The biomimetic hydrofoils are frequently employed to enhance cavitation performance,although the underlying mechanisms remain to be fully elucidated.This study utilizes a cavitation visualization experimental system a...The biomimetic hydrofoils are frequently employed to enhance cavitation performance,although the underlying mechanisms remain to be fully elucidated.This study utilizes a cavitation visualization experimental system and mechanical characterization to experimentally investigate the transient cavitation features of a NACA0015 hydrofoil and its biomimetic counterparts with modified lending-edge.The findings demonstrate that,in comparison with the flat hydrofoil,the biomimetic hydrofoil experiences a cavitation morphology transition at a lower cavitation number,with a reduction of up to 0.38.Moreover,the maximum cavity length and the maximum cavitation area are reduced by 17.11%,17.32%,signifying a reduction in cavitation intensity.Proper orthogonal decomposition(POD)analysis revealed that the primary mechanism for the enhanced cavitation performance of the leading-edge wave structured biomimetic hydrofoil is the suppression of cloud cavitation shedding.At an attack angle of 6°,the biomimetic hydrofoil exhibited the highest lift coefficient increase of 18.56%,corresponding to a lift-to-drag ratio improvement of 9.56%.By analyzing the cavitation patterns of the two hydrofoils,it is evident that the rate of change in the maximum cavity length isolines for the biomimetic hydrofoil is lower than that of the flat hydrofoil.For an equivalent level of cavitation intensity,the biomimetic hydrofoil exhibits a lower cavitation number compared with the flat hydrofoil.These demonstrate that the wavy leading-edge design of the biomimetic hydrofoil effectively reduces the severity of cavitation,thereby confirming the efficacy of the biomimetic hydrofoil in enhancing cavitation performance.展开更多
The numerical simulation of cavitation flow on a 2D NACA0015 hydrofoil under high pressure and temperature is performed. The Singhal＇s cavitation model is adopted combined with an improved RNG k-ε turbulence model t...The numerical simulation of cavitation flow on a 2D NACA0015 hydrofoil under high pressure and temperature is performed. The Singhal＇s cavitation model is adopted combined with an improved RNG k-ε turbulence model to study the cavitation flow. The thermal effect in the cavitation flow is taken into account by introducing the energy equation with a source term based on the latent heat transfer. The code is validated by a case of a hydrofoil under two different temperatures in a comparison between the simulation and the experiment. Computational results show that the latent heat of vaporization has a significant impact on the cavitation process in the high temperature state, and the cavity in the high temperature state is thinner and shorter than that in a normal state with the same cavitation number, due to the fact that the heat absorption in the cavitation area reduces the local temperature and the saturated vapor pressure. This numerical study provides some guidance for the design of machineries in the High Pressure and Temperature （HPT） state.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.U24A20139)supported by the Key Research and Development Project of Zhejiang Province(Grant No.22024C01117)the KeyResearch and Development Project of Hangzhou(Grant No.2023SZD0041).
文摘The biomimetic hydrofoils are frequently employed to enhance cavitation performance,although the underlying mechanisms remain to be fully elucidated.This study utilizes a cavitation visualization experimental system and mechanical characterization to experimentally investigate the transient cavitation features of a NACA0015 hydrofoil and its biomimetic counterparts with modified lending-edge.The findings demonstrate that,in comparison with the flat hydrofoil,the biomimetic hydrofoil experiences a cavitation morphology transition at a lower cavitation number,with a reduction of up to 0.38.Moreover,the maximum cavity length and the maximum cavitation area are reduced by 17.11%,17.32%,signifying a reduction in cavitation intensity.Proper orthogonal decomposition(POD)analysis revealed that the primary mechanism for the enhanced cavitation performance of the leading-edge wave structured biomimetic hydrofoil is the suppression of cloud cavitation shedding.At an attack angle of 6°,the biomimetic hydrofoil exhibited the highest lift coefficient increase of 18.56%,corresponding to a lift-to-drag ratio improvement of 9.56%.By analyzing the cavitation patterns of the two hydrofoils,it is evident that the rate of change in the maximum cavity length isolines for the biomimetic hydrofoil is lower than that of the flat hydrofoil.For an equivalent level of cavitation intensity,the biomimetic hydrofoil exhibits a lower cavitation number compared with the flat hydrofoil.These demonstrate that the wavy leading-edge design of the biomimetic hydrofoil effectively reduces the severity of cavitation,thereby confirming the efficacy of the biomimetic hydrofoil in enhancing cavitation performance.
基金supported by the National Natural Science Foundation of China (Grant Nos.10602030,10802075)the National Key Basic Research Program of China (973 Program,Grant No.2009CB724303)
文摘The numerical simulation of cavitation flow on a 2D NACA0015 hydrofoil under high pressure and temperature is performed. The Singhal＇s cavitation model is adopted combined with an improved RNG k-ε turbulence model to study the cavitation flow. The thermal effect in the cavitation flow is taken into account by introducing the energy equation with a source term based on the latent heat transfer. The code is validated by a case of a hydrofoil under two different temperatures in a comparison between the simulation and the experiment. Computational results show that the latent heat of vaporization has a significant impact on the cavitation process in the high temperature state, and the cavity in the high temperature state is thinner and shorter than that in a normal state with the same cavitation number, due to the fact that the heat absorption in the cavitation area reduces the local temperature and the saturated vapor pressure. This numerical study provides some guidance for the design of machineries in the High Pressure and Temperature （HPT） state.
