不同外激励参数下射流的附壁振荡特性

为获得新型外激励振荡器的振荡性能跟随外激励流参数和时变模态的改变而变化的规律和敏感性,为该振荡器的高效应用提供依据与参考,采用计算流体动力学(computational fluid dynamics,简称CFD)数值模拟和实验的方法,对激振能力和振荡射流的总压保持率K的变化进行了考察。结果表明:总压保持率K随外激励流总压的降低而减小;非激励侧泄漏的激励流也使K略降,但却显著降低了激振能力;而激励流占空比减小即提前关断,会显著降低振荡射流总压保持率;激励流起始压力渐升的影响较小,而中后期压力丧失或渐降,会使K有较大跌落。研究证明,外激励振荡器对激励流参数的变化具有较强的适应性,20%以内的变化不影响振荡稳定,仍能维持较高的总压保持率K,可振区间内最低K比现有的自激励振荡器高出10%以上。

Characteristics of the Jet Wall Oscillation Corresponding to Different External Excitation Parameters

This paper investigates the changing rules and sensitivity of the external excitation oscillator when the parameters and time-varying modality of the external excitation stream changes. The numerical simulation and experiment are employed to investigate the changes of stimulation ability and retention ratio of total pressure K of oscillation jet flow. The results show that K decreases when the total pressure of external excitation steam drops. The leaking excitation stream on the non-excitation side also makes K slightly down and significantly reduces the excitation power. The retention ratio of the total pressure K is observably reduced when the duty ratio decreases due to the early shut-off of the excitation stream. The gradual advance of initial pressure of excitation stream has little effect on K, but loss or gradual decline of the pressure during the middle and later periods markedly decreases K. The studies show that external excitation oscillator adapts better to the changes of excitation stream parameters. When the parameters fluctuate less than 20%, the performance of the oscillation can still maintain higher retention ratio of total pressure K. The lower limit of K is 10% higher than that of the existing self-excitation oscillator. The study provides the basis and reference for effective application of the oscillator.