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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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10 Jan 2005
TL;DR: In this article, a novel numerical configuration has been devised in order to investigate active control of separated airfoil flows in a comprehensive and systematic manner, which consists of a flat plate at zero degrees angle-of-attack in a freestream on which a separation bubble of prescribed size is created at a prescribed location through blowing and suction on the top boundary of the computational domain.
Abstract: A novel numerical configuration has been devised in order to investigate active control of separated airfoil flows in a comprehensive and systematic manner. The configuration consists of a flat plate at zero degrees angle-of-attack in a freestream on which a separation bubble of prescribed size is created at a prescribed location through blowing and suction on the top boundary of the computational domain. Numerical simulations of this configuration show that these canonical separated airfoil flows exhibit three distinct characteristic time scales corresponding to the shear layer, the separation zone and the wake vortex shedding. The vortex dynamics associated with these distinct phenomena are described. Preliminary simulations of this flow subjected to zero-net-mass-flux perturbation are also presented.
59 citations
Patent•
09 Oct 2003
TL;DR: In this article, the authors define a slot (12) defined by an aircraft wing during at least one transonic condition of the wing, which allows a portion of the air flowing along the lower surface (18) of the leading airfoil element (36) to split and flow over the upper surface (20) of a trailing aerodynamic element (38) so as to achieve a performance improvement in transonic conditions.
Abstract: An aircraft wing includes a leading airfoil element (36) and a trailing airfoil element (38). At least one slot (12) is defined by the wing during at least one transonic condition of the wing. The slot (12) may either extend spanwise along only a portion of the wingspan, or it may extend spanwise along the entire wingspan. In either case, the slot (12) allows a portion of the air flowing along the lower surface (18) of the leading airfoil element (36) to split and flow over the upper surface (20) of the trailing airfoil element (38) so as to achieve a performance improvement in the transonic condition.
59 citations
TL;DR: In this paper, Wang et al. presented visual observation of enlarged fin-and-tube heat exchangers with and without the presence of vortex generators, showing that vortex generators significantly increase the vortrical motions of the horseshoe vortices hitting on the tubes.
59 citations
TL;DR: In this article, an analysis of the wake structure and the forces on a delta wing as it undergoes non-steady motion is made, wherein the flow separates at the leading edge.
Abstract: An analysis is made of the wake structure and the forces on a delta wing as it undergoes nonsteady motion, wherein the flow separates at the leading edge. Comparisons of these predictions with existing experimental and theoretical data for the nonsteady linear and nonlinear motions indicate good agreement. It was found that the time-dependent, wake-shedding numerical procedure applied here for the wake rollup and the lift force calculation resulted in considerable saving of computer time over methods using the iterative wake rollup procedure. Calculated results for various motions of the delta wing, including the plunging motion, are presented for both the separated and the attached flow cases.
59 citations
01 Jan 1987
TL;DR: In this paper, a two-component laser-Doppler velocimeter with frequency bias is used to measure the velocity field produced by the oblique collision of two laminar vortex rings.
Abstract: A two-component laser-Doppler velocimeter with frequency bias is used to measure the velocity field produced by the oblique collision of two laminar vortex rings. The Reynolds number, defined here as the ratio of ring circulation to kinematic viscosity, is about 1800. The rings are generated underwater and approach each other along intersecting paths. The plane defined by the two paths is a plane of symmetry, and is the plane in which the measurements were done. The out-of-plane components of vorticity and strain rate are computed from finite differences of the velocity data. The state of the rings prior to the collision is determined in order to provide a set of starting conditions for future numerical simulations. In addition, the circulation of each vortex core is computed as a function of time during the collision. The principal result of this work is that the circulation of each vortex core is observed to decrease during the interaction; furthermore, the fluid viscosity is shown to be responsible for this decrease. The exact mechanism by which the reduction in circulation is effected is unclear, but it appears to be related to the out-of-plane stretching. A time scale is proposed for this cancellation process which combines the effects of viscosity and stretching. The measurements also show that the structure of the vorticity field changes during the collision. In particular, each vortex core is observed to split into two vortices under the action of the local in-plane strain field.
59 citations