Simulating dust monomer collisions: expansion of the JKR theory
Speaker: Yuki Yoshida
Abstract:
Dust is aggregate of monomers. Monomer is minimum building block of dust and have sub-μm size. Dust grows by collisional sticking, but fragmentation can occur for large dust, and the dust growth is stopped. Therefore investigating dust maximum size and critical velocity of sticking is important to understand the dust growth. Numerical simulations of aggregate collisions have investigated the critical velocity of dust compression and disruption, and the dust size evolution (e.g., Wada et al. 2013; Suyama et al. 2012). They used the JKR theory to calculate the monomer interactions. However, dust collision experiments showed that the bouncing velocity is larger than the theoretical value (e.g., Poppe et al. 2000, Wada et al. 2008). It is suggested that this is because the JKR theory does not consider microscopic physics (Tanaka et al. 2015). Therefore, we construct a new contact model by Molecular Dynamics (MD) simulation.
First, we performed MD simulations of monomers’ head-on collisions and investigated the coefficient of restitution, e, changing the monomer size, impact velocity, and temperature. We found that e decreases with decreasing monomer radius, increasing impact velocity larger than 50 m/s and increasing temperature. Next, we extended the contact model by adding dissipative forces to the JKR theory to reproduce the MD results. We found that a dissipative force model proportional to (relative velocity)3 and (contact radius)3/2 can reproduce the MD results well. However, another energy dissipation is required to reproduce the MD simulations for high-velocity collisions. We discuss the MD results and the new model in my presentation.