The influence of streamline bending inertia force on power loss is investigated.In order to analyze the combined effect of the inertia force and the path on the power loss,the accumulation effect expression of the ine...The influence of streamline bending inertia force on power loss is investigated.In order to analyze the combined effect of the inertia force and the path on the power loss,the accumulation effect expression of the inertia force on its path is derived.The calculation result shows that the accumulation effect of the unit inertia force on its path depends merely upon the velocity magnitude and the path scroll angle.As long as they are given,the accumulation effect is a constant and independent of the intermediate path.An important conclusion drawn is that the maximum inertia force rather than its accumulation effect plays a predominant role in the power loss.Thus,a new design method,minimum streamline curvature method,is proposed.Fluid particle movement inside a hydrodynamic torque converter can be regarded as curved movement on the circular surface and decomposed into a meridional component and a circumferential component.Each meridional streamline is designed to be close to a circular arc,while each torus streamline is constructed with a circular arc and a straight line segment.Based on the meridional streamline equation,the torus streamline equation and a streamlined thickness function,a blade surface equation of three-element centripetal-turbine hydrodynamic torque converter can be obtained.展开更多
Seepage flow through soils,rocks and geotechnical structures has a great influence on their stabilities and performances,and seepage control is a critical technological issue in engineering practices.The physical mech...Seepage flow through soils,rocks and geotechnical structures has a great influence on their stabilities and performances,and seepage control is a critical technological issue in engineering practices.The physical mechanisms associated with various engineering measures for seepage control are investigated from a new perspective within the framework of continuum mechanics;and an equation-based classification of seepage control mechanisms is proposed according to their roles in the mathematical models for seepage flow,including control mechanisms by coupled processes,initial states,boundary conditions and hydraulic properties.The effects of each mechanism on seepage control are illustrated with examples in hydroelectric engineering and radioactive waste disposal,and hence the reasonability of classification is demonstrated.Advice on performance assessment and optimization design of the seepage control systems in geotechnical engineering is provided,and the suggested procedure would serve as a useful guidance for cost-effective control of seepage flow in various engineering practices.展开更多
为探究跨声速工况下超临界翼型RAE2822带下表面射流(jet on the lower surface of trailing edge,LSTE jet)的气动力特性,采用Navier-Stokes(Reynolds Average Navier-Stokes,RANS)控制方程结合Spalart-Allmaras(SA)湍流模型的方法进行...为探究跨声速工况下超临界翼型RAE2822带下表面射流(jet on the lower surface of trailing edge,LSTE jet)的气动力特性,采用Navier-Stokes(Reynolds Average Navier-Stokes,RANS)控制方程结合Spalart-Allmaras(SA)湍流模型的方法进行数值模拟分析。研究发现,在上翼面存在激波的情况下,下表面射流在增大翼型升力的同时也增大了波阻。提出下表面射流伴随优化进程的射流翼型一体优化思路。采用基于Kriging代理模型的优化方法,以最大化升阻比为目标,对RAE2822翼型分别进行了基准外形优化和带下表面射流(cμ=0.0002)的翼型优化。结果表明:在Ma=0.73、Re=6.5×10^(6)、α=2°的工况下,相较于基准翼型,下表面射流翼型等效升阻比提高了4.9%,下表面射流优化翼型等效升阻比提高了26.2%。带下表面射流翼型的射流翼型一体优化设计方法,能够显著提高超临界翼型的等效升阻比,研究结果有助于下表面射流的应用研究。展开更多
基金Sponsored by Henan Province Key Scientific and Technological Program(0424260038)
文摘The influence of streamline bending inertia force on power loss is investigated.In order to analyze the combined effect of the inertia force and the path on the power loss,the accumulation effect expression of the inertia force on its path is derived.The calculation result shows that the accumulation effect of the unit inertia force on its path depends merely upon the velocity magnitude and the path scroll angle.As long as they are given,the accumulation effect is a constant and independent of the intermediate path.An important conclusion drawn is that the maximum inertia force rather than its accumulation effect plays a predominant role in the power loss.Thus,a new design method,minimum streamline curvature method,is proposed.Fluid particle movement inside a hydrodynamic torque converter can be regarded as curved movement on the circular surface and decomposed into a meridional component and a circumferential component.Each meridional streamline is designed to be close to a circular arc,while each torus streamline is constructed with a circular arc and a straight line segment.Based on the meridional streamline equation,the torus streamline equation and a streamlined thickness function,a blade surface equation of three-element centripetal-turbine hydrodynamic torque converter can be obtained.
基金Supported by the National Natural Science Foundation of China(51079107,50839004)the Program for New Century Excellent Talents in University(NCET-09-0610)
文摘Seepage flow through soils,rocks and geotechnical structures has a great influence on their stabilities and performances,and seepage control is a critical technological issue in engineering practices.The physical mechanisms associated with various engineering measures for seepage control are investigated from a new perspective within the framework of continuum mechanics;and an equation-based classification of seepage control mechanisms is proposed according to their roles in the mathematical models for seepage flow,including control mechanisms by coupled processes,initial states,boundary conditions and hydraulic properties.The effects of each mechanism on seepage control are illustrated with examples in hydroelectric engineering and radioactive waste disposal,and hence the reasonability of classification is demonstrated.Advice on performance assessment and optimization design of the seepage control systems in geotechnical engineering is provided,and the suggested procedure would serve as a useful guidance for cost-effective control of seepage flow in various engineering practices.
文摘为探究跨声速工况下超临界翼型RAE2822带下表面射流(jet on the lower surface of trailing edge,LSTE jet)的气动力特性,采用Navier-Stokes(Reynolds Average Navier-Stokes,RANS)控制方程结合Spalart-Allmaras(SA)湍流模型的方法进行数值模拟分析。研究发现,在上翼面存在激波的情况下,下表面射流在增大翼型升力的同时也增大了波阻。提出下表面射流伴随优化进程的射流翼型一体优化思路。采用基于Kriging代理模型的优化方法,以最大化升阻比为目标,对RAE2822翼型分别进行了基准外形优化和带下表面射流(cμ=0.0002)的翼型优化。结果表明:在Ma=0.73、Re=6.5×10^(6)、α=2°的工况下,相较于基准翼型,下表面射流翼型等效升阻比提高了4.9%,下表面射流优化翼型等效升阻比提高了26.2%。带下表面射流翼型的射流翼型一体优化设计方法,能够显著提高超临界翼型的等效升阻比,研究结果有助于下表面射流的应用研究。
