基于Van der Pol方程的双脉冲射流控制机理研究

Study on the control mechanism of dual pulsed jets based on the van der pol equation

针对双脉冲射流流动控制机理不明的问题,建立了双激励受迫Van der Pol理论模型,用于指导双脉冲射流流动控制参数选取及揭示其流动控制机理。该理论模型基于弱非线性稳定性理论,通过对不同参数下模型方程的求解,将理论模型与典型分离流场中双脉冲射流的数值模拟进行对比研究,发现该理论模型与数值模拟结果在频率、相位等特性上相吻合,验证了该模型的有效性。其中,理论模型和数值模拟结果均表明:双脉冲射流在折合频率都为1且同相位时控制效果最好。进一步的分析表明,脉冲射流依靠流动不稳定性增强主流与分离流间的动量传递以抑制流动分离,邻近双脉冲射流的相位具有相干效果,且双脉冲射流通过预锁频效应产生相比单脉冲射流的控制效果增益。针对双脉冲射流流动控制的机理为脉冲射流器的设计和应用指出了一种可能方向。

Because the control mechanism of dual pulsed jets is not clear,a theoretical forced van der Pol model with dual excitation was established to guide the selection of dual pulsed jets parameters and reveal its flow control mechanism.The theoretical model was based on the flow stability theory with weak nonlinearity.By solving the model equations under different parameters,the theoretical results were compared with the numerically simulated results of the dual pulsed jets in typical flow separation.It is found that the theoretical model is consistent with the simulated results in the characteristics of excitation frequency and phase,which verify the validity of the model.Both the theoretical model and numerically simulated results show that the dual pulsed jets reach the best control performance when their reduced frequencies are 1 and their phases synchronize.Further analysis shows that the flow separation is restrained by the momentum transfer between the main stream and the separated flow,which is enhanced by the flow instability.The dual adjacent pulsed jets interfere with each other and the control performance gains compared with the single pulsed jet through the pre-locking effect.According to the flow control mechanism of dual pulsed jets,a possible direction for the design and application of pulsed jets is presented.