本文目的是研究声激励对自由射流流场结构的影响。采用多重网格方法对声激励下三维自由射流（Re=2200）的空间演化做大涡模拟。比较了无激励情况和不同频率声激励下射流涡量场的改变。计算表明，当声激励频率接近射流优势频率时，涡量场结构变化显著。周向涡量集中卷起形成大的涡环，射流径向扩展增大。当激励频率接近优势频率两倍时，有涡合并现象，说明出现次谐波。当激励频率远高于优势频率时，流场结构与无激励情况差别不大。本文还给出在接近优势频率的激励下射流中的流向涡量的分布，定性上与实验观察相同。
The motivation of this paper is to investigate the effects of acoustic modulation on the structures of free jet. Large eddy simulation is performed on three dimensional free jet of Re number 2200 with multigrid method. Comparisons of the vorticity fields are made between the unmodulated jet and perturbed jets with different modulation frequencies. When the modulation fi-equency is near the preferred mode of the natural jet, the flow field changes significantly. The azimuthal vorticity rolls up into large vortex rings, and the jet spreads more widely. When the modulation frequency is about the twice of the preferred mode, vortex pairing happens and the subharmonie wave becomes dominant. The flow fields are almost the same as the natural jet when the modula- tion frequency is much higher than the preferred mode. The distribution of streamwise vorticity is examined for the modulated jet near the preferred mode, and agrees qualitatively with the experiments.
参考文献
| [1] | J. Gullbrand;X. S. Bai;L Fuchs .High-order Cartesian grid method for calculation of incompressible turbulent flows[J].International Journal for Numerical Methods in Fluids,2001(6):687-709. |
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