一种非线性房间模态决定了大腔体合成射流致动器在低频下的工作条件
A nonlinear room mode determines the operating conditions of a large-cavity synthetic jet actuator at low frequencies
AI总结：
本文研究大腔体合成射流致动器中第三种极低频非线性房间模态，揭示其与亥姆霍兹共振的竞争关系及对射流速度的影响，提出将其纳入设计准则以扩展最佳频率响应。
摘要：
合成射流（SJ）致动器本质上是电子、电气与机械系统的复杂组合。在理论研究中，这些元件常被简化为耦合的阻尼谐振子（DHO），它们在腔体内诱导压力场并驱动动量交换。因此，SJ致动器的性能源于这些DHO之间的耦合，自然会产生若干共振模态。专门文献中有充分证据表明，SJ致动器中存在两种共振模态：膜/压电模态和亥姆霍兹共振。在本工作中，我们报告了第三种共振模态的影响，该模态由于腔体远大于致动器所排开的体积而在极低频率下产生。我们提出证据表明，大腔体动力学与已充分描述的形成准则共同决定了SJ的性能。我们使用标准频率分析将该共振模态的强度与一阶房间模态进行了比较。与典型的房间模态不同，该共振模态的分布强烈偏向较低频率。我们还表明，通过在腔体不同位置添加障碍物，可以在较低声强下使该共振模态变暗并聚焦。该模态克服了亥姆霍兹共振，在较高声强下主导动力学。我们表明，射流和涡旋速度在低频范围内与声压曲线相似。在较高频率范围内，由于通过更小的冲程长度深入运动，其影响有所缓解，这被表征为雷诺数与斯托克斯数之间的固定关系。我们认为，大腔体动力学是一个额外要素，如果将其纳入设计准则，可以扩展SJ的最佳频率响应。
英文摘要：
Synthetic Jet (SJ) actuators are an intrinsically complex combination of electronics, electric and mechanical systems. When studied theoretically, these elements are often simplified to coupled damped harmonic oscillators (DHO) that induce a pressure field within the cavity and drive momentum exchange. Thus, the performance of an SJ actuator results from coupling these DHOs, naturally leading to a few resonant modes. There is good evidence in the specialized literature of two resonant modes developing in SJ actuators: the membrane/piezoelectric mode and the Helmholtz resonance. In this work, we report on the effect of a third resonant mode that develops at very low frequencies due to a cavity much larger than the volume displaced by the actuator. We present evidence that the large-cavity dynamics determine the SJ performance in combination with the well-described formation criteria. We compare the intensity of this resonant mode with the first room modes using standard frequency analysis. Unlike typical room modes, the distribution of this resonant mode is very biased to lower frequencies. We also show that the resonant mode may be dimmed and focused by adding an obstacle in different cavity positions for the lower sound intensities. This mode overcomes the Helmholtz resonance, dominating the dynamics for higher sound intensities. We show that jet and vortex velocities mimic the sound pressure curve for the low-frequency range. Its effect mitigates for the higher range due to a delve through smaller stroke lengths, characterized as a fixed relation between the Reynolds and the Stokes numbers. We consider that the large-cavity dynamics is an additional element that, if integrated as design criteria, could extend the optimum frequency response of SJs.
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