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《应用力学学报》2020,(1)
采用三阶WENO有限差分格式,耦合求解爆轰产物质量分数输运方程与可压缩欧拉方程,并通过建立内能与热容之间的关系求得瞬态温度,自主开发密闭空间内炸药爆炸温度场三维数值计算程序。基于所开发的程序开展密闭空间内炸药爆炸温度场数值计算,初步探讨内爆炸温度场演化过程及其分布规律。研究表明:密闭空间内爆炸温度载荷在爆炸初期呈现出多峰值特征,在爆炸后期,逐渐趋近于准静态平稳值,且内爆炸温度场分布具有空间上的不均匀性;数值计算准静态温度与理论计算吻合较好,相对误差控制在1%以内,初步验证了所开发程序的可靠性和正确性。本文的研究可为进一步探讨考虑后燃烧效应爆炸温度场数值计算及毁伤评估提供一定的参考和指导。 相似文献
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本文提出多点线弹簧模型(MPLSM),用于分析沿壳厚应力变化剧烈的三维表面裂纹问题:外场采用三维有限元数值模拟,而在内场以受多个集中力作用的平面应变板条边裂纹为基础,将内场解化为二维问题,同外场进行渐近匹配求解,从而避免了在裂纹尖端附近进行精细的三维有限元的分析。将这一模型编制成相应的计算程序模块,实现了同ADINA&T的装配。就第一类边界条件的热冲击瞬态温度场,本文还给出一种渐近解,在此基础上,求解了圆筒形容器轴向表面裂纹的应力强度因子随时间的变化规律。 相似文献
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在腔体内部有高温流体,其外壳等固体材料的物性温度而为化的瞬态非线性问题中,其边界条件的确定十分困难。本文采用流一固“混合流”模式进行温度场的计算,由于方程计及了瞬态、复杂形状、浮动外边界条件等因系,采用变步长的控制容积法及时域有限元进行计算。对某个高温燃气配气阀的温度场及热变形进行了数值计算,得到与实测相符的结果。 相似文献
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发展了一种用于辐射换热条件下瞬态热一结构分析的空间薄壁杆单元,其截面形式可以是任意形状的闭口截面和单支开口截面。该单元温度场分解为平均温度和多谐摄动温度,沿杆轴方向采用两结点线性插值,沿杆截面周向用三角函数展开,每结点含多个解耦的自由度,其中结点平均温度方程同传统一维温度有限元方程为非线性,各谐摄动温度方程为线性,然后利用Wilson-θ法求解结构的瞬态温度场。本文选择了两节点Bernoulli直梁单元得到准静态热弹性有限元方程并求解,针对非对称开口截面考虑了翘曲变形及弯扭耦合的影响。温度场引起的等效热载荷不仅包括常规的热轴力,还包括热弯矩以及热双力矩。本文针对不同截面形式的粱单元给出了瞬态温度场以及热变形的验证算例,并通过与商业程序中二维壳元计算结果的比较说明了本文所提出方法的正确性和高效性。 相似文献
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研究了一个用于混凝土的基于塑性的损伤模型本构参数辨识问题。把从实验获得的应力-应变曲线与数值计算中获得的应力-应变曲线的差别,作为局部水平上最小二乘法的目标函数。为了求解这个反问题,局部水平上求解损伤弹塑性正问题的子程序被嵌入到本文的反问题的迭代格式之中。灵敏度系数矩阵是通过有限差分方法近似计算得到的。给出的数值计算例子计算了单轴压缩试验结果的参数辨识问题。采用反分析得到的模型参数值,对单向拉伸及三种不同侧压作用下的压缩试验进行了数值模拟。数值结果表明:本文采用的应力反分析计算格式稳定,且具有合理的准确性,数值计算得到的应力-应变结果可以较准确地拟合实验曲线。 相似文献
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This paper is concerned with a method for solving inverse heat conduction problem. The method is based on the controlled random
search (CRS) technique in conjunction with modified Newton–Raphson method. The random search procedure does not need the computation
of derivative of the function to be evaluated. Therefore, it is independent of the calculation of the sensitivity coefficient
for nonlinear parameter estimation. The algorithm does not depend on the future-temperature information and can predict convective
heat transfer coefficient with random errors in the input temperature data. The technique is first validated against an analytical
solution of heat conduction equation for a typical rocket nozzle. Comparison with an earlier analysis of inverse heat conduction
problem of a similar experiment shows that the present method provides solutions, which are fully consistent with the earlier
results. Once validated, the technique is used to investigate another estimation of heat transfer coefficient for an experiment
of short duration, high heating rate, and employing indepth temperature measurement. The CRS procedure, in conjunction with
modified Newton–Raphson method, is quite useful in estimating the value of the convective heat-transfer coefficient from the
measured transient temperature data on the outer surface or imbedded thermocouple inside the rocket nozzle. Some practical
examples are illustrated, which demonstrate the stability and accuracy of the method to predict the surface heat flux. 相似文献
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The inverse problem of determining time-variable surface heat flux in a plane wall, with constant or temperature dependent thermal properties, is numerically studied. Different kinds of incident heat flux, including rectangular waveform, are assumed. The solution is numerically solved as a function estimation problem, so that no a priori information for the functional waveforms of the unknown heat flux is needed. In all cases, a solution in the form of a piece-wise function is used to approach the incident flux. Transient temperature measurements at the boundary, from the solution of the direct problem, served as the simulated experimental data needed as input for the inverse analysis. Both direct and inverse heat conduction problems are solved using the network simulation method. The solution is obtained step-by-step by minimising the classical functional that compares the above input data with those obtained from the solution of the inverse problem. A straight line of variable slope and length is used for each one of the stretches of the desired solution. The influence of random error, number of functional terms and the effect of sensor location are studied. In all cases, the results closely agree with the solution. 相似文献
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PRECISE INTEGRAL ALGORITHM BASED SOLUTION FOR TRANSIENT INVERSE HEAT CONDUCTION PROBLEMS WITH MULTI-VARIABLES 总被引:2,自引:0,他引:2
IntroductionIHCPs (InverseHeatConductionProblems)arecloselyassociatedwithmanyengineeringaspects,andwelldocumentedintheliteratures,coveringtheidentificationsofthermalparameters[1,2 ],boundaryshapes[3],boundaryconditions[4 ]andsource_relatedterms[5 ,6 ]etc .Howeveritseemsthatonlylittleworkisdirectlyconcernedwithmulti_variablesidentificationsbyauthors’knowledge.Tsengetal.presentedanapproachtodeterminingtwokindsofvariables[7],butonlygavefewnumericalexamplestodeterminethemsimultaneously .Thesol… 相似文献
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In this paper, we consider the efficient estimation of local boiling heat fluxes from transient temperature measurements in
the heater close to the heater surface. For accurate prediction, heat flux estimation is formulated as a transient three-dimensional
(3D) inverse heat conduction problem (IHCP). This inverse problem is ill-posed and cannot be treated straightforwardly by
established numerical methods. In order to obtain a regularized stable solution, a large-scale time-dependent PDE-constrained
optimization problem has to be solved and an appropriate stopping criterion for the termination of the iterative solution
process has to be chosen. Since the boiling heat flux is non-uniformly distributed on the heater surface due to the strong
local activity of the boiling process, the use of a fixed uniform spatial discretization is not efficient. Instead, an adaptive
mesh refinement strategy can be used to obtain an appropriate discretization which significantly reduces the total computational
effort. In this work, we present an automatic algorithm incorporating an adaptive mesh refinement via a heat flux-based a-posteriori
error estimation technique. The suggested algorithm can cope with both spatially point-wise or highly resolved temperature
observations efficiently. It is applied to real measurement data obtained from two different types of pool boiling experiments.
The numerical results show that the computational effort can be reduced significantly for given estimation quality. This adaptive
IHCP solution technique can be also viewed as an efficient soft sensor to deduce unmeasurable local boiling heat fluxes. 相似文献
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热流密度点测量结果并不能完全反映详细的热流分布特征, 尤其是针对热流梯度较大、热流分布复杂的区域, 需要热流密度场测量技术以获取全场精细的热流分布特征. 应用温敏漆测量热流密度场的方法得到了广泛应用, 但实验条件来流总温较低, 与真实飞行环境存在明显差异, 真实飞行条件下的辐射效应严重限制了温敏漆技术的应用. 针对高超声速高焓条件下缺乏热流密度场测量方法的难题, 提出了内嵌式温敏漆测量方法, 基本思想是利用温敏漆测量内壁面温度的变化历程结合热传导反问题的求解确定热流密度. 本文详细介绍了内嵌式温敏漆测量方法的测量原理、测量系统构成、数据处理方法、设计原则及该测量方法的优势. 针对高超声速风洞实验中常见的阶跃、线性和局部突变等热流密度分布进行了数值验证, 验证了内嵌式温敏漆测量方法的可行性, 并分析了风洞实验温度测量精度及噪声对测量结果的影响. 内嵌式温敏漆测量方法可用于测量高超声速真实飞行环境下细致的气动热特征, 扩展了温敏漆测量方法的应用范围, 解决了高超声速高焓条件下缺乏热流密度场测量方法的难题. 相似文献
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基于状态空间理论研究功能梯度圆球的球对称瞬态热传导问题。根据热传导方程和热流密度的定义,取温度场和热流密度为系统的状态向量,通过将圆球分层和在时域内应用差分格式对控制方程进行离散,建立了系统的状态方程,给出了功能梯度圆球瞬态热传导问题的半解析解。算例分析表明:本文解不但结果正确、计算效率高,而且适用于材料参数沿径向任意梯度变化的圆球瞬态热传导分析。 相似文献
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带源参数的二维热传导反问题的无网格方法 总被引:1,自引:1,他引:1
利用无网格有限点法求解带源参数的二维热传导反问题,推导了相应的离散方程. 与
其它基于网格的方法相比,有限点法采用移动最小二乘法构造形函数,只需要节点信息,不
需要划分网格,用配点法离散控制方程,可以直接施加边界条件,不需要在区域内部求积分.
用有限点法求解二维热传导反问题具有数值实现简单、计算量小、可以任意布置节点等优点.
最后通过算例验证了该方法的有效性. 相似文献
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二阶非定常多宗量热传导反问题的正则解 总被引:1,自引:0,他引:1
引入Bregman距离函数及其加权函数作为正则项,应用Tikhonov正则
化方法,对二阶非定常多宗量热传导反问题进行求解. 利用测量信息和计算信息构造最小二
乘函数,将多宗量反演识别问题转化为一个优化问题. 空间上采用8节点等参元进行离散,
时域上采用时域精细算法进行离散,建立了二阶非定常多宗量热传导问题的有限元正/反演数
值模型. 该模型不仅考虑了非均质和参数分布的影响,而且也便于正反演问题的敏度分析,
可对导热系数和边界条件等宗量进行有效的单一和组合识别. 给出了相关的数值验证,对信
息测量误差以及不同正则项的计算效率作了探讨. 数值结果表明,该方法能够对二阶非定常
多宗量热传导反问题进行有效的求解,并具有较高的计算精度. 相似文献
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The inverse heat conduction problem (IHCP) is a severely ill-posed problem in the sense that the solution ( if it exists) does not depend continuously on the data. But now the results on inverse heat conduction problem are mainly devoted to the standard inverse heat conduction problem. Some optimal error bounds in a Sobolev space of regularized approximation solutions for a sideways parabolic equation, i. e. , a non-standard inverse heat conduction problem with convection term which appears in some applied subject are given. 相似文献
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In an attempt to minimize the numerical computations associated with the solution of transient heat conduction with radiation
in a slab, a perturbation type of analysis is being applied to the temperature field and radiation heat flux simultaneously.
The resulting partial differential equations for the perturbation functions for the temperature are solved in explicit forms
by use of the energy integral methods, while the radiation heat flux is determined by an appropriate scheme of approximating
the temperature distribution in the slab. Included in the analysis are the effects of the parameters: the optical thickness,
the ratio of conduction transport to radiation and the wall emissivity. It is found that, in a wide range of these governing
parameters, the results compare very favorably with those obtained by the numerical solution of the formulated integro-differential
equation. With the present analysis, the temperature, conduction and radiation heat fluxes can be predicted without resorting
to lengthy numerical analysis. 相似文献