63 research outputs found
Radiative magneto-micropolar fluid flow over a stretching/shrinking sheet with slip flow model
No full text© Published under licence by IOP Publishing Ltd. This paper presents a study of mixed convective magneto-micropolar fluid flow over a porous stretching/shrinking surface under slip boundary condition in the presence of the thermal radiation effect. The impact of the Newtonian heating is assumed in the thermal boundary condition. The proposed governing flow model is transformed and solved by a semi-analytical technique named Homotopy Analysis Method, and the obtained solutions have excellent agreements with the analytical and the numerical results under special cases. The obtained results reveal that when the sheet stretches at a higher magnetic field parameter, the velocity boundary layer thickness becomes shorter with an increase in the thermal radiation parameter as compared to the lower value of the magnetic field parameter. On the other hand, a higher value of the thermal radiation parameter causes to produce a wider thermal boundary layer thickness as the value of the magnetic field parameter enhances. However, at a lower value of the thermal radiation parameter yields a significant change in the temperature of the micropolar fluid flow. MHD radiative micropolar fluid flow may have an important consideration in magnetic resonance imaging (MRI) and in the circulatory system to control the blood flow by considering the slip flow regime
Chemical reaction and Newtonian heating effects on steady convection flow of a micropolar fluid with second order slip at the boundary
No full text© 2018 Elsevier Masson SAS. In this paper, asymptotic analysis of the chemical reaction and the Newtonian heating parameters is carried out. A mathematical model of a convective micropolar fluid flow over a permeable stretching/shrinking sheet is taken into account in the presence of the slip flow regime. A nonlinear system of transformed equations is solved by a semi-analytical technique called Homotopy Analysis Method (HAM). The current investigation is in a good agreement with the already published analytical and the numerical results with the help of tabular and graphical representations. In comparison with the stretching sheet, it is observed that the shrinking sheet produces a wider concentration boundary layer thickness by a small change in the chemical reaction parameter. In contrast to the stretching sheet, the Newtonian heating parameter raises the thermal boundary layer thickness by 39.93% for the shrinking sheet. The chemical reaction with the Newtonian heating effect is an important consideration in the solidification process of the liquid crystals and the polymeric suspensions
Effects of the wind speeds on heat transfer in a street canyon with a skytrain station
No full text© 2019, The Author(s).
The street under a skytrain station can be seen in many urban cities. Due to the cavity geometry of the street canyon, natural ventilation is decreased. The reduction of the ventilation causes the heat accumulation in the street canyon. To keep the thermal climate at an acceptable level in the street canyon, controlling the air movement with proper temperature is important. In this paper, mathematical models of air flow and heat transfer in the skytrain street canyon are developed. The governing equations are the Reynolds-averaged Navier–Stokes equations and the energy equation. Finite element method is applied for the solution of the problem. The effect of wind speeds on temperature distribution in the street canyon is investigated. Three levels of wind speed including gentle, moderate, and strong wind speeds are chosen in this study. The results indicate that our model can capture the air flow and temperature distribution within a street canyon with a skytrain station
Functions with constant Laplacian satisfying Robin boundary conditions on an ellipse
No full textWe study the problem of finding functions, defined within and on an ellipse,
whose Laplacian is -1 and which satisfy a homogeneous Robin boundary condition
on the ellipse. The parameter in the Robin condition is denoted by beta. The
general solution and various asymptotic approximations are obtained. To find
the general solution, the boundary value problem is formulated in elliptic
cylindrical coordinates. A Fourier series solution is then derived. The Fourier
coefficients satisfy a 3-term recurrence relation which can be solved. The
integral of the solution over the ellipse, denoted by Q, is a quantity of
interest in some physical applications. The dependence of Q on beta and the
ellipse geometry is found. Finding asymptotics directly from the pde
formulations is easier than from our series solution. We use the asymptotic
approximations to Q as checks on the series solution. Several other
inequalities are also used to check the solution. It is intended that this
arXiv preprint will be referenced by the journal version, which will be
submitted soon, as the arXiv contains material, e.g. codes for calculating Q,
not in the much shorter journal version. Maple codes used in deriving or
checking results in this paper are in the process of being tidied prior to
being made available via links given at the URL given in the pdf version
Some isoperimetric results concerning undirectional flows in microchannels
No full textThree isoperimetric results are treated. (i) At a given pressure gradient, for all channels with given (cross-sectional) area that which maximises the steady flow has a circular cross-section. (ii) Consider flows starting from prescribed initial conditions developing from a prescribed imposed pressure gradient, either periodic or steady. For such flows, amongst all channels with given area, that which generically has the slowest approach to the long-term, periodic or steady, flow is the circular disk cross-section. (iii) Similar results for polygonal, -gon, channels, with the optimising shape being the regular -gon are discusse
Simulation of transient blood flows in the artery with an asymmetric stenosis
No full textThis article focuses on the transient behaviour of blood flow in stenotic arteries. Human blood is modelled as an incompressible non-Newtonian fluid. A numerical technique based on the finite element method is developed to simulate the blood flow taking into account of the transient periodic behaviour of the blood flow in cardiac cycles. The flow pattern, the distribution of pressure and the wall shear stresses, are computed. The results show that the pulsatile pressure and the time variation of wall shear rate have patterns similar to that for the pulsatile velocity during the cardiac cycles. On the back toe of the stenosis there exists a small recirculation region which causes the direction of the wall shear stress in some part to oscillate, likely leading to atherosclerotic disease. The back toe is thus an ideal location for applying a clot dissolving drug.
References D. N. Ku, Blood flow in arteries, Annual Review of FLuid Mechanics 29 (1997) 399--434. D. Mann and J. Tarbell, Flow of non-Newtonian blood analog fluids in rigid curved and straight artery models, Biorheology 27 (1990) 711--733. M. Grigioni, C. Daniele and G. D'Avenio, The role of wall shear stress in unsteady vascular dynamics, Progress in Biomedical Research 7 (3) (2002) 204--212. K. B. Chandran, J. H. Mun, K. K. Choi, J. S. Chen, A. Hamilton, A. Nagaraj and D. D. McPherson, A method for in-vivo analysis for regional arterial wall material property alterations with alterosclerosis: preliminary results, Medical Engineering and Physics 25 (2003) 289--298. M. Bonert, J. G. Myers, S. Fremes, J. Williams and C. R. Ethier, A numerical study of blood flow in coronary artery bypass graft Side-to-Side Anastomoses, in Annals of Biomedical Engineering 30 (2002) 599--611. D. Y. Fei, J. D. Thomas and S. E. Rittgers, The effect of angle and flow rate upon hemodynamics in distal vascular graft anastomoses: a numerical model study, Journal of Biomechanical Engineering 116 (1994) 331--336. M. H. Song, M. Sato, Y. Ueda, Three dimensional simulation of coronary artery bypass grafting with the use of computational fluid dynamics, Surg Today 30(2000), 993--998. B. Wiwatanapataphee, D. Poltem, Y. H. Wu and Y. Lenbury, Simulation of pulsatile flow of blood in stenosed coronary artery bypass with graft, Mathematical Biosciences 3 (2) (2006) 371--383. S. Glagov and C. K. Zarins and D. P. Giddens and D. N. Ku, Hemodynamics and Atherosclerosis, Insights and perspectives gained from studies of human arteries, Archieves of Pathology and Laboratory Medicine 112 (1988) 1018--1031
Numerical simulation of blood flow in the right coronary artery with particle chain
No full textIn this paper, we study the effect of blood flow in the right coronary artery with a particle chain. Blood is assumed to be incompressible non-Newtonian fluid and its motion is described by the continuity equation and the Navier-Stokes equations. The pulsatile condition due to the heart pump is imposed on the inlet and outlet boundaries. Numerical technique based on finite volume method (FVM) is implemented for the solution of the problem. Two shapes of the particle chain including S-shape and U-shape are used to analyze the flow pattern and pressure distribution along the flow direction. The results indicate that the shape of particle chain has significant effect on the blood flow behavior. At the bifurcation area, blood speed is high around the arterial center of the model with U-shape set of particles, but in the model with S-shape set of particles, it is high near the arterial wall. © 2014 IEEE
Numerical simulation of granular mixing in static mixers with different geometries
No full text© 2019, The Author(s). A static mixer is a fidelity engineered device for the continuous mixing of fluid/solid materials. To meet the requirements for mixing purpose, a proper design of the static mixer is important. In this study, we proposed various designs of static mixer based on the blade geometry. Six blade patterns including four twisted blades, four elliptical blades and other four combined geometries of two twisted blades and two elliptical blades are chosen to investigate its mixing performance. Mathematical model of the two-phase flow with fluid/solid interaction in the static mixer is presented. Numerical solution of the flow patterns of particulate solids, and the velocity and the pressure fields of the fluid in the static mixer with different blade geometries are carried out. To evaluate the quality of the mixing performance, the results obtained from six blade designs are compared via the relative standard deviation and the amount of pressure drop along the mixing path
Oscillating pressure-driven slip flow and heat transfer through an elliptical microchannel
No full text© 2019, The Author(s).
This paper studies the transient slip flow and heat transfer of a fluid driven by the oscillatory pressure gradient in a microchannel of elliptic cross section. The boundary value problem for the thermal-slip flow is formulated based on the assumption that the fluid flow is fully developed. The semi-analytical solutions of velocity and temperature fields are then determined by the Ritz method. These solutions include some existing known examples as special cases. The effects of the slip length and the ratio of minor to major axis of the elliptic cross section on the velocity and temperature distribution in the microchannel are investigated
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