Noise Correction and Length Scale Estimation for Scalar Dissipation Rate Measurements in Turbulent Partially Premixed Flames
Noise Correction and Length Scale Estimation for Scalar Dissipation Rate Measurements in Turbulent Partially Premixed Flames
复制标题
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：
--
复制
发表时间：
2010
期刊：
影响因子：
--
通讯作者：
C. Tong
中科院分区：
文献类型：
--
作者：
Jian Cai;R. Barlow;A. Karpetis;C. Tong
用一种新发展的基于条件采样的方法来修正标量耗散率测量中的噪声影响，并估计耗散率的分辨率。该方法使用条件采样来选择瞬时完全分辨的局部标量场，对其进行分析以确定测量噪声并校正Favre平均、条件和条件滤波耗散率。对同样使用条件采样选择的潜在欠分辨局部标量场进行噪声校正，并进行分析以检查分辨率范围。误差函数被用作潜在欠分辨局部标量的模型，以估计标量耗散长度尺度和耗散分辨率。结果表明，Favre平均耗散率、以混合分数为条件的平均耗散率和以混合分数为条件过滤的平均耗散率在火焰中一般都能得到很好的分辨。对混合分数和温度的条件过滤的耗散率的分析表明，由于较低的耗散率和较高的扩散系数，长度尺度随着温度的增加而增加。耗散率在1300K以上的温度下分辨率很好，但在较低温度下分辨率较低，尽管发生极低温度事件的概率很低。为了完全解决这些罕见事件，需要将样本间距减少大约一半。本研究进一步证明了新的噪声校正和长度尺度估计方法的有效性。
A recently developed conditional sampling-based method for correcting noise effects in scalar dissipation rate measurements and for estimating the extent of resolution of the dissipation rate is employed to analyze the data obtained in turbulent partially premixed (Sandia) flames. The method uses conditional sampling to select instantaneous fully resolved local scalar fields, which are analyzed to determine the measurement noise and to correct the Favre mean, conditional, and conditionally filtered dissipation rates. The potentially under-resolved local scalar fields, also selected using conditional sampling, are corrected for noise and are analyzed to examine the extent of resolution. The error function is used as a model for the potentially under-resolved local scalar to evaluate the scalar dissipation length scales and the percentage of the dissipation resolved. The results show that the Favre mean dissipation rate, the mean dissipation rate conditional on the mixture fraction, and dissipation rate filtered conditionally on the mixture fraction generally are well resolved in the flames. Analyses of the dissipation rates filtered conditionally on the mixture fraction and temperature show that the length scale increases with temperature, due to lower dissipation rate and higher diffusivity. The dissipation rate is well resolved for temperatures above 1,300 K but is less resolved at lower temperatures, although the probability of very low temperature events is low. To fully resolve these rare events the sample spacing needs to be reduced by approximately one half. The present study further demonstrates the effectiveness of the new noise correction and length scale estimation method.