To understand the vortex-ring state and to develop an approach for predicting its boundary, a series of model rotor tests of vertical descent and oblique descent have been conducted on a newly-built test apparatus - t...To understand the vortex-ring state and to develop an approach for predicting its boundary, a series of model rotor tests of vertical descent and oblique descent have been conducted on a newly-built test apparatus - the Whirling Beam. The test results showed some unsteady aerodynamic behavior of the model rotor operating in the vortex-ring state. A very irregular variation of the rotortorque at low rate-of-descent was observed here for the first time. We considered it to be the start of the 'power settling' and determined the critical descent velocity according to this observation. A previous criterion for the vortex-ring state was modified to give a semi-empirical method for predicting the entire vortex-ring state boundary. The computed boundary shows a good correlation with the model test results and the flight experiences.展开更多
A vortex ring impinging on a three-dimensional bump is studied using large eddy simulation for a Reynolds number Re = 4 × 104 based on the initial translation speed and diameter of the vortex ring. The effects of...A vortex ring impinging on a three-dimensional bump is studied using large eddy simulation for a Reynolds number Re = 4 × 104 based on the initial translation speed and diameter of the vortex ring. The effects of bump height on the vortical flow phenomena and the underlying physical mechanisms are inves- tigated. Based on the analysis of the evolution of vortical structures, two typical kinds of vortical structures, i.e., the wrapping vortices and the hair-pin vortices, are identified and play an important role in the flow state evolution. The circu- lation of the primary vortex ring reasonably elucidates some typical phases of flow evolution. Furthermore, the mechanism of flow transition from laminar to turbulent state has been revealed based on analysis of turbulent kinetic energy.展开更多
The charge distribution in thin mesoscopic superconducting ring is studied by the phenomenological GinzburgLandau theory. In the giant vortex states we find that the mesoscopic rings may present three kinds of charge ...The charge distribution in thin mesoscopic superconducting ring is studied by the phenomenological GinzburgLandau theory. In the giant vortex states we find that the mesoscopic rings may present three kinds of charge distribution while the disk only owns the first two kinds. The charge near the inner radius may change its sign from negative to positive with increasing applied field. In the multivortex state we find that there exist saddle-point states and stable multivortex states. The distribution of charge and the superconducting electron density in the （0：2） saddle states and the （0：4）, and （1：5） stable multivortex states has also been studied. The contour plot of the charge distribution and the Cooper pair density distribution are given.展开更多
文摘To understand the vortex-ring state and to develop an approach for predicting its boundary, a series of model rotor tests of vertical descent and oblique descent have been conducted on a newly-built test apparatus - the Whirling Beam. The test results showed some unsteady aerodynamic behavior of the model rotor operating in the vortex-ring state. A very irregular variation of the rotortorque at low rate-of-descent was observed here for the first time. We considered it to be the start of the 'power settling' and determined the critical descent velocity according to this observation. A previous criterion for the vortex-ring state was modified to give a semi-empirical method for predicting the entire vortex-ring state boundary. The computed boundary shows a good correlation with the model test results and the flight experiences.
基金supported by the National Natural Science Foundation of China(11202100)the Natural Science Fund in Jiangsu Province(BK2011723)
文摘A vortex ring impinging on a three-dimensional bump is studied using large eddy simulation for a Reynolds number Re = 4 × 104 based on the initial translation speed and diameter of the vortex ring. The effects of bump height on the vortical flow phenomena and the underlying physical mechanisms are inves- tigated. Based on the analysis of the evolution of vortical structures, two typical kinds of vortical structures, i.e., the wrapping vortices and the hair-pin vortices, are identified and play an important role in the flow state evolution. The circu- lation of the primary vortex ring reasonably elucidates some typical phases of flow evolution. Furthermore, the mechanism of flow transition from laminar to turbulent state has been revealed based on analysis of turbulent kinetic energy.
基金supported by the National Natural Science Foundation of China （Grant No.60371033）
文摘The charge distribution in thin mesoscopic superconducting ring is studied by the phenomenological GinzburgLandau theory. In the giant vortex states we find that the mesoscopic rings may present three kinds of charge distribution while the disk only owns the first two kinds. The charge near the inner radius may change its sign from negative to positive with increasing applied field. In the multivortex state we find that there exist saddle-point states and stable multivortex states. The distribution of charge and the superconducting electron density in the （0：2） saddle states and the （0：4）, and （1：5） stable multivortex states has also been studied. The contour plot of the charge distribution and the Cooper pair density distribution are given.
