h1

TY  - THES
AU  - Đorđić, Vladimir
TI  - Moment method for polyatomic gases : from modelling to numerical simulations
PB  - RWTH Aachen University
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2025-10887
SP  - 1 Online-Ressource : Illustrationen
PY  - 2025
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2026
N1  - Dissertation, RWTH Aachen University, 2025
AB  - This thesis presents models for polyatomic gases at both mesoscopic and macroscopic levels. At the mesoscopic level, the Boltzmann equation with a polyatomic collision operator is used, and new collision kernels are proposed allowing flexibility to match specific gas properties. At the macroscopic level, moment equations – specifically the 14- and 17-moment systems – are used to model flows in the transition regime. The collision operator is evaluated to obtain transport coefficients, and a data-driven approach is used to fit model parameters to reproduce experimental values for viscosity, bulk-to-shear viscosity ratio, and the Prandtl number. To validate the models, numerical simulations of heat conduction in polyatomic gases are performed using a finite element method within the FEniCS framework. Regularized version of the 17-moment system with entropy-stable boundary conditions is developed, and its linear, steady-state form is implemented. The simulations demonstrate mesh convergence and reveal that, for small Knudsen numbers, non-equilibrium temperatures converge, consistent with previous results for polyatomic gases. The impact of bulk viscosity is also examined, showing that it primarily affects the dynamical pressure, while the total temperature profile remains stable.
LB  - PUB:(DE-HGF)11
DO  - DOI:10.18154/RWTH-2025-10887
UR  - https://publications.rwth-aachen.de/record/1023966
ER  -