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Main Title: Comparison of macro- and microscopic solutions of the Riemann problem I. Supercritical shock tube and expansion into vacuum
Author(s): Hitz, Timon
Heinen, Matthias
Vrabec, Jadran
Munz, Claus-Dieter
Type: Article
Language Code: en
Abstract: The Riemann problem is a fundamental concept in the development of numerical methods for the macroscopic flow equations. It allows the resolution of discontinuities in the solution, such as shock waves, and provides a powerful tool for the construction of numerical flux functions. A natural extension of the Riemann problem involves two phases, a liquid and a vapour phase which undergo phase change at the material boundary. For this problem, we aim at a comparison with the macroscopic solution from molecular dynamics simulations. In this work, as a first step, the macroscopic solution of two important Riemann problem scenarios, the supercritical shock tube and the expansion into vacuum, were compared to microscopic solutions produced by molecular dynamics simulations. High fidelity equations of state were used to accurately approximate the material behaviour of the model fluid. The results of both scenarios compare almost perfect with each other. During the vacuum expansion, the fluid obtained a state of non-equilibrium, where the microscopic and macroscopic solutions start to diverge. A limiting case was shown, where liquid droplets appeared in the expansion fan, which was approximated by the macroscopic solution, assuming an undercooled vapour.
Issue Date: 31-Oct-2019
Date Available: 27-Jan-2020
DDC Class: 532 Mechanik der Fluide, Mechanik der Flüssigkeiten
Subject(s): Riemann problem
real gas
supercritical fluid
vacuum Riemann problem
finite volume
molecular dynamics simulation
Sponsor/Funder: DFG, 84292822, TRR 75: Tropfendynamische Prozesse unter extremen Umgebungsbedingungen
Journal Title: Journal of Computational Physics
Publisher: Elsevier
Publisher Place: Amsterdam [u.a.]
Volume: 402
Article Number: 109077
Publisher DOI: 10.1016/
EISSN: 1090-2716
ISSN: 0021-9991
Appears in Collections:FG Thermodynamik und Thermische Verfahrenstechnik » Publications

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