The aerodynamics of gas-particle suspensions is simulated as an Euler-Euler two-fluid model in a revolving rotor over a particle bed. The interactions of collisions between the blade and particles and particle-particl...The aerodynamics of gas-particle suspensions is simulated as an Euler-Euler two-fluid model in a revolving rotor over a particle bed. The interactions of collisions between the blade and particles and particle-particle interactions are modeled using the kinetic theory of granular flow(KTGF). The gas turbulence induced by the rotation of the rotor is modeled using the kg-εg model. The flow field of a revolving rotor is simulated using the multiple reference frame(MRF) method. The distributions of velocities, volume fractions, and gas pressure are predicted while the aircraft hovers at different altitudes.The gas pressure decreases from the hub to the tip of the blade, and it is higher at the pressure side than that at the suction side of the rotor. The turbulent kinetic energy of the gas increases toward the blade tip. The volume fraction of particles decreases as the hovering altitude increases. The simulated pressure coefficient is compared with that in experimental measurements.展开更多
The characteristics of asteroids are vital parameters for planning asteroid exploration missions.These characteristics have been explored in close range for some typical asteroids,and are summarized in the article.Thi...The characteristics of asteroids are vital parameters for planning asteroid exploration missions.These characteristics have been explored in close range for some typical asteroids,and are summarized in the article.This allows estimates of the characteristics of asteroid 2016HO_(3),the target of the first Chinese asteroid exploration mission,Tianwen 2.We obtain 80 characteristic parameters in 9 categories and analyze their impacts on the mission.By comparing three close-range exploration modes,we provide advantages and disadvantages of each,and propose suitable methods for the exploration of 2016HO_(3).Owing to the weak gravity and small size of 2016HO_(3),a combination of multiple hovering positions and active orbiting is recommended for scientific exploration.展开更多
The threat of potential hazardous near-Earth asteroid(PHA)impact on Earth is increasingly attracting public attention.Monitoring and early warning of those PHAs are the premise of planetary defense.In this paper,we pr...The threat of potential hazardous near-Earth asteroid(PHA)impact on Earth is increasingly attracting public attention.Monitoring and early warning of those PHAs are the premise of planetary defense.In this paper,we proposed a novel concept of surveillance constellation of heterogeneous wide-field near-Earth asteroid(NEA)surveyors(CROWN),in which six spacebased surveyors are loosely deployed in Venus-like orbits to detect the NEAs along the direction of the sunlight.First,the concept and overall design of the NEA surveillance constellation are discussed.Second,the transfer and deployment trajectory of the surveyors are investigated based on the Sun-Venus three-body system.The Sun-Venus libration orbit is taken as the parking orbit,and its stable invariant manifolds are used to reduce the deployment fuel consumption.Next,the detection performance of the CROWN was evaluated considering constraints of apparent visual magnitude and field of view.The NEA orbit determination(OD)using the CROWN was studied and verified.Simulation results show that the CROWN can be deployed with a total velocity increment of approximately 300 m/s.During the 5 years of observation,99.8%of PHAs can be detected and the OD precision is better than a single-surveyor system.This paper can provide a reference for the construction of future asteroid defense system.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.91752115 and 51776059)
文摘The aerodynamics of gas-particle suspensions is simulated as an Euler-Euler two-fluid model in a revolving rotor over a particle bed. The interactions of collisions between the blade and particles and particle-particle interactions are modeled using the kinetic theory of granular flow(KTGF). The gas turbulence induced by the rotation of the rotor is modeled using the kg-εg model. The flow field of a revolving rotor is simulated using the multiple reference frame(MRF) method. The distributions of velocities, volume fractions, and gas pressure are predicted while the aircraft hovers at different altitudes.The gas pressure decreases from the hub to the tip of the blade, and it is higher at the pressure side than that at the suction side of the rotor. The turbulent kinetic energy of the gas increases toward the blade tip. The volume fraction of particles decreases as the hovering altitude increases. The simulated pressure coefficient is compared with that in experimental measurements.
文摘The characteristics of asteroids are vital parameters for planning asteroid exploration missions.These characteristics have been explored in close range for some typical asteroids,and are summarized in the article.This allows estimates of the characteristics of asteroid 2016HO_(3),the target of the first Chinese asteroid exploration mission,Tianwen 2.We obtain 80 characteristic parameters in 9 categories and analyze their impacts on the mission.By comparing three close-range exploration modes,we provide advantages and disadvantages of each,and propose suitable methods for the exploration of 2016HO_(3).Owing to the weak gravity and small size of 2016HO_(3),a combination of multiple hovering positions and active orbiting is recommended for scientific exploration.
基金supported by the National Natural Science Foundation of China(Grant Nos.12002028 and 51827806)the Beijing Institute of Technology Research Fund Program for Young Scholars(Grant No.XSQD-202101012)the Qian Xuesen Laboratory of Space Technology Initiative Key Program.
文摘The threat of potential hazardous near-Earth asteroid(PHA)impact on Earth is increasingly attracting public attention.Monitoring and early warning of those PHAs are the premise of planetary defense.In this paper,we proposed a novel concept of surveillance constellation of heterogeneous wide-field near-Earth asteroid(NEA)surveyors(CROWN),in which six spacebased surveyors are loosely deployed in Venus-like orbits to detect the NEAs along the direction of the sunlight.First,the concept and overall design of the NEA surveillance constellation are discussed.Second,the transfer and deployment trajectory of the surveyors are investigated based on the Sun-Venus three-body system.The Sun-Venus libration orbit is taken as the parking orbit,and its stable invariant manifolds are used to reduce the deployment fuel consumption.Next,the detection performance of the CROWN was evaluated considering constraints of apparent visual magnitude and field of view.The NEA orbit determination(OD)using the CROWN was studied and verified.Simulation results show that the CROWN can be deployed with a total velocity increment of approximately 300 m/s.During the 5 years of observation,99.8%of PHAs can be detected and the OD precision is better than a single-surveyor system.This paper can provide a reference for the construction of future asteroid defense system.
