The Yarkovsky-O'Keefe-Radzievskii-Paddack(YORP)effect is a net torque caused by solar radiation directly reflected and thermally re-emitted from the surface of small asteroids and is considered to be crucial in th...The Yarkovsky-O'Keefe-Radzievskii-Paddack(YORP)effect is a net torque caused by solar radiation directly reflected and thermally re-emitted from the surface of small asteroids and is considered to be crucial in their dynamical evolution.By long-term photometric observations of selected near-Earth asteroids,it is hoped to enlarge asteroid samples with a detected YORP effect to facilitate the development of a theoretical framework.Archived light-curve data are collected and photometric observations are made for(1685)Toro and(85989)1999 JD6,which enables measurement of their YORP effect by inverting the light curve to fit observations from a convex shape model.For(1685)Toro,a YORP accelerationυ=(3.2±0.3)×10^(-9)rad·day^(-2)(1σerror)is updated,which is consistent with previous YORP detection based on different light-curve data;for(85989)1999 JD6,it is determined that the sidereal period is 7.667749±0.000009 hr,the rotation pole direction is located atλ=232°±2°,β=-59°±1°,the acceleration is detected to beυ=(2.4±0.3)×10^(-8)rad·day^(-2)(1σerror)and in addition to obtaining an excellent agreement between the observations and model.YORP should produce both spin-up and spin-down cases.However,including(85989)1999 JD6,the dω/dt values of 11 near-Earth asteroids are positive totally,which suggests that there is either a bias in the sample of YORP detections or a real feature needs to be explained.展开更多
This paper deals with the numerical solution of inviscid compressible flows. The threedimensional Euler equations describing the mentioned problem are presented and solved numerically with the finite volume method. Th...This paper deals with the numerical solution of inviscid compressible flows. The threedimensional Euler equations describing the mentioned problem are presented and solved numerically with the finite volume method. The evaluation of the numerical flux at the interfaces is performed by using the Toro Vazquez-Harten Lax Leer(TV-HLL) scheme. An essential feature of the proposed scheme is to associate two systems of differential equations, called the advection system and the pressure system. It can be implemented with a very simple manner in the standard finite volume Euler and Navier–Stokes codes as extremely simple task. The scheme is applied to some test problems covering a wide spectrum of Mach numbers, including hypersonic, low speed flow and three-dimensional aerodynamics applications.展开更多
基金supported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(GrantNo.XDB41010104)the National Natural Science Foundation of China(Grant No.11633009)+2 种基金the Space Debris and NearEarth Asteroid Defense Research Project(Grant Nos.KJSP2020020204,KJSP2020020102)the Civil Aerospace Pre-research Project(Grant Nos.D020304,D020302)Minor Planet Foundation。
文摘The Yarkovsky-O'Keefe-Radzievskii-Paddack(YORP)effect is a net torque caused by solar radiation directly reflected and thermally re-emitted from the surface of small asteroids and is considered to be crucial in their dynamical evolution.By long-term photometric observations of selected near-Earth asteroids,it is hoped to enlarge asteroid samples with a detected YORP effect to facilitate the development of a theoretical framework.Archived light-curve data are collected and photometric observations are made for(1685)Toro and(85989)1999 JD6,which enables measurement of their YORP effect by inverting the light curve to fit observations from a convex shape model.For(1685)Toro,a YORP accelerationυ=(3.2±0.3)×10^(-9)rad·day^(-2)(1σerror)is updated,which is consistent with previous YORP detection based on different light-curve data;for(85989)1999 JD6,it is determined that the sidereal period is 7.667749±0.000009 hr,the rotation pole direction is located atλ=232°±2°,β=-59°±1°,the acceleration is detected to beυ=(2.4±0.3)×10^(-8)rad·day^(-2)(1σerror)and in addition to obtaining an excellent agreement between the observations and model.YORP should produce both spin-up and spin-down cases.However,including(85989)1999 JD6,the dω/dt values of 11 near-Earth asteroids are positive totally,which suggests that there is either a bias in the sample of YORP detections or a real feature needs to be explained.
文摘This paper deals with the numerical solution of inviscid compressible flows. The threedimensional Euler equations describing the mentioned problem are presented and solved numerically with the finite volume method. The evaluation of the numerical flux at the interfaces is performed by using the Toro Vazquez-Harten Lax Leer(TV-HLL) scheme. An essential feature of the proposed scheme is to associate two systems of differential equations, called the advection system and the pressure system. It can be implemented with a very simple manner in the standard finite volume Euler and Navier–Stokes codes as extremely simple task. The scheme is applied to some test problems covering a wide spectrum of Mach numbers, including hypersonic, low speed flow and three-dimensional aerodynamics applications.
