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首页> 外文期刊>Experiments in Fluids: Experimental Methods and Their Applications to Fluid Flow >Corrections for underresolved scalar measurements in turbulent flows using a DNS database
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Corrections for underresolved scalar measurements in turbulent flows using a DNS database

机译：使用DNS数据库对湍流中未解决的标量测量进行校正

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摘要

We estimate the effect of finite spatial resolution of a probe for scalar measurements, using a database from direct numerical simulations (DNS). These are for homogeneous isotropic turbulence in temporal decay, Schmidt number unity, and low Taylor-microscale Reynolds number (similar or equal to 27-42). The probe could be a cold wire for measuring temperature in a turbulent flow. Correction factors for the scalar variance, scalar dissipation rate, and mixed velocity-scalar derivative skewness are estimated, for a sensor length up to 15 times the Batchelor length scale. It is shown that the lack of resolution yields the largest attenuation on the dissipation rate, followed by the scalar variance. On the contrary, the mixed skewness, which is affected the least, is overestimated. Further, it is shown that if one estimates the mixed skewness via the scalar variance dynamical equation and neglects the term involving the time derivative of the scalar energy spectrum, large errors in the correction factor of the mixed skewness are introduced. Finally, it is found that correction factors obtained assuming Kraichnan scalar model spectrum and following Wyngaard (in Phys Fluids 14:2052-2054, 1971) approach are close to those from the DNS.
机译：我们使用直接数值模拟（DNS）中的数据库，估计标量测量的有限空间分辨率探针的效果。这些是针对时间衰减中的均质各向同性湍流，Schmidt数统一和低泰勒-微米雷诺数（近似或等于27-42）。探针可以是用于测量湍流温度的冷线。对于传感器长度最大为Batchelor长度标度15倍的传感器，估计了标量方差，标量耗散率和混合速度标量导数偏斜的校正因子。结果表明，缺乏分辨率会导致耗散率的最大衰减，其次是标量方差。相反，受影响最小的混合偏度被高估了。此外，示出了如果通过标量方差动力学方程来估计混合偏度并且忽略涉及标量能谱的时间导数的项，则引入了混合偏度的校正因子中的大误差。最后，发现假设采用Kraichnan标量模型频谱并遵循Wyngaard（在Phys Fluids 14：2052-2054，1971）方法获得的校正因子与DNS中的校正因子接近。

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