Projects per year
Abstract
A kinetic model of the Boltzmann equation for nonvibrating polyatomic gases is proposed, based on the Rykov model for diatomic gases. We adopt two velocity distribution functions (VDFs) to describe the system state; inelastic collisions are the same as in the Rykov model, but elastic collisions are modelled by the Boltzmann collision operator (BCO) for monatomic gases, so that the overall kinetic model equation reduces to the Boltzmann equation for monatomic gases in the limit of no translationalrotational energy exchange. The free parameters in the model are determined by comparing the transport coefficients, obtained by a ChapmanEnskog expansion, to values from experiment and kinetic theory. The kinetic model equations are solved numerically using the fast spectral method for elastic collision operators and the discrete velocity method for inelastic ones. The numerical results for normal shock waves and planar Fourier/Couette flows are in good agreement with both conventional direct simulation Monte Carlo (DSMC) results and experimental data. Poiseuille and thermal creep flows of polyatomic gases between two parallel plates are also investigated. Finally, we find that the spectra of both spontaneous and coherent RayleighBrillouin scattering (RBS) compare well with DSMC results, and the computational speed of our model is approximately 300 times faster. Compared to the Rykov model, our model greatly improves prediction accuracy, and reveals the significant influence of molecular models. For coherent RBS, we find that the Rykov model could overpredict the bulk viscosity by a factor of two.
Original language  English 

Pages (fromto)  2450 
Number of pages  27 
Journal  Journal of Fluid Mechanics 
Volume  763 
DOIs  
Publication status  Published  9 Dec 2014 
Keywords
 computational methods
 kinetic theory
 rarefied gas flow
 RayleighBrillouin scattering
 Boltzmann equation
 direct simulation Monte Carlo
 fast spectral method
 densityfluctuations
 collision operator
 lightscattering
 shock wave
 transition
Projects
 2 Finished

The First OpenSource Software for NonContinuum Flows in Engineering
Reese, J. & Borg, M.
1/10/13 → 31/03/18
Project: Research

NonEquilibrium Fluid Dynamics for Micro/Nano Engineering Systems
Reese, J., Lockerby, D. A., Emerson, D. R. & Borg, M.
1/01/11 → 16/02/16
Project: Project from a former institution
Profiles

Yonghao Zhang
 School of Engineering  Jason Reese Chair in Multiscale Fluid Mechanics
Person: Academic: Research Active