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Starting vortex

About: Starting vortex is a research topic. Over the lifetime, 4785 publications have been published within this topic receiving 100419 citations.


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Proceedings ArticleDOI
01 Jan 1982
TL;DR: The results of an experimental study to document the effects of separation and transition on the performance of an airfoil designed for low Reynolds number operation are presented in this paper, where lift, drag, and flow visualization data were obtained for the Eppler 61 airfoIL section for chord Reynolds numbers from about 30,000 to over 200,000.
Abstract: The results of an experimental study to document the effects of separation and transition on the performance of an airfoil designed for low Reynolds number operation are presented. Lift, drag and flow visualization data were obtained for the Eppler 61 airfoil section for chord Reynolds numbers from about 30,000 to over 200,000. Smoke flow visualization was employed to document the boundary layer behavior and was correlated with the Eppler airfoil design and analysis computer program. Laminar separation, transition and turbulent reattachment had significant effects on the performance of this airfoil.

49 citations

Journal ArticleDOI
TL;DR: In this paper, an experimental technique is described which corroborates the predictions of several new analyses of the unsteady response of an airfoil to high frequency flow fluctuations and shows a chordwise variation of pressure phase angle which is not predicted by the incompressible analysis of Sears.
Abstract: An experimental technique is described which corroborates the predictions of several new analyses of the unsteady response of an airfoil to high frequency flow fluctuations. The periodically fluctuating flowfield was produced by the natural shedding of vortices from a transverse cylinder to yield a reduced frequency of 3.9 based on airfoil semichord. Unsteady pressure measurements were made on an instrumented airfoil mounted downstream and above the turbulent wake of the cylinder. These unsteady pressures were found to be in good agreement with current compressible theories and show a chordwise variation of pressure phase angle which is not predicted by the incompressible analysis of Sears. Large reductions of the unsteady lift and phase angle were also observed for large airfoil incidence angles.

49 citations

Journal ArticleDOI
TL;DR: In this paper, a local approach based on the study of the oscillation zone is proposed to obtain the length of this zone, which is found to be independent of the turbulence level.
Abstract: Fluctuation of the separation point on an airfoil under high turbulence level is investigated using pressure measurements and flow visualisations. The characteristics of the unsteady loads induced by Karman vortex shedding are studied. This is related with a local approach based on the study of the oscillation zone. A method based on the pressure standard deviation is proposed to obtain the length of this zone, which is found to be independent of the turbulence level. This result is in agreement with that obtained by spectral analysis which shows no effect of the turbulence level on the Karman vortex shedding frequency.

49 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the spatiotemporal evolution of a turbulent vortex ring with an initial Reynolds number of 7500 using the technique of digital particle image velocimetry.
Abstract: The spatiotemporal evolution of a turbulent vortex ring with an initial Reynolds number of 7500 is experimentally investigated using the technique of digital particle image velocimetry. The flow is initially characterized by the laminar/turbulent transition via azimuthal bending instabilities. After transition, the shedding of vorticity from peripheral regions of the ring is found to be responsible for the formation of a wake region. This shedding process results in the staircase‐like decay of the circulation and propagation speed of the vortex ring.

49 citations

Journal ArticleDOI
TL;DR: In this paper, a model of the vortex-airfoil interaction is presented in which the finite-area of the real vortices is taken into consideration, and the method is applied to the calculation of the pressure induced on the surface of the airfoil by the interacting vortex.
Abstract: A modeling of the vortex-airfoil interaction is presented in which the finite-area of the real vortices is taken into consideration. Two vortex models are used. In the first, a disturbed piece of vorticity layer is simulated by four rows of discrete vortices of small strength. In the second, a number of discrete vortices is arranged within a circle. The first model may simulate a shear layer or a wake, while the second, a well-formed vortex. The method was applied to the calculation of the pressure induced on the surface of the airfoil by the interacting vortex. Both models give similar results. It was found that for large distances of the vortex from the surface of the airfoil, the consideration or not of the finite-area of the vortex is not a significant factor in determining the induced pressure field. However, when the distance of the vortex from the surface is reduced, its shape is distorted and the induced pressure pulses have lower amplitude than the ones induced by an equivalent point vortex. In the limit, where the vortex impinges on the leading edge of the airfoil, it is split into two and the time dependent pressure coefficient takes even negative values at some time intervals.

49 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202336
202278
20217
20207
20196
201815