DUFOUR EFFECT ON THREE-DIMENSIONAL FLOW PAST A POROUS VERTICAL PLATE IN A POROUS MEDIUM WITH PERIODIC SUCTION AND PERMEABILITY

Purpose The purpose of this study is to find the multiple branches of the three-dimensional flow of Cu-Al2 O3/water rotating hybrid nanofluid perfusing a porous medium over the stretching/shrinking surface. The extended model of Darcy due to Forchheimer and Brinkman has been considered to make the hybrid nanofluid model over the pores by considering the porosity and permeability effects. Design/methodology/approach The Tiwari and Das model with the thermophysical properties of spherical particles for efficient dynamic viscosity of the nanoparticle is used. The linear similarity transformations are applied to convert the partial differential equations into ordinary differential equations (ODEs). The system of governing ODEs is solved by using the three-stage Lobatto IIIa scheme in MATLAB for evolving parameters. Findings The system of governing ODEs produces dual branches. A unique stable branch is identified with help of stability analysis. The reduced heat transfer rate has been shown to increase with the reduced ϕ2 in both branches. Further, results revealed that the presence of multiple branches depends on the ranges of porosity, suction and stretching/shrinking parameters for the particular value of the rotating parameter. Originality/value Dual branches of the three-dimensional flow of Cu-Al2 O3/water rotating hybrid nanofluid have been found. Therefore, stability analysis of the branches is also conducted to know which branch is appropriate for the practical applications. To the best of the authors’ knowledge, this research is novel and there is no previously published work relevant to the present study.

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Heat and mass transfer in three-dimensional flow through a porous medium with periodic permeability

Heat Transfer-Asian Research ◽

10.1002/htj.21399 ◽

2018 ◽

Vol 48 (2) ◽

pp. 644-662

Author(s):

Nazibuddin Ahmed ◽

Kangkan Choudhury

Keyword(s):

Mass Transfer ◽

Porous Medium ◽

Heat And Mass Transfer ◽

Three Dimensional ◽

Three Dimensional Flow ◽

Dimensional Flow ◽

Flow Through

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Three-dimensional instabilities in oscillatory flow past elliptic cylinders

Journal of Fluid Mechanics ◽

10.1017/jfm.2016.319 ◽

2016 ◽

Vol 798 ◽

pp. 371-397 ◽

Cited By ~ 1

Author(s):

José P. Gallardo ◽

Helge I. Andersson ◽

Bjørnar Pettersen

Keyword(s):

Circular Cylinder ◽

Flow Direction ◽

Three Dimensional ◽

Circular Cylinders ◽

Flow Structures ◽

Three Dimensional Flow ◽

Elliptical Cross ◽

Dimensional Flow ◽

Aspect Ratios ◽

Flow Past

We investigate the early development of instabilities in the oscillatory viscous flow past cylinders with elliptic cross-sections using three-dimensional direct numerical simulations. This is a classical hydrodynamic problem for circular cylinders, but other configurations have received only marginal attention. Computed results for some different aspect ratios ${\it\Lambda}$ from 1 : 1 to 1 : 3, all with the major axis of the ellipse aligned in the main flow direction, show good qualitative agreement with Hall’s stability theory (J. Fluid Mech., vol. 146, 1984, pp. 347–367), which predicts a cusp-shaped curve for the onset of the primary instability. The three-dimensional flow structures for aspect ratios larger than 2 : 3 resemble those of a circular cylinder, whereas the elliptical cross-section with the lowest aspect ratio of 1 : 3 exhibits oblate rather than tubular three-dimensional flow structures as well as a pair of counter-rotating spanwise vortices which emerges near the tips of the ellipse. Contrary to a circular cylinder, instabilities for an elliptic cylinder with sufficiently high eccentricity emerge from four rather than two different locations in accordance with the Hall theory.

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