Journal of Marine Science and Engineering

Editorial

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2 pages, 148 KiB

Open AccessEditorial

Marine Propulsors

by Sverre Steen and Kourosh Koushan

J. Mar. Sci. Eng. 2018, 6(3), 97; https://doi.org/10.3390/jmse6030097 - 22 Aug 2018

Cited by 1 | Viewed by 3223

Abstract

This Special Issue is following up the success of the latest Symposium on Marine Propulsors (www.marinepropulsors.com, smp’17) by publishing extended or improved versions of the selected papers presented at the symposium[…] Full article

(This article belongs to the Special Issue Marine Propulsors)

Research

Jump to: Editorial

22 pages, 20593 KiB

Open AccessArticle

Panel Method for Ducted Propellers with Sharp Trailing Edge Duct with Fully Aligned Wake on Blade and Duct

by Seungnam Kim, Spyros A. Kinnas and Weikang Du

J. Mar. Sci. Eng. 2018, 6(3), 89; https://doi.org/10.3390/jmse6030089 - 23 Jul 2018

Cited by 21 | Viewed by 6247

Abstract

A low-order panel method is used to predict the performance of ducted propellers. A full wake alignment (FWA) scheme, originally developed to determine the location of the force-free trailing wake of open propellers, is improved and extended to determine the location of the [...] Read more.

A low-order panel method is used to predict the performance of ducted propellers. A full wake alignment (FWA) scheme, originally developed to determine the location of the force-free trailing wake of open propellers, is improved and extended to determine the location of the force-free trailing wakes of both the propeller blades and the duct, including the interaction with each other. The present method is applied on a ducted propeller with sharp trailing edge duct, and the predicted results over a wide range of advance ratios, with or without full alignment of the duct wake, are compared with each other, as well as with results from RANS simulations and with measurements from an experiment. Full article

(This article belongs to the Special Issue Marine Propulsors)

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17 pages, 9828 KiB

Open AccessArticle

Numerical Simulation and Uncertainty Analysis of an Axial-Flow Waterjet Pump

by Ji-Tao Qiu, Chen-Jun Yang, Xiao-Qian Dong, Zong-Long Wang, Wei Li and Francis Noblesse

J. Mar. Sci. Eng. 2018, 6(2), 71; https://doi.org/10.3390/jmse6020071 - 11 Jun 2018

Cited by 24 | Viewed by 4722

Abstract

Unsteady Reynolds-averaged Navier–Stokes simulations of an axial-flow pump for waterjet propulsion are carried out at model scale, and the numerical uncertainties are analyzed mainly according to the procedure recommended by the twenty-eighth International Towing Tank Conference. The two-layer realizable k-ε model is [...] Read more.

Unsteady Reynolds-averaged Navier–Stokes simulations of an axial-flow pump for waterjet propulsion are carried out at model scale, and the numerical uncertainties are analyzed mainly according to the procedure recommended by the twenty-eighth International Towing Tank Conference. The two-layer realizable k-ε model is adopted for turbulence closure, and the flow in viscous sub-layer is resolved. The governing equations are discretized with second-order schemes in space and first-order scheme in time and solved by the semi-implicit method for pressure-linked equations. The computational domain is discretized into block-structured hexahedral cells. For an axial-flow pump consisting of a seven-bladed rotor and a nine-bladed stator, the uncertainty analysis is conducted by using three sets of successively refined grids and time steps. In terms of the head and power over a range of flow rates, it is verified that the simulation uncertainty is less than 4.3%, and the validation is successfully achieved at an uncertainty level of 4.4% except for the lowest flow rate. Besides this, the simulated flow features around rotor blade tips and between the stator and rotor blade rows are investigated. Full article

(This article belongs to the Special Issue Marine Propulsors)

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32 pages, 995 KiB

Open AccessArticle

Boundary Element Modelling Aspects for the Hydro-Elastic Analysis of Flexible Marine Propellers

by Pieter Maljaars, Mirek Kaminski and Henk Den Besten

J. Mar. Sci. Eng. 2018, 6(2), 67; https://doi.org/10.3390/jmse6020067 - 5 Jun 2018

Cited by 18 | Viewed by 4497

Abstract

Boundary element methods (BEM) have been used for propeller hydrodynamic calculations since the 1990s. More recently, these methods are being used in combination with finite element methods (FEM) in order to calculate flexible propeller fluid–structure interaction (FSI) response. The main advantage of using [...] Read more.

Boundary element methods (BEM) have been used for propeller hydrodynamic calculations since the 1990s. More recently, these methods are being used in combination with finite element methods (FEM) in order to calculate flexible propeller fluid–structure interaction (FSI) response. The main advantage of using BEM for flexible propeller FSI calculations is the relatively low computational demand in comparison with higher fidelity methods. However, the BEM modelling of flexible propellers is not straightforward and requires several important modelling decisions. The consequences of such modelling choices depend significantly on propeller structural behaviour and flow condition. The two dimensionless quantities that characterise structural behaviour and flow condition are the structural frequency ratio (the ratio between the lowest excitation frequency and the fundamental wet blade natural frequency) and the reduced frequency. For both, general expressions have been derived for (flexible) marine propellers. This work shows that these expressions can be effectively used to estimate the dry and wet fundamental blade frequencies and the structural frequency ratio. This last parameter and the reduced frequency of vibrating blade flows is independent of the geometrical blade scale as shown in this work. Regarding the BEM-FEM coupled analyses, it is shown that a quasi-static FEM modelling does not suffice, particularly due to the fluid-added mass and hydrodynamic damping contributions that are not negligible. It is demonstrated that approximating the hydro-elastic blade response by using closed form expressions for the fluid added mass and hydrodynamic damping terms provides reasonable results, since the structural response of flexible propellers is stiffness dominated, meaning that the importance of modelling errors in fluid added mass and hydrodynamic damping is small. Finally, it is shown that the significance of recalculating the hydrodynamic influence coefficients is relatively small. This fact might be utilized, possibly in combination with the use of the closed form expressions for fluid added mass and hydrodynamic damping contributions, to significantly reduce the computation time of flexible propeller FSI calculations. Full article

(This article belongs to the Special Issue Marine Propulsors)

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17 pages, 380 KiB

Open AccessArticle

The Effect of Propeller Scaling Methodology on the Performance Prediction

by Stephan Helma, Heinrich Streckwall and Jan Richter

J. Mar. Sci. Eng. 2018, 6(2), 60; https://doi.org/10.3390/jmse6020060 - 24 May 2018

Cited by 9 | Viewed by 5078

Abstract

In common model testing practise, the measured values of the self propulsion test are split into the characteristics of the hull, the propeller and into the interaction factors. These coefficients are scaled separately to the respective full scale values and subsequently reassembled to [...] Read more.

In common model testing practise, the measured values of the self propulsion test are split into the characteristics of the hull, the propeller and into the interaction factors. These coefficients are scaled separately to the respective full scale values and subsequently reassembled to give the power prediction. The accuracy of this power prediction depends inter alia on the accuracy of the measured values and the scaling procedure. An inherent problem of this approach is that it is virtually impossible to verify each single step, because of the complex nature of the underlying problem. In recent years the scaling of the open-water characteristics of propeller model tests attracted a renewed interest, fuelled by competitive tests, which became the norm due to requests of the customer. This paper shows the influence of different scaling procedures on the predicted power. The prediction is compared to the measured trials data and the quality of the prediction is judged. The procedures examined are the standard ITTC 1978 procedure plus derivatives of it, the Meyne method, the strip method developed by the Hamburgische Schiffbau-Versuchsanstalt (HSVA) and the

β_{i}

-method by Helma. Full article

(This article belongs to the Special Issue Marine Propulsors)

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26 pages, 16667 KiB

Open AccessArticle

DDES of Wetted and Cavitating Marine Propeller for CHA Underwater Noise Assessment

by Ville M. Viitanen, Antti Hynninen, Tuomas Sipilä and Timo Siikonen

J. Mar. Sci. Eng. 2018, 6(2), 56; https://doi.org/10.3390/jmse6020056 - 21 May 2018

Cited by 36 | Viewed by 8735

Abstract

In this paper we present results of delayed detached eddy simulation (DDES) and computational hydroacoustics (CHA) simulations of a marine propeller operating in a cavitation tunnel. DDES is carried out in both wetted and cavitating conditions, and we perform the investigation at several [...] Read more.

In this paper we present results of delayed detached eddy simulation (DDES) and computational hydroacoustics (CHA) simulations of a marine propeller operating in a cavitation tunnel. DDES is carried out in both wetted and cavitating conditions, and we perform the investigation at several propeller loadings. CHA analyses are done for one propeller loading both in wetted and cavitating conditions. The simulations are validated against experiments conducted in the cavitation tunnel. Propeller global forces, local flow phenomena, as well as cavitation patterns are compared to the cavitation tunnel tests. Hydroacoustic sources due to the propeller are evaluated from the flow solution, and corresponding acoustic simulations utilizing an acoustic analogy are made. The propeller wake flow structures are investigated for the wetted and cavitating operating conditions, and the acoustic excitation and output of the same cases are discussed. Full article

(This article belongs to the Special Issue Marine Propulsors)

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30 pages, 4062 KiB

Open AccessArticle

Marine Turbine Hydrodynamics by a Boundary Element Method with Viscous Flow Correction

by Francesco Salvatore, Zohreh Sarichloo and Danilo Calcagni

J. Mar. Sci. Eng. 2018, 6(2), 53; https://doi.org/10.3390/jmse6020053 - 8 May 2018

Cited by 18 | Viewed by 4959

Abstract

A computational methodology for the hydrodynamic analysis of horizontal axis marine current turbines is presented. The approach is based on a boundary integral equation method for inviscid flows originally developed for marine propellers and adapted here to describe the flow features that characterize [...] Read more.

A computational methodology for the hydrodynamic analysis of horizontal axis marine current turbines is presented. The approach is based on a boundary integral equation method for inviscid flows originally developed for marine propellers and adapted here to describe the flow features that characterize hydrokinetic turbines. For this purpose, semi-analytical trailing wake and viscous flow correction models are introduced. A validation study is performed by comparing hydrodynamic performance predictions with two experimental test cases and with results from other numerical models in the literature. The capability of the proposed methodology to correctly describe turbine thrust and power over a wide range of operating conditions is discussed. Viscosity effects associated to blade flow separation and stall are taken into account and predicted thrust and power are comparable with results of blade element methods that are largely used in the design of marine current turbines. The accuracy of numerical predictions tends to reduce in cases where turbine blades operate in off-design conditions. Full article

(This article belongs to the Special Issue Marine Propulsors)

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14 pages, 4576 KiB

Open AccessArticle

Prediction of Propeller-Induced Hull Pressure Fluctuations via a Potential-Based Method: Study of the Effects of Different Wake Alignment Methods and of the Rudder

by Yiran Su, Seungnam Kim and Spyros A. Kinnas

J. Mar. Sci. Eng. 2018, 6(2), 52; https://doi.org/10.3390/jmse6020052 - 8 May 2018

Cited by 15 | Viewed by 4743

Abstract

In order to predict ship hull pressure fluctuations induced by marine propellers, a combination of several numerical schemes is used. The propeller perturbation flow is solved by the boundary element method (BEM), while the coupling between a BEM solver and a Reynolds-averaged Navier-Stokes [...] Read more.

In order to predict ship hull pressure fluctuations induced by marine propellers, a combination of several numerical schemes is used. The propeller perturbation flow is solved by the boundary element method (BEM), while the coupling between a BEM solver and a Reynolds-averaged Navier-Stokes (RANS) solver can efficiently predict the effective wake. Based on the BEM solution under the predicted effective wake, the propeller-induced potential on the ship hull can be evaluated. Then, a pressure-BEM solver is used to solve the diffraction pressure on the hull in order to obtain the solid boundary factor which leads to the total hull pressure. This paper briefly introduces the schemes and numerical models. To avoid numerical instability, several simplifications need to be made. The effects of these simplifications are studied, including the rudder effect and the wake alignment model effect. Full article

(This article belongs to the Special Issue Marine Propulsors)

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23 pages, 12339 KiB

Open AccessArticle

Experimental Validation of Fluid–Structure Interaction Computations of Flexible Composite Propellers in Open Water Conditions Using BEM-FEM and RANS-FEM Methods

by Pieter Maljaars, Laurette Bronswijk, Jaap Windt, Nicola Grasso and Mirek Kaminski

J. Mar. Sci. Eng. 2018, 6(2), 51; https://doi.org/10.3390/jmse6020051 - 7 May 2018

Cited by 34 | Viewed by 4789

Abstract

In the past several decades, many papers have been published on fluid–structure coupled calculations to analyse the hydro-elastic response of flexible (composite) propellers. The flow is usually modelled either by the Navier–Stokes equations or as a potential flow, by assuming an irrotational flow. [...] Read more.

In the past several decades, many papers have been published on fluid–structure coupled calculations to analyse the hydro-elastic response of flexible (composite) propellers. The flow is usually modelled either by the Navier–Stokes equations or as a potential flow, by assuming an irrotational flow. Phenomena as separation of the flow, flow transition, boundary layer build-up and vorticity dynamics are not captured in a non-viscous potential flow. Nevertheless, potential flow based methods have been shown to be powerful methods to resolve the hydrodynamics of propellers. With the upcoming interest in flexible (composite) propellers, a valid question is what the consequences of the potential flow simplifications are with regard to the coupled fluid–structure analyses of these types of propellers. This question has been addressed in the following way: calculations and experiments were conducted for uniform flows only, with a propeller geometry that challenges the potential flow model due to its sensitivity to leading edge vortex separation. Calculations were performed on the undeformed propeller geometry with a Reynolds-averaged-Navier–Stokes (RANS) solver and a boundary element method (BEM). These calculations show some typical differences between the RANS and BEM results. The flexible propeller responses were predicted by coupled calculations between BEM and finite element method (FEM) and RANS and FEM. The applied methodologies are briefly described. Results obtained from both calculation methods have been compared to experimental results obtained from blade deformation measurements in a cavitation tunnel. The results show that, even for the extreme cases, promising results have been obtained with the BEM-FEM coupling. The BEM-FEM calculated responses are consistent with the RANS-FEM results. Full article

(This article belongs to the Special Issue Marine Propulsors)

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18 pages, 5459 KiB

Open AccessArticle

A Semi-Empirical Prediction Method for Broadband Hull-Pressure Fluctuations and Underwater Radiated Noise by Propeller Tip Vortex Cavitation ^†

by Johan Bosschers

J. Mar. Sci. Eng. 2018, 6(2), 49; https://doi.org/10.3390/jmse6020049 - 2 May 2018

Cited by 38 | Viewed by 5486

Abstract

A semi-empirical method is presented that predicts broadband hull-pressure fluctuations and underwater radiated noise due to propeller tip vortex cavitation. The method uses a hump-shaped pattern for the spectrum and predicts the centre frequency and level of this hump. The principal parameter is [...] Read more.

A semi-empirical method is presented that predicts broadband hull-pressure fluctuations and underwater radiated noise due to propeller tip vortex cavitation. The method uses a hump-shaped pattern for the spectrum and predicts the centre frequency and level of this hump. The principal parameter is the vortex cavity size, which is predicted by a combination of a boundary element method and a semi-empirical vortex model. It is shown that such a model is capable of representing the variation of cavity size with cavitation number well. Using a database of model- and full-scale measured hull-pressure data, an empirical formulation for the maximum level and centre frequency has been developed that is a function of, among other parameters, the cavity size. Acceptable results are obtained when comparing predicted and measured hull-pressure and radiated noise spectra for various cases. The comparison also shows differences that require adjustments of parameters that need to be further investigated. Full article

(This article belongs to the Special Issue Marine Propulsors)

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20 pages, 14699 KiB

Open AccessArticle

Influence of Propulsion Type on the Stratified Near Wake of an Axisymmetric Self-Propelled Body

by Matthew C. Jones and Eric G. Paterson

J. Mar. Sci. Eng. 2018, 6(2), 46; https://doi.org/10.3390/jmse6020046 - 1 May 2018

Cited by 9 | Viewed by 4019

Abstract

To better understand the influence of swirl on the thermally-stratified near wake of a self-propelled axisymmetric vehicle, three propulsor schemes were considered: a single propeller, contra-rotating propellers (CRP), and a zero-swirl, uniform-velocity jet. The propellers were modeled using an Actuator-Line model in an [...] Read more.

To better understand the influence of swirl on the thermally-stratified near wake of a self-propelled axisymmetric vehicle, three propulsor schemes were considered: a single propeller, contra-rotating propellers (CRP), and a zero-swirl, uniform-velocity jet. The propellers were modeled using an Actuator-Line model in an unsteady Reynolds-Averaged Navier–Stokes simulation, where the Reynolds number is

R e_{L} = 3.1 \times 10^{8}

using the freestream velocity and body length. The authors previously showed good comparison to experimental data with this approach. Visualization of vortical structures shows the helical paths of blade-tip vortices from the single propeller as well as the complicated vortical interaction between contra-rotating blades. Comparison of instantaneous and time-averaged fields shows that temporally stationary fields emerge by half of a body length downstream. Circumferentially-averaged axial velocity profiles show similarities between the single propeller and CRP in contrast to the jet configuration. Swirl velocity of the CRP, however, was attenuated in comparison to that of the single propeller case. Mixed-patch contour maps illustrate the unique temperature distribution of each configuration as a consequence of their respective swirl profiles. Finally, kinetic and potential energy is integrated along downstream axial planes to reveal key differences between the configurations. The CRP configuration creates less potential energy by reducing swirl that would otherwise persist in the near wake of a single-propeller wake. Full article

(This article belongs to the Special Issue Marine Propulsors)

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24 pages, 4050 KiB

Open AccessArticle

Experimental and Numerical Investigation of Propeller Loads in Off-Design Conditions

by Fabrizio Ortolani, Giulio Dubbioso, Roberto Muscari, Salvatore Mauro and Andrea Di Mascio

J. Mar. Sci. Eng. 2018, 6(2), 45; https://doi.org/10.3390/jmse6020045 - 24 Apr 2018

Cited by 27 | Viewed by 6108

Abstract

The understanding of the performance of a propeller in realistic operative conditions is nowadays a key issue for improving design techniques, guaranteeing safety and continuity of operation at sea, and reducing maintenance costs. In this paper, a summary of the recent research carried [...] Read more.

The understanding of the performance of a propeller in realistic operative conditions is nowadays a key issue for improving design techniques, guaranteeing safety and continuity of operation at sea, and reducing maintenance costs. In this paper, a summary of the recent research carried out at CNR-INSEAN devoted to the analysis of propeller loads in realistic operative scenarios, with particular emphasis on the in-plane loads, is presented. In particular, the experimental results carried out on a free running maneuvering model equipped with a novel force transducer are discussed and supported by

C F D

(Computational Fluid Dynamics) analysis and the use of a simplified propeller model, based on Blade Element Momentum Theory, with the aim of achieving a deeper understanding of the mechanisms that govern the functioning of the propeller in off-design. Moreover, the analysis includes the scaling factors that can be used to obtain a prediction from model measurements, the propeller radial force being the primary cause of failures of the shaft bearings. In particular, the analysis highlighted that cavitation at full scale can cause the increment of in-plane loads by about 20% with respect to a non-cavitating case, that that in-plane loads could be more sensitive to cavitation than thrust and torque, and that Reynolds number effect is negligible. For the analysis of cavitation, an alternative version of the

B E M T

solver, improved with cavitation linear theory, was developed. Full article

(This article belongs to the Special Issue Marine Propulsors)

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19 pages, 2800 KiB

Open AccessArticle

Coupling Numerical Methods and Analytical Models for Ducted Turbines to Evaluate Designs

by Bradford Knight, Robert Freda, Yin Lu Young and Kevin Maki

J. Mar. Sci. Eng. 2018, 6(2), 43; https://doi.org/10.3390/jmse6020043 - 16 Apr 2018

Cited by 10 | Viewed by 5696

Abstract

Hydrokinetic turbines extract energy from currents in oceans, rivers, and streams. Ducts can be used to accelerate the flow across the turbine to improve performance. The objective of this work is to couple an analytical model with a Reynolds averaged Navier–Stokes (RANS) computational [...] Read more.

Hydrokinetic turbines extract energy from currents in oceans, rivers, and streams. Ducts can be used to accelerate the flow across the turbine to improve performance. The objective of this work is to couple an analytical model with a Reynolds averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) solver to evaluate designs. An analytical model is derived for ducted turbines. A steady-state moving reference frame solver is used to analyze both the freestream and ducted turbine. A sliding mesh solver is examined for the freestream turbine. An efficient duct is introduced to accelerate the flow at the turbine. Since the turbine is optimized for operation in the freestream and not within the duct, there is a decrease in efficiency due to duct-turbine interaction. Despite the decrease in efficiency, the power extracted by the turbine is increased. The analytical model under-predicts the flow rejection from the duct that is predicted by CFD since the CFD predicts separation but the analytical model does not. Once the mass flow rate is corrected, the model can be used as a design tool to evaluate how the turbine-duct pair reduces mass flow efficiency. To better understand this phenomenon, the turbine is also analyzed within a tube with the analytical model and CFD. The analytical model shows that the duct’s mass flow efficiency reduces as a function of loading, showing that the system will be more efficient when lightly loaded. Using the conclusions of the analytical model, a more efficient ducted turbine system is designed. The turbine is pitched more heavily and the twist profile is adapted to the radial throat velocity profile. Full article

(This article belongs to the Special Issue Marine Propulsors)

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22 pages, 779 KiB

Open AccessArticle

Modelling a Propeller Using Force and Mass Rate Density Fields

by David Hally

J. Mar. Sci. Eng. 2018, 6(2), 41; https://doi.org/10.3390/jmse6020041 - 12 Apr 2018

Cited by 1 | Viewed by 3503

Abstract

A method to replace a propeller by force and mass rate density fields has been developed. The force of the propeller on the flow is calculated using a boundary element method (BEM) program and used to generate the force and mass rate fields [...] Read more.

A method to replace a propeller by force and mass rate density fields has been developed. The force of the propeller on the flow is calculated using a boundary element method (BEM) program and used to generate the force and mass rate fields in a Reynolds-averaged Navier–Stokes (RANS) solver. The procedures to calculate the fields and to allocate them to the cells of a RANS grid are described in detail. The method has been implemented using the BEM program PROCAL and the RANS solver OpenFOAM and tested using the propeller DTMB P4384 operating in open water. Close to the design advance coefficient, the time-average flow fields generated by PROCAL and by OpenFOAM with the force and mass rate fields match to within 1.5% of the inflow speed over almost all of the flow field, including the swept volume of the blades. At two-thirds of the design advance coefficient, the match is about 4% of the inflow speed. The sensitivity of the method to several of its free parameters is investigated. Full article

(This article belongs to the Special Issue Marine Propulsors)

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24 pages, 10773 KiB

Open AccessFeature PaperArticle

Numerical Analysis of Azimuth Propulsor Performance in Seaways: Influence of Oblique Inflow and Free Surface

by Nabila Berchiche, Vladimir I. Krasilnikov and Kourosh Koushan

J. Mar. Sci. Eng. 2018, 6(2), 37; https://doi.org/10.3390/jmse6020037 - 5 Apr 2018

Cited by 8 | Viewed by 4732

Abstract

In the present work, a generic ducted azimuth propulsor, which are frequently installed on a wide range of vessels, is subject to numerical investigation with the primary focus on performance deterioration and dynamic loads arising from the influence of oblique inflow and the [...] Read more.

In the present work, a generic ducted azimuth propulsor, which are frequently installed on a wide range of vessels, is subject to numerical investigation with the primary focus on performance deterioration and dynamic loads arising from the influence of oblique inflow and the presence of free surface. An unsteady Reynolds-Averaged Navier-Stokes (RANS) method with the interface Sliding Mesh technique is employed to resolve interaction between the propulsor components. The VOF formulation is used to resolve the presence of free surface. Numerical simulations are performed, separately, in single-phase fluid to address the influence of oblique inflow on the characteristics of a propulsor operating in free-sailing, trawling and bollard conditions, and in multi-phase flow to address the influence of propulsor submergence. Detailed comparisons with experimental data are presented for the case of a propulsor in oblique flow conditions, including integral propulsor characteristics, loads on propulsor components and single blade loads. The results of the study illustrate the differences in propulsor performance at positive and negative heading angles, reveal the frequencies of dynamic load peaks, and provide quantification of thrust losses due to the effect of a free surface without waves. The mechanisms of ventilation inception found at different propulsor loading conditions are discussed. Full article

(This article belongs to the Special Issue Marine Propulsors)

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14 pages, 1202 KiB

Open AccessArticle

Nominal vs. Effective Wake Fields and Their Influence on Propeller Cavitation Performance

by Pelle Bo Regener, Yasaman Mirsadraee and Poul Andersen

J. Mar. Sci. Eng. 2018, 6(2), 34; https://doi.org/10.3390/jmse6020034 - 5 Apr 2018

Cited by 18 | Viewed by 5896

Abstract

Propeller designers often need to base their design on the nominal model scale wake distribution because the effective full scale distribution is not available. The effects of such incomplete design data on cavitation performance are examined in this paper. The behind-ship cavitation performance [...] Read more.

Propeller designers often need to base their design on the nominal model scale wake distribution because the effective full scale distribution is not available. The effects of such incomplete design data on cavitation performance are examined in this paper. The behind-ship cavitation performance of two propellers is evaluated, where the cases considered include propellers operating in the nominal model and full scale wake distributions and in the effective wake distribution, also in the model and full scale. The method for the analyses is a combination of RANS for the ship hull and a panel method for the propeller flow, with a coupling of the two for the interaction of ship and propeller flows. The effect on sheet cavitation due to the different wake distributions is examined for a typical full-form ship. Results show considerable differences in cavitation extent, volume, and hull pressure pulses. Full article

(This article belongs to the Special Issue Marine Propulsors)

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17 pages, 9893 KiB

Open AccessArticle

Prediction of the Open-Water Performance of Ducted Propellers with a Panel Method

by João Manuel Baltazar, Douwe Rijpkema, José Falcão de Campos and Johan Bosschers

J. Mar. Sci. Eng. 2018, 6(1), 27; https://doi.org/10.3390/jmse6010027 - 19 Mar 2018

Cited by 16 | Viewed by 5691

Abstract

In the present work, a comparison between the results obtained by a panel code with a Reynolds-averaged Navier-Stokes (RANS) code is made to obtain a better insight on the viscous effects of the ducted propeller and on the limitations of the inviscid flow [...] Read more.

In the present work, a comparison between the results obtained by a panel code with a Reynolds-averaged Navier-Stokes (RANS) code is made to obtain a better insight on the viscous effects of the ducted propeller and on the limitations of the inviscid flow model, especially near bollard pull conditions or low advance ratios, which are important in the design stage. The analysis is carried out for propeller Ka4-70 operating inside duct 19A. From the comparison, several modelling aspects are studied for improvement of the inviscid (potential) flow solution. Finally, the experimental open-water data is compared with the panel method and RANS solutions. A strong influence of the blade wake pitch, especially near the blade tip, on the ducted propeller force predictions is seen. A reduction of the pitch of the gap strip is proposed for improvement of the performance prediction at low advance ratios. Full article

(This article belongs to the Special Issue Marine Propulsors)

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