Numerical simulation of the compressible mixing layer past an axisymmetric trailing edge
Numerical simulation of the compressible mixing layer past an axisymmetric trailing edge
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DOI：
10.1017/s0022112007008129
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发表时间：
2007-10
影响因子：
3.7
通讯作者：
Franck Simon;S. Deck;P. Guillen;P. Sagaut;A. Merlen
中科院分区：
文献类型：
--
作者：
Franck Simon;S. Deck;P. Guillen;P. Sagaut;A. Merlen
对后缘直径约为2.9×106的雷诺数进行了轴对称后缘可压缩混合层的数值模拟。分离时的自由流马赫数等于2.46，这与实验相符，并导致了很高的可压缩性。本文主要研究了湍流在附加应变率作用下的演化过程，以及环形剪切层的非定常特性。时间平均和瞬时数据都被用来进一步了解流动的动态。对时均流场的研究表明，剪切层在初始阶段有一个重要的增长速率，湍流场具有很强的各向异性。发现涡旋的对流速度比估计的等熵值略高。这证实了平面超音速/亚音速混合层中超音速模式占主导地位的结果。剪切层的发展导致各向异性迅速减小，直到流线与轴线重排开始。由于轴对称约束的增加，流线曲率的变化产生了不利的压力梯度。这种再压缩被发现减缓了涡旋对流。脚部激波的特征是几个从涡旋上部发出的对流激波，它们在自由气流中合并为再压缩激波。然后，在湍流发展尾迹中，流动加速，可压缩性水平迅速下降。对于后缘直径为0.26的Strouhal数，通过方位向模m=1的支配，发现了在近尾迹中存在大尺度结构的一些证据。
Numerical simulation of a compressible mixing layer past an axisymmetric trailing edge is carried out for a Reynolds number based on the diameter of the trailing edge approximately equal to 2.9 × 106. The free-stream Mach number at separation is equal to 2.46, which corresponds to experiments and leads to high levels of compressibility. The present work focuses on the evolution of the turbulence field through extra strain rates and on the unsteady features of the annular shear layer. Both time-averaged and instantaneous data are used to obtain further insight into the dynamics of the flow. An investigation of the time-averaged flow field reveals an important shear-layer growth rate in its initial stage and a strong anisotropy of the turbulent field. The convection velocity of the vortices is found to be somewhat higher than the estimated isentropic value. This corroborates findings on the domination of the supersonic mode in planar supersonic/subsonic mixing layers. The development of the shear layer leads to a rapid decrease of the anisotropy until the onset of streamline realignment with the axis. Due to the increase of the axisymmetric constraints, an adverse pressure gradient originates from the change in streamline curvature. This recompression is found to slow down the eddy convection. The foot shock pattern features several convected shocks emanating from the upper side of the vortices, which merge into a recompression shock in the free stream. Then, the flow accelerates and the compressibility levels quickly drop in the turbulent developing wake. Some evidence of the existence of large-scale structures in the near wake is found through the domination of the azimuthal mode m = 1 for a Strouhal number based on trailing-edge diameter equal to 0.26.