We use the car-following model （Phys. Rev. E 72 （2005） 066124） to further analyse the two-lane traffic waves. Our numerical results show that in the two-lane traffic, there exist triangular shock, soliton wave and...We use the car-following model （Phys. Rev. E 72 （2005） 066124） to further analyse the two-lane traffic waves. Our numerical results show that in the two-lane traffic, there exist triangular shock, soliton wave and kink wave which appear in the stable, mestastable and unstable regions of headway-sensitivity space, respectively. Compared with the single-lane traffic, it is found that the lateral distance has little effect on the formation of triangular shock and soliton wave although the lateral distance can enlarge the stable region and can reduce the mestastable and unstable regions.展开更多
The transition from an axisymmetric stationary flow to three-dimensional time-dependent flows is carefully studied in a vertical cylinder partially heated from the side, with the aspect ratio A = 2 and Prandtl number ...The transition from an axisymmetric stationary flow to three-dimensional time-dependent flows is carefully studied in a vertical cylinder partially heated from the side, with the aspect ratio A = 2 and Prandtl number Pτ=0.021. The flow develops from the steady toroidal pattern beyond the first instability threshold, breaks the axisymmetric state at a Rayleigh number near 2000, and transits to standing or travelling azimuthal waves. A new result is observed that a slightly unstable flow pattern of standing waves exists and will transit to stable travelling waves after a long time evolution. The onset of oscillations is associated with a supercritical Hopf bifurcation in a system with O（2） symmetry.展开更多
We assess the performance of a few turbulence models for Reynolds averaged Navier-Stokes （RANS） simulation of supersonic boundary layers, compared to the direct numerical simulations （DNS） of supersonic flat-plate...We assess the performance of a few turbulence models for Reynolds averaged Navier-Stokes （RANS） simulation of supersonic boundary layers, compared to the direct numerical simulations （DNS） of supersonic flat-plate turbulent boundary layers, carried out by Gao et al. [Chin. Phys. Lett. 22（2005）1709] and Huang et al. [Sci. Chin. 48 （2005） 614], as well as some available experimental data. The assessment is made for two test cases, with incoming Mach numbers and Reynolds numbers M = 2.25, Re = 365, 000//in, and M = 4.5, Re = 1.7 × 10^7/m, respectively. It is found that in the first case the prediction of RANS models agrees well with the DNS and the experimental data, while for the second case the agreement of the DNS models with experiment is less satisfactory. The compressibility effect on the RANS models is discussed.展开更多
基金Supported by the National Basic Research Programme of China under Grant No 2006CB705503, and the National Natural Science Foundation of China under Grant No 70521001.
文摘We use the car-following model （Phys. Rev. E 72 （2005） 066124） to further analyse the two-lane traffic waves. Our numerical results show that in the two-lane traffic, there exist triangular shock, soliton wave and kink wave which appear in the stable, mestastable and unstable regions of headway-sensitivity space, respectively. Compared with the single-lane traffic, it is found that the lateral distance has little effect on the formation of triangular shock and soliton wave although the lateral distance can enlarge the stable region and can reduce the mestastable and unstable regions.
文摘The transition from an axisymmetric stationary flow to three-dimensional time-dependent flows is carefully studied in a vertical cylinder partially heated from the side, with the aspect ratio A = 2 and Prandtl number Pτ=0.021. The flow develops from the steady toroidal pattern beyond the first instability threshold, breaks the axisymmetric state at a Rayleigh number near 2000, and transits to standing or travelling azimuthal waves. A new result is observed that a slightly unstable flow pattern of standing waves exists and will transit to stable travelling waves after a long time evolution. The onset of oscillations is associated with a supercritical Hopf bifurcation in a system with O（2） symmetry.
文摘We assess the performance of a few turbulence models for Reynolds averaged Navier-Stokes （RANS） simulation of supersonic boundary layers, compared to the direct numerical simulations （DNS） of supersonic flat-plate turbulent boundary layers, carried out by Gao et al. [Chin. Phys. Lett. 22（2005）1709] and Huang et al. [Sci. Chin. 48 （2005） 614], as well as some available experimental data. The assessment is made for two test cases, with incoming Mach numbers and Reynolds numbers M = 2.25, Re = 365, 000//in, and M = 4.5, Re = 1.7 × 10^7/m, respectively. It is found that in the first case the prediction of RANS models agrees well with the DNS and the experimental data, while for the second case the agreement of the DNS models with experiment is less satisfactory. The compressibility effect on the RANS models is discussed.
