Abstract
Noise generated by ships is one of the most significant noises in seas, and the propeller has a significant impact on the noise of ships, which reducing it can significantly lower the noise of vessels. In this study, a genetic algorithm was used to optimize the hydro-acoustic and hydrodynamic performance of propellers. The main objectives of this optimization were to reduce the propeller noise and increase its hydrodynamic efficiency. Modifying the propeller geometry is one of the most effective methods for optimizing a propeller performance. One of the numerical methods for calculating propeller noise is the Ffowcs Williams and Hawkings (FW-H) Model. A numerical code was developed by authors which solved these equations using the velocity and pressure distribution around the propeller and calculated its noise. To obtain flow quantities and to investigate the hydrodynamic performance of the propeller, a code was developed using a Boundary Element Method, the panel method. The geometry of DTMB 4119 propeller was selected for optimization, where geometric modifications included skew angle, rake angle, pitch to diameter (P/D) distribution, and chord to diameter (c/D) distribution. Finally, the results of geometric optimization were presented as Pareto optimal solutions. The results indicated that the optimum geometries had rake angles between 8.14 and 12.05 degrees and skew angles between 31.52 and 39.74 degrees. It was also observed that the increase in the chord up to a specific limit enhanced the efficiency and reduced the noise of the propeller.
Highlights
Marine propellers play an essential role in the maritime industry and shipping
Cho and Lee [4] developed a numerical method for optimization of a blade shape to improve the hydrodynamic performance of the propeller
Numerical simulation of the propeller is performed by code developed for various advance ratios, with Figure 4 comparing the hydrodynamic coefficients of the propeller obtained by panel method with experimental data
Summary
Marine propellers play an essential role in the maritime industry and shipping. Due to the increasing importance of propellers, extensive research has been carried out on various aspects of design, such as hydrodynamics and hydro-acoustic performance. The purpose of this research is to present an optimization procedure for a marine propeller in terms of generated noise and hydrodynamic efficiency. In previous research on marine propellers, in most cases, only one aspect of the design, hydrodynamic performance or generated noise has been studied, and multi-objective optimization has not been carried out. Cho and Lee [4] developed a numerical method for optimization of a blade shape to improve the hydrodynamic performance of the propeller They used a lifting line theory (vortex lattice method) and a lifting surface theory (panel method) for calculating the efficiency of propellers. The last term in the right-hand side of Equation (4) becomes zero This formulation can be interpreted as distributing a source with the strength of ∂φ/∂n on each panel of the body surface and a doublet with the strength of φ on each panel of the body surface, Kutta strip, and wake surface. The total thrust force (T ) and torque (Q) of propeller are obtained as [12]:
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