论文标题
不利压力梯度下湍流边界层的对流速度
Convection Velocity in Turbulent Boundary Layers under Adverse Pressure Gradient
论文作者
论文摘要
对对流速度（$ u_c $）的湍流结构已经以不良压力级别（APG）的湍流边界层（TBL）进行了研究，以范围广泛的Reynolds编号$re_τ= 1400-4000 $。该研究基于对对流速度的估计，使用（Drozdz A.，Elsner W.，Int。J.of Heat and Flod Flow。63（2017）67 \ -74）中引入的对流速度，并通过两点相关方法进行了验证。 It was shown that in the overlapping region of APG flows, the convection velocity profiles (when scaled in viscous units) reassemble the universal logarithmic law characteristic for the ZPG flows up to Clauser-Rota pressure gradient parameter $β\lesssim 19$ for the considered range of Reynolds number, what means that in the inner region of TBL the friction velocity in APG is not proportional到$ u $（如ZPG中），而是$ u_c $。提出了解释对流速度对平均流量增加的影响的物理机制。 $ u_c $和$ u $之间的差异随着APG的函数增加，这会导致更强的扫描增强动量转移到墙壁上，并补偿墙壁附近较低的涡流所产生的较弱的平均剪切轮廓。这种效果是通过大规模运动对小尺度调制的增强的结果。随着涡流密度的增长，该过程变得更加明显，因此随着RE的增加。所提出的模型介绍了在不良压力梯度流中发现的许多文献观察，这些观察结果已经远远没有得到充分的解释。
The convection velocity ($U_C$) of turbulent structures has been studied in adverse-pressure-gradient (APG) turbulent boundary layers (TBLs) for a wide range of Reynolds numbers $Re_τ= 1400 - 4000$. The study is based on estimation of the convection velocity using decomposed streamwise skewness factor introduced in (Drozdz A., Elsner W., Int. J. of Heat and Fluid Flow. 63 (2017) 67\-74) and verified by means of two-point correlation method. It was shown that in the overlapping region of APG flows, the convection velocity profiles (when scaled in viscous units) reassemble the universal logarithmic law characteristic for the ZPG flows up to Clauser-Rota pressure gradient parameter $β\lesssim 19$ for the considered range of Reynolds number, what means that in the inner region of TBL the friction velocity in APG is not proportional to $U$ (as in ZPG) but to $U_C$ instead. The physical mechanism that explains the impact of increased convection velocity on the mean flow is proposed. The difference between $U_C$ and $U$ increases as a function of APG, which causes the stronger sweeping that enhances momentum transfer to the wall and compensates the weaker mean shear profile that is created by lower vorticity near the wall. This effect is a result of an enhancement of amplitude modulation of the small scales by large scale motion. The process becomes more pronounced as eddy density grows, so with increasing Re. The proposed model addresses a number of literature observations found in adverse pressure gradient flows which have been so far left without a well-founded explanation.
