脉冲射流控制现象的自激-外激耦合模型

Coupling model of self-and external-excitation for phenomena in pulsed jet flow control

为了阐释脉冲射流控制中出现的频率依赖性、位置依赖性、条件同步性及强度依赖性这4种现象,在弱非线性稳定性理论的基础上,建立了一种简化的自激-外激耦合模型,用于近似描述脉冲射流流动控制现象。该模型由偏微分方程组构成,特定情形下可简化为常微分方程进行求解,通过将求解结果与脉冲射流控制的数值模拟及实验数据进行对比,研究发现:该自激-外激耦合模型能定性或半定量反映实际脉冲射流控制中出现的4种现象。结合模型的分析表明:脉冲射流主要利用流动的非线性不稳定性机制,通过使流场与非定常激励产生同步运动,促进主流和分离流间的动量传递,从而实现自激-外激耦合流动控制作用,并表现出脉冲射流控制的4种典型现象。

In order to explain four phenomena such as frequency-dependent, position-dependent,synchronization and intensity-dependent effects in pulsed jet flow control,a simplified coupling model of self-and external-excitation was established to approximately describe pulsed jet flow control based on the flow stability theory with weak nonlinearity. Composed of two partial differential equations, the model can be simplified as ordinary differential equations for solution in particular cases. By comparing the model results with those from numerical simulation and experiment of pulsed jet flow control,it can be found that the coupling model can qualitatively or semi-quantitatively reflect the four phenomena in actual pulsed jet flow control. Further analysis of the model showed that the pulsed jet mainly used the nonlinear flow instability mechanism to promote the momentum transfer between the main flow and the separated flow by making the flow field synchronize with unsteady excitation. As a result of self-and external-excitation coupling,flow control effects were realized and four typical and unique phenomena were presented.