船舶碰撞的研究方法和进展

本文简要评述船舶碰撞的研究进展和发展趋势。介绍了船舶碰撞研究的内容和方法（包括理论的和实验的）。本文重点阐述实船试验方法，包括实尺试验的基本步骤，实尺试验的输入参数选择和试验地点选择。最后提出了综合性意见，并介绍了国内在碰撞研究方面已做的工作和将要做的工作。     

液压节制杆式模拟汽车碰撞吸能装置研究

提出了一种新型液压节制杆式模拟汽车碰撞吸能装置，并对它的基本结构和工作原理进行了分析，给出较实用的力学模型和节制杆设计方法，试验结果表明，该吸能装置可以很好地再现实车碰撞过程中的速度和加速度变化过程，为车辆被动安全系统的研究提供实验手段，该方法也可用来设计其它缓冲控制装置。     

船舶工程中的力学问题

简要介绍了船舶工程的发展概况，重点介绍了船舶工程结构中的一些主要力学问题，包括船舶稳定性、推进的运动与阻力分析、船舶与海洋结构物的水动力学、静动强度问题、介绍了随机响应分析的概率方法和上述结构的可靠性分析，对21世纪船舶工程面临的挑战以及我国在该领域内的发展前景作了展望．     

结构碰撞的动力响应分析

本文研究结构在动力作用下发生碰撞时的动力响应的分析方法，其中碰撞包括结构与刚（弹）性性支座的碰撞和两个结构物之间的碰撞；碰掸的速度假定为中低速度分析时不考虑局部的破坏问题，本文方法的关键点是提出了碰撞过程中的碰撞反力的模拟表达式。它是通过碰撞时结构与碰撞物体的碰撞力和碰撞变形关系的假定，并利用非完全弹性碰撞过程，当然也可考虑结构阻尼的影响。文末给出了几个算例，其中与有解析解的做了比较，符合得很好。     

基于能量原理确定系泊碰撞载荷的有限元法

准确地确定出船舶系泊时的撞击载荷, 对船舶及海洋平台的强度研究都是极其重要的. 提出了通过能量原理和有限元分析确定系泊撞击载荷的方法. 碰撞时, 动能和变形能满足能量守恒, 动能是包括附连水质量在内的船体总动能, 此动能在撞击时转化为变形能, 根据变形能与载荷的关系, 求出碰撞载荷. 通过具有碰撞载荷理论解的梁的验证, 表明该方法是完全可行的. 为实际工程提供了确定护舷撞击力的理论依据和计算方法.     

桥梁结构地震碰撞问题理论分析模型及试验研究进展

介绍了桥梁结构地震碰撞效应理论分析模型及相关试验研究的最新进展情况。对最近30年来的强地震中发生的桥梁结构地震碰撞损坏现象进行了回顾,评述了已经发展的各种桥梁地震碰撞作用模拟方法,主要分为恢复系数法和接触单元法两类;其中接触单元法又包括线性弹簧单元模型、Kelvin模型、Hertz模型、Hertz-damp模型、改进的Hertz-damp模型以及三维接触-摩擦模型。同时又介绍了有关结构地震碰撞的试验研究进展情况并展望了有待进一步研究的问题。     

两自由度振动系统的斜碰撞分析

研究斜碰撞振动系统动力学的一个关键问题是对系统在碰撞前后的状态进行合理描述和正确计算．针对两弹性体斜碰撞问题，基于瞬间碰撞假设，提出了采用步进冲量来分析和求解斜碰撞前后的状态关系；并以弹簧摆和振子组成的两自由度斜碰撞振动系统为例，具体介绍了该算法如何实现．用解析方法讨论了该系统在斜碰撞过程中可能出现的各种力学现象，将冲量步进算法得到的数值解与解析结果进行对比，取得了完全一致的结果．该数值方法能适应多种斜碰撞问题的计算．     

船舶兴波理论

本文评述了船舶兴波理论的发展概况,及其在船舶工程设计中的应用情况。讨论了船舶兴波理论研究的难点。指出了船舶兴波问题理论研究与试验研究相结合的重要性,波形测量分析工作的意义,有限元数值计算方法在船舶兴波非线性理论中的发展,并讨论了粘性流体兴波理论中的碎波理论和奇异波理论。     

结构碰撞的动力响应分析

本文研究结构在动力作用下发生碰撞时的动力响应的分析方法。其中碰撞包括结构与刚（弹）性支座的碰撞和两个结构物之间的碰撞；碰撞的速度假定为中低速度，分析时不考虑局部的破坏问题。本文方法的关键点是提出了碰撞过程中的碰撞反力的模拟表达式。它是通过碰撞时结构与碰撞物体的碰撞力和碰撞变形关系的假定，并利用能量守恒原理，动量守恒原理和冲量定理建立的，既可描述完全弹性碰撞过程也可描述非完全弹性碰撞过程，当然也可考虑结构阻尼的影响。文末给出了几个算例，其中与有解析解的做了比较，符合得很好；至于没有解析解可比较的，在理论上也是合理的，算法上采用了中央差分的逐步积分法，在碰撞过程中采用非常小的积分步长，获得了预想的理想结果。     

卷弧翼气动特性研究进展

本文列举了卷弧翼在战术武器中的应用实例，介绍了卷弧翼的几何特性、气动特性、优缺点及布局设计，评述了对卷弧翼气动特性所做的理论与试验研究工作。最后指出了有待进一步研究的问题。     

Computation of the stability derivatives via CFD and the sensitivity equations

The method to calculate the aerodynamic stability derivates of aircrafts by using the sensitivity equations is ex- tended to flows with shock waves in this paper. Using the newly developed second-order cell-centered finite volume scheme on the unstructured-grid, the unsteady Euler equations and sensitivity equations are solved simultaneously in a non-inertial frame of reference, so that the aerodynamic stability derivatives can be calculated for aircrafts with complex geometries. Based on the numerical results, behavior of the aerodynamic sensitivity parameters near the shock wave is discussed. Furthermore, the stability derivatives are analyzed for supersonic and hypersonic flows. The numerical results of the stability derivatives are found in good agree- ment with theoretical results for supersonic flows, and variations of the aerodynamic force and moment predicted by the stability derivatives are very close to those obtained by CFD simulation for both supersonic and hypersonic flows.     

翼型跨声速气动特性的不确定性及全局灵敏度分析

针对马赫数和仰角的随机不确定性会导致气动性能波动的现象, 采用非嵌入式的混沌多项式方法对绕NACA0012 翼型跨声速随机气动特性进行不确定性及全局灵敏度分析. 具体分析了飞行状态的不确定性对气动载荷分布、流场及气动力系数的影响并通过全局灵敏度分析找出重要因素. 不确定性分析结果表明翼型上表面的激波以及激波后分离泡是造成气动性能剧烈波动的主要原因. 灵敏度分析结果表明在跨声速区域马赫数对激波处气动性能影响最大, 此外, 虽然马赫数和仰角相互耦合作用对气动力系数贡献比较小, 但对于激波位置处的流场, 这种互耦合作用不可忽略.     

平流层飞艇空气动力估算

本文采用有限基本解方法与工程估算方法相结合的气动力工程计算方法,用以计算平流层飞艇的气动力。将飞艇所受的气动力分成飞艇艇身和尾翼所受气动力两部分,每一部分的气动力按照无粘性流产生的线性气动力和粘性引起的非线性气动力分别进行计算。根据势流理论对飞艇艇身线性气动力进行分析计算,由于飞艇艇体是旋成体,故根据Allen的横流阻力理论对其所受的非线性气动力进行计算;尾翼的线性气动力采用有限基本解方法进行计算,非线性气动力用Polhamus-Lamar吸力比拟方法估算。该方法中考虑了由于尾翼安装在体上后,处于艇体产生的上洗流场中,尾翼气动力的变化和尾翼对艇身气动力的干扰作用。通过算例的计算与实验结果比较得出该方法可以快速、准确的计算飞艇所受的气动力。     

平流层飞艇气动参数辨识

进入21世纪以来，随着科技的飞速发展，世界上掀起了研究和开发平流层平台的热潮。飞艇作为平流层平台可以实现无线通信、空间观测、大气测量以及军事侦查等目的。本文首先将飞艇所受的气动力分成由于来流速度产生的定常气动力和飞艇转动引起的非定常气动力两部分，通过理论分析建立了飞艇的气动力模型，从而得到需要辨识的气动参数。其次建立了以浮心为原点的六自由度非线性动力学模型和一种基于混合遗传算法的气动力系数辨识方法——混合遗传算法（遗传算法＋单纯型法）与极大似然法相结合的方法，并利用该方法对飞艇的气动参数进行辨识。通过仿真结果验证了该方法实用性和有效性。最后通过对气动参数的准确值与辨识值的分析比较，得出各个参数对飞艇运动性能的影响情况。     

Direct,adjoint and mixed approaches for the computation of Hessian in airfoil design problems

In this paper, four approaches to compute the Hessian matrix of an objective function used often in aerodynamic inverse design problems are presented. The computationally less expensive among them is selected and applied to the reconstruction of cascade airfoils that reproduce a prescribed pressure distribution over their walls, under inviscid and viscous flow considerations. The selected approach is based on the direct sensitivity analysis method for the computation of first derivatives, followed by the discrete adjoint method for the computation of the Hessian matrix. The applications presented in this paper show that the Newton method, based on exact Hessian matrices, outperforms other gradient‐based algorithms such as steepest descent or BFGS algorithm. Copyright © 2007 John Wiley & Sons, Ltd.     

Wake impacts on aerodynamic and aeroelastic behaviors of a horizontal axis wind turbine blade for sheared and turbulent flow conditions

The magnitude and temporal variations of wind speed considerably influence aerodynamic and structural responses of MW-sized horizontal axis wind turbines. Thus, this paper investigates the variations in airloads and blade behavior of a wind turbine blade resulting from operations in sheared and turbulent flow conditions. First, in order to validate the present methods, comparisons of aerodynamic results were made among the blade element momentum method, free-wake method, and numerical results from the previous studies. Then, the validated methods were applied to a national renewable energy laboratory 5 MW reference wind turbine model for fluid–structure interaction analyses. From the numerical simulations, it can be clearly seen that unfavorable airloads and blade deformations occur due to the sheared and turbulent flow conditions. In addition, it is clear that wake impacts are not as substantial at those of high wind speeds; however, the effects obviously affect the aerodynamic and structural behaviors of the blade at lower wind speeds. Therefore, it is concluded that the numerical results markedly indicate the demand for accurate assessment of wake dynamics for accurate estimations of the aerodynamic and structural responses for sheared and turbulent flow environments.     

弹射救生高速气流吹袭防护气动特性数值模拟

对弹射救生中高速气流吹袭防护装置对人椅系统气动特性影响进行了数值模拟.采用基于面的有限体积方法求解N-S方程,空间离散采用中心格式,时间离散采用五步显式Runge-Kutta方法.基于Spalart-Allmaras(S-A)紊流模型的DES方法,数值模拟了人椅系统在马赫数0.6、迎角-90°～90°的气动特性,获得了与风洞试验结果较为吻合的计算结果.对有无导流挡板和抬腿机构人椅系统的气动特性及飞行员胸腹部表面压力分布进行比较,结果显示两种防护装置均可有效改善人椅系统的气动特性,不同程度降低飞行员胸腹部所承受的气动力,充分说明高速气流防护装置的有效性.为进一步研究高速气流防护装置提供参考.     

Calculation of nonlinear aerodynamic characteristics of a wing using a 3‐D panel method

The nonlinear aerodynamic characteristic of a wing is investigated using the frequency‐domain panel method. To calculate the nonlinear aerodynamic characteristics of a three‐dimensional wing, the iterative decambering approach is introduced into the frequency‐domain panel method. The decambering approach uses the known nonlinear aerodynamic characteristic of airfoil and calculates two‐variable decambering function to take into consideration the boundary‐layer separation effects for the each section of the wing. The multidimensional Newton iteration is used to account for the coupling between the different sections of wing. The nonlinear aerodynamic analyses for a rectangular wing, a tapered wing, and a wing with the control surface are performed. Present results are given with experiments and other numerical results. Computed results are in good agreement with other data. This method can be used for any wing having different nonlinear aerodynamic characteristics of airfoil. The present method will contribute to the analysis of aircraft in the conceptual design because the present method can predict the nonlinear aerodynamic characteristics of a wing with a few computing resources and significant time. Copyright © 2007 John Wiley & Sons, Ltd.     

Nonlinear airship aeroelasticity

The aeroelastic derivatives for today's aircraft are calculated in the concept phase using a standard procedure. This scheme has to be extended for large airships, due to various nonlinearities in structural and aerodynamic behaviour. In general, the structural model of an airship is physically as well as geometrically nonlinear. The main sources of nonlinearity are large deformations and the nonlinear material behaviour of membranes. The aerodynamic solution is also included in the nonlinear problem, because the deformed airship influences the surrounding flow. Due to these nonlinearities, the aeroelastic problem for airships can only be solved by an iterative procedure. As one possibility, the coupled aerodynamic and structural dynamic problem was handled using linked standard solvers. On the structural side, the Finite-Element program package ABAQUS was extended with an interface to the aerodynamic solver VSAERO. VSAERO is based on the aerodynamic panel method using potential flow theory. The equilibrium of the internal structural and the external aerodynamic forces leads to the structural response and a trimmed flight state for the specified flight conditions (e.g. speed, altitude). The application of small perturbations around a trimmed state produces reaction forces and moments. These constraint forces are then transferred into translational and rotational acceleration fields by performing an inertia relief analysis of the disturbed structural model. The change between the trimmed flight state and the disturbed one yields the respective aeroelastic derivatives. By including the calculated derivatives in the linearised equation of motion system, it is possible to judge the stability and controllability of the investigated airship.     

大型飞机气动载荷向有限元节点等效分配的方法

将气动载荷分配到有限元节点上是工程实际中的一项重要而繁琐的工作.对于二维的翼面气动载荷,根据原始的气动压力点的压力值,采用样条曲面拟合的方法,拟合得到翼面压力分布曲面,由该曲面得到有限元节点上的压力值,再在有限元模型单元上积分得到有限元节点载荷供强度设计使用.大型飞机具有复杂的增升装置,增升装置的气动载荷可能是三维的,对于三维的翼面载荷,直接在气动网格上积分得到气动载荷的小块集中力,然后按照沿某一方向投影的方法,找到该集中力作用的单元,最后按照二次规划的方法,将其分配到有限元节点上.