为了改善离心压气机叶片多工况优化设计时面临的设计空间大、冗余搜索、灵活性不足、优化效率低等问题,提出了基于自由曲面变形技术(free form deform,FFD)的离心压气机复杂曲面叶片参数化方法,建立了叶片局部几何区域与三维空间网格控...为了改善离心压气机叶片多工况优化设计时面临的设计空间大、冗余搜索、灵活性不足、优化效率低等问题,提出了基于自由曲面变形技术(free form deform,FFD)的离心压气机复杂曲面叶片参数化方法,建立了叶片局部几何区域与三维空间网格控制体的映射模型,研究了样条曲线基函数几何特性对叶片几何构型的影响,实现了离心压气机叶片几何外形的局部精细化改型.结合B样条基FFD参数化方法、多目标进化算法和计算流体动力学对复杂叶片的局部区域进行了多工况气动寻优,优化结果表明:在满足约束条件的情况下,流场结构得到进一步的改善,额定工况和常用工况等熵效率分别提高了0.48%和0.40%,喘振裕度分别提升了1.6%和1.8%,利用较少的设计变量实现了离心压气机复杂曲面叶片高效灵活的精细化设计,为离心叶轮的气动优化设计提供了新的理论依据.展开更多
A simulation of stratification and penetration was performed over a range of structural parameters that included screen width, aperture size, inclination angle, and wire diameter. The discrete element method （DEM） w...A simulation of stratification and penetration was performed over a range of structural parameters that included screen width, aperture size, inclination angle, and wire diameter. The discrete element method （DEM） was used for the simulations. The terms stratification and penetration are defined and the change in fine panicle concentration is discussed. Mathematical models relating fine particle ratio to time are established using the least squares method. The effect of structural parameters on fine panicle ratio is analyzed. Stratification and penetration rate are discussed by considering the time derivative of the fine panicle ratio. The conclusions are： an increase in inclination or wire diameter has a positive effect on par- ticle stratifying; The optimal screen width is 40 mm for panicle stratification; The inclination angle has a negative effect on the penetration; The effect of wire diameter and screen width on the penetration rate is negligible.展开更多
Diapycnal mixing （DM） in the upper 600 m of the Pacific Ocean was estimated based on the huge amount of the observations from Global Temperature-Salinity Profile Programme （GTSPP）, using the strain version of the ...Diapycnal mixing （DM） in the upper 600 m of the Pacific Ocean was estimated based on the huge amount of the observations from Global Temperature-Salinity Profile Programme （GTSPP）, using the strain version of the finescale parameterization. It is found that DM in each season exhibits similar distribution pattern, but differs in details. The intensification of DM is related to bottom roughness, surface near-inertial energy, and proximity to the equator. The intensified DM caused by rough topography shows in the profiles near the Mendocino fracture zone in the northeast Pacific, and the heightened DM caused by wind-generated near-inertial energy appears in the westerly region of the Southern Ocean. As compared to previous estimates, the DM estimate in this work has better spatial coverage and finer resolution, and more importantly it contains the seasonal variability, Furthermore, the resulting DM dataset is gridded, rendering it suitable for modeling applications.展开更多
文摘为了改善离心压气机叶片多工况优化设计时面临的设计空间大、冗余搜索、灵活性不足、优化效率低等问题,提出了基于自由曲面变形技术(free form deform,FFD)的离心压气机复杂曲面叶片参数化方法,建立了叶片局部几何区域与三维空间网格控制体的映射模型,研究了样条曲线基函数几何特性对叶片几何构型的影响,实现了离心压气机叶片几何外形的局部精细化改型.结合B样条基FFD参数化方法、多目标进化算法和计算流体动力学对复杂叶片的局部区域进行了多工况气动寻优,优化结果表明:在满足约束条件的情况下,流场结构得到进一步的改善,额定工况和常用工况等熵效率分别提高了0.48%和0.40%,喘振裕度分别提升了1.6%和1.8%,利用较少的设计变量实现了离心压气机复杂曲面叶片高效灵活的精细化设计,为离心叶轮的气动优化设计提供了新的理论依据.
基金the Special Topic Fund of Key Science and Technology of Fujian Province (No. 2006HZ0002-2) for the financial support
文摘A simulation of stratification and penetration was performed over a range of structural parameters that included screen width, aperture size, inclination angle, and wire diameter. The discrete element method （DEM） was used for the simulations. The terms stratification and penetration are defined and the change in fine panicle concentration is discussed. Mathematical models relating fine particle ratio to time are established using the least squares method. The effect of structural parameters on fine panicle ratio is analyzed. Stratification and penetration rate are discussed by considering the time derivative of the fine panicle ratio. The conclusions are： an increase in inclination or wire diameter has a positive effect on par- ticle stratifying; The optimal screen width is 40 mm for panicle stratification; The inclination angle has a negative effect on the penetration; The effect of wire diameter and screen width on the penetration rate is negligible.
基金The National Natural Science Foundation of China under contract No.41206012the National Basic Research Program(973Program)of China under contract No.2012CB316206the Program for Public from State Oceanic Administration of China under contract No.201105017
文摘Diapycnal mixing （DM） in the upper 600 m of the Pacific Ocean was estimated based on the huge amount of the observations from Global Temperature-Salinity Profile Programme （GTSPP）, using the strain version of the finescale parameterization. It is found that DM in each season exhibits similar distribution pattern, but differs in details. The intensification of DM is related to bottom roughness, surface near-inertial energy, and proximity to the equator. The intensified DM caused by rough topography shows in the profiles near the Mendocino fracture zone in the northeast Pacific, and the heightened DM caused by wind-generated near-inertial energy appears in the westerly region of the Southern Ocean. As compared to previous estimates, the DM estimate in this work has better spatial coverage and finer resolution, and more importantly it contains the seasonal variability, Furthermore, the resulting DM dataset is gridded, rendering it suitable for modeling applications.
