Numerical Study of Vortex Evolution and Correlation between Twin Swirling Flows

2012 ◽  
Vol 516-517 ◽  
pp. 976-979 ◽  
Author(s):  
Nan Gui
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Numerical Study ◽  
Swirling Flows ◽  
Cyclone Separator ◽  
Velocity Correlation ◽  
Swirl Number ◽  
Swirling Jets ◽  
Swirl Flows ◽  
Energy Engineering

Swirling flows are widely used in energy engineering, such as swirling combustor, cyclone separator in pulverized coal burners. The vortex evolution and correlation between twin swirling flows are investigated via direct numerical simulation. Three typical swirl flows with different swirl number are simulated. The structure of vortex evolution, velocity correlation between the twin flows are illustrated and analyzed in detail. The results show the phase-locked correlation of flow velocity between the twin swirling jets which would be useful and helpful for improving the understanding of aerodynamics of multi-swirling systems.

scholarly journals Anisotropic Characteristics of Turbulence Dissipation in Swirling Flow: A Direct Numerical Simulation Study

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Xingtuan Yang ◽  
Nan Gui ◽  
Gongnan Xie ◽  
Jie Yan ◽  
Jiyuan Tu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Energy Dissipation ◽  
Direct Numerical Simulation ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Turbulent Energy ◽  
Swirling Flows ◽  
Small Scale

This study investigates the anisotropic characteristics of turbulent energy dissipation rate in a rotating jet flow via direct numerical simulation. The turbulent energy dissipation tensor, including its eigenvalues in the swirling flows with different rotating velocities, is analyzed to investigate the anisotropic characteristics of turbulence and dissipation. In addition, the probability density function of the eigenvalues of turbulence dissipation tensor is presented. The isotropic subrange of PDF always exists in swirling flows relevant to small-scale vortex structure. Thus, with remarkable large-scale vortex breakdown, the isotropic subrange of PDF is reduced in strongly swirling flows, and anisotropic energy dissipation is proven to exist in the core region of the vortex breakdown. More specifically, strong anisotropic turbulence dissipation occurs concentratively in the vortex breakdown region, whereas nearly isotropic turbulence dissipation occurs dispersively in the peripheral region of the strong swirling flows.

Direct Numerical Simulation of Gas-Particle Turbulent Swirling Flows in an Axially Rotating Pipe

2003 ◽  
Author(s):  
Kazuyoshi Matsuzaki ◽  
Mizue Munekata ◽  
Hideki Ohba
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Particle Concentration ◽  
Fluid Motion ◽  
Swirling Flows ◽  
Particle Collisions ◽  
Pipe Radius ◽  
The One ◽  
Very High

The purpose of this study is to investigate the effect of the turbulent structure of the swirling flows on the particle motions using numerical simulation. In this work, we deal with the swirling turbulent flows in an axially rotating pipe because of focusing on the influence of swirl effect on the particle motions. Direct numerical simulation (DNS) of gas-particle turbulent swirling flows in the axially rotating pipe at the Reynolds number 180, based on the friction velocity and the pipe radius, and the rotating ratios 0.25 and 0.3 based on the bulk velocity was performed. Particle motions were treated by a Lagragian method with inter-particle collisions calculated by a deterministic method. In order to investigate the influence of swirl effect on the particle motions in detail, the one-way method in which fluid motion is not affected by particles is adopted. In particular, the effect of the inter-particle collisions on particle motions was carefully investigated because it is considered that particles accumulate near the wall due to the centrifugal force and local particle concentration is very high in the region.

Direct numerical simulation of confined swirling jets

2014 ◽  
Vol 28 (1-2) ◽  
pp. 76-88 ◽  
Author(s):  
Nan Gui ◽  
Jie Yan ◽  
Zhenlin Li ◽  
Jianren Fan
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Swirling Jets

Numerical study on edge tone with compressible direct numerical simulation: Sound intensity and jet motion

2021 ◽  
pp. 1475472X2110032
Author(s):  
Sho Iwagami ◽  
Ryoya Tabata ◽  
Taizo Kobayashi ◽  
Yuji Hattori ◽  
Kin’ya Takahashi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Transition Region ◽  
Power Law ◽  
Numerical Study ◽  
Sound Intensity ◽  
Mode Transition ◽  
The Third ◽  
Velocity Variance ◽  
Jet Velocity

A two-dimensional model of the edge tone is studied by a highly accurate and reliable method of direct numerical simulation of the compressible Navier-Stokes equations, and used to verify key features observed in previous experimental and numerical studies, and to discover new features related to the jet motion and the edge tone generation mechanism. The first and second modes of the edge tone that are numerically reproduced agree well with Brown’s equation. In the mode transition region, dynamical mode transition is observed at a fixed jet velocity. For both first and second modes, the pressure distributions are antisymmetric with respect to the edge plate, and the sound intensity is proportional to the fifth power of the jet velocity. These results are consistent with the edge tone being radiated from a dipole-like source. Spatial profiles of the velocity and the velocity variance of the oscillating jet are also investigated for each mode over a range of the jet velocity including the mode transition regime. The amplitude of the velocity oscillation becomes constant with increasing jet velocity, while a measure of the amplitude of the velocity variance profile, which is introduced to characterize the strength of the jet fluctuation and named the ’fluctuation strength’, is proportional to the third power of the jet velocity. Some properties of the fluctuation strength correspond to properties of the sound intensity, including the first mode having larger amplitude than the second mode, and the way of deviating from the power law at smaller values of jet velocity and in the mode transition region. It is proposed that the third-power law exhibited by behavior of the fluctuation strength could be related to the increase of the skewness observed in the velocity profile with increase of jet velocity, and a model calculation is used to support this proposal.

A STUDY ON CORRELATION MOMENTS OF TWO-PHASE FLUCTUATING VELOCITY USING DIRECT NUMERICAL SIMULATION

2013 ◽  
Vol 24 (10) ◽  
pp. 1350068 ◽  
Author(s):  
BING WANG ◽  
WEI WEI ◽  
HUIQIANG ZHANG
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Phase Velocity ◽  
Turbulent Flows ◽  
Local Equilibrium ◽  
Stokes Number ◽  
Phase Correlation ◽  
Particle Phase ◽  
Velocity Correlation ◽  
Two Phase

Existing models of two-phase fluctuating velocity correlation moments are unsatisfactory because of their inability to clearly identify the dependency of two-phase velocity covariance on fluid- and particle-phase velocity second moments. This is especially true of wall-bounded turbulent flows. In this paper, the statistical fluctuating velocity of both phases in particle-laden turbulent channel flows were obtained numerically by means of direct numerical simulation (DNS) coupled to the Lagrangian particle trajectory method. The effects of particle Stokes number on the scaling of two-phase fluctuating velocity correlation moments were analyzed considering effects of flow inhomogeneity. An improved two-phase correlation closure model of exponential decay with emphasis on the particle-phase kinetic energy was then proposed based on the results of an evaluation of five existing models. This new model was found to be better than previous models, which used local equilibrium assumption. The present investigations may facilitate understanding of two-phase flow physics and the construction of models capable of predicting the movements of particle-laden turbulent flows accurately using Reynolds-averaged Navier–Stokes (RANS) methods.

scholarly journals Direct Numerical Simulation and Visualization of Biswirling Jets

2014 ◽  
Vol 6 ◽  
pp. 193731 ◽  
Author(s):  
Jie Yan ◽  
Nan Gui ◽  
Gongnan Xie ◽  
Jinsen Gao
Keyword(s):  
Numerical Simulation ◽  
Kinetic Energy ◽  
Direct Numerical Simulation ◽  
Turbulent Kinetic Energy ◽  
Vortex Structures ◽  
Small Scale ◽  
Convergence Region ◽  
Swirling Jets ◽  
Vortex Interactions ◽  
Close Distance

Two parallel swirling/rotating jets with a distance between them are termed biswirling jets here, which have important and complicated vortex structures different from the single swirling jet due to the negligible vortex-vortex interactions. The visualization of vortex-vortex interaction between the biswirling jets is accomplished by using direct numerical simulation. The evolution of vortex structures of the biswirling jets is found rather complicated. The turbulent kinetic energy and turbulence dissipation in the central convergence region are augmented locally and rather strongly. The modulation of turbulent kinetic energy by jet-jet interaction upon different scales of vortices is dominated by the swirling levels and the distance between the jets. The turbulent kinetic energy upon intermediate and small scale vortices in bijets with not very high swirling level and at a very close distance is smaller than that in single swirling jets, whereas the opposite is true under a far distance, and so forth.

Numerical study on particle motions in swirling flows in a cyclone separator

2006 ◽  
Vol 15 (2) ◽  
pp. 181-185 ◽  
Author(s):  
Kazuyoshi Matsuzaki ◽  
Hideaki Ushijima ◽  
Mizue Munekata ◽  
Hideki Ohba
Keyword(s):  
Numerical Study ◽  
Swirling Flows ◽  
Cyclone Separator
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