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arXiv 2407.15469physics.flu-dyn
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高超声速流动中附着线边界层的数值模拟,第二部分:三维湍流边界层的特征

Numerical simulations of attachment-line boundary layer in hypersonic flow, Part II: the features of three-dimensional turbulent boundary layer

Youcheng Xi, Bowen Yan, Guangwen Yang, Song Fu

AI总结:

本研究数值模拟高超声速钝体附着线三维湍流边界层,发现展向均匀性成立,壁面律适用,温度-速度关系受压力梯度影响,并揭示剪切应力与平均流剪切的非线性/线性分区关系。

摘要:

在本研究中,我们探讨了受横向流动和压力梯度影响的三维湍流边界层的特性。我们的研究结果表明,即使不假设无限展长,当前钝体上的充分发展湍流边界层仍保持展向均匀性,这与无限展长假设一致。我们批判性地检验了通常应用于二维湍流边界层的壁面律和温度-速度关系在三维情境下的适用性。结果显示,在存在横向速度和压力梯度的情况下,流向速度遵循经典的速度变换关系,而经典温度-速度关系的预测精度因压力梯度而降低。我们发现近壁条带结构持续存在,并与外区的高能结构相对应,尽管三维效应重新分配能量,使其更倾向于与外部流动方向对齐。对剪切雷诺应力和平均流剪切方向的分析揭示,在近壁区域横向流速较低时两者方向一致,但在较高横向速度时出现显著偏差。横向压力梯度与横向速度的引入改变了速度剖面和平均流剪切方向,剪切雷诺应力经历类似变化,但滞后随横向速度增加而增大。外区方向的一致性表明剪切雷诺应力与平均流剪切之间存在分区关系:内区为非线性,外区近似线性。

英文摘要:

In this study,we investigate the characteristics of three-dimensional turbulent boundary layers influenced by transverse flow and pressure gradients. Our findings reveal that even without assuming an infinite sweep, a fully developed turbulent boundary layer over the present swept blunt body maintains spanwise homogeneity, consistent with infinite sweep assumptions.We critically examine the law-of-the and temperature-velocity relationships, typically applied two-dimensional turbulent boundary layers, in three-dimensional contexts. Results show that with transverse velocity and pressure gradient, streamwise velocity adheres to classical velocity transformation relationships and the predictive accuracy of classical temperaturevelocity relationships diminishes because of pressure gradient. We show that near-wall streak structures persist and correspond with energetic structures in the outer region, though three-dimensional effects redistribute energy to align more with the external flow direction. Analysis of shear Reynolds stress and mean flow shear directions reveals in near-wall regions with low transverse flow velocity, but significant deviations at higher transverse velocities. Introduction of transverse pressure gradients together with the transverse velocities alter the velocity profile and mean flow shear directions, with shear Reynolds stress experiencing similar changes but with a lag increasing with transverse. Consistent directional alignment in outer regions suggests a partitioned relationship between shear Reynolds stress and mean flow shear: nonlinear in the inner region and approximately linear in the outer region.

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