使用米氏散射方法测量液射流上的纳米级表面扰动

中文摘要 AI 辅助

液射流的Plateau--Rayleigh不稳定性控制着广泛的自然和工业过程。虽然经典线性稳定性理论能够准确预测扰动增长率和主导波长，但它无法量化纳米级初始表面扰动的幅度和频谱。这一关键缺失信息阻碍了对射流破碎长度和液滴生成的准确预测。传统光学成像受衍射极限限制，缺乏分辨此类纳米级表面波动的能力。本文提出一种基于米氏散射的测量技术，用于表征液射流上的纳米级表面扰动。该方法采用薄激光片照亮射流，并在指定的方位角观测角度捕获散射光。基于Lorenz--Mie理论，我们开发了一种结合余弦相似度和互相关的反演算法，从测量的散射条纹中重建射流表面扰动，实现了对直径变化的亚纳米分辨率检测，整体测量精度受限于0.18 nm RMS的背景噪声底。对前向散射和彩虹散射信号的比较分析进一步证实，当振幅达到几纳米时，表面扰动变为轴对称，从而满足散射模型的假设。与高速成像和扫描电子显微镜的同步验证证实了我们散射方法的定量准确性。应用于近喷嘴区域时，该技术识别出初始扰动的两个内在特征：随机脉冲状波动和低频振荡。

英文摘要

The Plateau--Rayleigh instability of liquid jets governs a wide range of natural and industrial processes. While the classical linear stability theory accurately predicts disturbance growth rates and dominant wavelengths, it cannot quantify the amplitude and frequency spectrum of nanoscale initial surface disturbances. This critical missing information prevents accurate forecasting of breakup lengths and droplet generation. Conventional optical imaging is constrained by the diffraction limit and lacks the capability to resolve such nanoscale surface fluctuations. Here we introduce a Mie-scattering-based measurement technique to characterize nanoscale surface disturbances on liquid jets. The method employs a thin laser sheet to illuminate the jet, with scattered light captured at designated azimuthal observation angles. Based on Lorenz--Mie theory, we develop an inversion algorithm incorporating cosine similarity and cross-correlation to reconstruct jet surface disturbances from measured scattering fringes, achieving a sub-nanometer resolution for detecting diameter variations, with an overall measurement precision limited by a background noise floor of 0.18 nm RMS. Comparative analyses of forward and rainbow scattering signals further confirm that the surface disturbances become axially symmetric as the amplitude reaches a few nanometers, and thus satisfies the assumptions of the scattering model. Synchronous validations against high--speed imaging and scanning electron microscopy corroborate the quantitative accuracy of our scattering method. Applied in the near-nozzle region, the technique identifies two intrinsic signatures of initial perturbations: stochastic pulse-like fluctuations and low-frequency oscillations.

发表机构

• School of Astronautics, Beihang University（北京航空航天大学宇航学院）
• Ningbo Institute of Technology, Beihang University（北京航空航天大学宁波研究院）
• National Key Laboratory of Aerospace Liquid Propulsion（航天液体动力国家重点实验室）
• State Key Laboratory of High-Efficiency Reusable Aerospace Transportation Technology（高效可重复使用航天运输技术国家重点实验室）

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