The major purpose of this paper is to numerically study the complex structure of vortex system occurring within transonic turbine cascade. The transonic viscous flow in turbine cascade is simulated by solving full 3D ...The major purpose of this paper is to numerically study the complex structure of vortex system occurring within transonic turbine cascade. The transonic viscous flow in turbine cascade is simulated by solving full 3D Reynolds average N S equations, and then detailed analyses of vortex system structure are presented. Under guidance of topology, the wall limiting streamlines are employed to reveal the flow structure near the wall, and an analysis of space streamlines and cross section streamlines is given for the investigation of flow structure in the flow field. Through the analysis, the formation and evolution of the vortex system and the whole process of separation occurring within this turbine cascade are revealed展开更多
A three dimensional numerical model based on the Reynolds equations is presented that can be used to predict the surface water flow in open channels.The model uses a computational mesh that conforms to the free water ...A three dimensional numerical model based on the Reynolds equations is presented that can be used to predict the surface water flow in open channels.The model uses a computational mesh that conforms to the free water sur- face and the bottom of the channel so that the accuracy of boundary condition application,code complexity,and e- conomy could be enhanced.The k-ε turbulence model is used to estimate the eddy viscosity coefficient.Instead of using the“rigid-lid”approximation a 2-D equation derived from integrating the continuity equation over the total depth is adopted to determine the elevation of the free water surface.A new algorithm is presented based on the conventional SIMPLE procedure.The block correction technique is employed to enhance rate of convergence. The model presented is applied to a bottom discharge into a rectangular straight channel for three dimensional phenomena to obtain the free water surface configuration,velocities and pressure.The computed results are in good agreement with the previous experimental values.展开更多
采用三维网格和VOF(Volume of Fluids)多相流模型,对非轴对称、X型舵的航行体水下点火这一非稳态过程进行了三维流场数值模拟,捕捉了燃气泡的形成、发展及断裂过程,得到了航行体水下点火初期的流场变化和阻力变化,并进行了相关因素探讨...采用三维网格和VOF(Volume of Fluids)多相流模型,对非轴对称、X型舵的航行体水下点火这一非稳态过程进行了三维流场数值模拟,捕捉了燃气泡的形成、发展及断裂过程,得到了航行体水下点火初期的流场变化和阻力变化,并进行了相关因素探讨和结果对比分析。研究表明,燃气泡的发展变化过程对航行体流场和阻力产生影响。该研究可为航行体水下点火设计及试验提供参考。展开更多
The numerical methods for computing the stability derivatives of the aircraft by solving unsteady sensitivity equations which was proposed in our previous papers was extended to solve three-dimensional problems in thi...The numerical methods for computing the stability derivatives of the aircraft by solving unsteady sensitivity equations which was proposed in our previous papers was extended to solve three-dimensional problems in this paper.Both the static and dynamic derivatives of the hypersonic blunt cone undergoing pitching oscillation around a fixed point were computed using the new methods.The predicted static derivative and dynamic derivative were found to be in reasonable agreement with the experimental data.For the present method,it is possible to distinguish the components of dynamic derivatives caused by different state parameters.It is found that C_(m_α) and C_(mq) are usually of opposite signs and tend to eliminate each other,which makes C_(m_α)+C_(mq) being much smaller than its individual components.Another feature of this method is that the moment of pressure derivatives proposed in the present paper can be used to predict the contribution of each part of the blunt cone to the overall stability quantitatively.It is found that the head region is crucial for the static stability and the body region contributes most to the dynamic stability.展开更多
文摘The major purpose of this paper is to numerically study the complex structure of vortex system occurring within transonic turbine cascade. The transonic viscous flow in turbine cascade is simulated by solving full 3D Reynolds average N S equations, and then detailed analyses of vortex system structure are presented. Under guidance of topology, the wall limiting streamlines are employed to reveal the flow structure near the wall, and an analysis of space streamlines and cross section streamlines is given for the investigation of flow structure in the flow field. Through the analysis, the formation and evolution of the vortex system and the whole process of separation occurring within this turbine cascade are revealed
基金This work is supported by Chinese National Natural Science Foundation.
文摘A three dimensional numerical model based on the Reynolds equations is presented that can be used to predict the surface water flow in open channels.The model uses a computational mesh that conforms to the free water sur- face and the bottom of the channel so that the accuracy of boundary condition application,code complexity,and e- conomy could be enhanced.The k-ε turbulence model is used to estimate the eddy viscosity coefficient.Instead of using the“rigid-lid”approximation a 2-D equation derived from integrating the continuity equation over the total depth is adopted to determine the elevation of the free water surface.A new algorithm is presented based on the conventional SIMPLE procedure.The block correction technique is employed to enhance rate of convergence. The model presented is applied to a bottom discharge into a rectangular straight channel for three dimensional phenomena to obtain the free water surface configuration,velocities and pressure.The computed results are in good agreement with the previous experimental values.
文摘采用三维网格和VOF(Volume of Fluids)多相流模型,对非轴对称、X型舵的航行体水下点火这一非稳态过程进行了三维流场数值模拟,捕捉了燃气泡的形成、发展及断裂过程,得到了航行体水下点火初期的流场变化和阻力变化,并进行了相关因素探讨和结果对比分析。研究表明,燃气泡的发展变化过程对航行体流场和阻力产生影响。该研究可为航行体水下点火设计及试验提供参考。
基金This work is supported by national numerical wind tunnel project under contract number 2018-ZT4A072016YFA0401200 of national key research and development program of China.
文摘The numerical methods for computing the stability derivatives of the aircraft by solving unsteady sensitivity equations which was proposed in our previous papers was extended to solve three-dimensional problems in this paper.Both the static and dynamic derivatives of the hypersonic blunt cone undergoing pitching oscillation around a fixed point were computed using the new methods.The predicted static derivative and dynamic derivative were found to be in reasonable agreement with the experimental data.For the present method,it is possible to distinguish the components of dynamic derivatives caused by different state parameters.It is found that C_(m_α) and C_(mq) are usually of opposite signs and tend to eliminate each other,which makes C_(m_α)+C_(mq) being much smaller than its individual components.Another feature of this method is that the moment of pressure derivatives proposed in the present paper can be used to predict the contribution of each part of the blunt cone to the overall stability quantitatively.It is found that the head region is crucial for the static stability and the body region contributes most to the dynamic stability.
