Propeller Design Research Articles

Wake Characteristic Analysis of a Marine Propeller under Different Loading Conditions in Coastal Environments

Sun, P.; Pan, L.; Liu, W.; Zhou, J., and Zhao, T., 2022. Wake characteristic analysis of a marine propeller under different loading conditions in coastal environments. Journal of Coastal Research, 38(3), 613–623. Coconut Creek (Florida), ISSN 0749-0208. The propeller wake field is closely related to the cavitation and noise performance of the propeller. The propeller wake fields under light and heavy loading conditions were numerically studied based on the delayed detached eddy simulation method. The characteristics of propeller wake dynamics under different loading conditions were analyzed to reveal the flow physics during the propeller wake evolution. The results showed that the pitch of the helicoidal vortex behind the propeller is large and the wake is relatively stable under light loading conditions with a high advance coefficient. In the heavy loading condition with a low advance coefficient, the pitch of the helicoidal vortex is smaller; the vortex system tends to be unstable and break down earlier. The downstream alternate strong- and weak-tip vortices indicate that the tip vortex evolution is accompanied by a dissipation process, which plays an important role in the interaction between adjacent tip vortices and the inception of propeller wake instability. The present work can provide a reference for the design and optimization of propellers used by ships sailing in coastal environments and zones farther out to sea.

Numerical study of nominal wake fields of a container ship in oblique regular waves

Accurate estimation of the actual nominal wake behind the ship in waves is important for propeller designers when improving efficiency and minimizing cavitation. The present CFD study investigates the nominal wake fields of the Kriso Container Ship (KCS) in regular waves with wavelength equal to the ship length in five different headings. The ship is sailing at design speed and the wave steepness is 1/60. The results show that when sailing in the studied waves, the nominal wake fraction fluctuate up to 39% of the mean nominal wake fraction. The mean nominal wake fraction is higher than in calm water for all headings besides head sea waves. The maximum mean nominal wake fraction is found to occur in stern quartering sea waves, with a 16% higher mean nominal wake fraction than in calm water. It is also found that the transient bilge vortex and shadow from the skeg have a significant influence on the nominal wake field. Finally the study shows that the modified advance angle on the r/R=0.7 circle in the propeller plane varies 3.5 degrees more in port stern quartering than in calm water, increasing the risk of cavitation.

A Preliminary Feasibility Study on Wind Resource and Assessment of a Novel Low Speed Wind Turbine for Application in Africa

This paper posits that a low-speed wind turbine design is suitable for harnessing wind energy in Africa. Conventional wind turbines consisting of propeller designs are commonly used across the world. A major hurdle to utilizing wind energy in Africa is that conventional commercial wind turbines are designed to operate at wind speeds greater than those prevalent in most of the continent, especially in sub-Sahara Africa (SSA). They are heavy and expensive to purchase, install, and maintain. As a result, only a few countries in Africa have been able to include wind energy in their energy mix. In this paper, the feasibility of a novel low-speed wind turbine based on a Ferris wheel is demonstrated for low wind speed applications in Africa. The performance of Ferris wheel wind turbines (FWT) with 61 m (200 ft), 73 m (240 ft) and 104 m (341 ft) diameter rims and an 800 kW generator are evaluated for selected African cities. The research also compares the Weibull wind distribution of the African cities of interest. A comparison between the FWT and the conventional commercial wind turbines in terms of efficiency, rated wind speed, cost, performance, and power to weight is included. Results show that the FWT has the potential for economic power generation at rated wind speeds of 6.74 m/s, which are lower than the average of 12 m/s for conventional wind turbines and have lower power to weight ratios of 5.2 kW/tonne as compared to 6.0–9.2 kW/tonne for conventional wind turbines.

How can ports act to reduce underwater noise from shipping? Identifying effective management frameworks

This paper aims to find mechanisms to align commercial interests with underwater noise reductions from commercial shipping. Through a survey and a series of interviews with representative stakeholders, we find that while acknowledging the wide variations in ports' specificities, port actions could support the reduction in underwater noise emissions from commercial shipping through changes in hull, propeller and engine design, and through operational measures associated with reduced speed, change of route and travel in convoy. Though the impact of underwater noise emissions on marine fauna is increasingly shown to be serious and wide-spread, there is uncertainty in the mechanisms, the contexts, and the levels which should lead to action, requiring precautionary management. Vessels owners are already dealing with significant investment and operating costs to comply with fuel, ballast water, NOx and CO2 requirements. To be successful, underwater noise programs should align with these factors.Based on a multiple criteria decision making (MCDM) approach, we find a set of compromise solutions for a wide range of stakeholders. Ports could propose actions such as discounted port fees and reduced ship waiting times at ports, both depending on underwater noise performance. Cooperation between ports to scale up actions through environmental indexes and classification societies' notations, and integration with other ports' actions could help support this. However, few vessels know their underwater noise baseline as there are very few hydrophone stations, and measurement methodologies are not standardized. Costs increase and availability decreases dramatically if the vessel buyer wants to improve the noise profile. Local demands regarding airborne noise close to airports boosted global pressure on the aviation industry to adopt existing quieting technology. This experience of the aviation noise control could inform the underwater noise process.

Optimum Operating Parameters and Blade Setting of a High-Speed Propeller

Traditionally, the design of propellers is accomplished on the bases of engineering experience and the availability of well-established experimental data. However, the emergence of computational fluid dynamics (CFD) tools coupled with advanced optimizers has made this task easier. This paper presents the essentials of an optimization-based CFD chain aimed at finding the optimal operating parameters and blade settings of a high-speed propeller. This fully automated procedure combines an improved hypercube sampling (IHS) for the initial design of experiment and a radial basis function (RBF) as the meta-model, hence leading to lesser CFD simulations. The coupling between IHS and RBF is judiciously implemented, and the sampling strategy and updates are thoroughly examined. The optimization procedure uses the multi-objective evolutionary algorithm nondominated sorting genetic algorithm to determine the operating parameters and blade setting that maximize the propeller efficiency and thrust. At the optimum point the blade operates with mild pressure gradients, whereas the transonic region is restricted to the upper corner of the blade tip.

A SOURCE OF PROPELLER EXCITED BROADBAND VIBRATION ON A HIGH-SPEED TWIN SCREW SHIP

The cause of the severe propeller excited broadband vibration on a twin screw ship’s stern was investigated in a cavitation tunnel using conventional modelling methods. At first sight the results did not indicate anything untoward about the stern and propeller designs tested, apart from some unusual cavitation patterns in the propellers’ slipstreams. The fluctuating pressure levels on the model hull varied considerably depending on the propeller designs and loading conditions used in the tests, but these did not provide an explanation for the vibration on the ship. Some unusual patterns in the relative levels of the harmonic pressures on the stern were noticed in addition to the presence of a large cavitation disturbance in a propeller trailing vortex that was captured in a single frame of a video recording. This latter observation led to a plausible explanation for the broadband vibration on the ship’s stern.

A REVIEW OF PRACTICAL METHODS FOR REDUCING UNDERWATER NOISE POLLUTION FROM LARGE COMMERCIAL VESSELS

Underwater noise pollution from shipping is of considerable concern for marine life, particularly due to the potential for raised ambient noise levels in the 10-300Hz frequency range to mask biological sounds. There is widespread agreement that reducing shipping noise is both necessary and feasible, and the International Maritime Organization is actively working on the issue. The main source of noise is associated with propeller cavitation, and measures to improve propeller design and wake flow may also reduce noise. It is likely that the noisiest 10% of ships generate the majority of the noise impact, and it may be possible to quieten these vessels through measures that also improve efficiency. However, an extensive data set of full scale noise measurements of ships under operating conditions is required to fully understand how different factors relate to noise output and how noise reduction can be achieved alongside energy saving measures.

COUPLED RANSE AND LIFTING LINE THEORY FOR ESTIMATION OF SHIP PROPULSION FACTORS

Advances in Computational Fluid Dynamics (CFD) techniques through the development of the Reynolds-Averaged Navier-Stokes Equations (RANSE) have assisted in estimation of resistance and propulsion characteristics of ships to a reasonable level of accuracy. The aim of this paper is to test and demonstrate the capabilities of the coupled RANSE and Lifting Line theory for undertaking ship resistance, propeller open-water and self-propulsion simulations. Further, parametric studies for generation of numerical propeller design sheets and optimisation of propulsive efficiency using the coupled simulation approach has been discussed. Commercial CFD solver “M/s Flowtech - Shipflow” has been used for the study. Initially, some benchmark experimental/numerical model results are validated with the results of the CFD simulations and then, further parametric analyses have been undertaken with the KRISO Container Ship and the KP505 Propeller. The numerical propeller series and the preliminary study methodology for optimization of location of propeller disc behind the ship’s hull are being proposed as an effective concept/feasibility design stage tool for estimation of ship propulsion characteristics.

Numerical investigation of BPF noise for flexible submarine propeller design including inertial force coupling

Numerical investigation of BPF noise for flexible submarine propeller design including inertial force coupling

Minimum Propulsion Power Assessment of a VLCC to Maintain the Maneuverability in Adverse Conditions

The International Maritime Organization (IMO) Guidelines for Determining Minimum Propulsion Power to Maintain the Maneuverability in Adverse Conditions is the sole regulation imposed on the routine design and approval of all new-built ships as a part of EEDI requirements. This study reviews the development of the guidelines and summarizes the recent amendments of MEPC76(2021). The present assessment is conducted for a new VLCC design following the new guidelines aiming at investigating the influence of alternative wave added resistance evaluation methods and the propeller design features on the assessment results. It is found that the most simple empirical formula method proposed by MEPC76 is not conservative enough, as could have been expected. On the other hand, spectral analysis methods based on empirically obtained and properly validated wave added resistance responses can produce consistent results. Moreover, discussions are made from the perspective of propeller design to meet the regulatory requirements. It is pointed out that the light running margin is a key design parameter, and propellers with larger light running margins are more advantageous for satisfying the minimum propulsion power regulation, thus ensuring the navigation safety in adverse conditions. These obtained insights and know-how can support the engineers in obtaining optimal design solutions.

Research on Optimization of Parametric Propeller Based on Anti-Icing Performance and Simulation of Cutting State of Ice Propeller

When a ship sails in an ice area, the ice could cause damage to ship hull and the propeller as well as the rudder. In the design process of an ice class propeller, the strength verification of the propeller has always been the focus of the design and research of the ice propeller. Based on the International Association of Classification Societies Unified Requirements for Polar Class (IACS Polar UR), it is required that the maximum torque from the propeller cannot exceed the required value to ensure the safety of the propeller shafting equipment. This paper investigates the hydrodynamic performance of the propeller under the condition of satisfying the propeller’s ice strength. A parametric propeller optimization design procedure was established in which the thrust coefficient and open water efficiency solved by CFD method were selected as the objective function and optimization target, the maximum ice torque was used as the optimization constraint under the condition that the ship’s shafting equipment remains unchanged, the propeller pitch, thickness, and camber at each radial direction were taken as the optimization design variables, and the optimization algorithm of SOBOL and NSGA-II was adopted. The interaction mode of propeller and ice was simulated by the method of explicit dynamics. The equivalent stress and displacement response of the blade during the cutting process of the ice propeller were calculated, monitoring the ice destruction process. The results show that the multi-objective Pareto optimal solution set of thrust coefficient and open water efficiency of the ice class propeller was formed at the design speed while maintain the maximum ice torque not exceeding the original ice torque.

Design of Propeller Series Optimizing Fuel Consumption and Propeller Efficiency

This paper presents a comparison between different types of propellers operated in calm water to evaluate their performance behind hulls and in open-water conditions. A bulk carrier is chosen as a case study to perform the simulation and to evaluate the performance of several propeller series, namely the Wagengein B-series, Kaplan 19A, and MAU. Firstly, optimization procedures are performed by coupling a propeller design tool and a nonlinear optimizer to find the optimum design parameters of a fixed-pitch propeller. This optimization model aims to design the propeller behind the hull at the engine operating point with minimum fuel consumption and maximum propeller efficiency. The two main objectives of this study and the constraints are defined in a single fitness function to find the optimum values of the propeller geometry and the gearbox ratio. By considering the benefits of the single-objective over the multi-objective optimization problem, this model helps to find the optimum propeller for both defined objectives instead of only considering one of them, as in previous studies. Then, based on the optimized parameters, the propeller performance is calculated in open-water conditions. From the computed results, one can observe the importance of considering the hull–propulsor interaction in propeller selection.

Application of CFD Technology to Marine Propeller Design

Application of CFD Technology to Marine Propeller Design

Pengaruh Pola Pemasangan dan Rasio Dimensi Propeller Terhadap Unjuk Kerja Perahu Tipe Penggerak Contra Rotation Propeller

The propeller is an important part of the ship's propulsion installation. Differences in propeller design can affect the propulsion performance of the ship. This study aims to determine the effect of variations in dimension ratio and propeller installation pattern on the performance of the contra rotation propeller type boat. The research was carried out experimentally by using variations of three-dimensional propeller ratios including R1 (1:1); R2 (1:1/2) and R3 (1:1/4), while the pattern of placement of the shaft tilt angle includes 15oand 20o. The flow pattern is conditioned with the waveless and wavy flow. Data collection includes boat speed and visualization of fluid flow behind the propeller which is then analyzed to obtain performance characteristics for each variation used. The results showed that the dimension ratio and the pattern of contra rotation propeller installation affected the speed and thrust of the boat, where the optimum power was obtained at the variation of the ratio R2 at a shaft tilt angle of 15owith the provision of a water flow mechanism without waves resulting in a speed of 0.576923 cm/second and under conditions of wavy at 0.523256 cm/second. The greatest thrust occurs in conditions of water flow without waves at the variation of the ratio R2 with a value of 33.23 kN and in wavy conditions of 30.13 kN. Visualization of fluid flow behind the shaft has shown the performance of the contra rotation propeller in various variations given through changes in the shape and length of the resulting path .Keywords: dimension ratio, installation pattern, contra rotation propeller, boat performance

Effects of Wavy Leading-Edge Protuberance on Hydrofoil Performance and Its Flow Mechanism

This paper examines the effects on a Clark-y three-dimensional hydrofoil of wavy leading-edge protuberances in a quantitative and qualitative way. The simulation is accompanied by a hybrid RANS-LES model in conjunction with Zwart-Gerber–Belamri model. Detailed discussions of the stable no-cavitating, unsteady cavitating flow fields and the control mechanics are involved. The force characteristics, complicated flow behaviors, cavitation–streamwise vortex interactions, and the cavitating flow instability are all presented. The results demonstrate that protuberances acting as vortex generators produce a continuous influx of boundary-layer vorticity, significantly enhancing the momentum transfer of streamwise vortices and therefore improving the hydrodynamics of the hydrofoil. Significant interactions are described, including the encouragement impact of cavitation evolution on the fragmentation of streamwise vorticities as well as the compartmentation effect of streamwise vorticities binding the cavitation inception inside the troughs. The variations in cavitation pressure are mainly due to the acceleration in steam volume. In summary, it is vital for new hydrofoils or propeller designs to understand in depth the effects of leading-edge protuberances on flow control.

Hydrodynamic analysis of cycloidal propellers

ABSTRACT The working principle of a cycloidal propeller is complicated given that its blades are engaged in multi- degrees of freedom (DOF) motions. The instantaneous forces developed on the blades were studied to analyse the hydrodynamic characteristics of the propeller. The results of this study show that the oscillating centre distributed in the chordwise direction will exert significant effects on the fluctuation of the thrust produced by the cycloidal propeller. It will also significantly affect the average value of the thrust and efficiency. In addition, the effect of eccentricity on the thrust produced by the cycloidal propeller was also analysed. A higher eccentricity will considerably increase the thrust, and will make the curve of hydrodynamic characteristics steeper. Therefore, for the design of the cycloidal propeller, it is crucial to choose an appropriate eccentric point and an eccentricity value so as to balance the magnitude of thrust and its fluctuation.

Optimization of palm shell pyrolysis parameters in helical screw fluidized bed reactor: Effect of particle size, pyrolysis time and vapor residence time

The production of bio-oil from palm shell pyrolysis was investigated using a helical screw fluidized bed reactor setup. This study was done by investigating the effects of particle size, pyrolysis time and vapor residence time on pyrolysis product yields. The pyrolysis experiments were performed at different particle sizes, pyrolysis times and vapor residence times from 0.25 mm to 10 mm; 20 min to 60 min and 0.25 s to 15 s, respectively. The optimum condition for PS pyrolysis in helical screw fluidized bed reactor is at 2 mm particle size, 30 min pyrolysis time and 0.25 s vapor residence time to produce PS derived bio-oil of the highest yield of 73.86 wt% and higher heating value of 43.14 MJ/kg. Here, we report of the capability of helical screw fluidized bed reactor in handling large biomass particle size ranging up to 10 mm with marginal deteriorations of less than 1% and 3% for bio-oil yield and higher heating value respectively. This feature was attributed to the screw propeller design system in helical screw fluidized bed reactor which provided high mass and heat transfer at large particle size range which is 5 times of the particle size limit as recommended in previous studies. This finding would enable the possibility of helical screw fluidized based pyrolysis to be done in the absence of biomass size reduction processes to reduce process cost and complexity.

Propeller optimization by interactive genetic algorithms and machine learning

ABSTRACT Marine propeller design can be carried out with the aid of automated optimization, but experience shows that a such an approach has still been inferior to manual design in industrial scenarios. In this study, the automated propeller design optimization is evolved by integrating human–computer interaction as an intermediate step. An interactive optimization methodology, based on interactive genetic algorithms (IGAs), has been developed, where the blade designers systematically guide a genetic algorithm towards the objectives. The designers visualize and assess the shape of the blade cavitation and this evaluation is integrated in the optimization method. The IGA is further integrated with a support-vector machine model, in order to avoid user fatigue, IGA's main disadvantage. The results of the present study show that the IGA optimization searches solutions in a more targeted manner and eventually finds more non-dominated feasible designs that also show a good cavitation behaviour in agreement with designer preference.

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.

STUDY ON INSTABILITY MECHANISM AND EVOLUTION MODEL OF PROPELLER TIP VORTICES

The propeller wake dynamics is a fundamental but very complicated fluid mechanics problem. Its complexity comes from its sophisticated vortex system, which keeps evolving in high-speed shear layer flow. The mechanism of propeller wake behaviors such as the evolution from stable regime to unstable regime and the flow phenomenon in a complex operating environment have always been difficult and hot topics in the field of fluid mechanics. From the perspective of engineering applications, propeller wakes are directly related to the macroscopic characteristics of marine structures, a better understanding of the dynamic characteristic of the propeller wake under multiple operating conditions helps to improve the propulsion performance related to vibration, noise, and structure problems and has important practical significance for the design and optimization of next-generation propellers with good comprehensive performance. In this paper, the propeller wake dynamics are analyzed numerically using DDES, LES and NTM methods and experimentally based on PIV flow measurements, and the triggering mechanism of the instability of the propeller wake is revealed. Based on the evolution mechanism of the tip vortex in the uniform inflow, an evolution model of the tip vortices is proposed. The proposed model can accurately reproduce the evolution process of propeller tip vortex, predict the instant and position of tip vortex merging, which is of great significance to the prediction and control of propeller flow noise and the design of propellers with excellent performance.