Development of meshless numerical method for simulation of compressible two-phase flow

Rana, Khush Bakhat (author), Šarler, Božidar (mentor)

The meshless diffuse approximate method and phase-field method have been combined to simulate compressible two-phase gas-liquid flow problems. The gas and the liquid behave in a Newtonian way. The model employs coupled mass, momentum, energy, equation of state and Cahn-Hilliard equations. The Navier-Stokes part is solved by pressure implicit with the splitting of operators pressure-velocity coupling. The space discretisation is performed by weighted least squares approximation on the nodes of overlapping subdomains, polynomial shape functions of second order and Gaussian weights. The numerical model's versatility is shown through its application to a wide range of single-phase and two-phase compressible and incompressible two-dimensional and axisymmetric test cases. A detailed parametric study of the influence of node density, shape function order, Gaussian weight’s shape and the local subdomain size on the meshless solution was performed. The accuracy and robustness of the developed numerical methods are verified by comparing the meshless results of the test cases with the classical mesh-based finite volume method studies performed with the open-source codes Gerris and OpenFOAM® and previously existing studies. A good agreement is achieved. The conducted research is directed towards numerically modelling gas-focused micro-jets used in serial femtosecond crystallography experiments.

• Language: English
• Keywords: computational fluid dynamics, two-phase gas-liquid flow, compressible flow, phase-field method, meshless method, diffuse approximate method, PISO algorithm, gas-focused micro-jet
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FS - Faculty of Mechanical Engineering
• Publisher: [K. B. Rana]
• Year: 2025
• Number of pages: XXX 149 str.
• PID: 20.500.12556/RUL-166922
• UDC: 532:544.27:004.942(043.3)
• COBISS.SI-ID: 224913923
• Publication date in RUL: 31.01.2025

Secondary language

• Language: Slovenian
• Title: Razvoj brezmrežne numerične metode za simulacijo stisljivega dvofaznega toka

Abstract

Za simulacijo problemov stisljivega dvofaznega toka plina in kaplejevine sta bili združeni brezmrežna difuzijska aproksimativna metoda in metoda faznega polja. Plin in kapljevina se obnašata Newtonsko. Model uporablja sklopljene enačbe ohranitve mase, gibalne količine, energije, enačbo stanja in Cahn-Hilliardovo enačbo. Navier-Stokesov del je rešen tlačno implicitno z razcepitvijo operaterjev za tlačno-hitrostno sklopitev. Prostorska diskretizacija je izdelana z aproksimacijo na podlagi uteženih najmanjših kvadratov na vozliščih prekrivajočih se poddomen, polinomskimi oblikovnimi funkcijami drugega reda in Gaussovimi utežmi. Vsestranskost numeričnega modela je prikazana z njegovo uporabo na številnih enofaznih in dvofaznih stisljivih in nestisljivih dvodimenzionalnih in osno simetričnih testnih primerih. Izvedena je bila podrobna parametrična študija vpliva gostote vozlišč, reda oblikovne funkcije, oblike Gaussove uteži in velikosti lokalnih poddomen na brezmrežno rešitev. Natančnost in robustnost razvite numerične metode sta verificirani s primerjavo brezmrežnih rezultatov testnih primerov s študijami izvedenimi s klasičnima odprtokodnima mrežnima računalniškima programoma na podlagi metode končnih volumnov Gerris in OpenFOAM®, ter predhodno izvedenimi študijami. Doseženo je dobro ujemanje. Izvedene raziskave so usmerjene v numerično modeliranje plinsko fokusiranih mikro-curkov, ki se uporabljajo v serijskih femtosekundnih kristalografskih eksperimentih.

• Keywords: računalniška dinamika tekočin, dvofazni tok plin-kapljevina, stisljivi tok, metoda faznega polja, brezmrežna metoda, difuzivna aproksimacijska metoda, algoritem PISO, plinsko fokusirani mikro-curek