Iasiello, Marcello (2016) Transport Phenomena in Porous Media: from Open-Cell Foams to Biological Systems. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Lingua: English
Title: Transport Phenomena in Porous Media: from Open-Cell Foams to Biological Systems
Iasiello, Marcellomarcello.iasiello@unina.it
Date: 30 March 2016
Number of Pages: 190
Institution: Università degli Studi di Napoli Federico II
Department: Ingegneria Industriale
Scuola di dottorato: Ingegneria industriale
Dottorato: Ingegneria dei sistemi meccanici
Ciclo di dottorato: 28
Coordinatore del Corso di dottorato:
Bozza, Fabiofabio.bozza@unina.it
Date: 30 March 2016
Number of Pages: 190
Uncontrolled Keywords: Porous media, Open-cell Foams, Biological Systems
Settori scientifico-disciplinari del MIUR: Area 09 - Ingegneria industriale e dell'informazione > ING-IND/10 - Fisica tecnica industriale
Date Deposited: 08 Apr 2016 09:01
Last Modified: 31 Oct 2016 11:09
URI: http://www.fedoa.unina.it/id/eprint/10863


The complex geometry of a porous medium makes challenging the study of transport phenomena through it. Investigations are carried out treating the whole macroscopic porous medium as an equivalent homogeneous medium, whose governing equations are averaged over a Representative Elementary Volume (REV). Governing equations are coupled with the microscopic problem scales by means of the so-called closing coefficients. Results of the study of transport phenomena in two classes of porous media: open-cell foams and biological systems, also with reference to human arteries are presented in this thesis. For open-cell foams, analysis of microscales pressure drop and convective heat transfer were carried out with both experimental and numerical techniques. Experiments were carried out for various open-cell aluminum foam samples with different porosities and PPI in order to study pressure drop. Local convection heat transfer in one foam sample, for different inlet velocities of the fluid, was analyzed. Numerical predictions were obtained by using a finite element scheme. The geometry for the numerical models was reconstructed by means of two techniques. In the first, tomographic scans on three open-cell aluminum foam samples with different porosities were carried out to obtain a real foam; in the second the geometry was computationally reconstructed with reference to Kelvin’s foam model, obtaining an ideal foam. The ideal foam geometry was further modified in order to analyze thermally developing effects and strut shape effects on pressure drop and convection heat transfer. Nusselt number was correlated to process parameters, for thermally developed flow, and it was shown that the accuracy of the ideal model improves when the strut shape is well-modeled. By using the macroscopic porous medium approach, two industrial applications of open-cell foams were studied with a numerical approach. The first application is a volumetric solar receiver, where an open-cell ceramic foam is employed as the porous absorber; the second one was an aluminum foam-based heat sink. In both cases, results are presented for different foam morphologies and thermo-fluid-dynamic conditions. Low density lipoprotein (LDL) deposition through the walls of human arteries was studied by using a macroscopic porous medium approach. Different arteries were analyzed: a straight artery, a stenosed artery and the aorta-iliac bifurcation. Governing equations, with the appropriate boundary conditions, were solved by using both a numerical approach and an analytical approach. For the straight artery, Numerical modeling allowed to analyze the non-Newtonian fluid effects on the prediction of LDL deposition in different size straight artery. The above effects were studied by comparing various non-Newtonian fluid models and showed that a Newtonian fluid assumption can be used without introducing remarkable differences. An analytical approach was used to investigate LDL deposition in an arterial wall under hyperthermia and hypertension, obtaining a simplified analytical solution. Energy and species equations were coupled by means of the Ludwig-Soret effect. LDL accumulation under hyperthermia in a stenosed artery modeled with a cosinusoidal function was numerically analyzed. In all cases, hyperthermia and hypertension increase LDL accumulation. For the aorta-iliac bifurcation, a numerical 2-D study of non-Newtonian effects on LDL mass transport showed that the Newtonian fluid assumption is weak in presence of recirculation zones.

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