A type of distributed pump-jet propulsion system （DPJP） is developed with two or four specially designed pump-jet pods located around the axisymmetric underwater vehicle body symmetrically. The flow field is numeric...A type of distributed pump-jet propulsion system （DPJP） is developed with two or four specially designed pump-jet pods located around the axisymmetric underwater vehicle body symmetrically. The flow field is numerically simulated by solving the RANS equations with the finite volume method. The computational method is validated by comparing the calculated hull resistances of the SUBOFF AFF-3 model and the open water performance of a ducted propeller with experimental data. The hydrodynamic performances of the DPJP with different axial or radial positions and numbers of pump-jet pods are obtained to analyze the interactions between the hull and the pump-jet pods. It is shown in the calculated results that the decrease of the distance between the pods and the hull leads to an increase both in the efficiency of the pods and the thrust deduction factor due to the effect of the stern wake. And, a negative thrust deduction factor can be obtained by locating the DPJP at the parallel middle body near the aftbody of the vehicle to improve the hydrodynamic performance of the DPJP. Besides, the increase of the number of pods will cause a remarkable decrease of the total propulsive efficiency of the DPJP with the pods mounted on the stern planes, while a small decline of the total propulsive efficiency of the DPJP is observed with the pods mounted on the parallel middle body.展开更多
The tip-clearance flow in a pump-jet propulsor exerts great impacts on the fluctuating pressures and resultant unsteady forces,which are important sources of structural vibrations and radiated noise underwater.The bla...The tip-clearance flow in a pump-jet propulsor exerts great impacts on the fluctuating pressures and resultant unsteady forces,which are important sources of structural vibrations and radiated noise underwater.The blade geometry close to the tip is an important factor determining the vortex strength in the tip-clearance flow.In the open-water condition,the effects of raking the rotor tips on the duct-surface fluctuating pressures and the resultant unsteady forces acting on different components of the propulsor are investigated via physical model experiments and the numerical solution of Reynolds-averaged Navier-Stokes(RANS)equations coupled with the SST k-ωturbulence model.The measured and simulated results of hydrodynamic pressures are consistent to each other,and the simulated flows help better understand why the fluctuating pressures change with the tip geometry.The strong fluctuations of duct-surface pressures are caused by intensive tip separation vortices.The duct-surface pressure fluctuations are effectively reduced by using the rake distribution near the tip towards blade back side and,for the combination of the five-bladed rotor and the seven-bladed stator,the resultant unsteady horizontal(and vertical)forces acting on the duct and stator are also reduced;while increasing rake leads to negative effect on pressure fluctuations and unsteady horizontal(and vertical)forces acting on all the components of the propulsor.展开更多
为合理地预测非定常力作用下泵喷推进系统的结构响应,流固耦合效应所产生的水动力阻尼不可忽略。不同模态的水动力阻尼量级决定了该模态对系统响应的贡献。针对泵喷推进系统的多模态水动力阻尼问题,首先基于计算流体动力学(computationa...为合理地预测非定常力作用下泵喷推进系统的结构响应,流固耦合效应所产生的水动力阻尼不可忽略。不同模态的水动力阻尼量级决定了该模态对系统响应的贡献。针对泵喷推进系统的多模态水动力阻尼问题,首先基于计算流体动力学(computational fluid dynamics,CFD)和耦合有限法(finite element method,FEM),采用能量法对螺旋桨水动力阻尼特性展开数值研究。结果表明,能量法适用于水下叶轮机械水动力阻尼的研究,满足工程分析的需要。随后,基于能量法对简化泵喷推进系统多模态水动力阻尼特性展开数值研究,从非定常力做功的角度揭示影响水动力阻尼大小的主导因素。结果表明:转子主导的模态水动力阻尼较轴系主导模态的水动力阻尼高,转子轴系耦合模态水动力阻尼幅值大小则不固定,其主要取决于耦合系统中转子的振型及固有频率的大小;导管振动主导的模态水动力阻尼远高于定子振动带动导管运动的模态。水动力阻尼具有明显的模态依赖性,不同模态阻尼比幅值差距大,非定常力做功的影响显著高于固有频率。展开更多
文摘A type of distributed pump-jet propulsion system （DPJP） is developed with two or four specially designed pump-jet pods located around the axisymmetric underwater vehicle body symmetrically. The flow field is numerically simulated by solving the RANS equations with the finite volume method. The computational method is validated by comparing the calculated hull resistances of the SUBOFF AFF-3 model and the open water performance of a ducted propeller with experimental data. The hydrodynamic performances of the DPJP with different axial or radial positions and numbers of pump-jet pods are obtained to analyze the interactions between the hull and the pump-jet pods. It is shown in the calculated results that the decrease of the distance between the pods and the hull leads to an increase both in the efficiency of the pods and the thrust deduction factor due to the effect of the stern wake. And, a negative thrust deduction factor can be obtained by locating the DPJP at the parallel middle body near the aftbody of the vehicle to improve the hydrodynamic performance of the DPJP. Besides, the increase of the number of pods will cause a remarkable decrease of the total propulsive efficiency of the DPJP with the pods mounted on the stern planes, while a small decline of the total propulsive efficiency of the DPJP is observed with the pods mounted on the parallel middle body.
基金supported by the National Key Project of China for Strengthening Fundamental Research(Grant No.2019-JCJQ-ZD-016-00).
文摘The tip-clearance flow in a pump-jet propulsor exerts great impacts on the fluctuating pressures and resultant unsteady forces,which are important sources of structural vibrations and radiated noise underwater.The blade geometry close to the tip is an important factor determining the vortex strength in the tip-clearance flow.In the open-water condition,the effects of raking the rotor tips on the duct-surface fluctuating pressures and the resultant unsteady forces acting on different components of the propulsor are investigated via physical model experiments and the numerical solution of Reynolds-averaged Navier-Stokes(RANS)equations coupled with the SST k-ωturbulence model.The measured and simulated results of hydrodynamic pressures are consistent to each other,and the simulated flows help better understand why the fluctuating pressures change with the tip geometry.The strong fluctuations of duct-surface pressures are caused by intensive tip separation vortices.The duct-surface pressure fluctuations are effectively reduced by using the rake distribution near the tip towards blade back side and,for the combination of the five-bladed rotor and the seven-bladed stator,the resultant unsteady horizontal(and vertical)forces acting on the duct and stator are also reduced;while increasing rake leads to negative effect on pressure fluctuations and unsteady horizontal(and vertical)forces acting on all the components of the propulsor.
文摘为合理地预测非定常力作用下泵喷推进系统的结构响应,流固耦合效应所产生的水动力阻尼不可忽略。不同模态的水动力阻尼量级决定了该模态对系统响应的贡献。针对泵喷推进系统的多模态水动力阻尼问题,首先基于计算流体动力学(computational fluid dynamics,CFD)和耦合有限法(finite element method,FEM),采用能量法对螺旋桨水动力阻尼特性展开数值研究。结果表明,能量法适用于水下叶轮机械水动力阻尼的研究,满足工程分析的需要。随后,基于能量法对简化泵喷推进系统多模态水动力阻尼特性展开数值研究,从非定常力做功的角度揭示影响水动力阻尼大小的主导因素。结果表明:转子主导的模态水动力阻尼较轴系主导模态的水动力阻尼高,转子轴系耦合模态水动力阻尼幅值大小则不固定,其主要取决于耦合系统中转子的振型及固有频率的大小;导管振动主导的模态水动力阻尼远高于定子振动带动导管运动的模态。水动力阻尼具有明显的模态依赖性,不同模态阻尼比幅值差距大,非定常力做功的影响显著高于固有频率。
