Modalna dekompozicija naravne konvekcije v nenewtonskih tekočinah

magistrsko delo

Miha Rot (Author), Martin Horvat (Mentor), Gregor Kosec (Co-mentor)

Abstract

V magistrskem delu predstavimo dinamično modalno dekompozicijo tokovnih struktur, ki nastanejo pri naravni konvekciji nenewtonskih tekočin v zaprti kotanji. Fizikalni model vsebuje ohranitev mase, prenos toplote in gibalne količine, Ostwald-de Waele potenčni model za opis nenewtonske viskoznosti in Boussinesqov približek temperaturne odvisnosti gostote. Fizikalni model rešimo numerično s posplošeno metodo končnih diferenc, eksplicitnim Eulerjevim korakanjem in Chorinovo projekcijsko metodo. Implementiran rešitveni postopek preverimo preko primerjave z objavljenimi rezultati za več različnih primerov. Pokažemo dobro ujemanje z referenčnimi rešitvami in konvergentno obnašanje metode. V nadaljevanju vpeljemo dinamično modalno dekompozicijo, metodo za določanje glavnih elementov dinamike sistema, in jo demonstriramo na sintetičnem primeru. V glavnem delu metodo uporabimo za analizo načinov dinamike naravne konvekcije nenewtonske tekočine v zaprti kotanji. Analiziramo več različnih nenewtonskih tekočin v dveh različnih geometrijah in pokažemo spremembo glavnih elementov dinamike pri prehodu med stacionarnimi in nihajočimi rešitvami. Identificiramo elemente, ki pri newtonskih tekočinah niso prisotni in pokažemo, da je dinamika za psevdoplastične nenewtonske tekočine bogatejša.

Keywords

modalna dekompozicija;nenewtonske tekočine;prenos toplote;naravna konvekcija;hidrodinamika;

Data

Language:	Slovenian
Year of publishing:	2020
Typology:	2.09 - Master's Thesis
Organization:	UL FMF - Faculty of Mathematics and Physics
Publisher:	[M. Rot]
UDC:	532.5
COBISS:	31313155
Views:	488
Downloads:	95
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Modal decomposition of natural convection in non-Newtonian fluids
Secondary abstract:	In this work, we present the dynamic mode decomposition of natural convection in a non-Newtonian fluid within a closed cavity. The physical model considers mass and momentum transport, Ostwald-de Waele power-law for a description of non-Newtonian viscosity, and Boussinesq approximation for description of density-temperature dependency. The model is numerically solved with generalised finite differences, explicit Euler stepping and Chorin's projection method. The implemented solution procedure is tested by comparison of computed results with published data with good agreement achieved. We introduce dynamic mode decomposition and demonstrate its performance on a synthetic case. The main part of this work is focused on a mode analysis of natural convection of non-Newtonian fluid in a closed cavity. We analyse different non-Newtonian fluids in two different geometries where we are in particular interested in the transition from stationary to oscillatory solutions. In addition, we identify elements of dynamics that are not present in Newtonian fluids and show that the pseudoplastic non-Newtonian fluids exhibit richer dynamics in comparison with Newtonian fluids.
Secondary keywords:	modal decomposition;non-Newtonian fluids;heat transport;natural convection;hydrodynamics;
Type (COBISS):	Master's thesis/paper
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko
Pages:	56 str.
ID:	12042919