arXiv subjects

Jiguang Hao

Publications and source records attributed to Jiguang Hao.

3 recordsLinked to original sources

arXiv2023

On the fluid slip along a solid surface

It is commonly assumed that fluid cannot slip along a solid surface. The experimental evidence generally supports this assumption. We demonstrate that when the change of the relative velocity of a fluid and a solid wall is sufficiently rapid, the slip does occur; the fluid is unable to adjust if acceleration is large enough, and it slips. We use droplet impact on a moving surface to demonstrate and estimate the slip length. We also estimate fluid acceleration, which is required to cause an observable slip.

physics.flu-dyn↗

arXiv2023

On droplet falling velocity

Droplet velocities used in impact studies were investigated using high-speed photography. It was determined that droplets do not reach terminal velocity before a typical impact, raising the question of how to predict impact velocity. This question was investigated experimentally, and the results were used to validate a theoretical model. Experiments used droplets with diameters 0.70mm to 4.0mm, liquids with a density of 791kg/m3 to 1261.5kg/m3, and viscosities 1.0mPa s to 1390.0mPa s, release height up to 1.0m. The ambient pressure was varied between atmospheric and 25kPa. It was shown that the droplet velocity increased with the droplet diameter, liquid density, release height, and ambient pressure reduction but changed marginally with viscosity. A simple dynamic model accounting for the aerodynamic drag was proposed. This model, which uses empirical formulae to determine the instantaneous drag coefficient, predicts velocity, which agrees well with the experimental data within the range of parameters used in this study. It provides a valuable tool for the design of droplet impact studies.

physics.flu-dyn↗

arXiv2022

Droplet penetration through an inclined mesh

Droplets with different Weber numbers We impacting meshes at various inclination angles were investigated using high-speed photography. It was found that the droplet mesh penetration can be completely suppressed by inclining the mesh. The phase diagrams in the (We, α) plane determining the expected type of penetration have been determined experimentally for meshes of various structures. It was shown that the Weber numbers for transition between no-penetration and incomplete penetration as well as for transition between incomplete penetration and complete penetration increase monotonically with α. A simple model for predicting the transition thresholds is proposed and is validated by comparisons with experimental results. It is shown that both the inclination angle and the mesh open area fraction determine the type of penetration.

physics.flu-dyn↗