A fast spectral method for the UehlingUhlenbeck equation for quantum gas mixtures : homogeneous relaxation and transport coefficients
Wu, Lei (2019) A fast spectral method for the UehlingUhlenbeck equation for quantum gas mixtures : homogeneous relaxation and transport coefficients. Journal of Computational Physics. pp. 127. ISSN 00219991 (In Press)
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Abstract
A fast spectral method (FSM) is developed to solve the UehlingUhlenbeck equation for quantum gas mixtures with generalized differential crosssections. The computational cost of the proposed FSM is O(Mdv1Ndv+1log N), where dv is the dimension of the problem, Mdv1 is the number of discrete solid angles, and N is the number of frequency nodes in each direction. Spatiallyhomogeneous relaxation problems are used to demonstrate that the FSM conserves mass and momentum/energy to the machine and spectral accuracy, respectively. Based on the variational principle, transport coefficients such as the shear viscosity, thermal conductivity, and diffusion are calculated by the FSM, which agree well with the analytical solutions. Then, the FSM is applied to find the accurate transport coefficients through an iterative scheme for the linearized quantum Boltzmann equation. The shear viscosity and thermal conductivity of threedimensional quantum Fermi and Bose gases interacting through hardsphere potential are calculated. For Fermi gas, the relative difference between the accurate and variational transport coefficients increases with fugacity; for Bose gas, the relative difference in thermal conductivity has similar behavior as the gas moves from the classical to degenerate limits, but the relative difference in shear viscosity decreases when the fugacity increases. Finally, the viscosity and diffusion coefficients have been calculated for a twodimensional equalmole mixture of Fermi gases. When the molecular masses of the two components are the same, our numerical results agree with the variational solutions. However, when the molecular mass ratio is not one, large discrepancies between the accurate and variational results are observed; our results are reliable because (i) the method does not rely on any assumption on the form of velocity distribution function and (ii) the ratio between shear viscosity and entropy density satisfies the minimum bound predicted by the string theory.


Item type: Article ID code: 69591 Dates: DateEvent29 August 2019Published29 August 2019AcceptedSubjects: Technology > Mechanical engineering and machinery Department: Faculty of Engineering > Mechanical and Aerospace Engineering
Strategic Research Themes > Ocean, Air and SpaceDepositing user: Pure Administrator Date deposited: 03 Sep 2019 09:20 Last modified: 05 Mar 2024 01:30 Related URLs: URI: https://strathprints.strath.ac.uk/id/eprint/69591