三维可压缩混合层中扰动演化的研究

An investigation for the evolvement of disturbances in 3-D compressible mixing layer

为了利用被动控制增强可压缩混合层中混合效率,本文用数值模拟的方法研究了三维可压缩混合层中扰动向下游的演化。通过在入口处引入不同的不稳定T-S波,给出了扰动随空间的演化过程,及马赫数对扰动演化的影响。计算结果表明在马赫数较小时,扰动波增长很快,当马赫数增大时,扰动所形成的流向涡的强度会减弱。这一结论与流动稳定性分析结果是一致的。

For enhancing the mixing of compressible mixing layers by passive control, the evolution of disturbances in three-dimensional compressible mixing layers was investigated using method of direct numerical simulation, in which high order compact finite difference schemes are employed. Putting different instability T- S waves upstream, the disturbances propagating downstream with different Mach numbers will be given. The results are as following: There will be spiral large-scale vortices structure in mixing layer when conjugate T-S waves are put in the inlet of mixing layer, and the direction of arising vortices is parallel to the flow direction, which accords with the conclusion of non-compressible flow experiment. Also the number of merging vortices can be controlled via putting sub-harmonic or 1/3 harmonic. The stream vortices developing from the disturbances go up quickly with small Mach number. Under different Mach number, the positions where vortices and the first merging appear ance are almost the same, while the intensity are weakening along with Mach number becoming large. These results are in agreement with the results of hydrodynamic stability (theory).