Starting vortex

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

Development of the trailing shear layer in a starting jet during pinch-off

Abstract: Experiments on a circular starting jet generated by a piston–cylinder arrangement, over a range of Reynolds number from to , are conducted so as to investigate the development of the trailing shear layer during the leading vortex ring formation, as well as the corresponding effects on the pinch-off process. Results obtained by digital particle image velocimetry (DPIV) show that secondary vortices start to develop in the trailing jet only after the critical time scale, the ‘formation number’, is achieved. The subsequent growth of the secondary vortices reduces the vorticity flux being fed into the leading vortex ring and, as a consequence, constrains the growth of leading vortex ring with larger circulation. Evolution of perturbation waves into secondary vortices is found to associate with growth and translation of the leading vortex ring during the formation process. A dimensionless parameter ‘’, defined as ), is therefore proposed to characterize the effect of the leading vortex ring on suppressing the nonlinear development of instability in the trailing shear layer, i.e. the initial roll-up of the secondary vortices. In a starting jet, follows a decreasing trend with the formation time . A critical value is identified experimentally, which physically coincides with the initiation of the first secondary vortex roll-up and, therefore, indicates the onset of pinch-off process.

Wake Vortex Alleviation Flow Field Studies

Abstract: Wake-vortex-allevialion research was conducted in the far-field vortex wake of a generic wing-tail aircraft model. The goats were to achieve accelerated vortex strength reduction and to map the conditions at which this reduction would occur. The wing-tail model was run in a water tow tank to generate a pair of unequal-strength counterrotating vortices on each side of centerline. Dye flow visualization provided physical insight into the nature of the vortex interactions, and three-component particle image velocimetry allowed quantification of key characteristics of the flowfield, including circulation, vorticity, vortex trajectory, and induced rolling moments. Experiments were conducted for a variety of model angles of attack, tail incidence angles, and tail spans

On the wake pattern of symmetric airfoils for different incidence angles at Re = 1000:

Abstract: In the current study, numerical simulations are performed in order to investigate effects of incidence angle and airfoil thickness on alternating vortex pattern of symmetric airfoils at Re = 1000. ...

Steady vortex force theory and slender-wing flow diagnosis

Abstract: The concept vortex force in aerodynamics is systematically examined based on a new steady vortex-force theory (Wu et al., Vorticity and vortex dynamics, Springer, 2006) which expresses the aerodynamic force (and moment) by the volume and boundary integrals of the Lamb vector. In this paper, the underlying physics of this theory is explored, including the general role of the Lamb vector in nonlinear aerodynamics, its initial formation, and its relevance to the total-pressure non-uniformity. As a typical example, the theory is applied to the flow over a slender delta wing at a large angle of attack. The highly localized flow structures with high Lamb-vector peaks are identified in terms of their net contribution to various constituents of the total aerodynamic force. This vortex-force diagnosis sheds new light on the flow control and configuration optimization.