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摘要:
采用激光诱导荧光的流动显示方法研究了在一对反对称模式工作的脉冲射流激励下，雷诺数约为33 000的圆形湍流射流的流场。捕捉了剪切层中大尺度展向涡结构的演化发展过程，研究了激励频率和振幅对涡结构以及强化混合效果的影响。结果表明：受激励后的主喷流剪切层中产生了交错的展向涡结构，引起了喷流的振荡，增强了卷吸能力。激励频率主要影响相邻涡环间的距离。存在最佳激励频率使喷流在受激励平面远场分叉、剪切层扩展最宽。激励振幅对涡结构也存在较大影响，振幅较大时产生的涡结构尺度更大、相干性更强、强化混合效果更好。
Abstract:In this paper, a turbulent jet with Reynolds number 33 000 forced by a pair of pulsed jets working in antisymmetric mode is investigated using laser-induced fluorescence technique. The evolution of large-scale vortex structures in the shear layer is captured and the effect of forcing frequency and amplitude of pulsed jets on vortex structure and mixing enhancement is studied. It is found that inclined and staggered vortex structures are generated in the shear layer, causing the oscillation of primary jet and promoting entrainment. The forcing frequency mainly influences the distance of neighboring vortex rings. There exists optimal excitation frequency that causes the primary jet bifurcating in the far field and spreading most in the shear layer in the forced plane. The forcing amplitude also has effect on the vortex structure. The vortex structures are larger and more coherent at high amplitude, resulting in better mixing enhancement.
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Key words:
- flow control /
- flow visualization /
- mixing enhancement /
- pulsed jet /
- vortex ring structure
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图 6 脉冲延时信号发生器以及固体继电器
Figure 6. Pulse time-delay signal generator and solid state relay
图 7 反对称模式时激励器产生脉冲射流速度时序
Figure 7. Time sequence of velocity of pulsed jet generated by actuator in antisymmetric mode
图 9 SrD=0.077时，受激励平面大尺度涡结构演化过程
Figure 9. Evolution of large-scale vortex structures at forced plane when SrD=0.077
图 10 不同激励频率时瞬态以及相位平均流场
Figure 10. Instantaneous and corresponding phase averaged images of flow field at forced plane at different excitation frequencies
图 11 不同激励频率下的时均流场
Figure 11. Time-averaged flow field at different excitation frequencies
图 12 不同激励振幅时瞬态和相位平均流场
Figure 12. Instantaneous and corresponding phase averaged images of flow field at different excitation amplitudes
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