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Numerical study of suspensions of nucleated capsules at finite inertia
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics.ORCID iD: 0000-0002-4346-4732
2021 (English)In: Physical Review Fluids, E-ISSN 2469-990X, Vol. 6, no 4, article id 044301Article in journal (Refereed) Published
Abstract [en]

We study the rheology of suspensions of capsules with a rigid nucleus at negligible and finite flow inertia by means of numerical simulations. The capsule membrane is modeled as a thin Neo-Hookean hyperelastic material and the nucleus as a rigid particle with radius equal to half the radius of the undeformed spherical capsules. The fluid and solid motion are coupled with an immersed boundary method, validated for both the deformable membrane and the rigid nucleus. We examine the effect of the Reynolds number, capillary number, and volume fraction on the macroscopic properties of the suspensions, comparing with the case of capsules without nuclei. To explain the rheological measurables, we examine the mean capsule deformation, the mean orientation with respect to the flow direction, and the stress budget. The results indicate that the relative viscosity decreases with the capillary number, i.e., increasing deformability, and increases with inertia. The presence of a nucleus always reduces the membrane deformation. Capsules align more in the flow direction at higher capillary numbers and at higher volume fractions, where we also see a significant portion of them oriented with their longer deformed axis in the spanwise direction. When increasing inertia, the alignment with the flow decreases while more capsules orient in the spanwise direction. The first normal stress difference increases with the capillary number and it is always less for the nucleated capsules. Finally, the relative viscosity and the first normal stress difference increase with the capsule volume fraction, an effect more pronounced for the first normal stress difference.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC , 2021. Vol. 6, no 4, article id 044301
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-296429DOI: 10.1103/PhysRevFluids.6.044301ISI: 000652857800002Scopus ID: 2-s2.0-85104854002OAI: oai:DiVA.org:kth-296429DiVA, id: diva2:1566012
Note

QC 20210614

Available from: 2021-06-14 Created: 2021-06-14 Last updated: 2022-10-25Bibliographically approved
In thesis
1. Numerical study of interface dynamics and phase change
Open this publication in new window or tab >>Numerical study of interface dynamics and phase change
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Multi-phase fluid flows are ubiquitous in natural phenomena and different industrial applications such as in food industry, the medical sector, heat exchangers, power generation systems, to name a few.  Understanding the underlining  physics of multi-phase flows  proved to be a challenging task due to presence of sophisticated dynamics, including the evolution of the interface between any pair of phases, thermodynamics and possibility of phase change, interactions between the fluid phases and a solid phase, etc.  Together with theoretical studies and experiments performed on a variety of multi-phase flow problems, numerical simulations have been employed by many researchers to scrutinise different aspects of the problem. During the last decades, a great many studies have been conducted aiming to provide more accurate numerical frameworks for investigating multi-phase flow problems.

Among the various complicated aspects of a multi-phase flow, the present thesis is focused on few characteristics of it the understanding of which requires more considerations and demands improvements in the numerical frameworks. First, we elaborate on the different interface tracking approaches suit the study of different multi-phase flows. In particular, a Volume of Fluid method, a compressible formulation of a diffuse interface approach, a Cahn-Hilliard phase field method, and an Immersed Boundary method are employed to study wetting phenomemna and fluxes at the interface. We have initially investigated biological-relevant membranes, extensional dynamics of a Elasto-viscoplastic material, and droplet spreading over rough surfaces.  In the second part of the thesis, we propose novel numerical methods and setups to investigate the phase change problems in both nanoscale and mesoscale. In particular, we developed a novel numerical method for the solidification problem, a pressure control setup for studying boiling at nanoscale, and a pressure based algorithm for modelling the boiling and evaporation.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022. p. 81
Series
TRITA-SCI-FOU ; 2022:55
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-320579 (URN)978-91-8040-393-1 (ISBN)
Public defence
2022-11-25, F3, Lindstedtsvägen 26 & 28, floor 2, No. 132, Floor 2, Stockhom, 13:00 (English)
Opponent
Supervisors
Note

QC 221026

Available from: 2022-10-26 Created: 2022-10-25 Last updated: 2022-11-09Bibliographically approved

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Banaei, Arash AlizadShahmardi, ArminBrandt, Luca

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