最近Rump S. M.研究了在范数意义下的结构化扰动问题,即对求解线性方程组的条件数和矩阵求逆的条件数作了探讨,并且刻画了非奇异矩阵到奇异矩阵的最小距离.把其部分结果推广到奇异情形,即对一类有特定右端项的值域对称的奇异线性方程组...最近Rump S. M.研究了在范数意义下的结构化扰动问题,即对求解线性方程组的条件数和矩阵求逆的条件数作了探讨,并且刻画了非奇异矩阵到奇异矩阵的最小距离.把其部分结果推广到奇异情形,即对一类有特定右端项的值域对称的奇异线性方程组,给出了其条件数的不同表示和估计,同时讨论了求矩阵广义逆的条件数.展开更多
A method of unstructured dynamic overset grids is developed for the numerical simulation of helicopter unsteady rotorairframe aerodynamic interaction.For the effective treatment of the relative motion between the roto...A method of unstructured dynamic overset grids is developed for the numerical simulation of helicopter unsteady rotorairframe aerodynamic interaction.For the effective treatment of the relative motion between the rotor and the airframe,the domain of flowfield is divided into two overset subzones,namely,a rotational subzone containing the blades and a stationary subzone containing the airframe.The overset part of two subzones is used to convect the flow variables of the two zones.The Taylor series expansion is used to obtain a second-order spatial accuracy,and dual-time stepping is adopted to improve the solution accuracy.Mesh deformation from the blade motion in forward flight is treated by using a spring analogy.Validation is made by numerically simulating the flows around a wind tunnel configuration and comparing the predicted time-averaged and instantaneous inflow and airframe surface pressure distributions with the experimental data.It shows that the present method is efficient and robust for the prediction of complicated unsteady rotor-airframe aerodynamic interaction phenomena.展开更多
基金supported by the Basic Research Program of Northwestern Polytechnical University (Grant No. JC201219)the Postdoctoral Science Foundation of China (Grant No. 20100481368)
文摘A method of unstructured dynamic overset grids is developed for the numerical simulation of helicopter unsteady rotorairframe aerodynamic interaction.For the effective treatment of the relative motion between the rotor and the airframe,the domain of flowfield is divided into two overset subzones,namely,a rotational subzone containing the blades and a stationary subzone containing the airframe.The overset part of two subzones is used to convect the flow variables of the two zones.The Taylor series expansion is used to obtain a second-order spatial accuracy,and dual-time stepping is adopted to improve the solution accuracy.Mesh deformation from the blade motion in forward flight is treated by using a spring analogy.Validation is made by numerically simulating the flows around a wind tunnel configuration and comparing the predicted time-averaged and instantaneous inflow and airframe surface pressure distributions with the experimental data.It shows that the present method is efficient and robust for the prediction of complicated unsteady rotor-airframe aerodynamic interaction phenomena.
