高速三维边界层稳定性问题的数值方法

本文把四阶精度紧致差分格式用于求解声速、高超声速三维边界层稳定性问题。提出了适用地求解高速边界层特征值问题的Ｃｈｅｂｙｓｈｅｖ多项式配置点方法,并将各种数值方法进行了比较。数值结果表明上述两种方法是求解高速三维边界层稳定性问题的有效数值方法。     

压气机转子叶片的气动弹性数值模拟

采用了交替迭代算法,对某压气机转子叶片进行了气动弹性数值模拟.自行开发了基于有限元的结构求解器用于结构动力学求解,引用他人开发的非定常流体求解器用于气动力的求解.结构求解器提供叶片的表面位移给流体求解器以改变流场,流体求解器提供气动载荷给结构求解器来计算叶片的变形,界面处理系统在这两个求解器之间进行信息传递.算例表明,这种交替迭代算法在气动弹性数值模拟中是可行的,可以得到叶片的瞬态响应,从而判断叶片是否发生颤振.      

角速率输入下的四元素微分方程算法研究

四元素法是求解刚体定点转动问题的有力数学工具.文中对一种传统的求解四元素微分方程三阶算法进行改造,将其用于四元素微分方程求解,并对其在捷联惯性导航系统姿态矩阵实时求解中的应用进行了仿真.结果表明,这种方法应用于四元素微分方程求解时,精度比经典的三阶数值解法提高大约四倍,对于提高捷联惯性导航系统姿态计算的精度有重要意义.     

弹性环式挤压油膜阻尼器减振机理研究（2）—弹性环式挤压油膜阻尼器油膜力特性的求解

分析了弹性环式挤压油膜阻尼器 (ERSFD)油膜压力场控制方程的求解 ,导出了求解ERSFD油膜压力场 (包括油膜刚度和油膜阻尼等 )的超松弛差分迭代格式和算法 ,结合弹性环的变形位移求解算法 ,编制了计算ERSFD油膜力特性的计算程序 ,并将该算法和程序用于某发动机机之ERSFD的油膜力特性的计算。     

全变差正则化方法对一类热传导反问题的应用

热传导终端反问题是典型的不适定问题,应用基于全变差的正则化方法来获得它的稳定数值解,将近似解的求解范围由连续函数空间扩大到了有界变差函数空间,并将固定点迭代法用于求解非线性的Euler方程,并进行了理论分析和数值实验。结果表明:该方法与算法具有高效稳定全局收敛等优点。     

预测控制综合设计算法设计及软件实现

预测控制综合设计方法通过设计一组满足特定要求的终端约束条件来保证系统的稳定性.给出了一组满足该要求的终端约束条件,然后依据多参数二次规划法求解预测控制器的基本思路,在Matlab环境下设计并实现了一个预测控制综合方法的控制器求解软件,最后通过一个仿真实验验证了该软件的基本功能.仿真结果表明,所设计的软件可以用于求解基于...     

弹塑性接触问题边界元缩聚法分析

给出了利用隐含对称条件的二维弹塑性边界元分析公式,并应用于弹塑性接触问题分析。根据接触条件列出了弹塑性接触问题迭代求解的耦合方程。利用接触问题局部非线性的特点,将缩聚法用于迭代求解。基于拟线性、双重迭代法的思想,解决了两重非线性相耦合的问题。最后给出了一个算例。     

基于混沌蚁群算法的应急物流路径优化算法

以医疗器械应急物流配送为研究对象,以配送时间最短为研究目标,建立了医疗器械应急物流配送路径优化的数学模型,并将混沌蚁群算法用于模型求解,给出了求解步骤。经计算机仿真表明,与基本蚁群算法相比,混沌蚁群算法优化质量明显改善,有效缩短了应急配送时间,提高了医疗器械应急物流的配送效率。     

跨声速风扇的流固耦合的颤振分析(英文)

发展了时间推进的叶片颤振的数值方法,采用了时间推进求解流体和固体相互作用的过程。气动模型是基于求解三维雷诺平均的N-S方程,采用了多块结构化网格的有限体积格式,对流和耗散通量的计算使用了二阶迎风格式和中心格式。在变形的动网格上流体运动的守恒型方程的求解采用双时间步,隐式格式和多重网格方法。叶片振动采用了振型叠加的线性气动弹性模型。该方法在气动弹性标准算例4进行了验证,并用于求解跨音速风扇的颤振问题。     

工程设计的求解方法

本讲讨论创造性思维的方法、主要特点及由创造性思维而表现出来的各种创造能力，讨论如何将创造性思维用于工程设计问题的求解，并分自由联想和结构化两大类讨论多种求解方法。     

基于传热反问题方法的N_2O/C_2H_4预混推进剂燃烧室热流测量研究

测量液体火箭发动机的热载荷是获取燃烧室内部信息的重要方法。为了获取N_2O/C_2H_4预混推进剂燃烧室内壁的热载荷,建立了液体火箭发动机的热流计算的反问题方法,该方法基于对燃烧室壁面温度场的直接求解,通过对轴向多个位置测量温度的反演计算得到燃烧室内壁热流和温度。研究表明:应用文中建立的传热反问题方法能够较为准确地获得热流随时间及空间的分布;热电偶的位置对计算准确性有明显的影响,与理论深度偏差在0.2mm以内的随机深度偏差可导致超过4%热流反演误差;N_2O/C_2H_4预混推进剂燃烧室热流及温度沿轴向逐渐降低,表明燃烧室内的反应释热过程主要在燃烧室头部附近发生。     

利用边界测点求解二维稳态导热逆问题

针对导热逆问题求解中的测点的选择提出了不同的方式,即采用边界测点取代内部测点进行导热逆问题的求解.通过数值计算揭示了测点选择不当将导致逆问题计算的失败及原因,验证了采用边界测点求解二维稳态导热逆问题的可行性.采用本文提出的方式将使逆问题的应用更为实际、合理.     

Non-Fourier heat conduction analysis of a 2-D plate with inner cracks at arbitrary direction angles

This paper investigates the problem of a 2-D plate containing internal cracks at arbitrary angles to the heating surface under thermal shock. The finite difference method is applied to solve the temperature distribution and a difference scheme of the oblique crack is developed. For the first time, a non-Fourier heat transfer analysis method of a 2-D plate with inner cracks at arbitrary direction angles is established. Specifically, for a strip with an inner crack paralleling to the surface,numer...     

多孔介质有效导热系数的计算方法

高孔隙率多孔介质如泡沫陶瓷在新型多孔介质燃烧器技术中应用日益广泛,其重要传热特性参数--有效导热系数反映了两相流气、固相导热、对流和辐射的综合效应,对其研究尚非常缺乏.本文基于实验测定的温度分布,给出多孔介质有效导热系数的初始估值,用有限体积法求解二维控制方程,采用二维寻优搜索的办法,确定使测定点上测量与计算温度均方根误差为最小的径向与轴向有效导热系数,是一种逆计算方法.对球粒子颗粒床进行的有效性试验证明了方法的可行性.     

金属蜂窝夹芯面板有效导热系数的数值计算

对具有漫灰体内壁的金属蜂窝夹芯面板,忽略蜂窝内腔的空气导热,综合考虑蜂窝结构的热传导和热辐射等热传递过程,利用有限元方法求解了周期性分布的蜂窝单胞稳态热传导控制方程,蜂窝内壁的边界条件是由净热量法得到的热辐射换热积分方程,由胞元的温度场分布数据及Fourier定律得到了蜂窝结构的有效导热系数。与现有文献相比,采用了较少近似的模型及较高精度的离散方法,计算结果表明计算模型及方法是可靠有效的。     

换热反问题输入数据的正则预处理及其对解的影响

ＲＥＧＵＬＡＲＩＺＡＴＩＯＮＰＲＯＣＥＳＳＩＮＧＯＦＩＮＰＵＴＤＡＴＡＩＮＩＮＶＥＲＳＥＨＥＡＴＴＲＡＮＳＦＥＲＰＲＯＢＬＥＭＡＮＤＩＴＳＩＮＦＬＵＥＮＣＥＯＮＴＨＥＳＯＬＵＴＩＯＮＺｈｏｕＪｉｎｇｗｅｉａｎｄＣｈｅｎｇＳｈａｎｇｍｏ（Ｄｅｐｔ．ｏｆ...     

屏蔽式总温热电偶的稳态误差分析及改型设计

针对航空发动机排气温度高精度测试的需求,采用流热耦合的数值模拟方法研究了某型屏蔽式热电偶在马赫数为0.2、0.3、0.4、0.5、0.6五种工况下的速度误差、导热误差、辐射误差的大小和变化趋势,以及偶丝长径比、屏蔽罩进出口面积比对屏蔽式热电偶稳态误差的影响规律。结果表明:在马赫数小于0.3工况下,辐射误差占总误差的比例最高;而在马赫数为0.6工况下,导热误差成为影响测温精度的最主要因素;合理地增加偶丝长径比能显著地降低导热误差,减小进出口面积比值会使速度误差增大辐射误差减少;因此,存在最佳的进出口面积比使得总稳态误差最小。最后选取了偶丝长径比为12,屏蔽罩进出口面积比为6对原屏蔽式热电偶进行了改型设计,使该屏蔽式热电偶的总稳态误差降低50%以上。      

Exact analytical solutions of a nonlinear nonstationary inverse problem of heat conduction for a body with low heat conduction coefficient

The analytical solution of a nonlinear nonstationary inverse problem of heat conduction for a bodies with low heat conduction coefficients of one-dimensional geometry is presented. The solutions obtained make it possible to restore the boundary conditions rather exactly using the results of heat flux measurements.     

On near wall measurements of wall bounded flows—The necessity of an accurate determination of the wall position

The present review paper is an account on the experimental determination of the wall position relative to the probe in wall-bounded turbulent flow studies. A thorough review on common measurement techniques as well as correction methods reveals, that there are a number of pitfalls, that—when not accounted for—can lead to wrong conclusions about the wall position and thereby also on the near-wall behaviour of mean and turbulence quantities. Employing the state-of-the-art databases from direct numerical simulations of wall-bounded turbulent flows various indirect methods have been tested and assessed in terms of their robustness and accuracy. It is also demonstrated that accurate measurements reaching the viscous sublayer are necessary in order to ensure a correctly deduced wall position, and dependent quantities as for instance the near-wall scaling of mean (e.g. Reynolds number dependence of the buffer region or the log law constants) and turbulence (e.g. the near-wall peak location of Reynolds stresses) quantities.In experiments using hot-wires near the wall it is well known that heat conduction between the hot-wire and the wall gives errors and mean velocity data from the viscous sublayer can usually not be used to determine the wall position. In this paper we introduce a new method which takes advantage of the similarity of the probability density distributions (pdf) in the near wall region. By using the high velocity data of the pdf, which is shown not to be affected by heat conduction, the heat conduction problem can be circumvented.Extensive appendices are included, describing the history and present knowledge about the scaling of the mean velocity in the near wall and overlap regions in wall bounded turbulent flows.     

Calculation of high-temperature insulation parameters and heat transfer behaviors of multilayer insulation by inverse problems method

In the present paper, a numerical model combining radiation and conduction for porous materials is developed based on the finite volume method. The model can be used to investigate high-temperature thermal insulations which are widely used in metallic thermal protection systems on reusable launch vehicles and high-temperature fuel cells. The effective thermal conductivities（ECTs） which are measured experimentally can hardly be used separately to analyze the heat transfer behaviors of conduction and radiation for high-temperature insulation. By fitting the effective thermal conductivities with experimental data, the equivalent radiation transmittance, absorptivity and reflectivity, as well as a linear function to describe the relationship between temperature and conductivity can be estimated by an inverse problems method. The deviation between the calculated and measured effective thermal conductivities is less than 4%. Using the material parameters so obtained for conduction and radiation, the heat transfer process in multilayer thermal insulation（MTI） is calculated and the deviation between the calculated and the measured transient temperatures at a certain depth in the multilayer thermal insulation is less than 6.5%.