Sphere bouncing on a wet plate (5X slower than real time)
The normal coefficient of restitution, first introduced by Isaac Newton in ‘The mathematical principles of natural philosophy’ (Corollary VI) as the relative rebound over the impact velocities, provides a convenient way of characterizing the energy dissipation associated with the impacts of spherical particles. It is not only a material property as Newton assumed, but also depends on the impact velocity, dimension of the particles, surface properties, etc. It represents the energy dissipation from viscoelasticity, plastic deformation, mechanical waves, friction, adhesion, etc.

Understanding the energy dissipation is one of the most fundamental questions to decipher wet granular dynamics. A reliable `microscopic’ impact model facilitates large scale computer simulations of wet granular flow in terms of efficiency and accuracy and sheds light on widespread applications in civil and chemical engineering.
 
The goal is to understand:
  • What is the role played by the wetting liquid?
  • Can we predict the coefficient of restitution for wet particle impact?

References

  • “A hard-sphere model for wet granular dynamics”, Kai Huang in Proceedings of China-Europe Conference on Geotechnical Engineering, Springer Series in Geomechanics and Geoengineering , 169 – 173 (2018) https://doi.org/10.1007/978-3-319-97112-4_38
  • [Use the model in numerical simulations for analyzing wave phenomena] “Internal and surface waves in vibrofluidized granular materials: Role of cohesion”, Kai Huang Phys.Rev. E 97, 052905 (2018) doi:10.1103/PhysRevE.97.052905 arXiv:1802.09615
  • [Explains why Stokes number matters in predicting wet CoR] “Influence of liquid film thickness on the coefficient of restitution for wet particles”, Thomas Mueller and Kai Huang Phys.Rev. E 93, 042904 (2016) doi:10.1103/PhysRevE.93.042904 arXiv:1601.07032
  • “Scaling of the normal coefficient of restitution for wet impacts”, Thomas Mueller, Frank Gollwitzer, Christof Kruelle, Ingo Rehberg and Kai Huang, AIP Conf. Proc. 1542, 787 (2013) doi:10.1063/1.4812049PDF
  • [How to predict wet CoR analytically] “Coefficient of restitution for wet particles “, Frank Gollwitzer, Ingo Rehberg, Christof Krülle and Kai Huang, Phys.Rev. E 86, 011303 (2012), doi:10.1103/PhysRevE.79.010301arXiv:1202.1750