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Abstract

Motivated by the pipe network problems, in this paper, we consider the Leray’s problem for the nonstationary flow of a micropolar fluid. We prove that in an unbounded domain with cylindrical outlets to infinity, there exists a unique solution to the nonlinear micropolar equations which exponentially tends to the generalized nonstationary micropolar Poiseuille solution in each cylindrical outlet.
Mediterr. J. Math. (2020) 17:50
https://doi.org/10.1007/s00009-020-1493-9
1660-5446/20/020001-32
published online February 20, 2020
c
Springer Nature Switzerland AG 2020
Leray’s Problem for the Nonstationary
Micropolar Fluid Flow
Michal Beneˇs, Igor Paˇzanin and Marko Radulovi´c
Abstract. Motivated by the pipe network problems, in this paper, we
consider the Leray’s problem for the nonstationary flow of a micropolar
fluid. We prove that in an unbounded domain with cylindrical outlets
to infinity, there exists a unique solution to the nonlinear micropolar
equations which exponentially tends to the generalized nonstationary
micropolar Poiseuille solution in each cylindrical outlet.
Mathematics Subject Classification. 35Q35, 76A05, 76D03.
Keywords. Micropolar fluid, nonstationary flow, Leray’s problem,
solvability, pipe networks.
1. Introduction
The micropolar fluid model has been introduced in mid 60s by Eringen in his
famous paper [1]. The main advantage of the micropolar model, as compared
to the classical Navier–Stokes system, lies in the fact that it takes into account
the microstructure of the fluid. More precisely, to capture the effects such as
rotation and shrinking of the particles, the microrotation field is introduced
(along with the standard velocity and pressure fields) and, accordingly, a new
vector equation coming from the conservation of angular momentum. In this
way, numerous non-Newtonian fluids (such as liquid crystals, animal blood,
muddy fluids, certain polymeric fluids, and even water in models with small
scales) can be successfully described by the coupled system of micropolar
equations. This has been acknowledged by the engineering community and,
thus, micropolar fluid flows have been extensively investigated in the last
decade. In particular, one can find a vast amount of recent results concerning
engineering applications in biomedicine, mostly in blood flow modeling (see,
e.g., [25]). Rigorous, mathematical justification of various effective models
describing flow of a micropolar fluid can be found in [611]. A detailed survey
of the mathematical theory underlying the micropolar fluid model can be
found in the monograph [12].
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Chapter
Micropolar fluids represent a fluid model that, unlike the classic model, does not only describe behavior at the macro level but also deals with fluid behavior at the microlevel. Describing microphenomena in this case was achieved through the introduction of a new hydrodynamic variable called microrotation. This work describes the micropolar gas model with special emphasis on the reactive micropolar gas, focusing on the initial boundary value problem describing the behavior of the micropolar reactive real gas in tubes with solid and thermally insulated walls. In other words, homogeneous boundary conditions for velocity, microrotation, and heat flux are studied. For the mentioned initial boundary value problem, the construction of the Faedo-Galerkin approximations and the corresponding numerical method for obtaining a numerical solution are described. The given numerical method was additionally analyzed with respect to the complexity of the initial conditions in terms of the number of terms in their Fourier expansions.
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In this paper, we consider the incompressible micropolar fluid flowing through a multiple pipe system via asymptotic analysis. Introducing the ratio between pipes thickness and its length as a small parameter (Formula presented.), we propose an approach leading to a macroscopic model describing the effective flow. In the interior of each pipe (far from the junction), we deduce that the fluid behavior is different depending on the magnitude of viscosity coefficients with respect to (Formula presented.). In particular, we prove the solvability of the critical case characterized by the strong coupling between velocity and microrotation. In the vicinity of junction, an interior layer is observed so we correct our asymptotic approximation by solving an appropriate micropolar Leray’s problem. The error estimates are also derived providing the rigorous mathematical justification of the constructed approximation. We believe that the obtained result could be instrumental for understanding the microstructure effects on the fluid flow in pipe networks.
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