用样条法研究高速滑行体的运动

研究高速滑行体在规则波浪中滑行时，得到了二阶常微分方程组，本文应用样条插值求积方法和三次样条配点计算，求解滑行体在不同波浪条件下的纵倾和升沉的响应，实例计算结果与实验值比较一致。     

结构动响应的样条插值加权残量算法

本文以样条函数近似表达结构的瞬态响应,然后利用加权残量法建立起多步和单步形式的逐步积分算法。着重分析了应用三次B样条函数的算法SW32,并推荐了一个具有合适特性的p方案,     

样条配点法分析结构动力响应的无条件稳定计算格式

本文以三次B样条函数作为位移时域函数,应用配点法,在任一时间步长中列出两个时刻的结构物运动方程式残值为零的条件并使结果满足了稳定条件得到一个计算结构物动力响应无条件稳定的计算格式。 这个计算格式于参数θ符合0.15<θ<0.05时是绝对无条件稳定的,研究证明,本文所提出的格式的精度根据三项指标:振幅衰减率 AD,周期伸长率 PE 及算法阻尼比都比较Wilson-θ法,Newmark法及Houbolt法的为优,例题计算也证明此点,即本文方法精度较上述三法为高,本文格式简单,准确,工作量不多,可以作为计算结构动力响应有效方法之一。     

样条状态变量法分析扁球壳的动力响应

基于瞬时变分原理与样条函数理论,建立扁球壳的动力方程,引入样条参数及其对时间的导数作为状态变量,导出状态方程,对空间域,采用样条有限元法,对时间域,采用现代控制论中的状态空间法,此外,建立了一种状态变量的递推计算格式,在计算过程中,不解线性方程组,也不需采用解耦技术,只要作矩阵运算,可直接算出动力响应量,文末给出的数值算例表明本文方法是可靠 与有效的。     

爆炸荷载作用下地下拱形结构动力响应样条小波有限元研究

采用小波有限元方法研究爆炸荷载作用下地下结构的动力响应,克服在模拟过程中由于材料的奇异性、地质条件的复杂性和加载的快速性出现的应力集中和计算效率低下,根据样条有限点法,构造了单向和双向区间B样条圆环扇形小波单元,用尺度函数作为插值函数;结合工程实例,通过Matlab软件编程对爆炸荷载作用地下拱形结构的动力响应进行了数值模拟,并与应用传统有限元程序模拟结果进行对比。结果表明,小波有限元用很少单元取得了较高的精度,计算效率比传统有限元提高一倍。     

某型水陆两栖飞机水面高速滑行振动研究

某型水陆两栖飞机在某次试飞过程中的水面高速滑行阶段出现海豚运动和机翼振动的异常现象,针对该现象展开原因分析研究。首先,建立飞机结构动力学有限元模型,研究弹性体飞机的固有动力特性;然后,建立双质量弹簧系统模型,结合水动力学研究飞机在水面滑行的运动特性;最后,结合飞机固有动力特性和水面高速滑行运动特性,分析飞机在水面高速滑行过程中机翼产生异常振动的原因。研究结果表明：飞机着水时因着水姿态以及自身静稳性等因素发生海豚运动;在某个运动时刻,当运动固有频率与机翼的一阶弹性模态频率耦合导致机翼振动。研究结果既为后续研究异常避免措施以及保证滑行试飞安全,提供了理论依据;也为水陆两栖飞机振动设计以及水面高速滑行振动分析提供了一种研究思路。     

非线性动力方程的三次样条-增维精细算法

提出一种针对非线性动力方程的改进精细积分方法。该方法是在时间步长内采用分段的三次样条函数拟合非齐次项,保持高精度拟合的同时避免了求导运算和高次多项式插值带来的Runge现象。通过引入4×2个变量将动力方程增加四维转化为齐次方程,并建立相应的通解格式,避免了状态空间下系统矩阵求逆。将指数矩阵分为四个子模块,利用各模块的特点分别进行理论推导及基于精细积分法进行分步、分块计算得到相应的理论解和高精度数值解,无需反复计算整个指数矩阵,提高了解算效率。针对含未知状态量的非齐次项,引入预测-校正的方法进行迭代求解。数值计算结果表明了本文方法的有效性。     

带尾裙跨介质航行体高速斜入水实验研究

为了研究带尾裙跨介质航行体高速斜入水过程中空泡的发展及运动特性,搭建了高速入水实验平台,并设计了带有内测单元的实验模型,对带尾裙跨介质航行体开展了入水角为20°、入水速度为30~130 m/s的实验研究。采用高速摄像机记录入水空泡,同时由内测单元测量航行体的运动参数和泡内压力,获得了航行体高速斜入水过程中空泡的发展特性、入水运动特性以及泡内压力的变化规律。实验结果表明：带尾裙跨介质航行体在入水过程中形成了滑行运动特性,入水空泡发生弯曲变形现象,随着入水速度的升高,入水弹道向上偏转的趋势更加明显;航行体入水轴向过载峰值作用时间较长,法向过载峰值在入水1.5倍航行体长度后逐渐降至零值附近波动;泡内压力随入水空泡的形成和发展呈现先降低后升高的趋势,且最低压力随入水速度呈线性趋势,形成时间基本一致。

     

一种快速稳健的并行多块结构动网格方法

为解决传统网格处理方法不能满足复杂外形在大设计空间内进行优化时对网格质量的要求的问题,提出了一种并行多块动网格方法,该方法基于初始外形的多块结构网格,根据优化过程中个体外形与初始外形拓扑结构相近的特性,利用体样条插值方法来拟合多块结构网格各块顶点的位移,得到几何外形变化后的拓扑结构,再利用无限插值方法并行地移动初始外形多块结构网格的边、面和块内的网格点,进行光顺处理后得到变形后几何外形的空间网格;该方法在保证网格质量的同时,可以极大地提高网格生成效率,本文以某翼身组合体为例结果表明,该方法在大设计空间的复杂外形设计问题中具有很强的实用性。     

用矩量法解阻尼介质中简支方板的塑性动力响应问题

本文用矩量法解薄板塑性动力响应问题，分析阻尼介质对简支方板塑性动力响应的影响，对计算结果进行了讨论．     

An unconditionally stable calculation scheme for the dynamic response of structures by the method of spline collocation

In this paper, by the method of collocation, using the cubic β-spline function as the trial function in the time domain and putting zero residuals of the differential equation of motion of the structure at two points of time, the authors obtain an unconditionally stable calculation scheme for the dynamic response of the structure. When a parameter σ in the scheme is within the interval 0.15<σ <0.5 the scheme is absolutely stable. It is shown that the accuracy of the scheme, as may be measured by AD (the decay of the amplitudes), PE (the elongation of periods) and the algorithmic damping ratio, is better than that of traditional methods—the Wilson-σ's method, the Newmark's method and the Houbolt's method. A numerical example is given in which a certain dynamic response problem is solved by the method of this paper and results are compared with that of the traditional methods and the analytic method showing that the accuracy of the method by this paper is superior to the other ones. The computational scheme for the dynamic response of structures by this paper may be regarded as an effective, convenient and accurate method for dynamic response of structures.     

Dynamic response of elastic rectangular plates by spline state variable method

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Characteristics method with cubic‐spline interpolation for open channel flow computation

In the framework of the specified‐time‐interval scheme, the accuracy of the characteristic method is greatly related to the form of the interpolation. The linear interpolation was commonly used to couple the characteristics method (LI method) in open channel flow computation. The LI method is easy to implement, but it leads to an inevitable smoothing of the solution. The characteristics method with the Hermite cubic interpolation (HP method, originally developed by Holly and Preissmann, 1977) was then proposed to largely reduce the error induced by the LI method. In this paper, the cubic‐spline interpolation on the space line or on the time line is employed to integrate with characteristics method (CS method) for unsteady flow computation in open channel. Two hypothetical examples, including gradually and rapidly varied flows, are used to examine the applicability of the CS method as compared with the LI method, the HP method, and the analytical solutions. The simulated results show that the CS method is comparable to the HP method and more accurate than the LI method. Without tackling the additional equations for spatial or temporal derivatives, the CS method is easier to implement and more efficient than the HP method. Copyright © 2004 John Wiley & Sons, Ltd.     

用样条函数法分析旋转组合壳

本文采用不等距三次Ｂ样条函数对旋转壳在整体坐标下的位移进行插值，给出了周向插值所必需满足的周期性条件，采用罚单元法，给出了组合壳体在整体坐标下的协调关系，与惯用方法相比，这种方法简单明了直观性强，易于接受。文末给出了算例。     

Isotropicalized spline integral equation method for the analysis of anisotropic plates

In the view of Reissner’s and Kirchhoff’s theories,respectively,we formulate theisotropicalized governing equations for the anisotropic plates,and give the proof of theequivalence relation between these two plate-models for the simply-supported rectangularorthotropic plates.The well-known fundamental solutions of the isotropic plates are utlizedfor the spline integral equation analysis of anisotropic plates.Even with sparse meshes thesatisfactory results can be obtained.The analysis of plates on two-parameter elasticfoundation is so simple as the common case that only a few terms should be added to theformulas of fictitious loads.     

An experimental method for studying the high speed impact of a liquid drop on a liquid surface

Summary An experimental method for studying the high speed impact of a liquid drop on a liquid surface is described in which the liquid surface is moved against the stationary drop. Photographs are presented of the impact of a water surface at 47,7 m/sec on a stationary water drop 0,175 cm diameter. Proposals are made for further work to resolve certain discrepancies between results obtained using this method and those derived from earlier work in which drops fall freely onto a standing surface.Übersicht Es wird eine experimentelle Methode zur Untersuchung des Aufprallens von Flüssigkeitstropfen auf eine Flüssigkeitsoberfläche beschrieben, bei der die flüssige Fläche mit hoher Geschwindigkeit gegen einen stationären Tropfen bewegt wird. Fotos des Aufprallvorgangs bei Geschwindigkeiten von 47,7 m/s mit Tropfen von 0,175 cm Durchmesser werden gezeigt. Weiterhin werden Vorschläge gemacht, wie bei künftigen Untersuchungen ] gewisse Unterschiede in den Ergebnissen nach der hier beschriebenen Methode und bei frei fallenden Tropfen aufgeklärt werden könnten.Acknowledgment is made to Mr. M. J. B. Nash for his assistance in doing the experimental work. This work was carried out at the Royal Aircraft Establishment, Farnborough, Hampshire, England.     

A 17-node quadrilateral spline finite element using the triangular area coordinates

Isopaxametric quadrilateral elements are widely used in the finite element method. However, they have a disadvantage of accuracy loss when elements are distorted. Spline functions have properties of simpleness and conformality. A 17onode quadrilateral element has been developed using the bivaxiate quaxtic spline interpolation basis and the triangular area coordinates, which can exactly model the quartic displacement fields. Some appropriate examples are employed to illustrate that the element possesses high precision and is insensitive to mesh distortions.     

轨道系统高频振动分析的动态子结构法

提出了包含钢轨断面弹性变形、轨下不连续支承、横垂向交叉导的轨道高频振动分析模型。根据轮轨特点,提出适合轮轨高频振动分析的阻抗聚缩法。预测结果与试验结果吻合较好。分析表明约８００Ｈｚ以下,钢轨振动表现为整体振动,再高频率钢轨发生断面弹性变形的振动。我国轨道系统第一、第二、阶二振频率分别为１５０Ｈｚ和３２０Ｈｚ,ｐｉｎｎｅｄ－ｐｉｎｎｅｄ共振频率的１２８０Ｈｚ。