Comparison in high-speed droplet impact between single and multiple collisions against a wall covered with a liquid film

Yoichiro Fukuchi, Tomoki Kondo, Keita Ando

Research output: Chapter in Book/Report/Conference proceedingConference contribution


In semiconductor industry, liquid jet cleaning plays an important role because of its high cleaning efficiency and low environmental load. However, its cleaning mechanism is not revealed in detail because the experimental observation of high-speed and sub-micron droplets is challenging. Furthermore, higher impact velocity may give rise to surface erosion due to water-hammer shock loading from the impingement. To study cleaning mechanisms and surface erosion, numerical simulation of droplet impingement accounting for both viscosity and compressibility is an effective approach. In the previous study, wall-shear-flow generation has evaluated from the simulation of high-speed single droplet impingement. To evaluate more practical model of jet cleaning application, simulation of two droplets simplifying mono-dispersed splay of droplet train is favorable. Here, we numerically simulated impingement of two droplets, which allows for evaluating water-hammer pressure and wall shear stress. We consider the case of two water droplets (200 µ m in diameter) that collides continuously, at speed 50 m/s, at the inter-droplet distance from 250 to 400 µ m, with a no-slip rigid wall covered with a water layer (100 µ m in thickness). The simulation is based on compressible Navier-Stokes equations for axisymmetric flow and the mixture of two components appears in numerically diffusion interface expressed by the volume average and advection equation. The simulation is solved by finite-volume WENO scheme that can capture both shock waves and material interface. In our simulation, the impingement of second droplet impingement gain higher shear stress than the single droplet impingement. At the case that the inter-droplet distance is 300 µ m, maximum shear stress is 30.22 kPa (at the second droplet impingement), which is much larger than at the first droplet impingement (8.42 kPa). This result indicates how the second droplet impingement make wall shear flow induced by first droplet impingement stronger. From the parameter study of the inter-droplet distance, we can say that wall shear stress gets stronger as water layer thickness decreases. Furthermore, the maximum wall pressure is 1.96 MPa at the second droplet impingement, which is larger than at the first droplet impingement (1.46 MPa). From this study, the evaluation of surface erosion caused by jet cleaning is expected. The simulation suggests that multiple droplets impingement continuously may gain higher cleaning efficiency, which will give us a fundamental insight into liquid jet cleaning technologies. For further study, simulation of water column impingement and comparing the result of impingement of two droplets are expected.

Original languageEnglish
Title of host publicationMultiphase Flow
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791859087
Publication statusPublished - 2019 Jan 1
EventASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019 - San Francisco, United States
Duration: 2019 Jul 282019 Aug 1

Publication series

NameASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019


ConferenceASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019
Country/TerritoryUnited States
CitySan Francisco


  • Droplet impact
  • Liquid jet cleaning
  • Wall shear flow

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes


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