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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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TL;DR: In this paper, a priori knowledge of the fluid mechanics involved in vortex shedding, supplemented by information obtained from observation (flow visualization) and measurement (spectral analysis), was used to direct the design process.
32 citations
TL;DR: In this article, a frequency response approach is taken to model unsteady aerodynamics resulting from plunging oscillations of an airfoil, with particular attention paid to the flow separation and consequent formation and convection of the leading edge vortex.
32 citations
TL;DR: The evolution of a viscous vortex ring through the use of the earlier obtained solution of the Stokes equations in the form of time-dependent vorticity distribution is studied in this article.
Abstract: The evolution of a viscous vortex ring through the use of the earlier obtained solution of the Stokes equations in the form of time-dependent vorticity distribution is studied. In the long-time limit this distribution transforms into the classical self-similar Phillips’ distribution and for t → 0 it reduces to a delta-function. Also, this distribution satisfies the condition of the total impulse conservation and for early times its leading-order approximation inside the viscous vortex core is described by the Oseen-Lamb vortices. The integral transforms method is used to derive the corresponding stream function and the translation velocity of the ring. The obtained stream function behaves similarly to the vorticity distribution: at large times it transforms into Phillips’ result and for t → 0 it reduces to a circular line vortex. The predicted velocity agrees with the asymptotic drift velocity at ∞ → t , the Saffman result for the rings with small crosssections, and with the available experimental data.
32 citations
TL;DR: The complex, three-dimensional, vortex structures formed via surface/vortex interaction and induction between vortices have been computed using the proposed technique implemented within a level-set method for both vertical and oblique droplet impacts in incompressible fluids.
32 citations
16 Jun 2014
TL;DR: In this paper, the authors investigated the steady and unsteady behavior of an airfoil with a morphing trailing edge and found that a phase shift between the deflection and the lift occurs.
Abstract: The length of wind turbine rotor blades has been increased during the last decades. Higher stresses arise especially at the blade root because of the longer lever arm. One way to reduce unsteady blade-root stresses caused by turbulence, gusts, or wind shear is to actively control the lift in the blade tip region. One promising method involves airfoils with morphing trailing edges to control the lift and consequently the loads acting on the blade. In the present study, the steady and unsteady behavior of an airfoil with a morphing trailing edge is investigated. Two-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations are performed for a typical thin wind turbine airfoil with a morphing trailing edge. Steady-state simulations are used to design optimal geometry, size, and deflection angles of the morphing trailing edge. The resulting steady aerodynamic coefficients are then analyzed at different angles of attack in order to determine the effectiveness of the morphing trailing edge. In order to investigate the unsteady aerodynamic behavior of the optimal morphing trailing edge, time- resolved RANS-simulations are performed using a deformable grid. In order to analyze the phase shift between the variable trailing edge deflection and the dynamic lift coefficient, the trailing edge is deflected at four different reduced frequencies for each different angle of attack. As expected, a phase shift between the deflection and the lift occurs. While deflecting the trailing edge at angles of attack near stall, additionally an overshoot above and beyond the steady lift coefficient is observed and evaluated.
32 citations