共查询到19条相似文献,搜索用时 147 毫秒
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采用三维Taylor-Green涡作为研究对象,利用工程中常用的低阶数值格式,研究格式本身的数值误差对大涡模拟计算的影响.结果表明:三种数值格式的数值耗散行为都与亚格子模型行为类似,即在小雷诺数下,流场比较光滑时,耗散很小,当雷诺数增加,流动转捩为湍流,流场梯度增大,耗散显著增大.对于MUSCL格式和二阶有界中心格式,在高雷诺数下,亚格子尺度模型没有明显改善计算结果,但也没有使计算结果恶化.中心格式相比其它两种格式,数值耗散最小,但是在高雷诺数湍流情况下,中心格式的数值耗散仍然主导了能量的耗散,再添加亚格子模型,计算结果反而变得稍差.对于工程中的低阶格式而言,采用中心格式计算大涡模拟是比较好的选择,而且在计算不存在稳定性问题时,采用不添加亚格子模型的隐式大涡模拟效果更好. 相似文献
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随着计算能力的飞速发展,在非结构网格上进行大涡模拟是研究叶轮机械真实几何结构下复杂流动问题的有效途径。本文针对非结构网格上数值格式人工黏性过大的缺点,利用湍流中动能级联特性,发展了适用于大涡模拟的低耗散数值格式,并结合亚格子模型,考察了其在基础湍流算例中的有效性。通过与传统迎风格式的对比,说明本文发展的低耗散格式可以显著提高非结构网格上大涡模拟的精度和可靠性。 相似文献
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随着计算能力的飞速发展,在非结构网格上进行大涡模拟是研究叶轮机械真实几何结构下复杂流动问题的有效途径。本文针对非结构网格上数值格式人工黏性过大的缺点,利用湍流中动能级联特性,发展了适用于大涡模拟的低耗散数值格式,并结合亚格子模型,考察了其在基础湍流算例中的有效性。通过与传统迎风格式的对比,说明本文发展的低耗散格式可以显著提高非结构网格上大涡模拟的精度和可靠性。 相似文献
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针对大涡模拟涡粘性亚格子模式中使用网格尺度为特征尺度存在的不足,提出一种改进的亚格子特征尺度表达式,利用结合Sagaut混合尺度模式获得的改进模式与Smagorinsky模式、Germano模式和Sagaut模式等进行对比研究.时间发展混合层和中性大气边界层的大涡模拟结果表明,改进的有效亚格子特征尺度能合理反映亚格子脉动的时空分布特性,同时扩展了适用范围.在对耗散程度、流动演化过程、可解湍流强度和可解雷诺应力等方面的模拟,改进模式优于基准模式,表明亚格子脉动有效特征尺度在大涡模拟中具有一定的理论基础和广泛的应用价值. 相似文献
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《物理学报》2016,(24)
采用多组分混合物质量分数模型和最小色散可控耗散格式的高分辨率有限体积方法,数值模拟了弱激波冲击不同角度的"V"形空气/SF_6界面的Richtmyer-Meshkov不稳定性问题.激波冲击界面后,在界面附近沉积涡量,形成沿界面规则排列的旋涡结构,同时界面扰动发展形成气泡和尖钉结构.本文统计了界面左端移动速度和界面混合宽度增长率等特征量的演化规律,并与已有的实验结果进行了对比,两者符合较好.讨论了物质界面处的流体向湍流混合发展的过程,随着界面旋涡结构的演化,涡结构之间开始发生相互诱导、并对等现象,并逐渐聚集在几个区域,而多尺度结构也因旋涡的诱导作用在这些区域中产生.通过对由雷诺数定义的惯性尺度进行分析,发现了具有上下边界的惯性尺度区域的形成,对动能能谱的分析发现了-5/3对数率的出现,这同样说明了惯性尺度区域的形成.由于湍流混合转捩与惯性尺度区域的形成是一致的,界面附近流场将发展为湍流. 相似文献
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Compressible turbulence: the cascade and its locality 总被引:1,自引:0,他引:1
Aluie H 《Physical review letters》2011,106(17):174502
We prove that interscale transfer of kinetic energy in compressible turbulence is dominated by local interactions. In particular, our results preclude direct transfer of kinetic energy from large-scales to dissipation scales, such as into shocks, in high Reynolds number turbulence as is commonly believed. Our assumptions on the scaling of structure functions are weak and enjoy compelling empirical support. Under a stronger assumption on pressure dilatation cospectrum, we show that mean kinetic and internal energy budgets statistically decouple beyond a transitional conversion range. Our analysis establishes the existence of an ensuing inertial range over which mean subgrid scale kinetic energy flux becomes constant, independent of scale. Over this inertial range, mean kinetic energy cascades locally and in a conservative fashion despite not being an invariant. 相似文献
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在多重网格驱动的,高效且得到充分验证的有限体积方法的基础上发展了可压缩流大涡模拟的方法.空间离散采用Jameson的中心格式附加二阶和四阶耗散的方法,时间推进则采用了双时间步长的方法.亚格子剪切应力张量和亚格子热通量用Smagorinsky模型进行模拟.通过对各向同性紊流能量衰减的模拟来验证本方法的准确性和高效性,模拟得到的能量谱和紊流动能衰减历程与过滤后的CBC实验数据吻合良好. 相似文献
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A fully developed compressible turbulent flow in a channel with a lower wavy wall and a upper plane wall is studied using large eddy simulation. We mainly attempt to deal with the curvature effect on compressible turbulent flow over the wavy wall. Some typical quantities including the mean turbulence statistics, dilatation and baroclinic terms in the enstrophy equation, turbulent kinetic energy budgets and the near-wall turbulent structures are analysed. The results obtained in this study provide physical insight into the understanding of the effects of curvature and compressibility on wall-bounded compressible turbulent flow. 相似文献
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《Proceedings of the Combustion Institute》2023,39(2):2107-2115
The multi-scale interaction between combustion and turbulence is of great importance in modifying the small-scale flame structure and kinetic energy, especially in swirling flames under practical conditions. In the present study, direct numerical simulation of swirling partially premixed flame is conducted within a model combustor under gas turbine conditions. The reactive flow is compared to the corresponding non-reactive one to investigate the influence of combustion on the scaled kinetic energy transport. Kinetic energy spectra demonstrate that the turbulent kinetic energy is reduced in the dissipative subrange while enhanced in the energetic one by the flame. The critical scale is located in the inertial subrange and close to the estimated turbulent flame thickness. Filtering analyses show that the resolved-scale kinetic energy is augmented by the increased large-scale pressure-gradient work in the reactive flow, while the subgrid-scale kinetic energy is attenuated by the enhanced small-scale viscous dissipation. The backscatter prevails in the heat release regions when the filter size is larger than the laminar flame thickness, and this effect decreases with the swirling flow developing downstream. The interaction between the kinetic energy flux and the local dilatation as well as the subgrid-scale pressure-gradient work is also investigated to achieve a comprehensive understanding about the effects of combustion on the backscatter. 相似文献
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L. V. Abdurakhimov M. Yu. Brazhnikov A. A. Levchenko I. A. Remizov S. V. Filatov 《JETP Letters》2012,95(12):670-679
In the dissipative range at frequencies above the inertial frequency range, the turbulent cascade of capillary waves on the surface of liquid helium and hydrogen decays according to an exponential law. The characteristic frequency of the quasi-Planck distribution is determined by the spectral characteristic of an exciting force. In the case of harmonic pumping on the surface of superfluid helium in the discrete turbulence regime, energy condensation is observed near the high-frequency edge of the inertial range. The effect is due to the influence of discreteness in the spectrum of the eigenfrequencies of surface excitations and in the turbulence distribution on the energy transfer through the cascade. 相似文献
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We investigate the locality of interactions in hydrodynamic turbulence using data from a direct numerical simulation on a grid of 1024(3) points; the flow is forced with the Taylor-Green vortex. An inertial range for the energy is obtained in which the flux is constant and the spectrum follows an approximate Kolmogorov law. Nonlinear triadic interactions are dominated by their nonlocal components, involving widely separated scales. The resulting nonlinear transfer itself is local at each scale but the step in the energy cascade is independent of that scale and directly related to the integral scale of the flow. Interactions with large scales represent 20% of the total energy flux. Possible explanations for the deviation from self-similar models, the link between these findings and intermittency, and their consequences for modeling of turbulent flows are briefly discussed. 相似文献
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This study is concerned with particle subgrid scale (SGS) modelling in large-eddy simulations (LESs) of particle-laden turbulence. Although many particle-laden LES studies have neglected the effect of the SGS on the particles, several particle SGS models have been proposed in the literature. In this research, the approximate deconvolution method (ADM) and the stochastic models of Fukagata et al. (Dynamics of Brownian particles in a turbulent channel flow, Heat Mass Transf. 40 (2004), 715–726) Shotorban and Mashayek (A stochastic model for particle motion in large-eddy simulation, J. Turbul. 7 (2006), 1–13) and Berrouk et al. (Stochastic modelling of inertial particle dispersion by subgrid motion for LES of high Reynolds number pipe flow, J. Turbul. 8 (2007), pp. 1–20) are analysed. The particle SGS models are assessed using both a priori and a posteriori simulations of inertial particles in a periodic box of decaying, homogeneous and isotropic turbulence with an initial Reynolds number of Reλ = 74. The model results are compared with particle statistics from a direct numerical simulation (DNS). Particles with a large range of Stokes numbers are tested using various filter sizes and stochastic model constant values. Simulations with and without gravity are performed to evaluate the ability of the models to account for the crossing trajectory and continuity effects. The results show that ADM improves results but is only capable of recovering a portion of the SGS turbulent kinetic energy. Conversely, the stochastic models are able to recover sufficient SGS energy, but show a large range of results dependent on the Stokes number and filter size. The stochastic models generally perform best at small Stokes numbers, but are unable to predict preferential concentration. 相似文献
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O. M. Belotserkovskii A. M. Oparin V. M. Chechetkin 《Journal of Experimental and Theoretical Physics》2004,99(3):504-509
A physical model of the development of turbulence in free shear flows is proposed. The model is based on the results of numerical simulations of turbulent flow development. The main ideas of the proposed theory of turbulence are stated as follows: the onset of turbulence begins with the formation of large vortices; spectral energy transfer involves both direct and inverse cascades; and the inertial range of the energy spectrum develops as a result of concurrent direct and inverse cascades. The dominant physical factors that determine the spectrum include Joukowski forces. 相似文献
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Incompressible magnetohydrodynamics is often assumed to describe solar wind turbulence. We use extended self-similarity to reveal scaling in the structure functions of density fluctuations in the solar wind. The obtained scaling is then compared with that found in the inertial range of quantities identified as passive scalars in other turbulent systems. We find that these are not coincident. This implies that either solar wind turbulence is compressible or that straightforward comparison of structure functions does not adequately capture its inertial range properties. 相似文献