Kinetic description of coagulation and fragmentation in dilute granular particle ensembles

¹ Institute of Physics, University Potsdam - Am Neuen Palais 10 14469 Potsdam, Germany
² School of Engineering, The University of Birmingham Edgbaston, Birmingham B15 2TT, UK

Corresponding author: F.Spahn@agnld.uni-potsdam.de

Received: 16 December 2003
Accepted: 4 June 2004

Abstract

We derive kinetic equations covering coagulation and fragmentation of granular gases including a combined dynamics of the mass spectrum and the velocity distribution. We will focus on coagulation, that can only occur at low impact velocities where attractive forces and dissipation prevent a post-collisional separation. We calculate an impact speed-dependent threshold velocity for coagulation to occur based on binary collision dynamics of viscoelastic granular particles including adhesive forces and determined by the masses, and the material of the colliding particles. Growth processes are immensely slowed down due to and the resulting restriction in phase space, and do furthermore depend on the ratio of threshold and thermal velocity of a considered particle ensemble. The Smoluchowski equation emerges from the general kinetic approach as a special case.