A Numerical Study of the Recirculation Zones During Spin-Up and Spin-Down for Confined Rotating Flows *

2003 ◽  
Vol 17 (1) ◽  
pp. 31-49 ◽  
Author(s):  
Xinjun Cui
Keyword(s):  
Numerical Study ◽  
Rotating Flows ◽  
Recirculation Zones

A Numerical Study of the Turbulent Flow over a Cylinder close to Moving Plane

2013 ◽  
Vol 394 ◽  
pp. 115-120
Author(s):  
Luciano Gonçalves Noleto ◽  
Jhon Nero Vaz Goulart ◽  
Manuel Nascimento Dias Barcelos Júnior ◽  
Antonio C.P. Brasil Junior
Keyword(s):  
Turbulent Flow ◽  
Pressure Field ◽  
Numerical Study ◽  
Plane Boundary ◽  
Projection Scheme ◽  
Oscillatory Pattern ◽  
Sst Model ◽  
Moving Plane ◽  
Recirculation Zones ◽  
Lift And Drag

Two-dimensional numerical simulations are performed to analyze the turbulent flow over a circular cylinder close to a moving plane. This flow receives interference from the plane boundary layer, being this effect identified by recirculation zones close to the wall and slight difference in pressure distribution around cylinder. URANS equations and SST modeling are employed to calculate velocity and pressure field. The simulation was performed by a finite element projection scheme. Four distances between the cylinder and the plane are analyzed by the SST model. The SST results showed the generation and development of vortex shedding. Lift and drag coefficients show the flow oscillatory pattern. All results are similar with other numerical results at the literature.

Modeling of Emissions in a Laboratory Swirl Combustor

2015 ◽  
Author(s):  
Viswanath R. Katta ◽  
William M. Roquemore
Keyword(s):  
Chemical Kinetics ◽  
Numerical Study ◽  
Flame Structure ◽  
Detailed Chemical Kinetics ◽  
Swirl Combustor ◽  
Detailed Chemistry ◽  
Hydrocarbon Emission ◽  
Recirculation Zones ◽  
Fuel Mixtures ◽  
Detailed Chemical

A swirl-stabilized combustor utilizes recirculation zones for stabilizing the flame. The performance of such combustors could depend on the fuel used as the cracked fuel products may enter the recirculation-zones and alter their characteristics. A numerical study is conducted for understanding the effects of fuel variation on the combustion and unburned-hydrocarbon-emission characteristics of a laboratory swirl combustor. A time-dependent, detailed-chemistry CFD model UNICORN is used. Six binary fuel mixtures formulated with n-dodecane and n-heptane, m-xylene, iso-octane or hexadecane are considered. A semi-detailed chemical-kinetics model (CRECK-0810) involving 206 species and 5652 reactions for the combustion of these fuels is incorporated into UNICORN code. Calculations are performed for a fuel-lean condition, which represents cruise operation of an aircraft. Combustor flows simulated with different fuel mixtures yielded nearly the same flowfields and flame structures. Production of the intermediate cracked fuel species that are key for the final flame structure and emissions seems to be independent of the fuel used. This finding could greatly simplify the detailed chemical kinetics used for obtaining cracked products. As the cracked fuel species are completely consumed with in the flame zone, no emissions are observed at the combustor exit for the considered fuel-lean condition.

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.

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.

Numerical Study of Lean-Direct Injection Combustor With Discrete-Jet Swirlers Using Reynolds Stress Model

2003 ◽  
Vol 125 (4) ◽  
pp. 1059-1065 ◽  
Author(s):  
S. L. Yang ◽  
Y. K. Siow ◽  
C. Y. Teo ◽  
R. R. Tacina ◽  
A. C. Iannetti ◽  
...  
Keyword(s):  
Reynolds Stress ◽  
Turbulence Model ◽  
Numerical Study ◽  
Direct Injection ◽  
Reynolds Stress Model ◽  
Lean Direct Injection ◽  
Velocity Gradients ◽  
Recirculation Zones ◽  
Computational Fluid Dynamics Cfd ◽  
Reynolds Averaging

The flowfield in a lean-direct injection (LDI) combustor with discrete-jet swirlers is described and analyzed using a computational fluid dynamics (CFD) code with a Reynolds stress turbulence model (RSTM). The results from the RSTM are compared to time-averaged laser-Doppler velocimetry (LDV) data, as well as results from the National Combustion Code (NCC) that has a cubic nonlinear κ-ε turbulence model, and from the KIVA code using the standard κ-ε model. The comparisons of results indicate that the RSTM accurately describes the flow details and resolves recirculation zones and high velocity gradients while the κ-ε models are unable to capture most flow structures. This confirms that, within the Reynolds averaging approach, the higher-order RSTM is preferred for simulating complex flowfields where separations, strong anisotropy, and high swirl are present.

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