Experimental study on hydrodynamics of L-type podded propulsor in straight-ahead motion and off-design conditions

This paper presents the outcome of a numerical simulation based research program to evaluate the propulsive characteristics of puller and pusher podded propulsors in a straight course and at static azimuthing conditions while operating in open water. Methodologies to predict the propeller thrust and torque, and pod forces and moments in three dimensions using a Reynolds-Averaged Navier Stokes (RANS) solver at multiple azimuthing conditions and pod configurations are presented. To obtain insight into the reliability and accuracy of the results, grid and time step dependency studies are conducted for a podded propulsor in straight-ahead condition. The simulation techniques and results are first validated against measurements of a bare propeller and a podded propulsor in straight ahead condition for multiple loading scenarios and in both puller and pusher configurations. Next, simulations were carried out to model the podded propulsors in the two configurations at multiple loading conditions and at various azimuthing angles from +30° to –30° in 15° increments. The majority of the simulations are carried out using both steady state and unsteady state conditions, primarily to evaluate the effect of setup conditions on the computation time and prediction accuracy. The predicted performance characteristics of the pod unit using the unsteady RANS method were within 1% to 5% of the corresponding experimental measurements for all the loading conditions, azimuthing angles and pod configurations studied. The non-linear behaviour of the performance coefficients of the pod unit are well captured at various loading and azimuthing conditions in the predicted results. This study demonstrates that the RANS solver, with proper meshing arrangement, boundary conditions and setup techniques can predict the performance characteristics of the podded propulsor in multiple azimuthing angles, pod configurations and in the various loading conditions with a same level of accuracy as experimental results. Additionally, the velocity and pressure distributions on and around the pod-strut- propeller bodies are discussed as derived from the RANS predictions.

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Numerical and Experimental Research on a Podded Propulsor

Volume 8B: Ocean Engineering ◽

10.1115/omae2014-24015 ◽

2014 ◽

Author(s):

Mohammed Islam ◽

Ron Ryan ◽

David Molynuex

Keyword(s):

Preliminary Analysis ◽

Numerical Study ◽

Open Water ◽

Navier Stokes ◽

Experimental Program ◽

Propulsive Performance ◽

Podded Propulsor ◽

Thrust And Torque ◽

Straight Ahead ◽

Experimental Effort

This paper presents methodologies and some results of a numerical and experimental program to evaluate the effects of static azimuthing conditions on the propulsive characteristics of a puller podded propulsor in open water. In the experimental effort, the model propulsor was instrumented to measure thrust, torque and rotational speed of the propeller, and three orthogonal forces and moments, and azimuthing angle of the pod. The experimental results included the bare propeller (ahead only) and the combined propeller and pod over a range of advance coefficients at various static azimuthing angles in the range of −180° to 180°. A complementary numerical study is being carried out to predict the hydrodynamic forces of podded propulsor in static azimuthing conditions. A Reynolds-Averaged Navier Stokes solver is used to predict the propulsive performance of the bare propeller as well as the podded propulsor system. The thrust and torque for the bare propeller were compared to the corresponding measurements. The propeller thrust and torque as well as the loads on the pod in straight-ahead condition and at static azimuthing angles were then compared with the measurements. Preliminary analysis demonstrates that the RANS solver could predict the performance coefficients of the bare propeller as well as the podded propulsor in straight-ahead and static azimuthing angles in puller configurations.

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Experimental study on a model azimuthing podded propulsor in ice

Journal of Marine Science and Technology ◽

10.1007/s00773-008-0024-3 ◽

2008 ◽

Vol 13 (3) ◽

pp. 244-255 ◽

Cited By ~ 2

Author(s):

Jungyong Wang ◽

Ayhan Akinturk ◽

Neil Bose ◽

Stephen J. Jones ◽

Yun Young Song ◽

...

Keyword(s):

Experimental Study ◽

Podded Propulsor

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Hydrodynamics of Podded Propulsors With Highly Loaded Propellers and in Extreme Azimuthing Conditions

Volume 11: Prof. Robert F. Beck Honoring Symposium on Marine Hydrodynamics ◽

10.1115/omae2015-41997 ◽

2015 ◽

Author(s):

Mohammed Islam ◽

Fatima Jahra ◽

Ron Ryan ◽

Lee Hedd

Keyword(s):

Numerical Study ◽

Open Water ◽

Operating Conditions ◽

Navier Stokes ◽

Hydrodynamic Characteristics ◽

Podded Propulsor ◽

Order Of Magnitude ◽

Thrust And Torque ◽

Straight Ahead ◽

Highly Loaded

State of the art CFD capabilities has enabled the accurate prediction of forces and moments on the propeller as well as on the pod-strut body due to small to moderate azimuthing angles. The capability of CFD to predict the hydrodynamics at extreme azimuthing angles is yet to be demonstrated. The aim of this research is to develop a simulation capability to capture most of the dynamics of podded propulsion systems in regular to extreme operating conditions. The numerical methodologies to evaluate the hydrodynamic characteristics of podded propulsors in puller configurations in extremely oblique inflow and highly loaded condition in open water and the associated results are presented in this paper. A numerical study is carried out to predict the hydrodynamic forces of a podded propulsor unit in various extreme static azimuthing conditions. An unsteady Reynolds-Averaged Navier Stokes (RANS) solver is used to predict the propulsive performance of the podded propulsor system in puller configuration using both steady and unsteady state solutions. To obtain insight into the reliability and accuracy of the results, grid dependency studies are conducted for a podded propulsor in straight-ahead condition. RANS solver simulation technique is first validated against measurements of a puller podded propulsor in straight ahead condition for multiple loading scenarios. The propeller thrust and torque as well as the forces and moments of the pod unit in the three coordinate directions in straight-ahead condition and at static azimuthing angles in the range of −180° to 180° at advance coefficient of 0.20 are then compared with that of the measurements. Additionally, the velocity and pressure distribution on and around the pod-strut-propeller bodies are presented as derived from the RANS predictions. Analysis demonstrates that the RANS solver can predict the performance coefficients of the podded propulsor in extreme azimuthing and in the highly loaded conditions within the same level of accuracy of the same order of magnitude of the experimental results.

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Gap Effect on Performance of Podded Propulsors in Straight-Ahead and Azimuthing Conditions

Marine Technology and SNAME News ◽

10.5957/mtsn.2010.47.1.47 ◽

2010 ◽

Vol 47 (01) ◽

pp. 47-58

Author(s):

Mohammed F. Islam ◽

Brian Veitch ◽

Pengfei Liu ◽

Ayhan Akinturk

Keyword(s):

Open Water ◽

Operating Conditions ◽

Gap Effect ◽

Axial Distance ◽

Noticeable Effect ◽

Podded Propulsor ◽

Propeller Performance ◽

Thrust And Torque ◽

Straight Ahead ◽

Propeller Thrust

This paper presents results of an experimental study on the effect of gap distance on propulsive characteristics of puller and pusher podded propulsors in straight-ahead and static azimuthing open-water conditions. The gap distance is the axial distance between the rotating (propeller) and stationary (pod) parts of a podded propulsor. The propeller thrust and torque, unit forces, and moments in the three-coordinate directions of a model podded unit were measured using a custom-designed pod dynamometer in various operating conditions. The model propulsor was tested at the gap distances of 0.3%, 1%, and 2% of propeller diameter for a range of advance coefficients combined with the range of static azimuthing angles from +20_ to 20_ with a 10_ increment. The tests were conducted both in puller and pusher configurations in the same loading and azimuthing conditions. In the puller configuration, the gap distance did not have any noticeable effect on propeller torque in straight course condition, but had an effect in azimuthing conditions. The propeller thrust and efficiency were also influenced by the change of gap distance, and the effects were more pronounced at high azimuthing angles and high advance coefficients. For pusher configuration, however, the gap distance did not affect the propeller performance characteristics in straight-ahead and azimuthing conditions. Both in straight course and azimuthing conditions, the unit thrust and efficiency were not influenced by the gap distance in either puller or pusher configurations. The gap distance had a noticeable effect on unit transverse force and steering moment both in puller and pusher configurations, and both in straight course

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Experimental study on the restoration from a tilt-azimuth series for improvement in resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013955x ◽

1995 ◽

Vol 53 ◽

pp. 636-637

Author(s):

Norio Baba ◽

Norihiko Ichise ◽

Syunya Watanabe

Keyword(s):

Experimental Study ◽

Spherical Aberration ◽

Incident Beam ◽

Optical Parameters ◽

Beam Tilting ◽

Illumination Method ◽

Restoration Method ◽

Illumination Mode

The tilted beam illumination method is used to improve the resolution comparing with the axial illumination mode. Using this advantage, a restoration method of several tilted beam images covering the full azimuthal range was proposed by Saxton, and experimentally examined. To make this technique more reliable it seems that some practical problems still remain. In this report the restoration was attempted and the problems were considered. In our study, four problems were pointed out for the experiment of the restoration. (1) Accurate beam tilt adjustment to fit the incident beam to the coma-free axis for the symmetrical beam tilting over the full azimuthal range. (2) Accurate measurements of the optical parameters which are necessary to design the restoration filter. Even if the spherical aberration coefficient Cs is known with accuracy and the axial astigmatism is sufficiently compensated, at least the defocus value must be measured. (3) Accurate alignment of the tilt-azimuth series images.

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