The starting mechanism of wave-induced flow through a sharp-edged orifice

Evans, Ralph A.; Bloor, M. I. G.

doi:10.1017/s002211207700055x

Cited by 15 publications

(8 citation statements)

References 18 publications

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“…A.1. Conformal mapping Following Clements (1973), Evans & Bloor (1977), Cortelezzi (1996) and Coller et al (2000), the no-penetration condition is enforced by employing a conformal mapping. This procedure is computationally cheaper and more accurate for low-order vortex models compared with a computational panel approach (see e.g.…”

Section: Appendix a Vortex Modelmentioning

confidence: 99%

“…Approximately 650 vortices are required to resolve the dynamics of the coherent structures. Similar models have been investigated for the flow around a D-shaped body (Clements 1973), the flow over an edge (Evans & Bloor 1977), the wake flow past a plate (Cortelezzi 1996), the diffuser flow (Coller et al 2000), and the flow around a backward-facing step (Pastoor et al 2003). The no-penetration boundary condition at the walls for the potential flow is enforced by using a conformal mapping from the upper half-plane onto the D-shaped body (see § A.1).…”

Section: Vortex Modelmentioning

confidence: 99%

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Feedback shear layer control for bluff body drag reduction

et al. 2008

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Drag reduction strategies for the turbulent flow around a D-shaped body are examined experimentally and theoretically. A reduced-order vortex model describes the interaction between the shear layer and wake dynamics and guides a path to an efficient feedback control design. The derived feedback controller desynchronizes shear-layer and wake dynamics, thus postponing vortex formation. This actuation is tested in a wind tunnel. The Reynolds number based on the height of the body ranges from 23000 to 70000. We achieve a 40% increase in base pressure associated with a 15% drag reduction employing zero-net-mass-flux actuation. Our controller outperforms other approaches based on open-loop forcing and extremum-seeking feedback strategies in terms of drag reduction, adaptivity, and the required actuation energy.

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Section: Appendix a Vortex Modelmentioning

confidence: 99%

Section: Vortex Modelmentioning

confidence: 99%

Feedback shear layer control for bluff body drag reduction

et al. 2008

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“…To assess the degree to which the results depend on the computational parameters, we have carried out calculations using two different approaches, one involving a conformal transformation of the flow domain (Evans and Bloor, 1977) The results show that the circulation and vorticity centroid are, as described by the above-mentioned review articles, not sensitive to these variations. For example, there is less than a two percent difference in the computed tip vortex position (ye) for a factor of ten in time step.…”

Section: Computational Proceduresmentioning

confidence: 99%

Similarity Analysis of Compressor Tip Clearance Flow Structure

Chen

Greitzer

Tan

et al. 1990

Volume 1: Turbomachinery

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A new approach is presented for analyzing compressor tip clearance flow. The basic idea is that the clearance velocity field can be (approximately) decomposed into independent through-flow and cross-flow, since chordwise pressure gradients are much smaller than normal pressure gradients in the clearance region. As in the slender body approximation in external aerodynamics, this description implies that the three-dimensional, steady, clearance flow can be viewed as a two-dimensional, unsteady flow. Using this approach, a similarity scaling for the cross-flow in the clearance region is developed and a generalized description of the clearance vortex is derived. Calculations based on the similarity scaling agree well with a wide range of experimental data in regard to flow features such as cross-flow velocity field, static pressure field, and tip clearance vortex trajectory. The scaling rules also provide a useful way of exploring the parametric dependence of the vortex trajectory and strength for a given blade row. The emphasis of the approach is on the vortical structure associated with the tip clearance because this appears to be a dominant feature of the endwall flow; it is also shown that this emphasis gives considerable physical insight into overall features seen in the data.

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“…It should be remarked that the present method, unlike that of Evans & Bloor (1977), incorporates the velocity induced by the nascent vortex itself into the determination of its strength by (8).…”

Section: ( 7 )mentioning

confidence: 99%

Discrete-vortex simulation of a turbulent separation bubble

1982

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The discrete-vortex model is applied to simulate the separation bubble over a two- dimensional blunt flat plate with finite thickness and right-angled corners, which is aligned parallel to a uniform approaching stream. This flow situation is chosen because, unlike most previous applications of the model, the separation bubble is supposed to be strongly affected by a nearby solid surface. The major objective of this paper is to examine to what extent the discrete-vortex model is effective for such a flow. A simple procedure is employed to represent the effect of viscosity near the solid surface; in particular, the no-slip condition on the solid surface. A reduction in the circulation of elemental vortices is introduced as a function of their ages in order to represent the three-dimensional deformation of vortex filaments, An experiment was also performed for comparison purposes.The calculation yielded reasonable predictions of the time-mean and r.m.s. values of the velocity and the surface-pressure fluctuations, together with correlations between their fluctuating components, over most of the separation bubble. The interrelation between instantaneous spatial variations of the surface-pressure and velocity fluctuations were also obtained. A comparison between the calculated and measured results suggests that, in the real flow, the three-dimensional deformation of vortex filaments will become more and more dominant as the reattachment point is approached.

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The starting mechanism of wave-induced flow through a sharp-edged orifice

Cited by 15 publications

References 18 publications

Feedback shear layer control for bluff body drag reduction

Feedback shear layer control for bluff body drag reduction

Similarity Analysis of Compressor Tip Clearance Flow Structure

Discrete-vortex simulation of a turbulent separation bubble

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