ◽  
Mohammed Islam ◽  
Worakanok Thanyamanta ◽  
David Molyneux
Keyword(s):  
Flow Pattern ◽  
Measurement Data ◽  
Suction Side ◽  
The Public ◽  
Model Free ◽  
Oblique Flow ◽  
Image Velocimetry ◽  
Calm Water ◽  
Volume Method ◽  
Yaw Angle

The present research investigates the hydrodynamic forces and moments and the flow pattern near the hull of an escort tug at steady oblique flow conditions. An escort tug is modelled and numerical simulations have been carried out using a commercial RANS solver. In the simulations, the viscous flow field is calculated by the finite volume method, adapting the k-ε turbulence model. Free surface is modeled using the Volume of Fluid (VOF) approach for calm water condition. The hull is assumed fixed in space with an even keel. Grid dependency studies are conducted to obtain insight into the reliability and accuracy of the results. Flow velocities around the escort tug as well as integral variables are computed at different Froude numbers and compared to the corresponding measurement data available in the public domain. The measurements was completed using a Planar Motion Mechanism (PMM) apparatus to measure the resistance, side force and yaw moment of the tug hull. Additionally, the velocity distributions on the upstream and downstream sides of the tug were measured by Particle Image Velocimetry (PIV). The measurements and simulations have been completed at one draft, and at 15°, 30° and 45° inflow conditions. A reasonable agreement has been obtained between the predicted axial and lateral forces and the corresponding measurements. The flow pattern and the velocity distribution at different drift angle are comparable with the measurements. The variation of the pattern of flow separation at the suction side of the hull at different yaw angle is also analyzed and presented.

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