scholarly journals Влияние способа подачи воздуха на параметры прецессирующего вихревого жгута в гидродинамической вихревой камере

2018 ◽  
Vol 44 (5) ◽  
pp. 79
Author(s):  
C.В. Алексеенко ◽  
С.И. Шторк ◽  
Р.Р. Юсупов
Keyword(s):  
Gas Phase ◽  
Vortex Core ◽  
Vortex Chamber ◽  
Gas Content ◽  
Sudden Expansion ◽  
Effective Control ◽  
Optimum Conditions ◽  
Precessing Vortex Core ◽  
Vortex Core Precession ◽  
Full Pressure

AbstractThe effect of the method of gas-phase injection into a swirled fluid flow on parameters of a precessing vortex core is studied experimentally. Conditions of the appearance of the vortex-core precession effect were modeled in a hydrodynamic sudden expansion vortex chamber. The dependences of the vortexcore precession frequency, flow-pulsation level, and full pressure differential in the vortex chamber on the consumption gas content in the flow have been obtained. The results of measurements permit one to determine optimum conditions for the most effective control of vortex-core precession.

Study Of Strongly Swirling Gas-Liquid Flows In A Hydrodynamic Vortex Chamber

2016 ◽  
Vol 11 (1) ◽  
pp. 45-55
Author(s):  
Roman Yusupov ◽  
Sergey Shtork ◽  
Sergey Alekseenko
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Vortex Chamber ◽  
Vortex Structures ◽  
Precession Frequency ◽  
Sudden Expansion ◽  
Phase Flow ◽  
Two Phase ◽  
Full Pressure

The work is devoted to experimental study of one-phase and two-phase swirling flow in a horizontal vortex chamber with a tangential swirler. Special attention is paid to an emergence of unsteady vortex structures. Formation of a precessing vortex core (PVC) in the nozzle has been detected in the case of one-phase flow. Linear dependence of the PVC precession frequency and quadratic dependence of the full pressure drop in the vortex chamber on the fluid flow rate were confirmed experimentally. In the case of two-phase flow a high-speed visualization allowed to reveal the presence of the secondary vortex structures in cylindrical region behind the zone of sudden expansion. Adding a gas phase into the flow leads to a sharp decline of the precession frequency and full pressure drop decrease in the vortex chamber. The frequency smoothly decreases with further increase of gas content and pressure drop changes insignificantly: slightly increases or decreases depending on the water flow rate. At the same time there is a coherent change of the flow’s integral characteristics at changing the flow rates of liquid and gas.

Numerical modeling of the influence of bubbles on flow and heat transfer in the descending gas-liquid flow in a pipe

2012 ◽  
Vol 9 (1) ◽  
pp. 131-135
Author(s):  
M.A. Pakhomov
Keyword(s):  
Heat Transfer ◽  
Gas Phase ◽  
Liquid Flow ◽  
Bubble Diameter ◽  
Gas Content ◽  
Two Phase ◽  
Eulerian Description ◽  
Flow And Heat Transfer ◽  
Gas Liquid Flow ◽  
The Mathematical Model

The paper presents the results of modeling the dynamics of flow, friction and heat transfer in a descending gas-liquid flow in the pipe. The mathematical model is based on the use of the Eulerian description for both phases. The effect of a change in the degree of dispersion of the gas phase at the input, flow rate, initial liquid temperature and its friction and heat transfer rate in a two-phase flow. Addition of the gas phase causes an increase in heat transfer and friction on the wall, and these effects become more noticeable with increasing gas content and bubble diameter.

Investigations into the Precessing Vortex Core Phenomenon in Cyclone Dust Separators

1994 ◽  
Vol 208 (2) ◽  
pp. 147-154 ◽  
Author(s):  
P Yazdabadi ◽  
A J Griffiths ◽  
N Syred
Keyword(s):  
Vortex Core ◽  
Reynolds Numbers ◽  
Frequency Parameter ◽  
Experimental Investigations ◽  
Swirl Number ◽  
Significant Drop ◽  
Precessing Vortex Core ◽  
Dust Separator ◽  
The Relationship

Experimental investigations have been carried out to examine the effect of downstream pipework configurations on the precessing vortex core (PVC) generated within the exhaust region of a cyclone dust separator. Characterization of the PVC using a non-dimensionalized frequency parameter (NDFP) was used to determine the relationship between Reynolds number and geometrical swirl number of the cyclone. The results show that the NDFP tends towards an asymptotic value for Reynolds numbers of about 50 000 and high swirl numbers (> 3.043). This value is reached earlier with lower swirl numbers. It was concluded that any exhaust pipework configuration produced a significant drop in the PVC frequency, and certain configurations either delayed or promoted the development of the PVC.

The Role of the Centerbody Wake on the Precessing Vortex Core Dynamics of a Swirl Nozzle

2021 ◽  
Author(s):  
Arnab Mukherjee ◽  
Nishanth Muthichur ◽  
Chaitali More ◽  
Saarthak Gupta ◽  
Santosh Hemchandra
Keyword(s):  
Vortex Core ◽  
Precessing Vortex Core ◽  
Core Dynamics

Impact of Precessing Vortex Core Dynamics on Shear Layer Response in a Swirling Jet

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Mark Frederick ◽  
Kiran Manoharan ◽  
Joshua Dudash ◽  
Brian Brubaker ◽  
Santosh Hemchandra ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Shear Layer ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Vortex Core ◽  
Combustion Instability ◽  
Forced Response ◽  
Longitudinal Acoustic ◽  
Precessing Vortex Core ◽  
Acoustic Forcing

Combustion instability, the coupling between flame heat release rate oscillations and combustor acoustics, is a significant issue in the operation of gas turbine combustors. This coupling is often driven by oscillations in the flow field. Shear layer roll-up, in particular, has been shown to drive longitudinal combustion instability in a number of systems, including both laboratory and industrial combustors. One method for suppressing combustion instability would be to suppress the receptivity of the shear layer to acoustic oscillations, severing the coupling mechanism between the acoustics and the flame. Previous work suggested that the existence of a precessing vortex core (PVC) may suppress the receptivity of the shear layer, and the goal of this study is to first, confirm that this suppression is occurring, and second, understand the mechanism by which the PVC suppresses the shear layer receptivity. In this paper, we couple experiment with linear stability analysis to determine whether a PVC can suppress shear layer receptivity to longitudinal acoustic modes in a nonreacting swirling flow at a range of swirl numbers. The shear layer response to the longitudinal acoustic forcing manifests as an m = 0 mode since the acoustic field is axisymmetric. The PVC has been shown both in experiment and linear stability analysis to have m = 1 and m = −1 modal content. By comparing the relative magnitude of the m = 0 and m = −1,1 modes, we quantify the impact that the PVC has on the shear layer response. The mechanism for shear layer response is determined using companion forced response analysis, where the shear layer disturbance growth rates mirror the experimental results. Differences in shear layer thickness and azimuthal velocity profiles drive the suppression of the shear layer receptivity to acoustic forcing.

Why Non-Uniform Density Suppresses the Precessing Vortex Core

2013 ◽  
Author(s):  
Kilian Oberleithner ◽  
Steffen Terhaar ◽  
Lothar Rukes ◽  
Christian Oliver Paschereit
Keyword(s):  
Natural Gas ◽  
Vortex Core ◽  
Hydrodynamic Instability ◽  
Density Field ◽  
Density Stratification ◽  
Reacting Flow ◽  
Global Instability ◽  
Global Mode ◽  
Precessing Vortex Core ◽  
Flow Oscillations

Isothermal swirling jets undergoing vortex breakdown are known to be susceptible to self-excited flow oscillations. They manifest in a precessing vortex core and synchronized growth of large-scale vortical structures. Recent theoretical studies associate these dynamics with the onset of a global hydrodynamic instability mode. These global modes also emerge in reacting flows, thereby crucially affecting the mixing characteristics and the flame dynamics. It is, however, observed that these self-excited flow oscillations are often suppressed in the reacting flow, while they are clearly present at isothermal conditions. This study provides strong evidence that the suppression of the precessing vortex core is caused by density stratification created by the flame. This mechanism is revealed by considering two reacting flow configurations: The first configuration represents a detached steam-diluted natural gas swirl-stabilized flame featuring a strong precessing vortex core. The second represents a natural gas swirl-stabilized flame anchoring near the combustor inlet, which does not exhibit self-excited oscillations. Experiments are conducted in a generic combustor test rig and the flow dynamics are captured using PIV and LDA. The corresponding density fields are approximated from the seeding density using a quantitative light sheet technique. The experimental results are compared to the global instability properties derived from hydrodynamic linear stability theory. Excellent agreement between the theoretically derived global mode frequency and measured precession frequency provide sufficient evidence to conclude that the self-excited oscillations are, indeed, driven by a global hydrodynamic instability. The effect of the density field on the global instability is studied explicitly by performing the analysis with and without density stratification. It turns out that the significant change on instability is caused by the radial density gradients in the inner recirculation zone and not by the change of the mean velocity field. The present work provides a theoretical framework to analyze the global hydrodynamic instability of realistic combustion configurations. It allows relating the flame position and the resulting density field to the emergence of a precessing vortex core.

Numerical simulation of precessing vortex core dumping by localized nonstationary heat source

2016 ◽  
Author(s):  
Denis Porfiriev ◽  
Anastasiya Gorbunova ◽  
Igor Zavershinsky ◽  
Semen Sugak ◽  
Nonna Molevich
Keyword(s):  
Numerical Simulation ◽  
Heat Source ◽  
Vortex Core ◽  
Nonstationary Heat ◽  
Precessing Vortex Core

scholarly journals Stability and Sensitivity Analysis of Hydrodynamic Instabilities in Industrial Swirled Injection Systems

2017 ◽  
Author(s):  
Thomas L. Kaiser ◽  
Thierry Poinsot ◽  
Kilian Oberleithner
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Vortex Core ◽  
Large Eddy Simulations ◽  
Mode Shapes ◽  
Mean Flow ◽  
Precessing Vortex Core ◽  
Large Eddy ◽  
Good Agreement

The hydrodynamic instability in an industrial, two-staged, counter-rotative, swirled injector of highly complex geometry is under investigation. Large eddy simulations show that the complicated and strongly nonparallel flow field in the injector is superimposed by a strong precessing vortex core. Mean flow fields of large eddy simulations, validated by experimental particle image velocimetry measurements are used as input for both local and global linear stability analysis. It is shown that the origin of the instability is located at the exit plane of the primary injector. Mode shapes of both global and local linear stability analysis are compared to a dynamic mode decomposition based on large eddy simulation snapshots, showing good agreement. The estimated frequencies for the instability are in good agreement with both the experiment and the simulation. Furthermore, the adjoint mode shapes retrieved by the global approach are used to find the best location for periodic forcing in order to control the precessing vortex core.

scholarly journals Numerical study of the vortex breakdown and vortex reconnection in the flow path of high-pressure water turbine

2021 ◽  
Vol 2088 (1) ◽  
pp. 012040
Author(s):  
A V Sentyabov ◽  
D V Platonov ◽  
A V Minakov ◽  
A S Lobasov
Keyword(s):  
Vortex Core ◽  
Vortex Breakdown ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Hydraulic Turbine ◽  
Sliding Mesh ◽  
Precessing Vortex Core ◽  
Vortex Reconnection ◽  
Water Turbine ◽  
Pressure Water

Abstract The paper presents a study of the instability of the precessing vortex core in the model of the draft tube of a hydraulic turbine. The study was carried out using numerical modeling using various approaches: URANS, RSM, LES. The best agreement with the experimental data was shown by the RSM and LES methods with the modelling of the runner rotation by the sliding mesh method. In the regime under consideration, the precessing vortex rope is subject to instability, which leads to reconnection of its turns and the formation of an isolated vortex ring. Reconnection of the vortex core leads to aperiodic and intense pressure fluctuations recorded on the diffuser wall.

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