The Experts below are selected from a list of 4458 Experts worldwide ranked by ideXlab platform
Zhenguo Zhang - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of tip clearance effects on propulsion performance and pressure fluctuation of a Pump Jet propulsor
2019Co-Authors: Haiting Yu, Zhenguo ZhangAbstract:Abstract Rotor-stator interaction and tip clearance between rotor blade tip and shroud of a Pump-Jet propulsor can induce strong pressure fluctuations and vibrations, which may cause damage of the propulsion system at some severe working conditions. This paper investigates numerically the effects of tip clearance on propulsion performance and pressure fluctuations in a Pump-Jet propulsor. The shear-stress transport (SST) k–omega turbulence model together with the sliding mesh technique are adopted to simulate the three-dimensional unsteady flow. The accuracy of the computation results is verified through available experimental data of propulsion performance with a tip clearance of 1 mm. The comparison of hydrodynamic performance for Pump-Jet propulsor with tip clearance of 0, 1 mm, 2 mm and 4 mm shows that the thrust and propulsion efficiency can be reduced significantly due to the increase of tip clearance sizes. Further results indicate that the decrease of thrust and torque of the Pump-Jet propulsor with tip clearance is mainly caused by the change of time-averaged pressure distributions on the rotor blade in the range of 0.8R–1.0R (where R is the rotor diameter). In addition, a method based on Statistics is applied to reveal the characteristics of pressure fluctuations at all grid nodes on the whole blade surface, and the result shows that the amplitudes of pressure fluctuations increase significantly on the blade surface when the tip clearance size is enlarged, especially on the blade tip, blade root and the leading edge. Moreover, it is found that the tip clearance effects do not change the main frequency of thrust and torque fluctuations, while it has a significant impact on the amplitudes of fluctuations, especially in the higher frequency band.
Noblesse Francis - One of the best experts on this subject based on the ideXlab platform.
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Numerical investigation of tip geometry on the tip-clearance flow features of a Pump-Jet propulsor
2019Co-Authors: Ji Xue-qi, Dong Xiao-qia, Li Wei, Yang Chen-ju, Noblesse FrancisAbstract:The numerical simulation for Pump-Jet propulsors is based on the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations using a two-layer realizable k- model for turbulence closure. The computational domain is discretized into block-structured hexahedral cells. To establish a reliable simulation model, the numerical uncertainties are evaluated according to the procedure recommended by the 28th International Towing Tank Conference (ITTC). Three sets of grids, with a uniform refinement ratio, are generated for a generic Pump-Jet propulsor at model scale using the grid generator ICEM CFD 17.2, and the flow simulations are carried out using the software package STAR-CCM+. The tip-clearance flow features are numerically investigated for varied thickness and rake profiles of the sections close to the rotator tip. It is shown that the tip geometry has significant influence on the tip vortex
Haiting Yu - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of tip clearance effects on propulsion performance and pressure fluctuation of a Pump Jet propulsor
2019Co-Authors: Haiting Yu, Zhenguo ZhangAbstract:Abstract Rotor-stator interaction and tip clearance between rotor blade tip and shroud of a Pump-Jet propulsor can induce strong pressure fluctuations and vibrations, which may cause damage of the propulsion system at some severe working conditions. This paper investigates numerically the effects of tip clearance on propulsion performance and pressure fluctuations in a Pump-Jet propulsor. The shear-stress transport (SST) k–omega turbulence model together with the sliding mesh technique are adopted to simulate the three-dimensional unsteady flow. The accuracy of the computation results is verified through available experimental data of propulsion performance with a tip clearance of 1 mm. The comparison of hydrodynamic performance for Pump-Jet propulsor with tip clearance of 0, 1 mm, 2 mm and 4 mm shows that the thrust and propulsion efficiency can be reduced significantly due to the increase of tip clearance sizes. Further results indicate that the decrease of thrust and torque of the Pump-Jet propulsor with tip clearance is mainly caused by the change of time-averaged pressure distributions on the rotor blade in the range of 0.8R–1.0R (where R is the rotor diameter). In addition, a method based on Statistics is applied to reveal the characteristics of pressure fluctuations at all grid nodes on the whole blade surface, and the result shows that the amplitudes of pressure fluctuations increase significantly on the blade surface when the tip clearance size is enlarged, especially on the blade tip, blade root and the leading edge. Moreover, it is found that the tip clearance effects do not change the main frequency of thrust and torque fluctuations, while it has a significant impact on the amplitudes of fluctuations, especially in the higher frequency band.
Ji Xue-qi - One of the best experts on this subject based on the ideXlab platform.
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Numerical investigation of tip geometry on the tip-clearance flow features of a Pump-Jet propulsor
2019Co-Authors: Ji Xue-qi, Dong Xiao-qia, Li Wei, Yang Chen-ju, Noblesse FrancisAbstract:The numerical simulation for Pump-Jet propulsors is based on the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations using a two-layer realizable k- model for turbulence closure. The computational domain is discretized into block-structured hexahedral cells. To establish a reliable simulation model, the numerical uncertainties are evaluated according to the procedure recommended by the 28th International Towing Tank Conference (ITTC). Three sets of grids, with a uniform refinement ratio, are generated for a generic Pump-Jet propulsor at model scale using the grid generator ICEM CFD 17.2, and the flow simulations are carried out using the software package STAR-CCM+. The tip-clearance flow features are numerically investigated for varied thickness and rake profiles of the sections close to the rotator tip. It is shown that the tip geometry has significant influence on the tip vortex
Michele Viviani - One of the best experts on this subject based on the ideXlab platform.
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design and construction of a modular Pump Jet thruster for autonomous surface vehicle operations in extremely shallow water
2019Co-Authors: Angelo Odetti, Marco Altosole, Gabriele Bruzzone, Massimo Caccia, Michele VivianiAbstract:This paper describes a customized thruster for Autonomous Surface Vehicles (ASV). The thruster is a Pump-Jet Module (PJM), which has been expressly designed, modeled, constructed, and tested for small-/medium-sized ASVs that perform environmental monitoring in extremely shallow waters such as wetlands (rivers, lakes, swamps, marshes), where water depth is only a few centimeters. The PJM is a fully-electric propulsion unit with a 360-degree continuous steering capability. Its main advantage is that the unit is flush with the flat bottom of the vehicle. This makes the PJM suitable for operation in extremely shallow waters because the risk of damaging the thrusting unit in case of grounding is very limited. The PJM was produced using innovative materials, and the hydraulic components were all constructed using a 3D printer.
