Multi-particle model of coarse-grained scalar dissipation rate with volumetric tensor in turbulence
Multi-particle model of coarse-grained scalar dissipation rate with volumetric tensor in turbulence
复制标题
湍流中带有体积张量的粗粒标量耗散率的多粒子模型
DOI：
10.1016/j.jcp.2019.03.034
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发表时间：
2019
影响因子：
4.1
通讯作者：
Nagata Koji
中科院分区：
文献类型：
--
作者：
Tanaka Shusei;Watanabe Tomoaki;Nagata Koji
提出了粗粒标量耗散率的多粒子模型，其中粗粒量用有限体积内空间分布的流体粒子的系综平均值来定义。该模型计算粗粒度的标量耗散率从粗粒度的标量梯度与亚网格尺度模型的标量耗散率，这需要长度尺度估计的颗粒分布。一个体积张量的颗粒分布的特点是用于计算的长度尺度和粗粒度的标量和速度梯度的颗粒模型。该模型在先验和后验检验。与直接数值模拟（DNS）数据库的湍流平面射流的先验测试表明，本模型适用于广泛的长度尺度的颗粒分布时，颗粒数N M约为10-16。当N M = 10时，模型高估了粗粒标量耗散率，而N M = 16时，模型对粒子分布长度尺度的依赖性更强。该模型在混合大涡模拟/拉格朗日粒子模拟（LES/LPS）的平面射流，其中粗粒度的标量耗散率出现作为一个未知变量的混合体积模型，计算分子扩散项的基础上的多粒子相互作用的测试。LES/LPS和DNS产生类似的根均方标量波动，这强烈依赖于标量耗散率的配置文件。模型和DNS之间的平均标量耗散率的比较表明，本模型适用于LES/LPS以及预测粗粒度的标量耗散率在不同的射流雷诺数。
A multi-particle model is proposed for a coarse-grained scalar dissipation rate, where a coarse-grained quantity is defined with an ensemble average of spatially-distributed fluid particles within a finite volume. The model computes the coarse-grained scalar dissipation rate from the coarse-grained scalar gradient with a subgrid scale model of the scalar dissipation rate, which requires length-scale estimation for particle distribution. A volumetric tensor that characterizes the particle distribution is used in the model for computing the length scale and the coarse-grained scalar and velocity gradients from the particles. The model is examined in a priori and posteriori tests. A priori test with direct numerical simulation (DNS) databases of turbulent planar jets shows that the present model works well for a wide range of the length scale of particle distribution when the number of particles N M is about 10-16. The model with N M≲ 10 overestimates the coarse-grained scalar dissipation rate, while N M≳ 16 causes stronger dependence of the model on the length scale of particle distribution. The proposed model is tested in hybrid large-eddy-simulation/Lagrangian-particle-simulation (LES/LPS) of planar jets, where the coarse-grained scalar dissipation rate appears as an unknown variable in a mixing volume model that computes a molecular diffusion term based on a multi-particle interaction. LES/LPS and DNS yield a similar profile of the root-mean-squared scalar fluctuation, which strongly depends on the scalar dissipation rate. Comparison of the mean scalar dissipation rate between the model and the DNS shows that the present model applied to the LES/LPS well predicts the coarse-grained scalar dissipation rate at various jet Reynolds numbers.
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