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首页> 外文期刊>Mathematical models and computer simulations >Waves and Spatially Localized Structures in the Turbulent Flows of a Viscous Fluid: Calculation Results
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Waves and Spatially Localized Structures in the Turbulent Flows of a Viscous Fluid: Calculation Results

机译：粘性流体湍流中的波和空间局部结构：计算结果

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摘要

A direct numerical simulation was performed of intermittent and turbulent flows of viscous incompressible fluid in an infinite circular pipe. The Navier-Stokes equations were integrated at the Reynolds numbers of 1800 ≤Re≤ 4000 calculated from the mean velocity and a pipe diameter of D = 2R. The numerically obtained solutions belong to the class of mean streamwise periodic solutions with a very large period λmax = 16πR. The Fourier harmonic components of the velocity fluctuations corresponding to very low longitudinal wavenumbers are shown to be the most energetic. A detailed study was carried out of the structures of the calculated turbulent and intermittent flows. The accuracy and the very possibility of the approximation of the turbulent velocity field by the superposition of traveling and standing waves are analyzed. It is shown that the parameters of such a representation (wave amplitudes, phase velocities, and the position of the wave front) are strongly dependent on whether or not very low longitudinal wavenumbers are included in the mathematical model of the flow The numerical solutions at Re = 2200 and 2350 describe the intermittent type of the flow, for which the localized turbulent structures (turbulent puffs) propagate downstream while retaining their spatial dimensions. The space-time structure of the calculated turbulent puffs is compared with the available experimental data. The main statistical characteristics of the turbulence inside and outside the turbulent puff are calculated and the convective rate of the puffs downstream expansion is determined.
机译：对无限圆管中粘性不可压缩流体的间歇性和湍流进行了直接数值模拟。根据平均速度和管径D = 2R计算得出的Navier-Stokes方程的雷诺数为1800≤Re≤4000。数值获得的解属于具有很大周期λmax=16πR的平均流周期解的类别。对应于非常低的纵向波数的速度波动的傅立叶谐波分量显示为最有力的。对计算出的湍流和间歇流的结构进行了详细的研究。分析了行波和驻波叠加产生的湍流速度场的准确性和可能性。结果表明，这种表示的参数（波幅，相速度和波前的位置）在很大程度上取决于流动数学模型中是否包含非常低的纵向波数。 = 2200和2350描述了流的间歇性类型，对于这种类型的流，局部湍流结构（湍流抽吸）向下游传播，同时保留其空间尺寸。计算出的湍流抽吸的时空结构与可用的实验数据进行了比较。计算了湍流内部和外部湍流的湍流的主要统计特征，并确定了腔室下游膨胀的对流速率。

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