超声速大攻角旋成体迎风激波数值模拟

旋成弹体在大攻角超声速流动中其迎风面上有时会出现一种迎风激波．采用非定常雷诺平均的NavierStokes方程以及两方程kω—sst和代数B—L湍流模型成功地模拟了该现象,验证了该迎风激波是由于流场主旋涡导致超声速流动偏移造成的涡诱导激波的一部分的结论．     

用简化Acierno模型预测LDPE熔体的触变环实验

考察了简化Acierno型本构方程的预测能力．用简化Acierno方程预测了LDPE(Q200)熔体的触变环实验,比较了该方程和变型Huang方程在拟合和预测触变环实验方面的差异．虽然简化Acierno方程只能拟合LDPE熔体的部分触变环实验,但该方程预测的触变环与实验值的偏差较小,而同样的计算条件下,变型Huang方程的预测结果与实验值相差较大．简化Acierno方程的构造比变型Huang方程的构造更为合理．     

大挠度弯曲直梁混合变量最小势能原理的应用

应用大挠度弯曲直梁混合变量最小势能原理,求解均载两端固定大挠度柱面弯曲板条的轴向挠度分布和轴向弯矩分布．实例计算表明:该方法简单实用、精度高,是一种计算大挠度柱面弯曲板条变形的有效方法．     

Interval analysis method and convex models for impulsive response of structures with uncertain-but-bounded external loads

Two non-probabilistic, set-theoretical methods for determining the maximum and minimum impulsive responses of structures to uncertain-but-bounded impulses are presented. They are, respectively, based on the theories of interval mathematics and convex models. The uncertain-but-bounded impulses are assumed to be a convex set, hyper-rectangle or ellipsoid. For the two non-probabilistic methods, less prior information is required about the uncertain nature of impulses than the probabilistic model. Comparisons between the interval analysis method and the convex model, which are developed as an anti-optimization problem of finding the least favorable impulsive response and the most favorable impulsive response, are made through mathematical analyses and numerical calculations. The results of this study indicate that under the condition of the interval vector being determined from an ellipsoid containing the uncertain impulses, the width of the impulsive responses predicted by the interval analysis method is larger than that by the convex model; under the condition of the ellipsoid being determined from an interval vector containing the uncertain impulses, the width of the interval impulsive responses obtained by the interval analysis method is smaller than that by the convex model.The project supported by the National Outstanding Youth Science Foundation of China (10425208), the National Natural Science Foundation of China and Institute of Engineering Physics of China (10376002) The English text was polished by Keren Wang.     

经典弹塑性力学体系下岩土材料的本构方程

剑桥模型,修正剑桥模型以及近年来出现的适用于砂土和黏土的统一硬化模型在岩土工程中有重要的科研和实用价值．在经典弹塑性力学框架下重新推导了以上这些岩土材料本构方程,对岩土工程中常用的本构模型和经典弹塑性理论框架下的岩土本构模型进行了对比,将两个体系下的相关量建立了联系．     

叶片与蜗舌相对位置对离心泵性能数值模拟精度影响的研究

本文选择RANS方程和RNG k-ε湍流模型,采用有限体积法,在假定流动定常的前提下对离心泵中叶片与蜗舌不同相对位置时的流场进行数值模拟,总结分析了各性能参数的计算误差在不同的相对位置时的变化规律.通过叶片与蜗舌不同相对位置时对各性能参数计算误差的均方差进行比较,认为存在一个合适的相对位置使得对各性能参数的总体预测精度保持最高,为数值方法分析离心泵的性能提供了指导.     

基于Chebyshev-Taylor-Fourier混合级数模型函数的多源气动数据融合方法

针对飞行器气动力多源数据融合、 飞行试验气动辨识问题,提出了一种基于Chebyshev-Taylor-Fourier混合级数模型函数、不确定度平衡权函数和加权最小二乘原理的多源数据融合和辨识方法.该方法采用二元Cheby-shev级数、Taylor级数和Fourier级数技术建立飞行器气动模型函数,采用权函数技术平衡各...     

高频感应等离子体流动模型与微型电推进器流场特性分析

微型射频离子推力器具有结构简单、 工作寿命长、 推力动态范围大、 性能调节响应灵敏等特点,是国际微电推进领域的研究热点之一.射频离子推力器电离室内的感性耦合放电等离子体特性和推力器的性能密切相关.为此,文章建立了低气压、小尺寸微型射频离子推力器电离室内感性耦合等离子体流体模型,开展了电磁场、流场、化学反应浓度场的多物理...     

The effects of relative density of metal foams on the stresses and deformation of beam under bending

The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law (TG model) taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. One of the objects of this study is to generalize Hill’s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined. The English text was polished by Yunming Chen.     

Studies on structural safety in stochastically excited Duffing oscillator with double potential wells

The effects of the Gaussian white noise excitation on structural safety due to erosion of safe basin in Duffing oscillator with double potential wells are studied in the present paper. By employing the well-developed stochastic Melnikov condition and Monte–Carlo method, various eroded basins are simulated in deterministic and stochastic cases of the system, and the ratio of safe initial points (RSIP) is presented in some given limited domain defined by the system’s Hamiltonian for various parameters or first-passage times. It is shown that structural safety control becomes more difficult when the noise excitation is imposed on the system, and the fractal basin boundary may also appear when the system is excited by Gaussian white noise only. From the RSIP results in given limited domain, sudden discontinuous descents in RSIP curves may occur when the system is excited by harmonic or stochastic forces, which are different from the customary continuous ones in view of the first-passage problems. In addition, it is interesting to find that RSIP values can even increase with increasing driving amplitude of the external harmonic excitation when the Gaussian white noise is also present in the system. The project supported by the National Natural Science Foundation of China (10302025 and 10672140). The English text was polished by Yunming Chen.