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采用短脉冲激光加热浸没在丙酮液池的铂薄膜电阻的方法,以及高压电火花单次放电高速照相技术,在国内首次建立了超急速爆发实验台,达到了微秒级的温度频响和2×106帧/s的高速照相.研究发现,随着激光热流密度增加,试件表面温度快速升高到一饱和值,与过热液体的动力学理论极限温度非常接近.拍摄到了与常规沸腾很不相同的蘑菇云式爆发沸腾照片.试件表面及临近表面的微薄液层内瞬间爆发生成大量大小相当的细小汽泡,汽泡脱离直径远低于经典Fritz公式计算值,上浮速度先快后慢. 相似文献
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瞬态温度场有限元法求解的研究 总被引:3,自引:1,他引:2
介绍了瞬态热分析的定义和步进积分的特点;研究了两点时问差分格式的瞬态导热温度场有限元法数值解的稳定性和振荡现象;比较和分析了几种差分格式的特点,并应用算例对几种差分算法进行了验证;总结说明了几种差分算法在实际当中的应用。 相似文献
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We examine two key stochastic processes of interest for warranty modeling: (1) remaining total warranty coverage time exposure and (2) warranty load (total items under warranty at time t). Integral equations suitable for numerical computation are developed to yield probability law for these warranty measures. These two warranty measures permit warranty managers to better understand time‐dependent warranty behavior, and thus better manage warranty cash reserves. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005. 相似文献
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The (standard) randomization method is an attractive alternative for the transient analysis of continuous time Markov models. The main advantages of the method are numerical stability, well‐controlled computation error, and ability to specify the computation error in advance. However, the fact that the method can be computationally very expensive limits its applicability. In this paper, we develop a new method called split regenerative randomization, which, having the same good properties as standard randomization, can be significantly more efficient. The method covers reliability‐like models with a particular but quite general structure and requires the selection of a subset of states and a regenerative state satisfying some conditions. For a class of continuous time Markov models, model class C2, including typical failure/repair reliability‐like models with exponential failure and repair time distributions and deferred repair, natural selections are available for both the subset of states and the regenerative state and, for those natural selections, theoretical results are available assessing the efficiency of the method in terms of “visible” model characteristics. Those results can be used to anticipate when the method can be expected to be competitive. We illustrate the application of the method using a large class C2 model and show that for models in that class the method can indeed be significantly more efficient than previously available randomization‐based methods. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006 相似文献
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带空气室脉冲水射流系统通用分析法 总被引:1,自引:0,他引:1
针对所提出的用空气室引发水力共振以增强脉冲水射流的设想,应用水力瞬变特征线解法,建立系统的数学模型,差分网格只取脉冲源、空气室和喷嘴3个边界点,采用变时步法解算。这种方法具有灵活性大、受限制小、便于使用的突出优点。 相似文献
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研究了履带车辆主离合器瞬时转速测试方法,在数据处理过程中两次运用样条插值算法,较好地解决主、被部分实测转速精度低及转速数据长度不一致的问题,得到较为理想的瞬时转速曲线。 相似文献
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通过对有脱空缺陷的方钢管混凝土柱试件进行瞬态冲击作用下的检测试验,提出了根据振动信号频率变化、频谱峰值和WVD时频分布中频率的时间连续性等特征来进行脱空检测的新方法。基于WVD时频分布特性,提出了使用平均频率作为脱空判别指标。结果表明:当方钢管混凝土柱存在脱空,振动信号的平均频率发生明显降低,频谱图中频率成分简单,归一化频谱峰值高,在WVD时频分布三维图上呈现沿时间轴连续的偏平峰。说明该方法对检测方钢管混凝土柱脱空具有一定的有效性。 相似文献
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本文给出了一种求解一维结构瞬态响应问题的解析方法。通过对控制方程及其定解条件进行Laplace变换,将问题写成状态空间形式,用传递函数法求得统一形式的解析解。通过Laplace逆变换求得结构在时域内的瞬态响应。文中给出了一些一维结构动力响应问题的算例。 相似文献
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采用有限差分格式的特征线方法 ,对某姿控推进系统发动机真实推进剂管路在脉冲工作情况下的瞬变特性进行了数值研究 ,对影响发动机多次脉冲启动的重要参数进行了定量计算 ,对比分析了试验结果与计算结果的一致性。说明该方法可方便地对包括许多管路、阀门和推力室的复杂系统进行动态性能分析 ,所得结果对于液体火箭发动机管路工程设计具有重要参考价值 相似文献