Experimental estimation of fluctuating velocity and scalar gradients in turbulence
Experimental estimation of fluctuating velocity and scalar gradients in turbulence
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湍流中脉动速度和标量梯度的实验估计
DOI：
10.1007/s00348-012-1318-0
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发表时间：
2012
影响因子：
2.4
通讯作者：
Hearst R
中科院分区：
文献类型：
--
作者：
Hearst R
数值微分的效果进行了研究的上下文中评估湍流中的脉动速度和标量。特别是，2点前向差分和3-，5-，7-和9点中心差分格式进行了研究。Wyngaard（在J Sci Instr 1（2）：1105-1108，1968中）介绍的用于均匀湍流的谱技术被用来量化方案的效果。数值微分衰减梯度谱在一定范围内的波数。光谱衰减，这与该计划的顺序而变化，在测量的均方梯度的减少的结果。高阶方案（例如7点或9点）显着降低了所有波数的衰减，从而产生更准确的梯度。热线测量和衰减均匀，各向同性湍流的直接数值模拟被发现是在良好的协议与分析的预测，这表明高阶计划可以用来提高经验梯度估计。的概率密度函数的形状也被发现是敏感的数值微分方案的选择。数值微分的效果也进行了讨论相对于粒子图像测速（PIV）测量的名义上二维平面混合层。据发现，在典型的PIV测量固有的相对较低的信噪比需要使用低阶计划，以防止过度的噪声放大，这与该计划的顺序增加。本工作的结果表明，高阶数值微分方案可以更准确地解决梯度测量在给定的分辨率提供的测量具有足够的信噪比。
The effect of numerical differentiation is investigated in the context of evaluating fluctuating velocity and scalar quantities in turbulent flows. In particular, 2-point forward-difference and 3-, 5-, 7-, and 9-point centred-difference schemes are investigated. The spectral technique introduced by Wyngaard (in J Sci Instr 1(2):1105–1108, 1968) for homogeneous turbulence is used to quantify the effects of the schemes. Numerical differentiation is shown to attenuate gradient spectra over a range of wavenumbers. The spectral attenuation, which varies with the order of the scheme, results in a reduction in the measured mean-squared gradients. High-order schemes (e.g. 7- or 9-point) are shown to significantly decrease the attenuation at all wavenumbers and as a result produce more accurate gradients. Hot-wire measurements and direct numerical simulations of decaying homogeneous, isotropic turbulence are found to be in good agreement with the predictions of the analysis, which suggests that high-order schemes can be used to improve empirical gradient estimates. The shape of the probability density functions is also found to be sensitive to the choice of numerical differentiation scheme. The effect of numerical differentiation is also discussed with respect to particle image velocimetry (PIV) measurements of a nominally two-dimensional planar mixing layer. It is found that the relatively low signal-to-noise ratio inherent in typical PIV measurements necessitates the use of low-order schemes to prevent excessive noise amplification, which increases with the order of the scheme. The results of the present work demonstrate that high-order numerical differentiation schemes can be employed to more accurately resolve gradients measured at a given resolution provided the measurements have an adequate signal-to-noise ratio.
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影响因子：
4.6
作者：
J. Wyngaard
通讯作者：
J. Wyngaard
从惯性范围到耗散长度尺度的剪切流湍流中应变率和旋转之间的相互作用
影响因子：
4.6
作者：
Buxton O
通讯作者：
Buxton O
影响因子：
4.6
作者：
Y. Pao
通讯作者：
Y. Pao
湍流部分预混火焰中标量耗散率测量的噪声校正和长度尺度估计
DOI：
--
发表时间：
2010
期刊：
影响因子：
--
作者：
Jian Cai;R. Barlow;A. Karpetis;C. Tong
通讯作者：
C. Tong
空间分辨率对湍流非预混射流火焰中标量方差和标量梯度测量的影响
DOI：
--
发表时间：
2008
期刊：
影响因子：
--
作者：
Guanghua Wang;R. Barlow
通讯作者：
R. Barlow