We investigate the photon sphere and marginally stable circular orbit of massive particles over the re-cently proposed regular black holes with sub-Planckian curvature and a Minkowskian core.We derive the effective po...We investigate the photon sphere and marginally stable circular orbit of massive particles over the re-cently proposed regular black holes with sub-Planckian curvature and a Minkowskian core.We derive the effective potential for geodesic orbits and determine the radius of circular photon orbits,with an analysis of the stability of these orbits.We extend our analysis to the background of a compact massive object(CMO)without a horizon,whose mass is below the lowest bound for the formation of a black hole.For massive particles,marginally stable cir-cular orbits become double-valued in the CMO phase.Through a comparison with Bardeen and Hayward black holes,we also find that the locations of the photon sphere and marginally stable circular orbit in the CMO phase with a Minkowskian core are evidently different from those in the CMO phase with a dS core,which potentially provides a way to distinguish between these two types of black holes by astronomical observation.Finally,we present the ob-servational constraint on the deviation parameter for such regular black holes using observed data from the black hole M87^(*).展开更多
Every compressor works in a limited operational range. Surge as one of the sources of this limitation has been studied for many years. In this research, an isolated blade row of compressor rotor is numerically modeled...Every compressor works in a limited operational range. Surge as one of the sources of this limitation has been studied for many years. In this research, an isolated blade row of compressor rotor is numerically modeled and solved. In order to improve operational limit and postpone the surge occurrence, a stepped blade of RAF6E with higher stall angle of attack is used to investigate the near stall flow behavior. In this study, several location of step on blades are tried and the results are compared with the case with no step on blades. It is shown that, as the step moves toward the leading edge of blades, the effect of delay on surge is reduced and even efficiency is also decreased significantly. By moving the step towards the trailing edge, surge is delayed due to the reattachment of flow after the step. Efficiency is also decreased but not in the order of the previous case.展开更多
基金Supported in part by the Natural Science Foundation of China(11875053,12035016)supported by the Beijing Natural Science Foundation(1222031)+1 种基金the Sichuan Youth Science and Technology Innovation Research Team with(21CXTD0038)Central Government Funds of Guiding Local Scientific and Technological Development for Sichuan Province with(2021ZYD0032)。
文摘We investigate the photon sphere and marginally stable circular orbit of massive particles over the re-cently proposed regular black holes with sub-Planckian curvature and a Minkowskian core.We derive the effective potential for geodesic orbits and determine the radius of circular photon orbits,with an analysis of the stability of these orbits.We extend our analysis to the background of a compact massive object(CMO)without a horizon,whose mass is below the lowest bound for the formation of a black hole.For massive particles,marginally stable cir-cular orbits become double-valued in the CMO phase.Through a comparison with Bardeen and Hayward black holes,we also find that the locations of the photon sphere and marginally stable circular orbit in the CMO phase with a Minkowskian core are evidently different from those in the CMO phase with a dS core,which potentially provides a way to distinguish between these two types of black holes by astronomical observation.Finally,we present the ob-servational constraint on the deviation parameter for such regular black holes using observed data from the black hole M87^(*).
文摘Every compressor works in a limited operational range. Surge as one of the sources of this limitation has been studied for many years. In this research, an isolated blade row of compressor rotor is numerically modeled and solved. In order to improve operational limit and postpone the surge occurrence, a stepped blade of RAF6E with higher stall angle of attack is used to investigate the near stall flow behavior. In this study, several location of step on blades are tried and the results are compared with the case with no step on blades. It is shown that, as the step moves toward the leading edge of blades, the effect of delay on surge is reduced and even efficiency is also decreased significantly. By moving the step towards the trailing edge, surge is delayed due to the reattachment of flow after the step. Efficiency is also decreased but not in the order of the previous case.
