双钟火箭喷管被动流动分离控制
Passive flow-separation control in a dual-bell rocket nozzle
摘要：
对高雷诺数海平面模式下的亚尺度冷气双钟形喷管流场进行了延迟分离涡模拟，喷管压比NPR=45.7。在这种状态下，过度膨胀流在拐点处（即两个钟形件之间的接合处）呈现对称且受控的流分离，从而导致相对于常规钟形喷嘴产生低含量的空气动力学侧载荷。在频域中对喷管壁面压力信号进行了分析，并与文献中相同几何形状和流动条件下的实验数据进行了比较。在时间和空间（方位波数）的傅立叶频谱显示存在一个持久的音调与对称的冲击运动。激波和湍流结构只会轻微地激发非对称模态。侧载荷幅值的低平均值与实验结果吻合较好，证实了拐点抑制了分离激波与分离剪切层之间的气动声学干扰。
英文摘要：
A delayed detached eddy simulation of a sub-scale cold-gas dual-bell nozzle flow at high Reynolds number and in sea-level mode is carried out at nozzle pressure ratio NPR=45.7. In this regime the over-expanded flow exhibits a symmetric and controlled flow separation at the inflection point, that is the junction between the two bells, leading to the generation of a low content of aerodynamic side loads with respect to conventional bell nozzles. The nozzle wall-pressure signature is analysed in the frequency domain and compared with the experimental data available in the literature for the same geometry and flow conditions. The Fourier spectra in time and space (azimuthal wavenumber) show the presence of a persistent tone associated to the symmetric shock movement. Asymmetric modes are only slightly excited by the shock and the turbulent structures. The low mean value of the side-loads magnitude is in good agreement with the experiments and confirms that the inflection point dampens the aero-acoustic interaction between the separation-shock and the detached shear layer.
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