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Showing papers on "Starting vortex published in 1967"


Journal ArticleDOI
TL;DR: In this article, the formation of vortex rings when a liquid drop falls into a stationary bath of the same liquid has been studied, and it is found that vortex rings are formed best if the drop is spherical and changing from an oblate to a prolate spheroid at the moment of contact with the bath.
Abstract: A study of the formation of vortex rings when a liquid drop falls into a stationary bath of the same liquid has been made. The investigation covered liquids with a wide range in surface tensions, densities and viscosities. The results confirm the reported existence of optimum dropping height from which the drop develops into a superior vortex ring. The optimum heights are analysed, by a photographic study, in terms of the liquid drop oscillation. It is found that vortex rings are formed best if the drop is spherical and changing from an oblate to a prolate spheroid at the moment of contact with the bath. A Reynolds number has been determined for vortex rings produced at optimum dropping heights; these numbers are approximately 1000. A possible mechanism for the ring formation is suggested.

91 citations


Journal ArticleDOI
TL;DR: In this paper, an attempt is made to understand the decay of a free vortex normal to a stationary, infinite boundary, where thin boundary layers develop along the rigid boundary and along the axis, the axial boundary layer being strongly influenced by the behaviour of the plate boundary.
Abstract: An attempt is made to understand the decay of a free vortex normal to a stationary, infinite boundary. For rapidly swirling flows in fluids of small viscosity, thin boundary layers develop along the rigid boundary and along the axis, the axial boundary layer being strongly influenced by the behaviour of the plate boundary. An over-all picture of the flow is sought, with only moderate success in the region far from the origin. Near the origin, the eruption of the plate boundary layer into the axial boundary layer is studied.

42 citations



18 Apr 1967
TL;DR: In this paper, the results of some flow visualization experiments on the trailing vortices from a model rotor blade are presented, and it is found that, at low tip-speed ratios, the trailing vortex close to the leading edge of the disc first pass up through the disc before entering the main flow field.
Abstract: : The results of some flow visualisation experiments on the trailing vortices from a model rotor blade are presented. It is found that, at low tip- speed ratios, trailing vortices close to the leading edge of the disc first pass up through the disc before entering the main flow field. At the rear of the disc the vortices maintain a regular pattern relative to each other. The vortices are fully rolled up in about 60 deg of azimuth movement of the blade. Measurements with a hot-wire anemometer show that the vortex core is about one- tenth of a blade chord in diameter, which is consistent with a laminar core state. Outside the core the velocity field is irrotational. Some observations were made of a trailing vortex as it approaches the support pylon. The vortex at first follows the pylon contours and remains a tightly-rolled core, but it ultimately leaves the pylon surface and its structure breaks down, rather like the vortices from the leading edges of a delta wing.

22 citations



01 Dec 1967
TL;DR: In this paper, a general method for the determination of aerodynamic characteristics of fan-in-wing configurations by means of incompressible potential-flow theory is presented, which is applicable to wings, flapped or unflapped, and to a wide variety of other potential flow boundary value problems.
Abstract: : A general method is presented for the determination of aerodynamic characteristics of fan-in-wing configurations by means of incompressible potential-flow theory. The method is applicable to wings, flapped or unflapped, and to a wide variety of other potential-flow boundary-value problems. Arbitrary wing and inlet geometry, fan inflow distribution, thrust vectoring, angle of attack, angle of yaw, and flight speeds from hover through transition can be treated. The theoretical model is completely three dimensional, with no linearization of boundary conditions. The calculated results include pressure distributions, lift, induced drag and side force, pitching moment, rolling moment and yawing moment. The numerical potential-flow solution is obtained with source and vortex distributions on the boundary surfaces. The representation is composed of small, constant-strength source sheet panels distributed over the exterior wing surfaces, internal vortex filaments which emanate from the wing trailing edge to provide circulation and to produce the trailing vortex sheet, and a vortex lattice across the fan face and along the periphery of the fan efflux. Source and vortex strengths are obtained by satisfying boundary conditions at discrete points on the boundary surfaces. Velocities and surface pressures are calculated from the induced effects of the source and vortex distributions. Internal fan loads, based on pressure and momentum relations across the fan and an assumed fan exit flow distribution, are added to integrated wing surface pressures to determine total forces and moments on a fan-in-wing configuration. The method was programmed for use with a high- speed digital computer.

11 citations



Journal ArticleDOI
TL;DR: In this paper, the Strouhal number and the Heisenberg parameter for mesoscale vortex streets in the atmosphere were derived and the horizontal coefficient of eddy diffusion was estimated.
Abstract: Calculations of the Heisenberg parameter and Strouhal number, for mesoscale vortex streets in the atmosphere, support the analogy with the classical Karman vortex wake. Revised estimates of the horizontal coefficient of eddy diffusion are obtained.

2 citations