标题： 轴向对称逆压梯度湍流边界层结构：大涡模拟研究 显示英文标题

标题： Structure of an axisymmetric turbulent boundary layer under adverse pressure gradient: a large-eddy simulation study

摘要： 轴对称湍流边界层在强逆压梯度和弱横向曲率下的空间特征和结构通过不可压缩大涡模拟进行研究。 边界层位于一个长度为基础雷诺数为$1.9\times10^6$的旋转体的$20^{\circ}$尾锥上。 模拟结果与 Balantrapu 等人的实验测量结果一致（J. Fluid Mech., 第 929 卷，2021 年），并以新的流动场细节和物理见解显著扩展了实验结果。 平均流向速度剖面相比零压梯度平面边界层表现出较短的对数区和较长的尾流区。 采用嵌入剪切层尺度，观察到平均速度和湍流强度的三个分量具有自相似性。 流向速度波动的方位波数谱在壁法向方向有两个峰值，一个内峰位于大约 100 壁面单位的波长处，一个外峰在尾流区，其强度、波长和离壁面的距离随着下游方向增加而增长。 流向速度波动的两点相关性显示，随着倾斜角的增加，湍流结构在下游方向有显著的增长和拉长。 然而，相对于边界层厚度，相关结构在下游方向尺寸减小。 跨越边界层厚度的流向和壁法向积分长度分布类似于零压梯度平面边界层，而方位积分长度在下游测站偏离了平面边界层的行为。 显示英文摘要

摘要： The spatial characteristics and structure of an axisymmetric turbulent boundary layer under strong adverse pressure gradient and weak transverse curvature are investigated using incompressible large-eddy simulation. The boundary layer is on a $20^{\circ}$ tail cone of a body of revolution at a length-based Reynolds number of $1.9\times10^6$. The simulation results are in agreement with the experimental measurements of Balantrapu et al. (J. Fluid Mech., vol. 929, 2021) and significantly expand the experimental results with new flow-field details and physical insights. The mean streamwise velocity profiles exhibit a shortened logarithmic region and a longer wake region compared with planar boundary layers at zero pressure gradient. With the embedded-shear-layer scaling, self-similarity is observed for the mean velocity and all three components of turbulence intensity. The azimuthal-wavenumber spectra of streamwise velocity fluctuations possess two peaks in the wall-normal direction, an inner peak at the wavelength of approximately 100 wall units and an outer peak in the wake region with growing strength, wavelength and distance to the wall in the downstream direction. Two-point correlations of streamwise velocity fluctuations show significant downstream growth and elongation of turbulence structures with increasing inclination angle. However, relative to the boundary-layer thickness, the correlation structures decrease in size in the downstream direction. The distributions of streamwise and wall-normal integral lengths across the boundary-layer thickness resemble those of zero-pressure-gradient planar boundary layers, whereas the azimuthal integral length deviates from the planar boundary-layer behavior at downstream stations.