-- A water drop hits a vibrating copper plate and flattens within milliseconds. In one published experiment, stronger vibration made the drop spread farther across the plate. As it pulled back, it reached a lower height. A high-speed camera recorded both changes.
Brief events like these were among the research topics at the 2026 Conference on Multiphase Flow of the Chinese Society of Engineering Thermophysics, held Oct. 30 to Nov. 1 in Nanjing, China. Southeast University, one of the co-hosts, reported that the meeting drew more than 1,000 people from universities, research institutes and companies.
Three studies published before the meeting show what high-speed cameras can measure in gas-liquid two-phase flow. The researchers tracked a drop hitting a surface, a jet breaking into spray and bubbles leaving a heated surface. The results have applications in spray cooling, mine dust control and heat transfer.
A drop spreads and pulls back
Xinwen Chen and colleagues used a Revealer 5KF10 high-speed camera at 5,000 frames per second to record water drops striking a copper plate. In one comparison, the surface roughness stayed the same and the drops struck while the plate was moving upward. At the higher vibration setting, the maximum spread was 22% wider and the peak height during recoil was 32% lower, the researchers reported in the International Journal of Heat and Mass Transfer.
The image sequence captures how quickly liquid spreads across a surface and how it moves afterward. Those are separate measurements for researchers studying how a spray wets a surface during cooling.
Four rows of high-speed images show water drops striking a vibrating copper plate under four vibration conditions. The surface roughness was 0.4 micrometers. The sequence shows impact, spreading, recoil and later oscillation. From Figure 5 in Chen et al. (2024), International Journal of Heat and Mass Transfer. Cropped from the source page.
A wider spray travels a shorter distance
Huitian Peng and colleagues aimed a Revealer high-speed camera at an air-atomizing nozzle to observe the liquid breaking up. With water supply pressure held at 0.5 megapascals, raising air supply pressure from 0.05 to 0.4 megapascals widened the spray angle from about 69 to 96 degrees. The spray traveled 2.52 meters, down from 3.16 meters, the team reported in the journal Energy.
In separate measurements at Wangpo Coal Mine, the team reported a 92.07% reduction in respirable dust at one sampling point with the air supply set to 0.4 megapascals. The spray images showed how the nozzle dispersed the liquid. The reduction figure came from dust sampling in the mine.
Bubbles leave a heated surface
Xiang Wang and colleagues used a high-speed camera to watch bubbles through a window in a low-pressure boiling chamber. In images taken at a heat flux of 180 kilowatts per square meter, a surface with narrower, more closely spaced pillars produced smaller departing bubbles. With wider pillars and gaps, bubbles could merge between pillars before breaking free.
Separate thermal measurements at 40 kilopascals showed that the surface with the smaller pillars reached a critical heat flux about 6.5% higher than that of a smooth surface at the same pressure. Critical heat flux marks the point at which boiling can no longer remove heat as efficiently. The researchers published the study in the International Journal of Heat and Mass Transfer.
For a nozzle meant to suppress dust, the angle and distance measurements help researchers assess whether the spray reaches its target. For a surface meant to cool equipment, bubble images can be compared with thermal measurements under matched conditions to study how changes to the surface affect heat transfer.
The drop on the copper plate also gives researchers a way to test computer models. A frame-by-frame comparison can show whether a model predicts when the drop reaches its widest point and how it pulls back. Those details help researchers assess whether the model captures how vibration affects the drop at each stage.
Sources
Xinwen Chen et al. Interaction between droplet impact and surface roughness considering the effect of vibration. International Journal of Heat and Mass Transfer, 220 (2024), 125018. Figure 5 and Section 3.3. 10.1016/j.ijheatmasstransfer.2023.125018
Huitian Peng et al. Atomization law and dust reduction effect of air-atomizing nozzles determined by CFD and experiments. Energy, 318 (2025), 134822. Figure 10 and Tables 4 and 7. 10.1016/j.energy.2025.134822
Xiang Wang et al. Correlation of pool boiling heat transfer and enhancement by microstructure surfaces at sub-atmospheric pressures. International Journal of Heat and Mass Transfer, 226 (2024), 125465. Figures 6 and 10. 10.1016/j.ijheatmasstransfer.2024.125465
Southeast University. Report on the 2026 multiphase flow conference in Nanjing. Nov. 5, 2026. Published in Chinese. University conference report
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