scholarly journals Occurrence of a Swirling Vortex without an Intake

2020 ◽  
Author(s):  
Kerem TAŞTAN ◽  
Nevzat YILDIRIM
Keyword(s):  
Swirling Vortex

Aerodynamic Interaction Between Incoming Vortex and Tip Leakage Flow in a Turbine Cascade

2018 ◽  
Author(s):  
Kai Zhou ◽  
Chao Zhou
Keyword(s):  
Numerical Study ◽  
Aerodynamic Performance ◽  
Leakage Flow ◽  
Computational Domain ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Swirl Generator ◽  
Swirling Vortex

In turbines, secondary vortices and tip leakage vortices develop and interact with each other. In order to understand the flow physics of vortices interaction, the effects of incoming vortex on the downstream tip leakage flow are investigated in terms of the aerodynamic performance in a turbine cascade. Experimental, numerical and analytical methods are used. In the experiment, a swirl generator was used upstream near the casing to generate the incoming vortex, which interacted with the tip leakage vortex in the turbine cascade. The swirl generator was located at ten different pitchwise locations to simulate the quasi-steady effects. In the numerical study, a Rankine-like vortex was defined at the inlet of the computational domain to simulate the incoming swirling vortex. Incoming vortices with opposite directions were investigated. The vorticity of the positive incoming swirling vortex has a large vector in the same direction as that of the tip leakage vortex. In the case of the positive incoming swirling vortex, the vortex mixes with the tip leakage vortex to form one vortex near the tip as it transports downstream. The vortices interaction reduces the vorticity of the flow near the tip, as well as the loss by making up for the streamwise momentum within the tip leakage vortex core. In contrast, the negative incoming swirling vortex has little effects on the tip leakage vortex and the loss. As the negative incoming swirling vortex transports downstream, it is separated from the tip leakage vortex and forms two vortices. A triple-vortices-interaction kinetic analytical model and one-dimensional mixing model are proposed to explain the mechanism of vortex interaction on the aerodynamic performance.

Influences of Rotational Speed Variations on the Flow-Induced Vibrational Performance of a Prototype Reversible Pump Turbine in Spin-No-Load Mode

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Xianghao Zheng ◽  
Yuning Zhang ◽  
Jinwei Li ◽  
Yuning Zhang
Keyword(s):  
Vibrational Level ◽  
Rotational Speed ◽  
Draft Tube ◽  
Dominant Frequency ◽  
Pump Turbine ◽  
Vortex Rope ◽  
Vibrational Levels ◽  
Load Mode ◽  
Swirling Vortex ◽  
Dominant Frequencies

Abstract During the spin-no-load mode, vibrational performance of the reversible pump turbine is an important criterion for the evaluation of the operational performances of the power station. In the present paper, the influences of rotational speed variations on the vibrational performances of the whole unit (including the top cover, the upper, and the lower brackets) are experimentally investigated with discussions of their sources and propagation characteristics. According to the whole vibrational levels and the dominant frequencies of the vibration signals obtained at the top cover, the investigated cases with different rotational speeds could be divided into three partitions with their main characteristics given as follows. In the first partition (with low rotational speeds), the vibrational level is quite limited, and its source is the pressure fluctuation generated by the swirling vortex rope in the draft tube. In the second partition (with medium rotational speeds), the vibrational level gradually increases and its source is the mechanical aspects of the impeller rotation. In the third partition (with high rotational speeds), the vibrational level is prominent with a prominent swirling vortex rope in the draft tube and intensive rotor–stator interactions in the vaneless space (VS). For the vibrations of the upper and the lower brackets, the vibrations mainly originate from the mechanical aspects of the impeller rotation and the amplitudes of the dominant frequency also increase with the increment of the rotational speed. Finally, differences between the vibrational performances of the spin-no-load mode and the generating mode are discussed.

scholarly journals The Formation and Evolution of Turbulent Swirling Vortex Rings Generated by Axial Swirlers

2019 ◽  
Vol 104 (4) ◽  
pp. 795-816 ◽  
Author(s):  
Chuangxin He ◽  
Lian Gan ◽  
Yingzheng Liu
Keyword(s):  
Propagation Velocity ◽  
Early Stage ◽  
Axial Direction ◽  
Vortex Rings ◽  
Eddy Simulation ◽  
Axis Parallel ◽  
3D Printed ◽  
Formation Number ◽  
Formation And Evolution ◽  
Swirling Vortex

AbstractThe present work investigates the formation process and early stage evolution of turbulent swirling vortex rings, by using planar Particle Image Velocimetry (PIV) and Large Eddy Simulation (LES). Vortex rings are produced in a piston-nozzle arrangement with swirl generated by 3D-printed axial swirlers in experiments. Idealised solid-body rotation is applied in LES to evaluate the effect of nozzle exit velocity profile in experiments. The Reynolds number (Re) based on the nozzle diameter D and the slug velocity U0 in the nozzle is 20,000. The swirl number S generated ranges from 0 (zero-swirl vortex ring) and 1.1, covering the two critical swirl numbers previously identified in a swirling jet. Both PIV and LES results show that the formation number F decreases linearly as S increases, with the maximum F ≈ 2.6 at S = 0 (produced by the swirler with straight vanes) and minimum F = 1.9 at S = 1.1. The corresponding maximum attainable circulation in the nozzle axis parallel plane also diminishes with increasing S. Evolution of compact rings produced by a stroke ratio L/D = 1.5 reveals that circulation decay rate is largely proportional to S. The trajectory of the vortex core in the axial direction, hence the ring axial propagation velocity, decreases as S, while that in the radial direction and the radial propagation velocity, increase with S. An empirical scaling function is proposed to scale these variables.

scholarly journals Interaction of a Vortex Induced by a Rotating Cylinder with a Plane

2017 ◽  
Vol 22 (3) ◽  
pp. 599-619
Author(s):  
Daozhi Han ◽  
Yifeng Hou ◽  
Roger Temam
Keyword(s):  
Boundary Layer ◽  
Weak Solutions ◽  
Rotating Cylinder ◽  
Existence Of Weak Solutions ◽  
Extension Method ◽  
Line Vortex ◽  
Perpendicular Plane ◽  
Swirling Vortex

AbstractIn this article, we study theoretically and numerically the interaction of a vortex induced by a rotating cylinder with a perpendicular plane. We show the existence of weak solutions to the swirling vortex models by using the Hopf extension method, and by an elegant contradiction argument, respectively. We demonstrate numerically that the model could produce phenomena of swirling vortex including boundary layer pumping and two-celled vortex that are observed in potential line vortex interacting with a plane and in a tornado.

Conical flows of fluid with variable viscosity

1988 ◽  
Vol 419 (1856) ◽  
pp. 91-106 ◽  
Keyword(s):  
Reynolds Number ◽  
Variable Viscosity ◽  
Ambient Medium ◽  
Jet Flow ◽  
Critical Value ◽  
The Other ◽  
Solution Existence ◽  
Supercritical Bifurcation ◽  
The Solution Existence ◽  
Swirling Vortex

It is proved that a model of a turbulent swirling vortex near a plane, which was studied by Wu ( Proc. R. Soc. Lond . A 403, 235–268 (1986)), is inconsistent. There is no regular solution for a swirling downward flow satisfying the adherence condition at the surface. If the flow is upward the solution existence is not excluded but it cannot appear owing to a bifurcation, because an initial solution for a non-swirling conically similar jet emerging from an origin on the plane does not satisfy the adherence condition for any angular distribution of viscosity that is physically meaningful. On the other hand, if a jet in an ambient medium is induced by a convergent motion of the plane matter then, firstly, the laminar solution ceases to exist when the Reynolds number exceeds a finite critical value, so the flow must become turbulent; and, secondly, for a jet flow with a turbulent core a supercritical bifurcation takes place if the rotation friction on the plane is zero. As a result, a self-swirling jet flow is developed together with a spiral motion of the plane matter. Such a scenario may serve as a simple hydrodynamical model for some astrophysical and geophysical phenomena.

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