Young Researchers Workshop: Kinetic theory with applications in physical sciences

Assessment of continuum breakdown in multi-scale, multi-physics flows from generalized Chapman-Enskog theory

Kelly Stephani

University of Illinois Urbana-Champaign


The distortion of the velocity distribution function from its equilibrium (Maxwellian) form is characterized according to a perturbation analysis following the formalism of Generalized Chapman-Enskog Theory. In particular, the Generalized Chapman-Enskog formulation is presented in its modified form for rapid and slow collisional processes, in which elastic processes and 'fast' inelastic processes (owing to rotational and near-resonant vibrational energy exchange) are considered as rapid collisional processes, while 'slow' inelastic processes (owing to non-resonant vibrational energy exchange and dissociation/recombination reactions) are grouped separately. This allows for the development of a general expression of the first order perturbation function and the resulting dimensionless continuum breakdown parameters. We use these quantities in an assessment of the primary breakdown mechanisms in several canonical flows.