Journal ArticleDOI
Unsteady flows in a semi-infinite contracting or expanding pipe
Shigeo Uchida,Hiroshi Aoki +1 more
TLDR
In this article, an exact solution of the Navier-Stokes equation for unsteady flow is a semi-infinite contracting or expanding circular pipe is calculated and reveals the following characteristics of this type of flow.Abstract:
Physiological pumps produce flows by alternate contraction and expansion of the vessel. When muscles start to squeeze its wall the valve at the upstream end is closed and that at the downstream end is opened, and the fluid is pumped out in the downstream direction. These systems can be modelled by a semi-infinite pipe with one end closed by a compliant membrane which prevents only axial motion of the fluid, leaving radial motion completely unrestricted. In the present paper an exact similar solution of the Navier–Stokes equation for unsteady flow is a semi-infinite contracting or expanding circular pipe is calculated and reveals the following characteristics of this type of flow. In a contracting pipe the effects of viscosity are limited to a thin boundary layer attached to the wall, which becomes thinner for higher Reynolds numbers. In an expanding pipe the flow adjacent to the wall is highly retarded and eventually reverses at Reynolds numbers above a critical value. The pressure gradient along the axis of pipe is favourable for a contracting wall, while it is adverse for an expanding wall in most cases. These solutions are valid down to the state of a completely collapsed pipe, since the nonlinearity is retained in full. The results of the present theory may be applied to the unsteady flow produced by a certain class of forced contractions and expansions of a valved vein or a thin bronchial tube.read more
Citations
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KKL correlation for simulation of nanofluid flow and heat transfer in a permeable channel
TL;DR: In this article, the effects of the nanoparticle volume fraction, Reynolds number, expansion ratio and power law index on Hydrothermal behavior of nanofluid fluid between two parallel plates is studied.
Journal ArticleDOI
Application of Neural Network for estimation of heat transfer treatment of Al2O3-H2O nanofluid through a channel
Mohsen Sheikholeslami,M. Barzegar Gerdroodbary,Rasoul Moradi,Ahmad Shafee,Zhixiong Li,Zhixiong Li +5 more
TL;DR: In this article, a numerical approach is applied to analyze the thermal behavior of alumina nanofluid in a duct, and neural network is employed to estimate the heat transfer rate.
Journal ArticleDOI
Two-dimensional viscous flow between slowly expanding or contracting walls with weak permeability
TL;DR: The current study focuses on the viscous flow driven by small wall contractions and expansions of two weakly permeable walls and finds that, when suction is coupled with wall contraction, rapid flow turning is precipitated near the wall where the boundary layer is formed.
Journal ArticleDOI
Random network peristalsis in Physarum polycephalum organizes fluid flows across an individual
TL;DR: Comparisons of theoretically generated contraction patterns with the patterns exhibited by individuals of P. polycephalum demonstrate that individuals maximize internal flows by adapting patterns of contraction to size, thus optimizing transport throughout an organism.
Journal ArticleDOI
Exact self-similarity solution of the Navier-Stokes equations for a porous channel with orthogonally moving walls
TL;DR: In this paper, a self-similarity solution of Navier-Stokes equations for a laminar, incompressible, and time-dependent flow that develops within a channel possessing permeable, moving walls is presented.
References
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Journal ArticleDOI
Peristaltic pumping with long wavelengths at low Reynolds number
TL;DR: In this article, the authors investigated the effect of peristaltic wave propagation on the flow of fluid in a tube and showed that the theoretical pressure rise per wavelength decreases linearly with increasing time-mean flow and that the percentage of reflux flow can be very high.
Peristaltic pumping with long wave lengths at low reynolds number.
TL;DR: In this paper, the authors investigated the effect of peristaltic wave propagation on the flow of fluid in the tube and showed that the theoretical pressure rise per wavelength decreases linearly with increasing time-mean flow, and that the percentage of reflux flow can be very high.
Journal ArticleDOI
Physiological fluid dynamics: a survey?
TL;DR: Problems of the microcirculation, including blood flow in the narrower capillaries, gas exchange with the terminal airways (alveoli), and exchange of gas and nutrients with peripheral tissue, are treated in the more specialized second section, which describes in some detail modern views concerning peripheral resistance.
Journal ArticleDOI
In vivo stresses in the human left ventricular wall: analysis accounting for the irregular 3-dimensional geometry and comparison with idealised geometry analyses.
TL;DR: The finite element analysis of the left ventricle is effectively able to incorporate the effect of variations in the curvature of theleft ventricular wall boundary on the stress distribution across the wall thickness and on, the level of stress concentrations.
Journal ArticleDOI
Motions of a liquid in a pulsating bulb with application to problems of blood flow.
TL;DR: The thickness of the pulsatile laminar boundary layer is found to be approximately one millimeter for conditions in the vicinity of the heart, and for separation and turbulence differ from those in steady flow.
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