共查询到18条相似文献,搜索用时 109 毫秒
1.
2.
基于带化学反应的二维轴对称Euler方程,利用带有Superbee限制函数的波传播算法,对共振腔中的氢气-空气预混气的聚心燃烧进行了数值模拟,讨论了共振腔不同抛物面对起爆的影响。数值结果表明,在开始阶段,燃烧诱导的激波在轴心、火焰和固壁的反射,使火焰失稳,随后共振腔中的抛物壁面上产生一定频率和强度的反射激波,不断穿越火焰,使火焰进一步失稳,加剧了燃烧速度,最终导致爆轰的形成。同时,火焰在与激波的作用过程中,形状扭曲变形,呈封闭端小敞口端大的扁平头部蘑菇云。共振腔抛物面的不同形状引起激波聚焦位置的变化,会影响激波和火焰的相互作用,使起爆提前或推迟,甚至不起爆。 相似文献
3.
4.
5.
提出了一个新的用于模拟可压缩Euler方程的格子Boltzmann模型,数值试验表明它可以模拟具有激波和接触面的问题。计算结果与经典算法的结果可以比较。 相似文献
6.
7.
对差分干涉计算机层析技术诊断激波加载下气柱界面不稳定性的可行性进行初步理论和实验研究。针对有限投影数的联合代数重建算法,提出了一种新的投影矩阵计算方法,采用特定投影方向,各投影方向具有不同采样间隔。投影方向的对称性和投影线的规律性使计算过程大为减化。用该重建算法对气柱密度场进行数值模拟,结果表明4方向投影能够重建激波作用下气柱演化初期的体密度场,8方向投影基本能够重建演化中期的体密度场。用差分干涉系统对激波管气柱进行3方向诊断的实验结果表明,差分干涉计算机层析技术用于激波冲击下的气柱不稳定性密度场诊断是可行的。 相似文献
8.
对差分干涉计算机层析技术诊断激波加载下气柱界面不稳定性的可行性进行初步理论和实验研究。针对有限投影数的联合代数重建算法,提出了一种新的投影矩阵计算方法,采用特定投影方向,各投影方向具有不同采样间隔。投影方向的对称性和投影线的规律性使计算过程大为减化。用该重建算法对气柱密度场进行数值模拟,结果表明4方向投影能够重建激波作用下气柱演化初期的体密度场,8方向投影基本能够重建演化中期的体密度场。用差分干涉系统对激波管气柱进行3方向诊断的实验结果表明,差分干涉计算机层析技术用于激波冲击下的气柱不稳定性密度场诊断是可行的。 相似文献
9.
高超声速飞行器激波位置的准确预测能够有效提升数值模拟的精度和效率。一方面,对高超声速飞行器激波附近网格进行正交和加密处理,可有效提升数值计算精度;另一方面,使用高超声速飞行器激波位置对计算网格进行修正,能够加速CFD计算收敛过程。提出了一种基于机器学习的高超声速飞行器激波智能预测方法,对典型高超声速飞行器外形进行激波位置的高效准确预测。首先,针对典型高超声速飞行器外形和典型飞行状态,使用数值模拟方法获得收敛的流场,并采用基于Mach数等值线的激波提取方法,从流场中判别激波面并提取构成激波面的关键点位置,形成训练数据;然后采用有监督学习算法,学习关键点位置,并利用二次曲线沿流向拟合关键点形成初步的激波线族;最后,基于剖面压力云图,构造基于投影压力图像的智能预测神经网络,对初步形成的激波线族进行修正,并获得三维激波面。大量的实验结果表明,激波预测模型能够对高超声速飞行器激波位置做出准确预测,预测的激波面与CFD数值计算结果中提取的激波面误差在10-4量级。 相似文献
10.
11.
We have developed a new algorithm and configuration for self-eliminating the autocorrelation of the object wave in Fourier-domain optical coherence tomography. A self-interferogram of the object wave is acquired synchronously with the standard interferogram of the recombined object and reference waves. The former is then subtracted from the latter after Fourier transformation. The algorithm is validated by numerical simulation and by experimental measurement of a U.S. Air Force target and a feline eye. 相似文献
12.
The impulse wave is made by the weak normal shock discharge from an open end of a shock tube. In order to understand the dynamic characteristics of the impulse wave impinging upon a flat plate, experiments are performed over the shock Mach number range from 1·01 to 1·20. A flat plate is placed downstream, normal to the axis of the shock tube, to simulate the impulse wave impingement on an object. The distance between the exit of the shock tube and flat plate is changed. The baffle plate is installed at the exit of the shock tube. The sizes of the baffle plate and impinging flat plate are varied to investigate the magnitude of the impulse wave impinging upon the flat plate. Computational analysis is applied to model the flow field subject to unsteady, axisymmetric, inviscid, compressible, equations. Computational results well predict the experimented dynamic behavior of the impinging impulse wave. The impulse wave impinging upon the flat plate has a sharp peak of very short rising time and its magnitude decreases with distance from the center of the flat plate. The magnitude of the impulse wave impinging upon the flat plate can be predicted by the empirical equations that are developed in the present study. 相似文献
13.
A. V. Konyukhov A. P. Likhachev V. E. Fortov K. V. Khishchenko S. I. Anisimov A. M. Oparin I. V. Lomonosov 《JETP Letters》2009,90(1):18-24
The results of the theoretical analysis and computer simulation of the behavior of neutrally stable shock waves with real
(van der Waals gas, magnesium) equations of state are presented. An approach is developed in which the region of the neutral
stability of a shock wave for each pressure value in front of the wave is determined from the analysis of the equation of
state. A simple algorithm is developed to determine the cause of acoustic perturbations (a shock front or an external source)
immediately from the flow pattern. In contrast to the predictions of the linear theory, the amplitude of the perturbations
of the neutrally stable shock wave decreases with time, although this process is noticeably slower than in the case of an
absolutely stable shock wave. 相似文献
14.
This study is focused on the propagation behavior and attenuation characteristics of a planar incident shock wave when propagating through an array of perforated plates. Based on a density-based coupled explicit algorithm, combined with a third-order MUSCL scheme and the Roe averaged flux difference splitting method, the Navier–Stokes equations and the realizable k-ε turbulence model equations describing the air flow are numerically solved. The evolution of the dynamic wave and ring vortex systems is effectively captured and analyzed. The influence of incident shock Mach number, perforated-plate porosity, and plate number on the propagation and attenuation of the shock wave was studied by using pressure- and entropy-based attenuation rates. The results indicate that the reflection, diffraction, transmission, and interference behaviors of the leading shock wave and the superimposed effects due to the trailing secondary shock wave are the main reasons that cause the intensity of the leading shock wave to experience a complex process consisting of attenuation, local enhancement, attenuation, enhancement, and attenuation. The reflected shock interactions with transmitted shock induced ring vortices and jets lead to the deformation and local intensification of the shock wave. The formation of nearly steady jets following the array of perforated plates is attributed to the generation of an oscillation chamber for the inside dynamic wave system between two perforated plates. The vorticity diffusion, merging and splitting of vortex cores dissipate the wave energy. Furthermore, the leading transmitted shock wave attenuates more significantly whereas the reflected shock wave from the first plate of the array attenuates less significantly as the shock Mach number increases. The increase in the porosity weakens the suppression effects on the leading shock wave while increases the attenuation rate of the reflected shock wave. The first perforated plate in the array plays a major role in the attenuation of the shock wave. 相似文献
15.
含冲击波流场干涉图的图像处理方法研究 总被引:2,自引:1,他引:1
本文研究了含冲击波流场干涉图的图像处理方法,它包括干涉条纹的快束细化算法,冲击波波阵面的提取算法和时间序列冲击波波阵面的配准算法.根据这些算法,在PC-VISION 100图像处理机上开发了应用软件.实验结果表明,该方法可用于定量计算冲击波的传播速度和压力分布,增加了流场干涉图的用途. 相似文献
16.
Xu XF Cai LZ Wang YR Meng XF Sun WJ Zhang H Cheng XC Dong GY Shen XX 《Optics letters》2008,33(8):776-778
An algorithm to extract the arbitrary unknown phase shift and then reconstruct the complex object wave in generalized phase-shifting interferometry (GPSI) without the iteration process and measurement of object wave intensity is proposed. This method can be used for GPSI of any frame number >or=2. Both computer simulations with smooth and diffusing object surfaces and optical experiments have verified the effectiveness of this method over a wide range of phase shifts with very satisfactory results. 相似文献
17.
The phase retrieval from a modulus of the scattered wave field at the Fourier transform plane of an object is considered in this paper by using the logarithmic Hilbert transform. When the phase is evaluated by using the logarithmic Hilbert transform from the modulus at the Fourier transform plane of the object with the direct component (for example, the phase object), the distortion appears in the reconstructed object obtained from an inverse Fourier transform of the complex wave consisting of the evaluated phase and the modulus. Here, the cause for the appearance of the distortion is made clear and a simple algorithm is presented to reduce the distortion of the reconstructed object. 相似文献