摘要
Some typical unsteady problems that are mainly dominated by shock waves,vortices, or both of them have been numerically simulated in the present study. The time history of unsteady flows is time-accurately computed and analyzed. The main factors influencing the unsteady flow features are disc-ussed. Furthermore, the key points for achieving time-accurate and cost-effective numerical simulations are systematically summarized. The whole dissertation is divided into three parts: the first, the numerical simulation of unsteady compressible inviscid flows; the second, the numerical simulation of unsteady incompressible viscous flows; and the last, studies on unsteady flow numerical simulation methods. The main contributions of this dissertation consist of : (1) The construction methods of total variation diminishing (TVD)schemes are analyzed in general, and a symmetric TVD scheme is developed in special: (2) The time-varying transonic flow fields and their influence on force features for a transonicperiodically pitching airfoil are successfully studied; (3) Using the same approach as before, theunsteady flow structures of a moving shock interacting with a vortex and with a vortex pair areinvestigated; (4) The numerical simulation of the near wake complex vortex formation for acircular cylinder oscillating in arbitrary directions in a free stream has ben conducted throughouta wide range of oscillation parameters. Many experimentally investigated phenomena areduplicated and even renewed numerically. A parameter map in the amplitude-frequency plane,showing restons of vortex shedding formation, is given. The influences of oscillation parametersand Reynolds numbers on the force characters and on the time-varying flow structures areexplained; (5) The force characters and vortex structures in the near wake of the pitching ortranslating air foils oscillating around a high incidence angle are successfully predicted bynumerically solving the Navier-Stokes equations; (6) Some key points for achieving timeaccurate and cost- effective numerical simulation of unsteady complex flows are initiallyreviewed. Some main work of all above also can be found in some our papers shown inreferences.
Some typical unsteady problems that are mainly dominated by shock waves,vortices, or both of them have been numerically simulated in the present study. The time history of unsteady flows is time-accurately computed and analyzed. The main factors influencing the unsteady flow features are disc-ussed. Furthermore, the key points for achieving time-accurate and cost-effective numerical simulations are systematically summarized. The whole dissertation is divided into three parts: the first, the numerical simulation of unsteady compressible inviscid flows; the second, the numerical simulation of unsteady incompressible viscous flows; and the last, studies on unsteady flow numerical simulation methods. The main contributions of this dissertation consist of : (1) The construction methods of total variation diminishing (TVD)schemes are analyzed in general, and a symmetric TVD scheme is developed in special: (2) The time-varying transonic flow fields and their influence on force features for a transonicperiodically pitching airfoil are successfully studied; (3) Using the same approach as before, theunsteady flow structures of a moving shock interacting with a vortex and with a vortex pair areinvestigated; (4) The numerical simulation of the near wake complex vortex formation for acircular cylinder oscillating in arbitrary directions in a free stream has ben conducted throughouta wide range of oscillation parameters. Many experimentally investigated phenomena areduplicated and even renewed numerically. A parameter map in the amplitude-frequency plane,showing restons of vortex shedding formation, is given. The influences of oscillation parametersand Reynolds numbers on the force characters and on the time-varying flow structures areexplained; (5) The force characters and vortex structures in the near wake of the pitching ortranslating air foils oscillating around a high incidence angle are successfully predicted bynumerically solving the Navier-Stokes equations; (6) Some key points for achieving timeaccurate and cost- effective numerical simulation of unsteady complex flows are initiallyreviewed. Some main work of all above also can be found in some our papers shown inreferences.
