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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 14 (2002), S. 1601-1616 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper aims to provide deeper insight into the suddenly contracted channel flow. The channels under investigation have a width of 18D, where D represents the channel height upstream of the step plane, and two contraction ratios: C=2 and 4. In the present three-dimensional finite volume analysis, the advective fluxes are discretized using an upwind scheme that provides a third-order accurate solution in uniform grid cases. For efficient calculation of field variables, working equations are solved separately based on the semi-implicit velocity-pressure coupling procedures. We exploit a theoretically appealing topological theory to determine lines of separation and reattachment, from which the pitchfork bifurcation flow can be identified in the contraction channel. To further elucidate the vortical details of the channel flow, we trace massless particles seeded in the flow, showing the spanwise spiraling flow motion. Emphasis is placed on flow phenomena in the upstream salient corner eddy and downstream tip corner eddy. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 862-874 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the present study we take a fresh look at a laminar flow evolving into a larger channel through a step configured in a backward-facing format. We conduct steady three-dimensional Navier–Stokes flow analysis in the channel using the step geometry and flow conditions reported by Armaly et al. This allows a direct comparison with the results of physical experiments, thus serving to validate the numerical results computed in the range of 100≤Re≤1000. Results show that there is generally excellent agreement between the present results and the experimental data for Re=100 and 389. Fair agreement for Re=1000 is also achieved, except in the streamwise range of 15≤x≤25. The main difference stems from the fact that the roof eddy is not extended toward the midspan in the channel with a span width 35 times of the height of the upstream channel. In the present study we also reveal that the flow at the plane of symmetry develops into a two-dimensional-like profile only when the channel width is increased up to 100 times of the upstream step height for the case with Re=800. The present computational results allow the topological features of the flow to be identified using critical point theory. The insight thus gained is useful in revealing a mechanism for the development of an end-wall-induced three-dimensional vortical flow with increasing Reynolds number. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Computational mechanics 20 (1997), S. 379-396 
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We present in this paper a detailed numerical study of the vortical flow structure in a confined lid-driven cavity which is defined by a depth-to-width aspect ratio of 1:1 and a span-to-width aspect ratio of 3:1. In this study we have carefully examined the computed data that the useful to gain an in-depth knowledge of the complex interactions among secondary eddies, primary eddies, and spiraling spanwise motions. Chief of conclusions drawn from this study is to explain how the secondary eddies are intimately coupled with the primary recirculating flow. We also enlighten in this paper why spiraling vortices inside the upstream secondary eddy tend to destabilize the incompressible flow system and aid development of laminar instabilities.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 325-346 
    ISSN: 0271-2091
    Keywords: Taylor-Görtler-like vortices ; spiralling corner vortices ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: With the purpose of providing physical insight into the developing spanwise flow motion and identifying the presence of Taylor-Görtler- like vortices, we conducted a flow simulation in a rectangular cavity defined by a square cross-section and a spanwise aspect ratio of 3:1. The governing equations were solved for the transient processes by using a finite volume method in conjunction with segregated solution procedures. In the present work, attention is placed on the spiralling corner vortices near the two end walls and the longitudinal meandering Taylor-Görtler-like vortices. The investigated Reynolds number is taken to be 1500. As a vehicle for the present flow simulation, validation against analytic data was carried out first for a configuration similar to the problem of interest. This study demonstrates the feasibility of the employed computer code.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 26 (1998), S. 557-579 
    ISSN: 0271-2091
    Keywords: lid-driven cavity ; Taylor-Görtler-like vortices ; instabilities ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this paper we apply a finite volume method, together with a cost-effective segregated solution algorithm, to solve for the primitive velocities and pressure in a set of incompressible Navier-Stokes equations. The well-categorized workshop problem of lid-driven cavity flow is chosen for this exercise, and results focus on the Reynolds number. Solutions are given for a depth-to-width aspect ration of 1:1 and a span-to width aspect ratio of 3:1. Upon increasing the Reynolds number, the flows in the cavity of interest were found to comprise a transition from a strongly two-dimensional character to a truly three-dimensional flow and, subsequently, a bifurcation from a stationary flow pattern to a periodically oscillatory state. Finally, viscous (Tollmien-Schlichting) travelling wave instability further induced longitudinal vortices, which are essentially identical to Taylor-Görtler vortices. The objective of this study was to extend our understanding of the time evolution of a recirculatory flow pattern against the Reynolds number. The main goal was to distinguish the critical Reynolds number at which the presence of a spanwise velocity makes the flow pattern become three-dimensional. Secondly, we intended to learn how and at what Reynolds number the onset of instability is generated. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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