event
Monday 11 Oct 2010: Non-equilibrium Brownian coagulation of dense aerosols
Dr Tomasz M. Trzeciak - University of Exeter, UK
Physics, 4th Floor interaction area 11:00-12:00
Due to the fact that particle collisions in the coagulation process are inelastic, part of particles' translational kinetic energy is lost to the internal heat. With an increasing rarefaction of the suspending gas there is a point, when the particle relaxation time becomes longer than the characteristic coagulation time. At that point the average velocity of particles will decrease below the value predicted by the energy equipartition theorem for there is insufficient time between the collisions to restore the thermal equilibrium. This reduced particle velocity results in a lower coagulation rate and this effect is shown through first principle Brownian dynamics simulations. A model quantifying the effect of the coagulation rate suppression is proposed by introducing the concept of thermalization number defined as the reduced mean kinetic energy of particle motion. An expression for this quantity is derived and used to extend the classical coagulation theory to this new non-equilibrium regime of coagulation. Closed form, analytical formula for the coagulation kernel in this regime is obtained and its excellent agreement with the first principle simulations is demonstrated.
