In this paper,we present our analysis of the non-cavitating and cavitating unsteady performances of the Potsdam Propeller Test Case(PPTC)in oblique flow.For our calculations,we used the Reynolds-averaged Navier-Stokes...In this paper,we present our analysis of the non-cavitating and cavitating unsteady performances of the Potsdam Propeller Test Case(PPTC)in oblique flow.For our calculations,we used the Reynolds-averaged Navier-Stokes equation(RANSE)solver from the open-source OpenFOAM libraries.We selected the homogeneous mixture approach to solve for multiphase flow with phase change,using the volume of fluid(VoF)approach to solve the multiphase flow and modeling the mass transfer between vapor and water with the Schnerr-Sauer model.Comparing the model results with the experimental measurements collected during the SecondWorkshop on Cavitation and Propeller Performance– SMP’15 enabled our assessment of the reliability of the open-source calculations.Comparisons with the numerical data collected during the workshop enabled further analysis of the reliability of different flow solvers from which we produced an overview of recommended guidelines(mesh arrangements and solver setups)for accurate numerical prediction even in off-design conditions.Lastly,we propose a number of calculations using the boundary element method developed at the University of Genoa for assessing the reliability of this dated but still widely adopted approach for design and optimization in the preliminary stages of very demanding test cases.展开更多
Most of the Point Pattern Matching (PPM) algorithm performs poorly when the noise of the point's position and outliers exist. This paper presents a novel and robust PPM algorithm which combined Point Pair Topologi...Most of the Point Pattern Matching (PPM) algorithm performs poorly when the noise of the point's position and outliers exist. This paper presents a novel and robust PPM algorithm which combined Point Pair Topological Characteristics (PPTC) and Spectral Matching (SM) together to solve the afore mentioned issues. In which PPTC, a new shape descriptor, is firstly proposed. A new comparability measurement based on PPTC is defined as the matching probability. Finally, the correct matching results are achieved by the spectral matching method. The synthetic data experiments show its robustness by comparing with the other state-of-art algorithms and the real world data experiments show its effectiveness.展开更多
The characteristics of a two-layer structure on the basis of the layers of varistor ceramics and polymeric PPTC nanocomposite being in thermal contact for the purpose of using it as a limiter of constant voltage and l...The characteristics of a two-layer structure on the basis of the layers of varistor ceramics and polymeric PPTC nanocomposite being in thermal contact for the purpose of using it as a limiter of constant voltage and long-term varying electrical overvoltages are analyzed.A theoretical model of such a structure has been developed,and its main electrical characteristics are simulated.It is shown that the provision of the required output voltage limitation is performed by selecting the classification voltage of the varistor layer.The maximum current of the varistor layer required for heating the structure is determined by the intensity of heat transfer to the environment.It has established a satisfactory agreement between the theoretical and experimental electrical characteristics for the structure based on the layers used in commercial varistors and PPTC fuses.展开更多
文摘In this paper,we present our analysis of the non-cavitating and cavitating unsteady performances of the Potsdam Propeller Test Case(PPTC)in oblique flow.For our calculations,we used the Reynolds-averaged Navier-Stokes equation(RANSE)solver from the open-source OpenFOAM libraries.We selected the homogeneous mixture approach to solve for multiphase flow with phase change,using the volume of fluid(VoF)approach to solve the multiphase flow and modeling the mass transfer between vapor and water with the Schnerr-Sauer model.Comparing the model results with the experimental measurements collected during the SecondWorkshop on Cavitation and Propeller Performance– SMP’15 enabled our assessment of the reliability of the open-source calculations.Comparisons with the numerical data collected during the workshop enabled further analysis of the reliability of different flow solvers from which we produced an overview of recommended guidelines(mesh arrangements and solver setups)for accurate numerical prediction even in off-design conditions.Lastly,we propose a number of calculations using the boundary element method developed at the University of Genoa for assessing the reliability of this dated but still widely adopted approach for design and optimization in the preliminary stages of very demanding test cases.
文摘Most of the Point Pattern Matching (PPM) algorithm performs poorly when the noise of the point's position and outliers exist. This paper presents a novel and robust PPM algorithm which combined Point Pair Topological Characteristics (PPTC) and Spectral Matching (SM) together to solve the afore mentioned issues. In which PPTC, a new shape descriptor, is firstly proposed. A new comparability measurement based on PPTC is defined as the matching probability. Finally, the correct matching results are achieved by the spectral matching method. The synthetic data experiments show its robustness by comparing with the other state-of-art algorithms and the real world data experiments show its effectiveness.
文摘The characteristics of a two-layer structure on the basis of the layers of varistor ceramics and polymeric PPTC nanocomposite being in thermal contact for the purpose of using it as a limiter of constant voltage and long-term varying electrical overvoltages are analyzed.A theoretical model of such a structure has been developed,and its main electrical characteristics are simulated.It is shown that the provision of the required output voltage limitation is performed by selecting the classification voltage of the varistor layer.The maximum current of the varistor layer required for heating the structure is determined by the intensity of heat transfer to the environment.It has established a satisfactory agreement between the theoretical and experimental electrical characteristics for the structure based on the layers used in commercial varistors and PPTC fuses.
