Numerical Prediction of Marine Propeller Noise in Non-Uniform Inflow

A numerical study on the acoustic radiation of a propeller interacting with non-uniform inflow has been conducted. Real geometry of a marine propeller DTMB 4118 is used in the calculation, and sliding mesh technique is adopted to deal with the rotational motion of the propeller. The performance of the DES （Detached Eddy Simulation） approach at capturing the unsteady forces and moments on the propeller is compared with experiment. Far-field sound radiation is predicted by the formation 1A developed by Farassat, an integral solution of FW-H （Ffowcs Williams-Hawkings） equation in time domain. The sound pressure and directivity patterns of the propeller operating in two specific velocity distributions are discussed.

Numerical Analysis of Blade Stress of Marine Propellers

In this study,a series of numerical calculations are carried out in ANSYS Workbench based on the unidirectional fluid–solid coupling theory.Using the DTMB 4119 propeller as the research object,a numerical simulation is set up to analyze the open water performance of the propeller,and the equivalent stress distribution of the propeller acting in the flow field and the axial strain of the blade are analyzed.The results show that FLUENT calculations can provide accurate and reliable calculations of the hydrodynamic load for the propeller structure.The maximum equivalent stress was observed in the blade near the hub,and the tip position of the blade had the largest stress.With the increase in speed,the stress and deformation showed a decreasing trend.

Numerical Simulation of the Flow around Marine Propeller Series

The objective of marine propeller design optimization study is to obtain a propeller with minimum power absorption, maximum efficiency and good materials resistance. In this study, results of numerical simulation carried out on the flow around a conventional marine propeller are presented. The investigation focused on the aspects related to the influence of skew magnitude, thickness and blade number on the propeller performances. First, open water performances of a conventional propeller model DTMB 4148 was estimated using RANS （Reynolds Averaged Navier-Stokes） method. The flow around rotating propeller model was analyzed in the steady state using RANS approach of the commercial CFD （computational fluid dynamics） code fluent. The results provide good agreement with literature data. Numerical results show that the number of blades has an influence on the open water performances of marine propellers. It＇s noticed that the best propeller has four or five blades from only the hydrodynamic aspect. The thickness blade effect has been studied for the same propeller model and compared to the blade with three different thickness values. Results of the calculation show that the blade thickness increases moderately the propeller efficiency. Finally, numerical simulation is performed to study the magnitude skew effect on the propeller blade performance, so three different models were generated. The results of the simulation show that the skew distribution has a positive effect on the open water performances of the marine propellers.

A review of recent advances in the effects of surface and interface properties on marine propellers

Marine propellers are important propulsion devices for both surface ships and underwater vehicles.Increasingly severe environmental problems have required further performance enhancement for propellers.Nowadays,traditional methods to improve propeller performances through geometrical and structural optimizations have been extensively investigated,while the underlying mechanisms of the effects of surface and interface properties on marine propellers are still far from being fully understood.This paper presented a comprehensive review of recent advances in the effects of surface and interface properties,such as surface roughness and surface wettability,on marine propellers with an emphasis on the significant improvements in both hydrodynamic and cavitation performances,hoping to arouse more in-depth investigations in the field of surface/interface science and technologies on marine propellers,and also promote the state-of-the-art technologies,such as superlubricity technology,into practical applications.

Numerical analysis on propulsive efficiency and pre-deformated optimization of a composite marine propeller

The objectives of this paper are to numerically investigate the performance of a composite propeller through bidirectional FSI algorithm combining CFD and FEM,and to improve its propulsive efficiency by a pre-deformated method. Numerical results are presented for the composite propeller which has been modeled by unidirectionally stacking with glass-fiber reinforced composites. The propulsive efficiency of the composite and rigid propellers with different advance coefficients J has been compared.The results show that the efficiency of the composite propeller is obviously higher than that of the rigid propeller when J≤0.8,which is attributed to the decrease of pitch angle caused by the bend-twist coupling effects. But for the design condition J=0.851 and the cases with J>0.851,the efficiency of the composite propeller is significantly lower than that of the rigid propeller,which is because the angle of attack αcomposite is deviated from the optimal angle of attack αdesign more than that for the rigid case αrigid.Based on the optimization by the proposed pre-deformated method,the efficiency improvement of the composite propeller at the conditions with J≥0.851 could be obtained,and the composite material used in this work can meet the strength requirement of the designed propellers.

Hydro-elastic computational analysis of a marine propeller using two-way fluid structure interaction

Marine propellers have complex geometry and their performance is determined by costly and time consuming open water experiments.Use of numerical techniques helps researchers in effective design of propellers.Several approaches are used that predicted either hydrodynamic and acoustic response or structural response.Two-way fluid-structure interaction(FSI)analysis is a very useful approach providing all three responses which helps in the design,analysis and optimization of a propeller.The objective of this paper is to predict the hydro-elastic response of a propeller using two-way FSI on a 0.2m diameter,DTMB-4119 propeller using ANSYS software.Two-way FSI analysis is carried out using system coupling approach that transfers the data between the structural and fluid solvers.The turbulence effects are captured using the large-eddy simulation(LES)model and the Ffowcs Williams Hawkings(FWH)acoustic model is used for evaluating the sound pressure level(SPL)generated by propeller.Analysis is extended to evaluate the hydro-elastic and acoustic response of the propeller after validating the hydrodynamic performance with the experimental result in the literature.The results from Two-way FSI analysis are in close agreement when compared with the one-way FSI analysis.Two-way FSI can accommodate the peak value of stress and deformation developed during the initial part of the transient solution which is important in the design of propeller.This study reveals that metallic(NAB)propeller can be replaced by a composite propeller.The acoustic response from two-way FSI analysis will be more realistic due to the consideration of hydro-elastic effect of propeller.

Numerical Hydro-Acoustic Prediction of Marine Propeller Noise

A source-to-far-field computation procedure aiming at predicting the noise generated by the underwater propeller was presented. Detached eddy simulation(DES) was used to resolve the unsteady flow field,which was taken as input data as noise propagation. Far-field sound radiation was performed by means of Ffowcs Williams-Hawkings(FW-H) equation. The computation procedure was finally applied to a typical marine propeller,David Taylor Model Basin(DTMB) 4118. The sound pressure and directivity patterns of this propeller were discussed.

基于RANSE模型CFD预测E779A型螺旋桨空化及其在通用船体后的水动力性能

Ship propulsion performance heavily depends on cavitation,increasing the recent interest in this field to lower ship emissions.Academic research on the effects of cavitation is generally based on the open-water propeller performance but the interactions of the cavitating propeller with the ship hull significantly affect the propulsion performance of the ship.In this study,we first investigate the INSEAN E779A propeller by a RANSE-based CFD in open-water conditions.The numerical implementation and the selected grid after sensitivity analysis partially succeeded in modeling the cavitating flow around the propeller.Satisfactory agreement was observed compared to experimental measurements.Then,using the open-water data as input,the propeller’s performance behind a full-scale ship was calculated under self-propulsion conditions.Despite being an undesired incident,we found a rare condition in which cavitation enhances propulsion efficiency.Atσ=1.5;the propeller rotation rate was lower,while the thrust and torque coefficients were higher.

PREDICTION OF UNSTEADY CAVITATION OF PROPELLER USING SURFACE PANEL METHOD

This paper has predicted the range and volume of unsteady sheet cavitation of a propeller by using the surface panel method. The linearization in cavity thickness is adopted to reduce the computing time and storage space. The iteration scheme between chordwise strips has been used because the range and volume of cavitation are both unknown. The propeller cavitation range determined by the calculation method presented in this paper agrees with the observation results of cavity image at cavitation tunnel very well, and this proves the practicability of the method.

Cavitation Erosion Corrosion Behaviour of Manganese-nickel-aluminum Bronze in Comparison with Manganese-brass

The cavitation erosion corrosion behaviour of ZQMn12-8-3-2 manganese-nickel-aluminum bronze and ZHMn55- 3-1 manganese-brass was investigated by mass loss, electrochemical measurements （polarization curves and electrochemical impedance spectroscopy） and the cavitation damaged surfaces were observed by scanning electron microscopy （SEM）. The results showed that ZQMn12-8-3-2 had better cavitation erosion resistance than ZHMn55-3-1. After the cavitation erosion for 6 h, the cumulative mass loss of ZQMn12-8-3-2 was about 1/3 that of ZHMn55-3-1. The corrosion current density of ZQMn12-8-3-2 was less than that of ZHMn55-3-1 under both static and cavitaiton condition. The free-corrosion potentials of ZQMn12-8-3-2 and ZHMn55-3-1 were all shifted in positive direction under cavitation condition compared to static condition. In the total cumulative mass loss under cavitation condition, the pure erosion played a key role for the two tested materials （74% for ZHMn55-3-1 and 60% for ZQMn12-8-3-2）, and the total synergism between corrosion and erosion of ZQMn12-8-3-2 （39%） was larger than that of ZHMn55-3-1 （23%）. The high cavitation erosion resistance of ZQMn12-8-3-2 was mainly attributed to its lower stacking fault energy （SFE）, the higher microhardness and work-hardening ability as well as the favorable propagation of cavitation cracks for ZQMn12-8-3-2, i.e., parallel to the surface rather than perpendicular to the surface for ZHMn55-3-1.