DataSheet1_Investigation of critical response characteristics of micro-droplets under the action of low-frequency acoustic waves.docx

For the droplets with different size distribution, reasonably selecting the frequency and period of acoustic waves are of great significance to acoustic agglomeration. To investigate critical responses of microdroplets under the action of low-frequency acoustic waves, laboratory experiments and numerical simulations of acoustic interference were conducted, and statistical test and theoretical analysis were carried out. A total of 1,680 sets of experiments were performed, from which about 300,000 particle size samples were collected, with sound frequency of 30–280 Hz and the sound pressure level (SPL) of 70–130 dB. Droplet size distribution (DSD), equilibrium response time (ERT), the nodal plane in the air chamber and entrainment coefficient were analyzed. The critical SPL of acoustic agglomeration was 110 ± 15 dB based on average droplet size increment, and the variation of droplet size indicated that the ERT of acoustic intervention on microdroplets under the critical SPL was 44 ± 12 s. In addition, lower sound frequencies corresponded to larger widths of droplet size with significant response (DSSR), which were jointly affected by sound pressure gradient (SPG), the entrainment coefficient and the droplet concentration. For microdroplets with unknown particle size distribution, acoustic intervention with variable frequencies is suggested for fog elimination and precipitation enhancement.

针对具有不同粒径分布的微滴，合理选取声波的频率与周期对声波团聚（acoustic agglomeration）过程具有重要意义。为探究低频声波作用下微滴的临界响应特性，本研究开展了声干涉的室内实验与数值模拟，并进行了统计检验与理论分析。本次实验共完成1680组，采集得到约30万个粒径样本，实验覆盖声频范围30~280 Hz，声压级（SPL）范围70~130 dB。研究分析了微滴粒径分布（DSD）、平衡响应时间（ERT）、气室节面以及夹带系数等参数。基于平均粒径增量的结果，声波团聚的临界声压级为110±15 dB；微滴粒径变化规律表明，临界声压级下声波干预微滴的平衡响应时间（ERT）为44±12 s。此外，较低的声频对应更宽的显著响应粒径宽度（DSSR），该参数同时受声压梯度（SPG）、夹带系数以及微滴浓度的共同影响。对于粒径分布未知的微滴体系，建议采用变频声波干预以实现消雾增雨作业。