Starting vortex

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

Ideal plug-flow properties of taylor vortex flow

Abstract: Mixing properties of Taylor vortex flow with small constant axial flow rates were investigated in an annulus between two concentric rotating cylinders by injecting a salt-solution tracer or by suspending small soluble particles. Longitudinal intermixing of fluid elements between the neighboring vortices was examined by a method of two-point measurement. Circumferential mixing in each cellular vortex was also evaluated by comparing two successive time variations of concentration at a certain point in the case of no axial flow. The modes of flow were mapped in terms of Taylor number and Reynolds number. This vortex flow has been found to be an ideal plug-flow for the range of 51.4

Transient energy growth for the Lamb–Oseen vortex

Abstract: The transient evolution of infinitesimal flow disturbances which optimally induce algebraic growth in the Lamb–Oseen (Gaussian) vortex is studied using a direct-adjoint technique. This optimal perturbation analysis reveals that the Lamb–Oseen vortex allows for intense amplification of kinetic energy for two-dimensional and three-dimensional perturbations of azimuthal wavenumber m=1. In both cases, the disturbances experiencing the most growth initially take the form of concentrated spirals at the outer periphery of the vortex which rapidly excite bending waves within the vortex core. In the limit of large wavelengths, the optimal perturbation leads to arbitrarily large growths via an original scenario combining the Orr mechanism with vortex induction.

Heat Transfer and Fluid Flow in a Square Duct With 12 Different Shaped Vortex Generators

Abstract: Detailed local Nusselt number distributions in the first pass of a sharp turning two-pass square channel with various configurations of longitudinal vortex generator arranged on one wall were measured using transient liquid crystal thermography. Flow patterns and friction factors were measured by the use of laser-Doppler velocimeter and pressure transducer, respectively. The Reynolds number, based on channel hydraulic diameter and bulk mean velocity, was fixed at 1.2 × 10 4 . The vortex generator height-to-hydraulic diameter ratio and pitch-to-height ratio were 0.12 and 10, respectively. Comparisons in terms of heat transfer augmentation and uniformity and friction loss are first performed on 12 configurations of single longitudinal vortex generator. The fluid dynamic mechanisms and wall confinement relevant to heat transfer enhancement are then documented for three-selected vortex generator models. In addition, the differences in fluid flow and heat transfer characteristics between a single vortex generator and a vortex generator array are addressed for the delta wing I and 45 deg V (with tips facing upstream) models which provide better thermal performance among the 12 configurations examined

The influence of vortex shedding on the generation of sound by convected turbulence

Abstract: This paper discusses the theory of the generation of sound which occurs when a frozen turbulent eddy is convected in a mean flow past an airfoil or a semi-infinite plate, with and without the application of a Kutta condition and with and without the presence of a mean vortex sheet in the wake. A sequence of two-dimensional mathematical problems involving a prototype eddy in the form of a line vortex is examined, it being argued that this constitutes the simplest realistic model. Important effects of convection are deduced which hitherto have not been revealed by analyses which assume quadrupole sources to be at rest relative to the plate or airfoil. It is concluded that, to the order of approximation to which the sound from convected turbulence near a scattering body is usually estimated, the imposition of a Kutta condition at the trailing edge leads to a complete cancellation of the sound generated when frozen turbulence convects past a semi-infinite plate, and to the cancellation of the diffraction field produced by the trailing edge in the case of an airfoil of compact chord.

Similitude in Free-Surface Vortex Formations

Abstract: Different fluids were used to investigate the effects of fluid viscosity and surface tension on the incipient conditions for vortex formation and on vortex size and shape. Experiments were conducted in two different sizes of cylindrical tanks with adjustable vanes at the perimetry to allow varying degrees of initial circulation to be generated at the entrance to the test section. The results of the experiments demonstrated that: (1) free surface vortex flow is affected by initial circulation and viscosity, but, for the ranges tested, is not affected by surface tension; (2) the coefficient of the discharge is a function of the Reynolds and circulation numbers; and (3) regions in which an air core will or will not form can be defined by the depth of flow, orifice size, and circulation and Reynolds numbers.