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Abstract: This paper presents and discusses the results of the “2022 International Computational Fluid Dynamics Challenge on violent expiratory events” aimed at assessing the ability of different computational codes and turbulence models to reproduce the flow generated by a rapid prototypical exhalation and the dispersion of the aerosol cloud it produces. Given a common flow configuration, a total of 7 research teams from different countries have performed a total of 11 numerical simulations of the flow dispersion by solving the Unsteady Reynolds Averaged Navier–Stokes (URANS) or using the Large-Eddy Simulations (LES) or hybrid (URANS-LES) techniques. The results of each team have been compared with each other and assessed against a Direct Numerical Simulation (DNS) of the exact same flow. The DNS results are used as reference solution to determine the deviation of each modeling approach. The dispersion of both evaporative and non-evaporative particle clouds has been considered in 12 simulations using URANS and LES. Most of the models predict reasonably well the shape and the horizontal and vertical ranges of the buoyant thermal cloud generated by the warm exhalation into an initially quiescent colder ambient. However, the vertical turbulent mixing is generally underpredicted, especially by the URANS-based simulations, independently of the specific turbulence model used (and only to a lesser extent by LES). In comparison to DNS, both approaches are found to overpredict the horizontal range covered by the small particle cloud that tends to remain afloat within the thermal cloud well after the flow injection has ceased.
Keywords: numerical simulations, computational fluid dynamics
Published in DKUM: 28.03.2024; Views: 456; Downloads: 464
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Abstract: V magistrskem delu je opisan proces izdelave numeričnega modela detekcije in obravnave ekscentričnega trka za namen raziskovanja problematike iz področja interakcij delcev v večfaznih tokovih. Matematični model temelji na predpostavki o idealno togem trku, z zanemarljivim prispevkom trenja. Numerična formulacija je sestavljena iz diskretizacije geometrije trodimenzionalnih delcev, detekcije trka med delci z določanjem stopnje prekrivanja, transformacije vektorskih veličin v koordinatni sistem obravnave, numeričnega reševanja sistema enačb in aplikacije rezultatov na gibalno stanje. Zgrajeni model je bil preverjen skozi proces verifikacije z poznanimi analitičnimi primeri trkov delcev, ter skozi proces validacije s spremljanjem ohranitve energije skozi obravnavo gruče naključnih trkov. Glede na rezultate je v zaključnem sklepu model bil prepoznan kot primeren za obravnavo namenske problematike, z upoštevanjem omejitev, predstavljenih skozi vsebino te naloge.
Keywords: večfazni tok, ekscentrični trk, detekcija trka, numerični model
Published in DKUM: 11.09.2018; Views: 1429; Downloads: 222
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Keywords: aerodinamika, dirkalna vozila, športni avtomobili
Published in DKUM: 08.10.2015; Views: 1980; Downloads: 164
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