The aim of this study is to suppress a cavitation near the orifice of arelief valve by changing the shape of a poppet. An experimental flow visualization technique and anumerical cavitating flow simulation, using a RN...The aim of this study is to suppress a cavitation near the orifice of arelief valve by changing the shape of a poppet. An experimental flow visualization technique and anumerical cavitating flow simulation, using a RNG kappa-epsilon turbulence model and a cavitationmodel, are employed to achieve the purpose. In the flow visualization, the cavitation phenomenonnear the orifice of a relief valve is observed using a transparent test valve body model and acamera. On the other hand, a three dimensional cavitating flow simulation is conducted to predictthe cavitation near the orifice of a relief valve. Six types of poppets are designed by changing theshape of a traditional poppet shape, which is expected to influence the cavitating flow in anorifice. In addition, the cavitation noise of a relief valve is measured and the noise spectrum isanalyzed. In conclusion, the cavitation intensity and the cavitation noise are reduced for anoptimal poppet geometry obtained in the present study.展开更多
Transient cavities generated from unsteady leading-edge cavitation may undergo aggressive collapses which are responsible for cavitation erosion.In this paper,we studied the hydrodynamic mechanisms of these events in ...Transient cavities generated from unsteady leading-edge cavitation may undergo aggressive collapses which are responsible for cavitation erosion.In this paper,we studied the hydrodynamic mechanisms of these events in the leading edge cavitation fonned over a modified NACA0009 hydrofoil using experimental and numerical methods.In the experimental investigation,high-speed visualization(HSV)and paint test are employed to study the behavior of the cavitating flow at σ=1.25,α=5°,U∞=20 m/s.In the numerical part,the same cavitating flow is simulated using an inviscid density-based compressible solver with a barotropic cavitation model.The numerical results are first compared with the experimental HSV to show that the simulation is able to reproduce the main features of the cavitating flow.Then,as the compressible solver is capable of capturing the shock wave upon the collapse of cavities,the location of collapse events with high erosion potential are determined.The location of these collapse events are compared with the paint test results with a qualitatively good agreement.It is clearly observed,in both the experiments and the numerical simulation,that there exists four distinct regions along the hydrofoil with higher risks of erosion:(1)A very narrow strip at the leading edge,(2)an area of accumulated collapses at around 60 percent of the sheet cavity maximum length,(3)an area around the closure line of the sheet cavity with the highest erosion damage,and(4)a wide area close to the trailing edge with dispersed collapse events.A combined analysis of the experimental and numerical results reveals that the small-scale structures generated by secondary shedding are more aggressive than the large-scale cloud cavities(primary shedding).It is also observed that the high risk of cavitation erosion in regions 2 and 3 is mainly due to the collapses of the small cavity structures that are formed around the sheet cavity closure line or the rolling cloud cavity.展开更多
基金This project is supported by Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE, China (No.2002123) National Natural Science Foundation of China (No.50175097).
文摘The aim of this study is to suppress a cavitation near the orifice of arelief valve by changing the shape of a poppet. An experimental flow visualization technique and anumerical cavitating flow simulation, using a RNG kappa-epsilon turbulence model and a cavitationmodel, are employed to achieve the purpose. In the flow visualization, the cavitation phenomenonnear the orifice of a relief valve is observed using a transparent test valve body model and acamera. On the other hand, a three dimensional cavitating flow simulation is conducted to predictthe cavitation near the orifice of a relief valve. Six types of poppets are designed by changing theshape of a traditional poppet shape, which is expected to influence the cavitating flow in anorifice. In addition, the cavitation noise of a relief valve is measured and the noise spectrum isanalyzed. In conclusion, the cavitation intensity and the cavitation noise are reduced for anoptimal poppet geometry obtained in the present study.
基金This work is funded through the EU H2020 project CaFE,a Marie Sklodowska-Curie Action Innovative Training Network project(Grant No.642536).The computations were performed on resources at Chalmers Centre for Computational Sciences and Engineering(CSE)provided by the Swedish National Infrastructure for Computing(SNIC).
文摘Transient cavities generated from unsteady leading-edge cavitation may undergo aggressive collapses which are responsible for cavitation erosion.In this paper,we studied the hydrodynamic mechanisms of these events in the leading edge cavitation fonned over a modified NACA0009 hydrofoil using experimental and numerical methods.In the experimental investigation,high-speed visualization(HSV)and paint test are employed to study the behavior of the cavitating flow at σ=1.25,α=5°,U∞=20 m/s.In the numerical part,the same cavitating flow is simulated using an inviscid density-based compressible solver with a barotropic cavitation model.The numerical results are first compared with the experimental HSV to show that the simulation is able to reproduce the main features of the cavitating flow.Then,as the compressible solver is capable of capturing the shock wave upon the collapse of cavities,the location of collapse events with high erosion potential are determined.The location of these collapse events are compared with the paint test results with a qualitatively good agreement.It is clearly observed,in both the experiments and the numerical simulation,that there exists four distinct regions along the hydrofoil with higher risks of erosion:(1)A very narrow strip at the leading edge,(2)an area of accumulated collapses at around 60 percent of the sheet cavity maximum length,(3)an area around the closure line of the sheet cavity with the highest erosion damage,and(4)a wide area close to the trailing edge with dispersed collapse events.A combined analysis of the experimental and numerical results reveals that the small-scale structures generated by secondary shedding are more aggressive than the large-scale cloud cavities(primary shedding).It is also observed that the high risk of cavitation erosion in regions 2 and 3 is mainly due to the collapses of the small cavity structures that are formed around the sheet cavity closure line or the rolling cloud cavity.
