scholarly journals Particle behavior in a turbulent flow within an axially corrugated geometry

2021 ◽  
Vol 13 (8) ◽  
pp. 168781402110360
Author(s):  
Ghulam Mustafa Majal ◽  
Lisa Prahl Wittberg ◽  
Mihai Mihaescu
Keyword(s):  
Gas Flow ◽  
Numerical Study ◽  
Stokes Number ◽  
Particle Dispersion ◽  
Particle Behavior ◽  
Eddy Simulation ◽  
Recirculation Zones ◽  
Pipe Geometry ◽  
Turbulent Gas Flow ◽  
Inflow Conditions

In this numerical study particle behavior inside a sinusoidal pipe geometry is analyzed. The 3D geometry consists of three identical modules, with a periodic boundary condition applied to the flow in the stream wise direction. The incompressible, turbulent gas flow is modeled using a Large Eddy Simulation (LES) approach. Furthermore, the particle dynamics are simulated using a Lagrangian point force approach incorporating the Stokes drag and slip correction factor. Four different sizes of particles, corresponding to a Stokes number less than unity, are considered along with two different inflow conditions: continuous and pulsatile. The pulsatile inflow has an associated flow frequency of 80 Hz. The fluid flow through the sinusoidal pipe is characterized by weak flow separation in the expansion zones of the sinusoidal pipe geometry, where induced shear layers and weak recirculation zones are identified. Particle behavior under the two inflow conditions is quantified using particle dispersion, particle residence time, and average radial position of the particle. No discernible difference in the particle behavior is observed between the two inflow conditions. As the observed recirculation zones are weak, the particles are not retained within the cavities for a long duration of time, thereby reducing their likelihood of agglomerating.

Large-eddy simulation of turbulent gas–particle flow in a vertical channel: effect of considering inter-particle collisions

2001 ◽  
Vol 442 ◽  
pp. 303-334 ◽  
Author(s):  
Y. YAMAMOTO ◽  
M. POTTHOFF ◽  
T. TANAKA ◽  
T. KAJISHIMA ◽  
Y. TSUJI
Keyword(s):  
Gas Flow ◽  
Vertical Channel ◽  
Stokes Number ◽  
Particle Collision ◽  
Experimental Measurements ◽  
Particle Collisions ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Good Agreement

The interaction between a turbulent gas flow and particle motion was investigated by numerical simulations of gas–particle turbulent downward flow in a vertical channel. In particular the effect of inter-particle collision on the two-phase flow field was investigated. The gas flow field was obtained by large-eddy simulation (LES). Particles were treated by a Lagrangian method, with inter-particle collisions calculated by a deterministic method. The spatial resolution for LES of gas–solid two-phase turbulent flow was examined and relations between grid resolution and Stokes number are presented. Profiles of particle mean velocity, particle wall-normal fluctuation velocity and number density are flattened as a result of inter-particle collisions and these results are in good agreement with experimental measurements. Calculated turbulence attenuation by particles agrees well with experimental measurements for small Stokes numbers, but not for large Stokes number particle. The shape and scale of particle concentrations calculated considering inter-particle collision are in good agreement with experimental observations.

Modeling of the Coal Particle Behavior in an Ultra-Supercritical Boiler With Large Eddy Simulation

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Haoshu Shen ◽  
Yang Zhang ◽  
Yuxin Wu ◽  
Minmin Zhou ◽  
Hai Zhang ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Large Scale ◽  
Stokes Number ◽  
Particle Number Density ◽  
Thermal Calculation ◽  
Particle Behavior ◽  
Eddy Simulation ◽  
Promising Tool ◽  
Main Burner ◽  
Large Eddy

Abstract Large eddy simulation (LES) is becoming a promising tool for the design and retrofit of utility boilers. It explicitly calculates the large-scale eddies which play an important role in the particle behavior inside the boilers. An ultra-supercritical tangentially fired boiler was simulated under the boiler maximum continuous rate (BMCR) condition by LES. The particle phase was tracked by the simplified direct quadrature method of moments in the Eulerian framework. Five particle sizes were adopted to represent the wide particle size distribution. The predicted gas velocities were in good agreement with the thermal calculation. The LES results showed that the particles were more likely to be concentrated in the main burner zone while quickly dispersed in the over fire air (OFA) zone. A theoretical analysis found that the particle Stokes number based on the sub-grid scale was much smaller than one. The particles would behave as tracers for the eddies resolved by LES. However, some differences between the small and large particles were observed in the particle number density distributed along the vertical and horizontal directions. It meant that the inertial effects on the particle motion cannot be neglected.

Development of Euler-Euler LES Approach for Gas-Particle Turbulent Jet Flow

2006 ◽  
Author(s):  
Eleonore Riber ◽  
Mathieu Moreau ◽  
Olivier Simonin ◽  
Be´ne´dicte Cuenot
Keyword(s):  
Gas Flow ◽  
Turbulent Jet ◽  
Simulation Approach ◽  
Number Density ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Homogeneous Particle ◽  
Turbulent Jet Flow ◽  
Turbulent Gas Flow

A Large Eddy Simulation approach for Eulerian-Eulerian dispersed two-phase flow is presented. It is shown that not only the Random Uncorrelated Motion but also Sub-Grid Scales term modeling the unresolved field in the particle mesoscopic momentum transport equation and the particle Random Uncorrelated Energy need to be accounted for. Simulations of a non-homogeneous particle laden turbulent gas flow allow to compare dispersed phase quantities such as number density, time-averaged and rms mesoscopic velocity, fluid-particle correlations with experimental results.

Numerical Study of the Turbulent Flow Inside an ORACLES Configuration

2012 ◽  
Vol 79 (5) ◽  
Author(s):  
Fethi Bouras ◽  
Azeddine Soudani ◽  
Mohamed Si-Ameur
Keyword(s):  
Eddy Viscosity ◽  
Numerical Study ◽  
Longitudinal Velocity ◽  
Large Eddy Simulations ◽  
The European Union ◽  
Combustion Chambers ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Recirculation Zones ◽  
Air Channels

This numerical investigation deals with the validation of the experimental results in the inert cases of Nguyen et al., obtained in the framework of the European Union-funded research program MOLECULES (Modelling of Low Emissions Combustors Using Large Eddy Simulations). This study is based on the benchmark of testing one rig for accurate comparisons with large eddy simulations configuration (ORACLES), aimed at helping the design of reliable lean premixed prevaporized) combustion chambers and supplied with two identical flows of air channels. Therefore, this study is based on the 3D numerical simulation using large eddy simulation-wall adapting local eddy viscosity (LES-WALE) model that aims to determine the longitudinal velocity, the longitudinal velocity fluctuation and the length of recirculation zone for the three cases of flow in different inlet Reynolds (Re = 25,000, 50,000, 75,000). Calculations are carried out by the FLUENT_CFD. The results obtained are compared with experimental measurements of Nguyen et al. The LES_WALE eddy viscosity computation presents a good agreement with the experimental data where we could observe the asymmetrical flow and also detect the recirculation zones and the differences between the cases of the flow.

Large Eddy Simulation of a Particle-Laden Turbulent Backward-Facing Step Flow

2003 ◽  
Author(s):  
Bing Wang ◽  
Hui-Qiang Zhang ◽  
Xi-Lin Wang ◽  
Yin-Cheng Guo ◽  
Wen-Yi Lin
Keyword(s):  
Coherent Structures ◽  
Velocity Slip ◽  
Stokes Number ◽  
Continuous Phase ◽  
Particle Dispersion ◽  
Particle Phase ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Instantaneous Concentration

Numerical simulations of the two-dimensional backward facing step gas-particle turbulent flow are reported. Both the evolution of large eddy coherent structures in spatially and temporally and the vortex-particle interactions are researched. Effects of the particle Stokes number and the initial two-phase velocity slip on the instantaneous concentration distribution of the particles with and without the influence of gravity are discussed. Continuous phase simulation is performed by the method of large eddy simulation (LES) while the particle phase is solved by a Lagrangian method. Simulations of the gas phase reproduce the character of the separation and reattachment flow and the essential features of the coherent structures. It is shown that the vortex structures become extraordinary abundant and complex under the high Reynolds number. Further more, the simulation shows the initial two-phase velocity slip plays an important role in enforcing particle dispersion and sharply changes the instantaneous particle distribution under the different particle Stokes numbers. Even more, results demonstrate the influence of gravity on particle dispersion and sedimentation. Such pronounces effect of gravity on instantaneous concentration of particles with increased Stokes number and initial slip coefficients emphasize the need for the consideration of gravity for horizontal particle-laden flow. Either the continuous phase results or particle phase results obtained from LES agree well with the experiment data both in quantitative and qualitative.

NUMERICAL STUDY OF DETONATION PROPAGATION IN VISCOUS TURBULENT FLOW IN A DUCT

2020 ◽  
Author(s):  
V. A. SABELNIKOV ◽  
◽  
V. V. VLASENKO ◽  
S. BAKHNE ◽  
S. S. MOLEV ◽  
...  
Keyword(s):  
Complex Geometry ◽  
Numerical Study ◽  
Navier Stokes ◽  
Detonation Waves ◽  
Detonation Propagation ◽  
Eddy Simulation ◽  
Detonation Structure ◽  
Classical Studies ◽  
Large Eddy ◽  
Physical Effects

Gasdynamics of detonation waves was widely studied within last hundred years - analytically, experimentally, and numerically. The majority of classical studies of the XX century were concentrated on inviscid aspects of detonation structure and propagation. There was a widespread opinion that detonation is such a fast phenomenon that viscous e¨ects should have insigni¦cant in§uence on its propagation. When the era of calculations based on the Reynolds-averaged Navier- Stokes (RANS) and large eddy simulation approaches came into effect, researchers pounced on practical problems with complex geometry and with the interaction of many physical effects. There is only a limited number of works studying the in§uence of viscosity on detonation propagation in supersonic §ows in ducts (i. e., in the presence of boundary layers).

scholarly journals A Numerical Study of the Effect of Particle Size on Particle Deposition on Turbine Vanes and Blades

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110178
Author(s):  
Zhengang Liu ◽  
Weinan Diao ◽  
Zhenxia Liu ◽  
Fei Zhang
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Numerical Study ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Factors Affecting ◽  
Pressure Surface ◽  
Deposition Area ◽  
Turbine Vanes

Particle deposition could decrease the aerodynamic performance and cooling efficiency of turbine vanes and blades. The particle motion in the flow and its temperature are two important factors affecting its deposition. The size of the particle influences both its motion and temperature. In this study, the motion of particles with the sizes from 1 to 20 μm in the first stage of a turbine are firstly numerically simulated with the steady method, then the particle deposition on the vanes and blades are numerically simulated with the unsteady method based on the critical viscosity model. It is discovered that the particle deposition on vanes mainly formed near the leading and trailing edge on the pressure surface, and the deposition area expands slowly to the whole pressure surface with the particle size increasing. For the particle deposition on blades, the deposition area moves from the entire pressure surface toward the tip with the particle size increasing due to the effect of rotation. For vanes, the particle capture efficiency increases with the particle size increasing since Stokes number and temperature of the particle both increase with its size. For blades, the particle capture efficiency increases firstly and then decreases with the particle size increasing.

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