Topic
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, the motion of vortex rings ejected from a circular or a lenticular orifice into water was studied, and the diameters and traveling velocities of the vortex rings were determined from these photographs.
Abstract: Experimental studies were made on the motion of vortex rings ejected from a circular or a lenticular orifice into water. The vortex rings were made visible by fine grains of tin made by electrolysis, and photographs were taken. The diameters and the traveling velocities of the vortex rings were determined from these photographs. There is a favorable range of impulse to produce the stable vortex ring. The traveling velocity of the vortex ring is composed of the velocity of the jet flow and the self-induced velocity of the vortex; the former decays rather rapidly and the latter decreases slowly in time as \(\sqrt{
u t}\), where t is the time and ν is the kinematic viscosity of water. The vortex ring ejected from a lenticular orifice changes its shape intermittently, and the period of deformation is prolonged continually, while the traveling distance during one period is nearly constant.
35 citations
TL;DR: In this article, a new method for characterizing cross-sections of vortices in turbulent flows is described. But the method is not robust, robust, not selective, and above all, much less contaminated by shear than the existing methods.
35 citations
TL;DR: In this article, the formation of afterbody vortex flows from cylindrical bodies with a slanted base, whose upsweep angle was varied between 24° and 32°, was studied.
Abstract: Experiments have been undertaken to study the formation of afterbody vortex flows from cylindrical bodies with a slanted base, whose upsweep angle was varied between 24° and 32°. Vortex roll-up is mostly completed in the first half of the upswept section, where the vortex causes largest suction on the surface. Towards the trailing-edge the vortices become more axisymmetric and stronger with increasing upsweep angle. Although there is some delay in vortex roll-up at lower Reynolds number, the main features of the vortex flow are similar to those at higher Reynolds number. The strength of the vortices at the trailing-edge was proportional to the time-averaged drag coefficient, which increased by nearly 50% in the range of upsweep angles tested. The vortex was more coherent with reduced meandering and a smaller core radius towards the trailing-edge. This reduction in meandering along the streamwise direction had not been observed previously with other external vortex flows in aerodynamics. Proper Orthogonal Decomposition revealed that the helical displacement mode with azimuthal wavenumber m = 1 was the dominant mode towards the trailing-edge, suggesting that the afterbody vortices bear much similarity with the more widely studied wing tip vortices and delta wing vortices. The instantaneous vortex pair exhibits time-dependent asymmetry; however, there is virtually no correlation between the displacements of the vortex centers.
34 citations
TL;DR: In this article, a novel energy transferring mechanism in the vortex tube was proposed, under the condition that stable oscillation of the boundary layer is the dominant mechanism for the heat and mass transfer process.
34 citations
TL;DR: In this paper, a mutual slip-through of two identical vortex rings traveling along a common axis in the same direction was achieved in air at various Reynolds numbers between 800 and 2000 and observed by using the smoke wire technique and cigarette smoke.
Abstract: Mutual slip‐through of two identical vortex rings, traveling along a common axis in the same direction, was experimentally achieved in air at various Reynolds numbers between 800 and 2000 and observed by using the smoke wire technique and cigarette smoke. The motions of a pair of vortices agree very well with an approximate potential theory based on the Biot–Savart law.
34 citations