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《应用力学学报》2019,(3)
突然对称扩散水跃被广泛地应用于实际工程。本文研究了突然扩散水跃方程及它的近似解特性,应用动量守恒原理推导了突然扩散水跃共轭水深关系式。通过级数展开处理,获得了突然扩散水跃方程的近似解,给出了确定有关参数的经验公式。不同突扩比时突然扩散水跃方程的近似解与实验结果的平均误差为5.642%,可见与实验结果吻合较好。另外,将近似解应用到矩形渠槽的水跃,结果说明与实验的平均误差为1.943%。在稳定水跃范围内,与矩形明渠水跃典型理论解的最大误差为1.2%。近似解能很好地与理论解及实验一致,这说明水跃方程近似解具有较高的精度,是可靠的。本文近似解可以应用到计算工程问题。 相似文献
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本文在Hung 提出的剪切干涉术的基础上,用散斑剪切干涉法测量了物体的曲率,其结果与Subra-manian 所得到的结果基本一致.并且用其测试了悬臂梁的受集中力作用后的曲率分布情况,理论解与实验值吻合得较好. 相似文献
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本文讨论了激光散斑照相术在测量密度(或温度)扬中的应用。提出了激光散斑——纹影干涉仪的光学系统,可在同一瞬时得到一张散斑图和一张差分干涉图。对沿竖直加热平板自然对流的温度边界层进行了定量地测量。从散斑图和从干涉图中获得的实验结果符合极好。为了说明本方法的应用范围,对一个非稳定的波动甚大的本申灯火焰进行了测量。实验结果表示,激光散斑照相术更适于研究湍流场,因为干涉术在这种情况下已失去其定量计量的作用。 相似文献
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纯滑动点接触弹流润滑反常现象的理论分析 总被引:4,自引:3,他引:1
对点接触纯滑动弹流润滑进行了理论分析 ,应用“温度 -粘度楔”机理给出了关于 Kaneta等在光干涉弹流实验中观察到的油膜局部增厚的反常现象的合理解释 .数值解说明上述实验中固体表面出现凹陷主要是因热效应所致 . 相似文献
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本文从实验上和理论上研究了液滴和固体表面碰击时的流体动力学特性,测定了液滴在表面上的瞬时扩展半径,利用能量分析法建立了液滴碰击后的扩展模型。由数值解得出的计算值与实验结果能较好地符合。 相似文献
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A method is developed to solve elliptic singular perturbation problems. Examples are presented in one and two dimensions for both linear and non-linear problems. In particular, examples are presented for fluid flow problems with boundary layers. In the one-dimensional case an approximating equation is developed using just three points. The method first presented is a fourth-order approximation but is extended to become a higher-order method. Results are included for the fourth-, sixth-, eighth- and tenth-order methods. The results are first compared with results found by Segal in an article about elliptic singular perturbation problems. The elliptic singular perturbation problems are compared with a method by Il'in and also with central and backward difference schemes from Segal's article. There was only one case where the results in Segal's paper were as accurate as the results presented in this paper. However, in this case the method used by Segal did not give accurate values for a second problem presented. The results are also compared with results given by Spalding and by Christie. The method of this paper was also tested on the solution of some non-linear diffusion equations with concentration-dependent diffusion coefficients. The results were superior to results presented by Lee and by Schultz. Finally, the method is extended to several two-dimensional problems. The method developed in this paper is accurate, easy to use and can be generalized to other problems. 相似文献
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非定常流函数涡量方程的一种数值解法的研究 总被引:16,自引:0,他引:16
对非定常流函数涡量方程的数值求解方法进行了改进,其中流函数一阶导数即速度项采用四阶精度的Hermitian公式,对流项由一般二阶精度的中心差分提高到四阶精度离散差分,包含温度方程在内的离散方程组采用ADI迭代方法求得定常解.以无内热体及有一内热体的封闭方腔内自然对流为例,进行了不同瑞利数(Ra)条件下的数值研究.结果表明,该方法推导简单,求解精度高且计算稳定,适用于封闭腔内高瑞利数复杂混合对流的数值模拟. 相似文献
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电子散斑和全息光弹法相结合测量透明材料的应力强度因子K1 总被引:2,自引:0,他引:2
全息光弹性中等和线是获得断裂力学中应力强度因子的一种有效方法之一。但用传统的全息光弹性方法获取等和线需暗房,要经过显影定影及再现,而且不能直接数字化使其应用受到限制。本文提出一种将全息光弹性与相移电子散斑干涉(Electric Speckle Pattern Interferometry,简称ESPI)有机结合的方法,不但克服传统全息光弹性的不足,而且使全息光弹性实现了数字化。文中将这一方法成功应用于有预制裂纹的三点弯曲试件上,定量求得其应力强度因子(Stress Intensity Factor,简称SIF)K1,而且实验值和理论值具有相一致的结果。 相似文献
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Yung-Chao Wu 《国际流体数值方法杂志》1988,8(7):803-811
This paper describes the characteristics of small-amplitude waves generated by a sinusoidally oscillating, inclined paddle-type wavemaker operating in a constant-depth channel. Two-dimensional, linearized potential flow is assumed. A semi-analytical method, the boundary collocation method, is used to establish the relationship between wave amplitude and paddle stroke. The numerical results are compared with the numerical results of the boundary integral equation method. It is found that the boundary collocation method is simpler and more flexible to implement and faster to compute. In addition, the numerical results are in reasonably good agreement with the laboratory experimental data. For the vertical wavemaker, which is a special case of the inclined wavemaker, an analytical series solution can be found. By using the boundary collocation method and the boundary integral equation method to solve the vertical wavemaker problem and comparing the results with the analytical series solution, it is found that the boundary collocation method yields a solution which is much more accurate than that from the boundary integral equation method. Finally, the relationships between wave amplitude and paddle stroke are established for different inclinations of the paddle-type wavemaker, based on the boundary collocation method. 相似文献
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谱体积方法是一种本质上解决网格依赖性的高精度CFD计算方法,本文研究了二维Euler方程的谱体积方法,提出一种基于切比雪夫多项式的单元分割方法,建立了基于WENO的变量限制器方法,并发展了结合谱体积和控制体的问题单元标记方法.采用15°超声速压缩拐角和NACA0012跨声速流动两个典型算例进行验证,结果表明,该分区方法具有更好的计算精度,标记方法可有效识别不连续区域,在较少的网格下即可获得与密网格传统有限体积法相当的计算精度. 相似文献
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《Particuology》2022
This study develops an extended unresolved CFD-DEM coupling method for simulation of the fluid–solid flow with non-spherical particles. The limitation of fluid grid size is discussed, by simulating the settling of a cylinder in a Newtonian fluid based on the resolved and unresolved CFD-DEM coupling method. Then, the calculation of porosity and the fluid–particle relative velocity based on the particle shape enlargement method for simulation of non-spherical particles is proposed. The availability of the particle shape enlargement method for the simulation of non-spherical particles with different sphericity is discussed in this work, by comparing it with the results from the equivalent diameter enlargement method. The limitation of the equivalent diameter enlargement method for non-spherical particles is revealed from the simulation results. Several typical cases are employed to elaborate and verify the extended unresolved CFD-DEM method based on particle shape enlargement method, by presenting a good consistency with the experimental results. It proves that the extended unresolved CFD-DEM method is suitable for different CFD grid size ratios, and consolidates that it is a universal calculation method for CFD-DEM coupling simulation. 相似文献
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IntroductionForcomputationoftheviscouscompressibleflowstheNavier_Stokesequationsaregenerallyrepresentedintheconservationlawformasahyperbolicsystem .Lackingthemathematicaltooltoanalyzethisnonlinearsystem ,thenumericalmethodsusedinsolvingthenonlinearhype… 相似文献
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基于线性随动强化理论和Von. Mises屈服准则,对蒙板结构直接安定分析法进行了扩展,建立了结构的三维安定直接分析法。根据投射原理,推导出结构发生塑性安定的存在条件,便于调整控制加载步长和载荷历程。采用逐次增量加载方式,确定出背应力的偏移范围,克服了原始直接分析法不能获得安定极限的缺陷,并得到安定极限条件下结构中残余应力与应变的分布状况。该数值方法将弹塑性问题分解为弹性问题和特征应变决定的残余问题,节约计算时间,提高计算效率,将该算法应用于相关算例,并与有关数值结果相比较,验证了该算法的有效性。 相似文献