Numerical investigation of the scale effects of pump-jet propulsor with a pre-swirl stator

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Rim-driven thrusters (RDT) are of great interest for the development of integrated electric motors for underwater vehicles. Gap flow is one of the most prominent flow characteristics and plays an important role in the hydrodynamic performance of RDT. In this study, the rim in a carefully designed RDT was modified with several concave cavities defined by four parameters, and their influence on hydrodynamics was carefully calculated and analyzed. The simulations were performed using the k-ω shear stress transport turbulence model by solving the unsteady Reynolds-averaged Navier–Stokes equations. The numerical method was verified using a popular combination. The numerical results showed that the concave cavities on the rim improve the propulsive efficiency of RDT by a maximum of 3.52%. The increase in the propulsive efficiency is directly associated with the parameters of the concave cavities. Nevertheless, the flow in the gap has a negligible effect on the main flow field through the RDT. According to the numerical analysis, the different pressure integrals at the front and back surfaces of the concave cavities are the main reason for the improvement of the propulsive efficiency. The modification of the rim is helpful and practical for the hydrodynamic optimization of the RDT.

Section: Convergence Analysis and Verificationmentioning

confidence: 82%

Improved efficiency with concave cavities on S3 surface of a rim-driven thruster

Li,

Yao,

Wang

et al. 2023

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Shape optimization and hydrodynamic simulation of a Magnus anti-rolling device based on fully parametric modeling

2023

Ship anti-rolling devices are an essential component of modern vessels. The core component of the Magnus effect-based ship anti-rolling device is a rotating cylinder, hereinafter referred to as the Magnus cylinders. In this paper, fully parametric three-dimensional modeling of Magnus cylinders was performed, and the design space dimension was reduced using the Sobol design optimization method while still providing accurate and reliable results. The Sobol method generates quasi-random sequences that are more uniformly spaced in the search space and can more efficiently cover the entire solution space. The shape optimization study of the Magnus cylinder was carried out in conjunction with the computational fluid dynamics method to find the geometry of the Magnus cylinder with excellent hydrodynamic performance. Critical design parameters include the diameters of the cylinder ends and the length of the cylinder. The hydrodynamic and flow field characteristics of Magnus cylinders before and after the optimization were compared. The results show that there can be multiple local optimal values for lift and drag of Magnus cylinders within the design space to increase the lift and decrease the drag. The Magnus effect primarily influences the position of the vortex-shedding separation point at the surface of Magnus cylinders and deflects the wake to one side. For the optimized Magnus cylinder, the distribution of pressure and velocity in the flow field is significantly different. This research forms the basis for improving the practical application of Magnus anti-rolling devices.

Control method of line spectrum excitation force for pump-jet propeller: Random unevenly spaced rotor blades

Zhang,

Han,

Huang

et al. 2023

The control of the excitation force of pump-jets is of great significance for the stealth performance of submarines. In a previous study, the authors found that the sinusoidal unevenly spaced rotor blades (SUSR) can control the excitation force of the rotor, but the suppression effect is limited by the low degree of freedom. This paper proposes random unevenly spaced rotor blades (RUSR) with higher degrees of freedom, achieving twice the suppression effect of the SUSR. A method for batch generation of RUSRs is proposed in this paper, and a large number of RUSRs are generated. The numerical simulation study was carried out by selecting the RUSRs with better suppression effects through theoretical methods, and the numerical simulation method used was improved based on the previous study. The RUSR also has an impact on the excitation force of the duct. The conclusion of this paper has guiding significance for the low excitation design of pump-jets and has the potential to promote the use of unevenly spaced rotor blades in the field of pump-jets.