Linear and nonlinear thermal instability of Newtonian and non-Newtonian fluid saturated porous media

Vayssière Brandão, Pedro (2022) Linear and nonlinear thermal instability of Newtonian and non-Newtonian fluid saturated porous media, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Meccanica e scienze avanzate dell'ingegneria, 34 Ciclo. DOI 10.48676/unibo/amsdottorato/10143.
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Abstract

The present work aims to investigate the influence of different aspects, such as non-standard steady solutions, complex fluid rheologies and non-standard porous-channel geometries, on the stability of a Darcy-Bénard system. In order to do so, both linear and nonlinear stability theories are considered. A linear analysis focuses on studying the dynamics of the single disturbance wave present in the system, while its nonlinear counterpart takes into consideration the interactions among the single modes. The scope of the stability analysis is to obtain information regarding the transition from an equilibrium solution to another one, and also information regarding the transition nature and the emergent solution after the transition. The disturbance governing equations are solved analytically, whenever possible, and numerical by considering different approaches. Among other important results, it is found that a cylinder cross-section does not affect the thermal instability threshold, but just the linear pattern selection for dilatant and pseudoplastic fluid saturated porous media. A new rheological model is proposed as a solution for singular issues involving the power-law model. Also, a generalised class of one parameter basic solutions is proposed as an alternative description of the isoflux Darcy--Bénard problem. Its stability is investigated.

Abstract
Tipologia del documento
Tesi di dottorato
Autore
Vayssière Brandão, Pedro
Supervisore
Co-supervisore
Dottorato di ricerca
Ciclo
34
Coordinatore
Settore disciplinare
Settore concorsuale
Parole chiave
stability analysis; flow in porous media; non-newtonian convection
URN:NBN
DOI
10.48676/unibo/amsdottorato/10143
Data di discussione
11 Aprile 2022
URI

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