Numerical and Experimental Research on a Podded Propulsor

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.

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

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.

STUDY ON PROPULSIVE PERFORMANCE OF TWO GEOMETRICALLY SIMILAR PODDED PROPULSORS

2021 ◽  
Vol 155 (A4) ◽  
Author(s):  
M Islam ◽  
A Akinturk ◽  
B Veitch ◽  
Pengfei Liu
Keyword(s):  
Open Water ◽  
Operating Conditions ◽  
Towing Tank ◽  
Propulsive Performance ◽  
Lower Reynolds Number ◽  
Custom Made ◽  
Flow Speeds ◽  
Four Quadrant ◽  
Thrust And Torque ◽  
Straight Ahead

This paper presents the outcome of a research to evaluate the effect of size on the propulsive performance of podded propulsors in cavitating and non-cavitating open water conditions. Two cases are examined, namely: propeller-only case and pod-unit case. In the propeller-only case, a commercial propeller dynamometer is used to measure the thrust and torque of two propellers of different size at the four quadrants of propellers with varied shaft and flow speeds. Also, both propellers are tested at different tunnel pressure to study and compare the behaviour under similar cavitation conditions. In the pod-unit case, two geometrically similar but different sized pod-units are tested using two separate custom-made pod dynamometer systems in two towing tank facilities in straight-ahead and static azimuthing conditions. The study showed that the performance characteristics stabilize at lower Reynolds Number for the smaller propeller than the larger propeller. The propulsive performance of the two propellers was comparable in the four-quadrant experiments. Also, the experiments at the cavitating conditions showed that the cavitation characteristics of the two propellers were consistent at corresponding operating conditions. The experiment results of the two pod-units were also comparable for forces and moments in the three coordinate directions in the straight-ahead and static azimuthing conditions. A brief discussion on the uncertainty assessments for each of the measurements is also presented.

Numerical Simulation of Turbulent Flow Around Podded Propeller in Azimuthing Conditions

2012 ◽  
Author(s):  
Reza Shamsi ◽  
Hassan Ghassemi
Keyword(s):  
Turbulent Flow ◽  
Open Water ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Characteristic Parameters ◽  
Hydrodynamic Analysis ◽  
Podded Propulsor ◽  
Performance Curves ◽  
Yaw Angle ◽  
Thrust And Torque

This paper investigates the numerical modeling of turbulent flow and hydrodynamic analysis of podded propeller in open water and azimuthing conditions. The RANS (Reynolds-Averaged Navier Stokes) based solver is used in order to study the variations of hydrodynamic characteristics of podded propeller at various angles. The variations of thrust and torque coefficients as functions of the advance coefficient are obtained at various yaw angles. Turbulent flow around the propeller and pod are presented. At first, the propeller is analyzed in open water condition in absence of pod and strut. Next flow around pod and strut are simulated without effect of propellers. Finally, the whole unit is studied in zero yaw angle and azimuthing condition. These investigations are performed for two podded propulsor configurations: puller and pusher. Total forces on the unit in each direction and propeller torque are computed for a range of advance coefficients from 0.2 to 1. Yaw angle of pod are modified from +15° to −15° by increments of 5°. Computational results are examined against with available experimental data. Characteristic parameters including torque and thrust of propeller, axial force, and side force of unit are presented as functions of advance coefficient and yaw angle. The performance curves of the propeller obtained by numerical method are compared and verified by the experimental results. The results show that the propeller thrust, torque, and podded unit forces and moments in azimuthing condition depend on propeller advance coefficient and yaw angle.

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

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

Study on Propulsive Performance of Two Geometrically Similar Podded Propulsors

2013 ◽  
Vol 155 (A4) ◽  
Keyword(s):  
Open Water ◽  
Operating Conditions ◽  
Towing Tank ◽  
Propulsive Performance ◽  
Lower Reynolds Number ◽  
Custom Made ◽  
Flow Speeds ◽  
Four Quadrant ◽  
Thrust And Torque ◽  
Straight Ahead

This paper presents the outcome of a research to evaluate the effect of size on the propulsive performance of podded propulsors in cavitating and non-cavitating open water conditions. Two cases are examined, namely: propeller-only case and pod-unit case. In the propeller-only case, a commercial propeller dynamometer is used to measure the thrust and torque of two propellers of different size at the four quadrants of propellers with varied shaft and flow speeds. Also, both propellers are tested at different tunnel pressure to study and compare the behaviour under similar cavitation conditions. In the pod-unit case, two geometrically similar but different sized pod-units are tested using two separate custom-made pod dynamometer systems in two towing tank facilities in straight-ahead and static azimuthing conditions. The study showed that the performance characteristics stabilize at lower Reynolds Number for the smaller propeller than the larger propeller. The propulsive performance of the two propellers was comparable in the four-quadrant experiments. Also, the experiments at the cavitating conditions showed that the cavitation characteristics of the two propellers were consistent at corresponding operating conditions. The experiment results of the two pod-units were also comparable for forces and moments in the three coordinate directions in the straight-ahead and static azimuthing conditions. A brief discussion on the uncertainty assessments for each of the measurements is also presented.

Optimization of RANS Solver Simulation Setup for Propeller Open Water Performance Prediction

2015 ◽  
Author(s):  
Mohammed Islam ◽  
Fatima Jahra ◽  
Michael Doucet
Keyword(s):  
Domain Size ◽  
Open Water ◽  
Fractional Factorial ◽  
Navier Stokes ◽  
Calm Water ◽  
Simulation Results ◽  
Open Water Performance ◽  
Thrust And Torque ◽  
Simulation Time ◽  
Fixed Pitch

Mesh and domain optimization strategies for a RANS solver to accurately estimate the open water propulsive characteristics of fixed pitch propellers are proposed based on examining the effect of different mesh and computation domain parameters. The optimized mesh and domain size parameters were selected using Design of Experiments (DoE) methods enabling simulations to be carried out in a limited memory environment, and in a timely manner; without compromising the accuracy of results. A Reynolds-Averaged Navier Stokes solver is used to predict the propulsive performance of a fixed pitch propeller. The predicted thrust and torque for the propeller were compared to the corresponding measurements. A total of six meshing parameters were selected that could affect the computational results of propeller open water performance. A two-level fractional factorial design was used to screen out parameters that do not significantly contribute to explaining the dependent parameters: namely simulation time, propeller thrust and propeller torque. A total of 32 simulations were carried out only to find out that the selected six meshing parameters were significant in defining the response parameters. Optimum values of each of the input parameters were obtained for the DOE technique and additional simulations were run with those parameters. The simulation results were validated using open water experimental results of the same propeller. It was found that with the optimized meshing arrangement, the propeller opens simulation time was reduced by at least a factor of 6 as compared to the generally popular meshing arrangement. Also, the accuracy of propulsive characteristics was improved by up to 50% as compared to published simulation results. The methodologies presented in this paper can be similarly applied to other simulations such as calm water ship resistance, ship propulsion to systematically derive the optimized meshing arrangement for simulations with minimal simulation time and maximum accuracy. This investigation was carried out using STAR-CCM+, a commercial CFD package; however the findings can be applied to any RANS solver.

METHODOLOGIES TO PREDICT HYDRODYNAMIC CHARACTERISTICS OF PUSHER AND PULLER PODDED PROPULSORS IN OBLIQUE FLOWS

2021 ◽  
Vol 158 (A4) ◽  
Author(s):  
M F Islam ◽  
F Jahra
Keyword(s):  
Computation Time ◽  
Performance Characteristics ◽  
Three Dimensions ◽  
Hydrodynamic Characteristics ◽  
Loading Conditions ◽  
Time Step ◽  
Podded Propulsor ◽  
Multiple Loading ◽  
Thrust And Torque ◽  
Straight Ahead

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.

scholarly journals Improving accuracy and efficiency of CFD predictions of propeller open water performance

2019 ◽  
Vol 16 (1) ◽  
pp. 1-20
Author(s):  
Mohammed Islam ◽  
Fatima Jahra
Keyword(s):  
Domain Size ◽  
Open Water ◽  
Navier Stokes ◽  
Calm Water ◽  
Open Water Performance ◽  
Improving Accuracy ◽  
Accuracy Of Results ◽  
Thrust And Torque ◽  
Simulation Time ◽  
Fixed Pitch

This research proposes mesh and domain optimization strategies for a popular Computational Fluid Dynamics (CFD) technique to estimate the open water propulsive characteristics of fixed pitch propellers accurately and time-efficiently based on examining the effect of various mesh and computation domain parameters. It used a Reynolds-Averaged Navier-Stokes (RANS) solver to predict the propulsive performance of a fixed pitch propeller with varied meshing, simulation domain and setup parameters. The optimized mesh and domain size parameters were selected using Design of Experiments (DoE) methods enabling simulations in a limited memory and in a timely manner without compromising the accuracy of results. The predicted thrust and torque for the propeller were compared to the corresponding measurements for determining the prediction accuracy. The authors found that the optimized meshing and setup arrangements reduced the propeller opens simulation time by at least a factor of six as compared to the generally popular CFD parameter setup. In addition, the accuracy of propulsive characteristics was improved by up to 50% as compared to published simulation results. The methodologies presented in this paper can be similarly applied to other simulations such as calm water ship resistance, ship propulsion etc. to systematically derive the optimized meshing arrangement for simulations with minimal simulation time and maximum accuracy. This investigation was carried out using a commercial CFD package; however, the findings can be applied to any RANS solver.

Parametric Numerical Study on the Self-Propulsive Performance of The DARPA Suboff Submarine via the Body-Force Propeller Method

2021 ◽  
Author(s):  
Kenshiro Takahashi ◽  
Takayuki Mori
Keyword(s):  
Reynolds Number ◽  
Free Surface ◽  
Body Force ◽  
Surface Effect ◽  
Numerical Study ◽  
The Body ◽  
The Self ◽  
Navier Stokes ◽  
Suction Force ◽  
Propulsive Performance

Abstract This study is based on previous works in a series of numerical studies on submarine hydrodynamics, which involved developing a computational fluid dynamics method to estimate the self-propulsive performance of underwater vehicles. Herein, the Defense Advanced Research Projects Agency SUBOFF submarine model was adopted as a benchmark. The computational modeling applied was based on the Reynolds-averaged Navier-Stokes turbulence model. A body-force propeller method was adopted to model the propulsion. The self-propulsive performance was verified via mesh refinement and validated by comparing the computational solutions with the results obtained from the experiments. The effect of the Reynolds number on the self-propulsive performance was investigated by varying the positions of the stern planes, while the free surface effect was determined by varying the Froude number (Fr) via the volume of fluid method. The computed Taylor wake fraction (w) and hull efficiency (ηH) depended on the Reynolds number as it decreased monotonically. The w and thrust deduction fraction (t) for the model of aft-fitted stern planes were approximately 3–7% and 8–10% higher than those of the baseline and fore-fitted stern planes, respectively. The differences in ηH between the models were insignificant. Regarding the free surface effects, the computations of w, t, and ηH generally decreased with Fr, thus exhibiting several humps and hollows. The computed upward suction force and pitching moment varied from negative to positive and vice versa, depending on Fr.

scholarly journals Numerical Simulations for the Wake Prediction of a Marine Propeller in Straight-Ahead Flow and Oblique Flow

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
E. Guilmineau ◽  
G. B. Deng ◽  
A. Leroyer ◽  
P. Queutey ◽  
M. Visonneau ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Open Water ◽  
Numerical Code ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Marine Propeller ◽  
Oblique Flow ◽  
Les Model ◽  
Straight Ahead ◽  
Good Agreement

This paper presents the capability of a numerical code, isis-cfd, based on the solution of the Navier–Stokes equations, for the investigation on the hydrodynamic characteristics of a marine propeller in open water. Two propellers are investigated: the Istituto Nazionale per Studi ed Esperienze di Architectura Navale (INSEAN) E779A model in straight-ahead flow and the Potsdam Propeller Test Case (PPTC) model in oblique flow. The objectives of this study are to establish capabilities of various turbulent closures to predict the wake propeller and to predict the instability processes in the wake if it exists. Two Reynolds-averaged Navier–Stokes (RANS) models are used: the k–ω shear stress transport (SST) of Menter and an anisotropic two-equation explicit algebraic Reynolds stress model (EARSM). A hybrid RANS–large eddy simulation (LES) model is also used. Computational results for global flow quantities are discussed and compared with experimental data. These quantities are in good agreement with the measured data. The hybrid RANS–LES model allows to capture the evolution of the tip vortices. For the INSEAN E779A model, the instability of the wake is only predicted with a hybrid RANS–LES model, and the position of these instabilities is in good agreement with the experimental visualizations.

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