This paper deals with the numerical stability of systems concerning multide- lay differential equations (MDDEs) with variable-coefficient, for which some new concepts of stability such as ANf(m)-stability and (strong)...This paper deals with the numerical stability of systems concerning multide- lay differential equations (MDDEs) with variable-coefficient, for which some new concepts of stability such as ANf(m)-stability and (strong) GPNm-stability are introduced. The approach yields some criteria on (strong) GPNm-stability for Runge-Kutta methods to MDDEs.展开更多
Unsteady effect of seriously separated flow is the main factor of modern aircraft buffeting. So accurate simulation of this complex flow becomes the basis associated with the research of aircraft buffeting. This paper...Unsteady effect of seriously separated flow is the main factor of modern aircraft buffeting. So accurate simulation of this complex flow becomes the basis associated with the research of aircraft buffeting. This paper constructs an unsteady numerical simulation method for separation flow based on modified delayed detached eddy simulation (MDDES) method by considering both modern computer resources and the credibility of simulating separation flow. The proposed method is also verified through the simulation of the separated flow by a typical fighter at high angle of attack. And then a robust and efficient technology for deforming mesh is established using radial basis function (RBF) and infinite interpolation method. Moreover, the platform for numerical simulation of buffeting is set up in combination with the structural dynamics equations in the modal space, by which the research of vertical tail buffeting caused by edge vortex is carried out on a fighter at large angle of attack. Through spectrum analysis of time-domain response of pressure pulsation on the location of vortex rupture, the results show that the pulsation frequency of vortex structure with different scales covers the inherent modal frequency of vertical tail structure. Compared to the Reynolds-averaged Navier-Stokes equations, the MDDES method can distinguish the more detailed and higher frequency small-scale vortex structure. Unlike flutter, displacement acceleration response of each mode in buffeting is dominated by its own mode. There exists strong coupling between the first bending mode and first torsion mode, and it leads to acceleration and large inertia impact of structure, which is the main factor causing structural fatigue. In sum, the obtained results verify the validity of the numerical means and the corresponding methods in the paper.展开更多
文摘This paper deals with the numerical stability of systems concerning multide- lay differential equations (MDDEs) with variable-coefficient, for which some new concepts of stability such as ANf(m)-stability and (strong) GPNm-stability are introduced. The approach yields some criteria on (strong) GPNm-stability for Runge-Kutta methods to MDDEs.
文摘Unsteady effect of seriously separated flow is the main factor of modern aircraft buffeting. So accurate simulation of this complex flow becomes the basis associated with the research of aircraft buffeting. This paper constructs an unsteady numerical simulation method for separation flow based on modified delayed detached eddy simulation (MDDES) method by considering both modern computer resources and the credibility of simulating separation flow. The proposed method is also verified through the simulation of the separated flow by a typical fighter at high angle of attack. And then a robust and efficient technology for deforming mesh is established using radial basis function (RBF) and infinite interpolation method. Moreover, the platform for numerical simulation of buffeting is set up in combination with the structural dynamics equations in the modal space, by which the research of vertical tail buffeting caused by edge vortex is carried out on a fighter at large angle of attack. Through spectrum analysis of time-domain response of pressure pulsation on the location of vortex rupture, the results show that the pulsation frequency of vortex structure with different scales covers the inherent modal frequency of vertical tail structure. Compared to the Reynolds-averaged Navier-Stokes equations, the MDDES method can distinguish the more detailed and higher frequency small-scale vortex structure. Unlike flutter, displacement acceleration response of each mode in buffeting is dominated by its own mode. There exists strong coupling between the first bending mode and first torsion mode, and it leads to acceleration and large inertia impact of structure, which is the main factor causing structural fatigue. In sum, the obtained results verify the validity of the numerical means and the corresponding methods in the paper.
