Propeller-hull Interaction Research Articles

Hydrodynamic performance of a full-scale ship with a Pre-Swirl Duct: A numerical study with partially rotating grid method

This study investigates the hydrodynamic performance of a full-scale KVLCC2-S ship fitted with a Pre-Swirl Duct using CFD simulations. Four different propeller rotation representations are employed to evaluate the impact of the Pre-Swirl Duct on the ship’s performance. The study introduces a partially rotating grid method for two-phase flows, implemented within the Naval Hydro Pack library based on foam-extend software. The results of the study reveal that prediction of power savings depends on the accuracy of the numerical propeller representation. Non-inertial, partial, and inertial propeller representations predicted power savings while the actuator disc method predicted increase in delivered power. The partially rotating grid method provides a less computationally expensive alternative to the inertial propeller rotation representation, but at the cost of reduced accuracy. Furthermore, the study challenges the conventional analysis that attributes the power savings to improved propeller-hull interaction, suggesting that increased propeller efficiency is the primary cause.

Investigation of the Effects of the Pre-Duct in a Ship on Propeller–Hull Interactions Using the CFD Method

The power requirement of a ship propulsion system is directly proportional to the fuel consumption and the emissions released. By reducing the engine power, the fuel consumption and emissions can be reduced. One of the energy saving devices (ESDs) that is positioned in a region between the stern hull and propeller is the pre-duct. The ESD can improve the propulsive coefficient of the propulsion system. This research explains the effect of a circular pre-duct on the hull-propeller interaction. A numerical simulation uses the Japan bulk carrier (JBC) standard model for the hull and propeller. A circular pre-duct was applied to the ship with different diameters, stands, and lengths of the chord. The simulation has already been validated with the result of the resistance and self-propulsion test in the towing tank. The results show that the diameter of the pre-duct affects the water flow to the propeller. The model with 1Dp can make the positive value of the propulsive coefficient be about 1.72%. The size of the foil chord of the pre-duct can improve the performance until 2.88% at 1D 2S NS model. The stand of the pre-duct has a bad effect on the propulsive coefficient. The enlarged shape of the foil pre-duct can increase the water flow on the suction side. Also, making the diameter larger than the propeller diameter and eliminating the stand on the pre-duct make the incoming flow has no resistance or damages the rotary flow before the propeller. So that, the rampant flow to the propeller becomes larger and there are no significant obstacles until the propulsive coefficient value increases significantly.

Numerical study on the hull–propeller interaction of autonomous underwater vehicle

The hull–propeller interaction of autonomous underwater vehicle (AUV) in straight and oblique flow is numerically studied. The study is performed based on computational fluid dynamics (CFD) and the general commercial software ANSYS Workbench. The multiple reference frames (MRF) method and the shear stress transport (SST) k−ω turbulence model are adopted. Firstly, the drag of Suboff AUV and the open water performance of the Wageningen B-3-50 propeller are simulated numerically. The errors are all within 5%, validating the reliability of the method in this paper. Then, the Sailfish AUV and B-3-35 propeller developed by the Underwater Vehicle Laboratory (UVL) of Ocean University of China are simulated. The maximum incremental drag produced by the appendages reaches even more than 1.5 times the hull drag. Propeller rotation causes an additional hull drag increment of over 25%. With an inlet velocity of 1.5 m/s, the thrust and torque behind the bare hull increase by 16.7% and 6.4%, respectively. The effect of angle of attack on drag is more significant at high velocity. Finally, the numerical simulation result 1.825 m/s and experimental result 1.75 m/s are compared. This study has implications for guidance on AUV integration analysis.

Propulsion performance prediction for towing ship

Towing of various objects is a common marine operation. There is a whole group of ships intended for this work, like tugs, fishing vessels, seismic survey ships and industrial vessels. Towing operations of these ships typically proceed at the speeds of 1–4 m/s. The assumptions used to determine pulling performance parameters of towing ships are usually over-simplified. This paper suggests an analytical and experimental method intended to determine pulling performance of propulsion systems for towing ships.Typically, pulling and propulsion performance parameters of ships are obtained through a calculation using the results of towing and self-propulsion model tests. However, this conventional approach is not applicable to pulling performance calculations of towing ships because self-propulsion test results for towing ships at the speeds corresponding to this operation scenario give absurd values for propeller-hull interaction coefficients. The classic system of propeller-hull interaction coefficients does not work for towing ships at low advance ratios.To overcome these difficulties, this paper suggests an alternative system of propeller-hull interaction coefficients that is applicable to towing ships and gives a calculation method of pulling performance calculation for towing ships based on this alternative system, taking Yuribei tugboat as a case study.

An improved BEMT model based on agent actuating disk with application to ship self-propulsion simulation

Propeller body-force model is a low-cost tool for numerical simulation of the ship self-propulsion test compared with discretized propeller model. As one of the most traditional theories of propeller model, Blade Element Momentum Theory (BEMT) has been proved to have considerable application potential with stability and accuracy. However, it's still hard for BEMT to keep accuracy in a relatively large range of working conditions due to unproved prior assumptions, which limits the application of BEMT in complex inflow conditions like ship self-propulsion. In the application of BEMT, the calculation method of Angle of Attack (AOA) has a great influence on the accuracy. In this paper, an "Agent Actuating Disk (AAD)" method is proposed to determine the AOA. AAD-BEMT method uses AAD to obtain the relationship between local velocity and inflow velocity so that the AOA can be defined by geometric Angle of Attack. This consideration avoids the inaccuracy of determining AOA by local velocity from discretized propeller flow field. The KP505 propeller open-water test is chosen to verify the accuracy of the proposed AAD-BEMT method. Then the numerical simulation of a KRISO Container Ship (KCS) self-propulsion test (Fr = 0.26) is carried out to investigate the performance of the AAD-BEMT body-force model as well as other different propeller models when dealing with non-uniform ship's wake. The open-water curve, propeller load distribution, and self-propulsion factor are presented and compared with the available experimental data. The results show that the predicted load distribution is accurate. In addition, not only the thrust and torque of the AAD-BEMT model can have a stable accuracy in a wide operating condition, but also the wake agrees well with the experimental result, which means that the proposed AAD-BEMT model can economically and accurately simulate the momentum transport of propeller under complex hull-propeller interaction condition.

Актуальные вопросы изучения реверса движителей

Object and purpose of research. This paper discusses crash-stop of ship propellers. The puspose of the study was to investigate a number of relevant challenges in this process, i.e. to refine the methods of crash-stop distance calculation, to update the scenarios for which crash-stop strength of propeller blades has to be verified, as well as to determine operational parameters and algorithms for automatic control systems of electric power plants in crash-stop conditions. Subject matter and methods. The study was based on the results of quasi-crash-stop model tests, as well as on previous publications about crash-stop maneuvers of ships and operations of their propulsion systems in these conditions. Main results. To obtain more accurate crash-stop distance estimates, it was suggested to use an alternative, bollard-pull system of propeller-hull interaction coefficients for crash-stop conditions. It was also suggested to perform crash-stop strength check of propellers not only for the scenarios with maximum hydrodynamic load, but also for the moment of propeller rotation direction reversal because it might be accompanied by considerable inertial loads. It is shown that model testing is not helpful in determination of operational parameters and automatic control system algorithms for electric power plants because shaft lines cannot be simulated correctly. These parameters can be obtained through calculations, but this will require more refined expressions for shaft line friction moments. Conclusion. The actual problems of ship reverse propulsion theory is presented in the paper. The possible approaches to their solution are proposed.

Propeller–hull interaction beyond the propulsive factors—A case study on the performance of different propeller designs

The propulsive factors are critical for scaling of model-test data, and hence important for the final power prediction. When comparing different propulsion systems based on model-scale tests, differences in propulsive factors, and hence the propeller–hull interaction, are often not well understood. In this study the propeller–hull interaction is instead described and compared using CFD for three different propulsion systems, a tip-unloaded ice-classed propeller, an ice-classed propeller with conventional radial load distribution and a non ice-classed propeller with conventional radial load distribution. To post-process the results KT/KQ is evaluated for one blade around a revolution and complemented with radial distributions of the same measure. Both tip-unloaded blades and sharp leading edges suffer in-behind due to poor performance at low load. Open water performance dependency on Reynolds number reveals that ice-classed propellers are more negatively influenced by the low Reynolds numbers of self-propulsion tests. Further, it is noted that a more even radial load distribution favours a low thrust deduction factor. Since the propulsive factors to a large extent are influenced by scale-effects and also due to that their association to the observed hydrodynamics makes the commonly applied scaling procedure of them questionable, they are not considered representative for ship-scale power prediction.

Resistance and wake distortion optimization of JBC considering ship-propeller interaction

In this paper, the self-propulsion performance of a full formed hull is optimized by the in-house hull form optimization software OPTShip-SJTU 2.1. In the field of hull form optimization, complex hull optimizations such as hull-propeller interaction optimization have not launched a full investigation. To break through this limitation, the hull-propeller interaction module is brought into the software. We conduct a hull-propeller interaction design optimization of Japan Bulk Carrier (JBC) with an actual propeller (AP) based on CFD considering ship resistance and propeller wake distortion at Fr = 0.142. Hull form deformation module is applied to change the stern shape of the JBC. The in-house CFD software naoe-FOAM-SJTU is applied to calculate the hull resistance and wake fraction. The dynamic overset grid method is used to achieve the interaction between hull and propeller and obtain the high-fidelity flow field during the optimization processing. A multi-objective genetic algorithm (NSGA-II) is applied to obtain the optimized hull forms based on the Kriging surrogate model. The influences of propeller for the flow field around stern are also studied. Results indicate: (I) OPTShip-SJTU 2.1 can optimize the coupled hydrodynamic performance in complex hull form optimization. (II) The hull resistance and wake fraction have a strong positive correlation under the deformation setting in this paper. (III) Contraction of hull line at the stern can suppress the flow separation around the stern which is benefit for reducing the pressure resistance and improving the propeller wake distortion. (IV) It is necessary to consider the interaction between propeller and hull together in hull form optimization. The interactions between the shape of stern, propeller performance, and flow field around stern are discussed preliminary, which provide several references for the subsequent research.

A Generalized Hybrid RANSE/BEM Approach for the Analysis of Hull–Propeller Interaction in Off-Design Conditions

During maneuvers, propellers’ operation differs from their design due to strong modification of the wake field with respect to the straight-ahead motion. The consequent modification of the loads overstresses the mechanical components of the shaftline, exacerbates propeller side effects and worsens overall efficiency. Therefore, the analysis of these situations in the early design phase is pivotal to increase the operation capabilities and safety at sea. This task relies on novel tools capable to accurately predict the complex flow field that develops past the hull and the propeller loads. Since the solution of the fully coupled problem with the rotating propeller by viscous flow solver is impractical for routine applications, hybrid approaches are a viable alternative. In this paper, an interactive RANSE/BEM methodology is presented, where the propeller is replaced by rotating body forces that map the actual loading state of the blades, allowing a fully unsteady analysis of hull–propeller interaction. The methodology is applied to the straight ahead and 8.4° pure drift motions of a twin screw propulsive configuration. Last, but not least, the study presents a validation study with accurate experimental data of the nominal wake field and single blade loads.

Hull–propeller interaction for planing boats: a numerical study

ABSTRACT Numerical simulations are performed to study the interaction between propeller and hull for two planing vessels: a hard-chine and a tunnelled craft. The numerical model used for reproduction of the problem is validated by comparing the obtained results against published data, showing that a morphing technique is more reliable compared to an overset one. It is demonstrated that propellers strongly affect the performance of a vessel by increasing trim angle and decreasing resistance, which are caused by a noticeable pressure reduction occurring near propellers. These changes are more significant for the case of a tunnelled hull since hydrodynamic pressure acting on the bottom of this vessel is larger compared to a hard-chine craft. While resistance of hulls is seen to be influenced by variation in the position of the propellers at early-planing mode, trim angle is seen to be insensitive to the position of propellers at all speeds.

Design of Wake Equalizing Ducts using RANSE-based SBDO

We propose a Simulation-Based Design Optimization (SBDO) approach for the design of an Energy Saving Device (ESD) based on the Wake Equalizing Duct (WED) concept. Pre-Ducts, like Wake Equalizing Ducts, reduce the wake losses, improve the propeller-hull interaction and generate an additional thrust. An integrated design approach, relying on a parametric description of the duct geometry of the WEDs and on a RANSE method, managed by a global convergence optimization algorithm, is developed to maximize the delivered thrust. The Japan Bulk Carrier (JBC) test case, for which model scale experimental data on the effectiveness of the WED are available in the literature, is considered as a baseline. Results obtained by using the adaptive, fully automated proposed design framework highlight significant improvements of the overall propulsive efficiency when the Pre-Duct design is tailored to the actual hull wake shape. In addition, off-design conditions are considered to verify the robustness of the proposed designs with respect to variations of the working point and discuss the opportunity of a robust optimization process.

Numerical Analysis of Full-Scale Ship Self-Propulsion Performance with Direct Comparison to Statistical Sea Trail Results

Accurate prediction of the self-propulsion performance is one of the most important factors for the energy-efficient design of a ship. In general, the hydrodynamic performance of a full-scale ship could be achieved by model-scale simulation or towing tank tests with extrapolations. With the development of CFD methods and computing power, directly predict ship performance with full-scale CFD is an important approach. In this article, a numerical study on the full-scale self-propulsion performance with propeller operating behind ship at model- and full-scale is presented. The study includes numerical simulations using the RANS method with a double-model and VOF (Volume-of-Fluid) model respectively and scale effect analysis based on overall performance, local flow fields and detailed vortex identification. The verification study on grid convergence is also performed for full-scale simulation with global and local mesh refinements. A series of sea trail tests were performed to collect reliable data for the validation of CFD predictions. The analysis of scale effect on hull-propeller interaction shows that the difference of hull boundary layer and flow separation is the main source of scale effect on ship wake. The results of the fluctuations of propeller thrust and torque along with circulation distribution and local flow field show that the propeller’s loading is significantly higher for model-scale ship. It is suggested that the difference of vortex evolution and interaction is more pronounced and has larger effects on the ship’s powering performance at model-scale than full-scale according to the simulation results. From the study on self-propulsion prediction, it could be concluded that the simplification on free surface treatment does not only affect the wave-making resistance for bare hull but also the propeller performance and propeller induced ship resistance which can be produced up to 5% uncertainty to the power prediction. Roughness is another important factor in full-scale simulation because it has up to an approximately 7% effect on the delivery power. As a result of the validation study, the numerical simulations of full-scale ship self-propulsion shows good agreement with the sea trail data especially for cases that have considered both roughness and free surface effects. This result will largely enhance our confidence to apply full-scale simulation in the prediction of ship’s self-propulsion performance in the future ship designs.

Numerical investigation of the unsteady flow of a hybrid CRP pod propulsion system at behind-hull condition

Flows induced by hybrid CRP pod propulsion systems (CRP-POD) are fundamentally characterized by unsteadiness. This work presents a numerical study on the unsteady flow of a CRP-POD at behind-hull condition based on CFD (Computational Fluid Dynamics). Unsteady RANS method is adopted, coupled with SST k-ω turbulence model and sliding mesh method. The propeller thrusts and torques obtained by CFD is validated by model tests and acceptable agreements are obtained. The time histories of shingle-blade loads and pressures near the hull surface are recorded for the analysis of unsteady flow features. The cases of forward propeller alone and aft propeller alone are also computed to distinguish the hull-propeller interaction and propeller-propeller interaction. The results show the blade loads of both forward and aft propellers strongly fluctuate with phase angles. For the forward propeller, the blade load fluctuation is mainly governed by the hull-propeller interaction, while the aft blade load is remarkably affected by the propeller-propeller interaction in terms of the load average and fluctuation pattern. The fields of pressure, vorticity and velocity are also analyzed to reveal the unsteady flow features.

Numerical Study on Flow Around Modern Ship Hulls with Rudder-Propeller Interactions

Reducing the fuel consumption of ships presents both economic and environmental gains. Although in the past decades, extensive studies were carried out on the flow around ship hull, it is still difficult to calculate the flow around the hull while considering propeller interaction. In this paper, the viscous flow around modern ship hulls is computed considering propeller action. In this analysis, the numerical investigation of flow around the ship is combined with propeller theory to simulate the hull-propeller interaction. Various longitudinal positions of the rudder are also analyzed to determine the effect of rudder position on propeller efficiency. First, a numerical study was performed around a bare hull using Shipflow computational fluid dynamics (CFD) code to determine free-surface wave elevation and resistance components. A zonal approach was applied to successively incorporate “potential flow solver” in the region outside the boundary layer and wake, “boundary layer solver” in the thin boundary layer region near the ship hull, and “Navier-Stokes solver” in the wake region. Propeller open water characteristics were determined using an open-source MATLAB code OpenProp, which is based on the lifting line theory, for the moderately loaded propeller. The obtained open water test results were specified in the flow module of Shipflow for self-propulsion tests. The velocity field behind the ship was recalculated into an effective wake and given to the propeller code that calculates the propeller load. Once the load was known, it was transferred to the Reynolds-averaged Navier-Stokes (RANS) solver to simulate the propeller action. The interaction between the hull and propeller with different rudder positions was then predicted to improve the propulsive efficiency.

A Numerical and Experimental Study on the Hull-Propeller Interaction of A Long Range Autonomous Underwater Vehicle

Range is an important factor to the design of autonomous underwater vehicles (AUVs), while drag reduction efforts are pursued, the investigation of body-propeller interaction is another vital consideration. We present a numerical and experimental study of the hull-propeller interaction for deeply submerged underwater vehicles, using a proportional-integral- derivative (PID) controller method to estimate self-propulsion point in CFD environment. The hydrodynamic performance of hull and propeller at the balance state when the AUV sails at a fixed depth is investigated, using steady RANS solver of Star-CCM+. The proposed steady RANS solver takes only hours to reach a reasonable solution. It is more time efficient than unsteady simulations which takes days or weeks, as well as huge consumption of computing resources. Explorer 1000, a long range AUV developed by Shenyang Institute of Automation, Chinese Academy of Sciences, was studied as an object, and self-propulsion point, thrust deduction, wake fraction and hull efficiency were analyzed by using the proposed RANS method. Behind-hull performance of the selected propeller MAU4-40, as well as the hull-propeller interaction, was obtained from the computed hydrodynamic forces. The numerical results are in good qualitative and quantitative agreement with the experimental results obtained in the Qiandao Lake of Zhejiang province, China.

Numerical analysis of propeller loading with a coupling RANS and potential approach

In this paper, we present a coupling potential and Reynolds-averaged Navier–Stokes (RANS) approach for the analysis of propeller loading and propulsion performance at self-propulsion condition. There is a presentation of a combination of unsteady RANS method for ship flow with free surface taking into account by volume of fluid method and Lifting Line Model for propeller operating behind ship. An intensified coupling strategy is proposed to simulate the propeller effect in the ship wake. The effective wake is re-examined through the iterations, and there is a presentation of the spatial distribution of propeller forces. Propeller unsteady loading of KCS test case is predicted by flow field from both Full RANS and the Coupling method and compared to experiment results. A circulation-based analysis is made to scrutinize the spatial distribution of propeller loading. The simulation results prove that the coupling method can estimate propeller’s loading and effect on averaged flow field. Ultimately, the coupling method is applied to design an optimal propeller accounting for hull–propeller interaction, which shows its potential for further integrated optimization application.

Design optimization for self-propulsion of a bulk carrier hull using a discrete adjoint method

Computational fluid dynamics (CFD) based optimization is becoming increasingly popular in hydrodynamic design of ship hulls because it provides a fully automatic framework with a shorter design cycle than a human-supervised design tool. Despite the above advantage, CFD-based optimization requires careful attention to relevant design considerations, such that the final design is useful in practice. These considerations include all relevant objectives (such as drag and wake distortion) and constraints (such as volume, thickness, and curvature). Although constraints have been included in previous hull shape optimization studies, these studies have typically considered only one objective. To address this shortcoming, we conduct design optimization for self-propulsion by simultaneously considering drag and propeller-wake distortion. We use a gradient-based optimization framework that includes a discrete adjoint method for efficient derivative computation, which allows us to use a large number of design variables to parameterize the complex hull shape and thus gain a large amount of freedom for geometric modification. We impose appropriate geometric constraints (volume, thickness, and curvature) on the hull surface to ensure a practical design. In addition, we use a weighted objective function that includes drag and wake distortion to construct a Pareto front with five optimizations. We also consider hull-propeller interaction by comparing optimization results with and without a propeller. We use the Japan bulk carrier (JBC) as the baseline model and focus on optimizing the stern region. We find that optimizing for only one objective results in a large penalty on the other objective, whereas a weighted objective balances the penalty and achieves simultaneous improvement in drag and wake distortion. Moreover, we observe that the suction effect of the propeller suppresses the flow separation near the bilge tube and smooths out the velocity distortion at the propeller plane; these are effects that would end up affecting the optimized shapes. Our results demonstrate that it is necessary to simultaneously consider drag and wake distortion in hull-shape-optimization studies, and that constrained shape optimization with a large number of design variables is possible with the discrete-adjoint method.

DES-based computation of the flow around the DARPA suboff

Flow modelling is a key issue not only for the correct prediction of hull-propeller interactions, manoeuvring characteristics and the flow field in the stern region of any marine vehicle, but also for the correct estimation of the fuel consumption. The paper describes a thorough investigation of the hydrodynamic performances of the DARPA suboff hull. The flow is numerically simulated by integrating in time the unsteady Navier-Stokes equations in which closure to the turbulence is achieved by means of a modified detached eddy simulation (DES hereafter) technique. The solver used for the purpose is the ISIS-CFD, part of the Numeca FineTM/Marine suite, which employs the finite volume of fluid technique. A comparative analysis between the numerical solutions based on the DES and explicit algebraic stress model (EASM hereafter) are provided in an attempt to sustain the choice for the turbulence model in the present study. Extensive parallel computations are carried out on 120 processors for which comparisons with the experimental data prove the accuracy of the chosen investigation methodology. A grid convergence test is performed for verification and validation purposes.

Numerical Prediction of Propeller-Hull Interaction Characteristics Using RANS Method

Abstract The paper presents the results of computational evaluation of the hull-propeller interaction coefficients, also referred to propulsive coefficients, based on the unsteady RANS flow model. To obtain the propulsive coefficients, the ship resistance, the open-water characteristics of the propeller, and the flow past the hull with working propeller were computed. For numerical evaluation of propeller open-water characteristics, the rotating reference frame approach was used, while for self-propulsion simulation, the rigid body motion method was applied. The rotating propeller was modelled with the sliding mesh technique. The dynamic sinkage and trim of the vessel were considered. The free surface effects were included by employing the volume of fluid method (VOF) for multi-phase flows. The self-propulsion point was obtained by performing two runs at constant speed with different revolutions. The well-known Japan Bulk Carrier (JBC) test cases were used to verify and validate the accuracy of the case studies. The solver used in the study was the commercial package Star-CCM+ from SIEMENS.

An integral calculation approach for numerical simulation of cavitating flow around a marine propeller behind the ship hull

In this paper, the unsteady cavitating turbulent flow around a marine propeller is simulated based on the unsteady Reynolds averaged Navier-Stokes (URANS) with emphasis on the hull-propeller interaction by an integral calculation approach, which means the propeller and hull are treated as a whole when the cavitating flow is calculated. The whole calculational domain is split to an inner rotating domain containing a propeller and an outer domain containing a hull. And the two split sections are connected together in ANSYS CFX by using the GGI interfaces and the transient rotor stator frame change/mixing model. The alternate rotation model is employed for the advection term in the momentum equations in order to reduce the numerical error. Comparison of predictions with measurements shows that the propeller thrust coefficient can be predicted satisfactorily. The unsteady cavitating flow around the propeller behind the ship hull wake shows quasi-periodic features including cavity inception, growth and shrinking. These features are effectively reproduced in the simulations which compare well to available experimental data. In addition, significant pressure fluctuations on the ship hull surface induced by the unsteady propeller cavitation are compared with experimental data at monitoring points on the hull surface. The predicted amplitudes of the first components corresponding to the first blade passing frequencies match well with the experimental data. The maximum error between the predictions and the experimental data for the pressure pulsations is around 8%, which is acceptable in most engineering applications.