Large-Eddy Simulations of Longitudinal Vortices Embedded in a Turbulent Boundary Layer

You, Donghyun; Wang, Meng; Mittal, Rajat; Moin, Parviz

doi:10.2514/1.22043

Cited by 20 publications

(14 citation statements)

References 15 publications

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“…Smith 1994) as well as computationally (see e.g. Liu, Piomelli & Spalart 1996;You et al 2006). The model of Smith (1994) predicts the flow field induced by low-profile triangular vanes (extending approximately to the logarithmic region of the boundary layer) in a zero pressure gradient boundary layer.…”

Section: Introductionmentioning

confidence: 99%

Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow

2009

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Embedded vortices in turbulent wall-bounded flow over a flat plate, generated by a passive rectangular vane-type vortex generator with variable angle β to the incoming flow in a low-Reynolds-number flow (Re = 2600 based on the inlet grid mesh size L = 0.039 m and free stream velocity U ∞ = 1.0 m s −1 ), have been studied with respect to helical symmetry. The studies were carried out in a low-speed closed-circuit wind tunnel utilizing stereoscopic particle image velocimetry (SPIV). The vortices have been shown to possess helical symmetry, allowing the flow to be described in a simple fashion. Iso-contour maps of axial vorticity revealed a dominant primary vortex and a weaker secondary one for 20 • 6 β 6 40 • . For angles outside this range, the helical symmetry was impaired due to the emergence of additional flow effects. A model describing the flow has been utilized, showing strong concurrence with the measurements, even though the model is decoupled from external flow processes that could perturb the helical symmetry. The pitch, the vortex core size, the circulation and the advection velocity of the vortex all vary linearly with the device angle β. This is important for flow control, since one thereby can determine the axial velocity induced by the helical vortex as well as the swirl redistributing the axial velocity component for a given device angle β. This also simplifies theoretical studies, e.g. to understand and predict the stability of the vortex and to model the flow numerically.

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Section: Introductionmentioning

confidence: 99%

Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow

2009

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“…However, most commercial electronic systems do not support such modifications. Recently, a virtualized technology [26], called virtual machine placement, has been developed to virtually move high server loads to other servers, [23,35,37]. However, most virtualization technologies do not consider enhancing energy efficiency from the viewpoints of thermodynamic loads and aerodynamics when moving such loads.…”

Section: Control Optimizationmentioning

confidence: 99%

Local and global dimensional CFD simulations and analyses to optimize server-fin design for improved energy efficiency in data centers

Sakaino

2014

Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)

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This paper presents numerical simulations based on the concept of local and global dimensional analysis to reproduce the thermodynamics and aerodynamics of server-fins, i.e., detachable flat/curved fms on the inlet/outlet of a server, for enhancing energy efficiency in data centers. Server-fin designs, combinations of shapes and opening angles, are evaluated by transient analysis, vorticity analysis, temperature change rate analysis, and a modified Return Heat Index. Various numerical simulations from local to global dimensions confirm the effectiveness of the server-fins proposed herein in enhancing energy efficiency in data centers compared to their omission.

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“…Recent Large-Eddy-Simulations (LES) (You et al, 2004(You et al, , 2006a complemented and extended the earlier experimental research by providing the full three-dimensional time dynamics of a tip-leakage flow. While we can undoubtedly expect in the future to witness increasing applications of the LES in studying the flow physics, the complex configuration of tip-leakage flows and associated uncertainties in the treatment of bounding solid walls and in the specification of the appropriate inflow turbulence, together with still very demanding computational resources, will most probably impede a wider use of LES for real-life industrial computations, leaving the RANS method still as the only viable option.…”

Section: Introductionmentioning

confidence: 96%

Computation of tip-leakage flow in a linear compressor cascade with a second-moment turbulence closure

Borello

Hanjalić

Rispoli

2007

International Journal of Heat and Fluid Flow

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Large-Eddy Simulations of Longitudinal Vortices Embedded in a Turbulent Boundary Layer

Cited by 20 publications

References 15 publications

Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow

Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow

Local and global dimensional CFD simulations and analyses to optimize server-fin design for improved energy efficiency in data centers

Computation of tip-leakage flow in a linear compressor cascade with a second-moment turbulence closure

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