Large Eddy Simulation of a Swirl-Stabilized Flame

2013 ◽  
Author(s):  
Cheng Zhang ◽  
Wei Zhao
Keyword(s):  
Experimental Data ◽  
Numerical Modeling ◽  
Large Eddy Simulation ◽  
Source Term ◽  
Flow Instabilities ◽  
Filtered Density Function ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Burner Flame ◽  
Mass Fractions

Swirl is used in a wide range of combustions systems such as engines, furnaces, gasifiers, and boilers, to enhance mixing, stabilize flames, and reduce pollutant emissions. Numerical modeling of swirling flows remains a challenging task, since there may exist complex recirculating flow patterns and flow instabilities associated with vortex breakdown, precessing vortex core, and jet precession. In swirling flames, the situation becomes more complex because the unsteady heat release can add other modes of instability. The origins and nature of these instabilities are still not well understood despite many experimental and numerical studies have been conducted in the area. The Sydney swirl burner flame series provide an excellent platform for validating numerical methods for turbulence-chemistry interactions and have been target flames for the TNF workshop series. The burner has well-defined boundary conditions and comprehensive experimental data sets have been documented for different fuel compositions and flow conditions. Compared with the piloted and bluff-body stabilized flames, swirl-stabilized flames pose an additional challenge to numerical modeling because of the complex flow patterns and inherent flow instabilities. In this study, a large eddy simulation (LES)-based multi-environment turbulent combustion model is used to model the Sydney swirl burner flame SMH1. The multi-environment filtered density function model (MEFDF) depicts the filtered density function (FDF) as a weighted summation of a small number of multi-dimensional Dirac delta functions in composition space. It is derived from the transport FDF equation using the direct quadrature method of moments (DQMOM). The MEFDF method with multiple reactive scalars retains the unique property of the joint FDF model of treating the chemical source term exactly. A 19-species mechanism reduced from GRI-Mech 2.11 is employed for chemical kinetics. The in situ adaptive tabulation algorithm (ISAT) is used to speed-up the evaluation of the chemical source term. The predicted radial profiles of the axial velocity, azimuthal velocity, mixture fraction, temperature, and species mass fractions of CO2, CO, and NO are in reasonable agreement with the experimental data. It has been found that, compared with the experimental data, the profiles of the temperature and species mass fractions shifted slightly outward in the radial direction at downstream locations and NO mass fraction is slightly over-predicted at most locations. Further work will be needed to find out possible reasons for these discrepancies.

scholarly journals Modeling of Breaching-Generated Turbidity Currents Using Large Eddy Simulation

2020 ◽  
Vol 8 (9) ◽  
pp. 728
Author(s):  
Said Alhaddad ◽  
Lynyrd de Wit ◽  
Robert Jan Labeur ◽  
Wim Uijttewaal
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Turbidity Current ◽  
Turbidity Currents ◽  
Eddy Simulation ◽  
Failure Evolution ◽  
Large Eddy ◽  
Flow Slides

Breaching flow slides result in a turbidity current running over and directly interacting with the eroding, submarine slope surface, thereby promoting further sediment erosion. The investigation and understanding of this current are crucial, as it is the main parameter influencing the failure evolution and fate of sediment during the breaching phenomenon. In contrast to previous numerical studies dealing with this specific type of turbidity currents, we present a 3D numerical model that simulates the flow structure and hydrodynamics of breaching-generated turbidity currents. The turbulent behavior in the model is captured by large eddy simulation (LES). We present a set of numerical simulations that reproduce particular, previously published experimental results. Through these simulations, we show the validity, applicability, and advantage of the proposed numerical model for the investigation of the flow characteristics. The principal characteristics of the turbidity current are reproduced well, apart from the layer thickness. We also propose a breaching erosion model and validate it using the same series of experimental data. Quite good agreement is observed between the experimental data and the computed erosion rates. The numerical results confirm that breaching-generated turbidity currents are self-accelerating and indicate that they evolve in a self-similar manner.

Comparison of Large Eddy Simulation Methods for Flows Over Gas Turbine Blades

2007 ◽  
Author(s):  
M. Karimi ◽  
M. Paraschivoiu
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Gas Turbine ◽  
Compressible Flows ◽  
Turbine Blades ◽  
Classical Problem ◽  
Numerical Dissipation ◽  
Simulation Methods ◽  
Eddy Simulation ◽  
Large Eddy

In recent years there has been a considerable effort toward applying large eddy simulation methods (LES) to real industrial problems. However, there are still several challenges to be addressed to achieve a reliable LES solution, especially in the context of compressible flows. Furthermore, complex geometries require the unstructured meshes which then interdict the use of very high order schemes. Therefore, LES models are mainly derived and tested on classical problem of simple geometry for incompressible flow and based on higher order schemes. Here, the flow over a gas turbine blade at high Reynolds and Mach numbers is investigated using a mixed finite-volume-finite-element method. Implicit LES method (ILES) as well as Smagorinsky and its dynamic version have been studied. Different variations of the Smagorinsky method have been examined too. The interaction of the numerical dissipation of the scheme with LES models has been explored. The results show the capability of the ILES to take into account the effective viscosity of the flow and the negligible difference of the different LES models in this flow condition. Fairly good agreement with experimental data is found which is superior to RANS results. It is found that there are still some challenges in industrial LES applications which have to be addressed to lead to a better agreement with experimental data.

Large Eddy Simulation for Prediction of Entropy Generation in a Nonpremixed Turbulent Jet Flame

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Mehdi Safari ◽  
M. Reza H. Sheikhi
Keyword(s):  
Heat Conduction ◽  
Large Eddy Simulation ◽  
Chemical Reaction ◽  
Entropy Generation ◽  
Irreversible Processes ◽  
Filtered Density Function ◽  
Jet Flame ◽  
Eddy Simulation ◽  
Entropy Transport ◽  
Large Eddy

Local entropy generation in a turbulent nonpremixed jet flame (Sandia Flame D) is predicted using large eddy simulation (LES) with inclusion of entropy transport. The filtered form of entropy transport equation contains several unclosed source terms which represent irreversibilities due to viscous dissipation, heat conduction, mass diffusion, and chemical reaction. The subgrid scale (SGS) closure is accounted for by the entropy filtered density function (En-FDF) methodology to include complete statistical information about SGS variation of scalars and entropy. The En-FDF provides closed forms for the chemical reaction effects. The methodology is applied for LES of Sandia Flame D and predictions are validated against experimental data. Entropy statistics are shown to compare favorably with the data. All individual irreversible processes in this flame are predicted and analyzed. It is shown that heat conduction and chemical reaction are the main sources of entropy generation in this flame.

Large Eddy Simulation of a Lean Gas Turbine Model Combustor

2009 ◽  
Author(s):  
M. Staufer ◽  
J. Janicka
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Flame Surface ◽  
Eddy Simulation ◽  
Partially Premixed Combustion ◽  
Large Eddy ◽  
Partially Premixed ◽  
Partially Premixed Flame ◽  
Presumed Pdf ◽  
Pdf Model

Partially premixed flames although common on many technical devices are difficult to model in numerical simulations. In this paper a Large Eddy Simulation of a lean combustor is presented. To account for mixing effects in case of partially premixed combustion, a suitable extension to the well known coherent flame model (CFM) is applied. The turbulent reaction rate of the partially premixed flame is approximated by solving an additional transport equation for the flame surface density which accounts for flame wrinkling effects as well as for the creation and destruction of flame surface due to stretch and strain effects. The variation of stoichiometry in the flame is accounted for by using a suitable presumed PDF methodology. The pdf-model represents finite rate, as well as non-equilibrium chemistry effects in the flame. The model has been validated against experimental data. The results show an overall reasonable agreement with experimental data, both in profile shapes as well as peak values.

Large Eddy Simulation of Cylindrical Jet Breakup and Correlation of Simulation Results With Experimental Data

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Shashank S. Moghe ◽  
Scott M. Janowiak
Keyword(s):  
Experimental Data ◽  
Kinetic Energy ◽  
Large Eddy Simulation ◽  
Turbulent Kinetic Energy ◽  
Experimental Results ◽  
Eddy Simulation ◽  
Jet Breakup ◽  
Large Eddy ◽  
Oil Jet ◽  
Piston Cooling

Modern engines with increasing power densities have put additional demands on pistons to perform in incrementally challenging thermal environments. Piston cooling is therefore of paramount importance for engine component manufacturers. The objective of this computational fluid dynamics (CFD) study is to identify the effect of a given piston cooling nozzle (PCN) geometry on the cooling oil jet spreading phenomenon. The scope of this study is to develop a numerical setup using the open-source CFD toolkit OpenFoam® for measuring the magnitude of oil jet spreading and comparing it to experimental results. Large eddy simulation (LES) turbulence modeling is used to capture the flow physics that affects the inherently unsteady jet breakup phenomenon. The oil jet spreading width is the primary metric used for comparing the numerical and experimental results. The results of simulation are validated for the correct applicability of LES by evaluating the fraction of resolved turbulent kinetic energy (TKE) at various probe locations and also by performing turbulent kinetic energy spectral analysis. CFD results appear promising since they correspond to the experimental data within a tolerance (of ±10%) deemed satisfactory for the purpose of this study. Further generalization of the setup is underway toward developing a tool that predicts the aforementioned metric—thereby evaluating the effect of PCN geometry on oil jet spreading and hence on the oil catching efficiency (CE) of the piston cooling gallery. This tool would act as an intermediate step in boundary condition formulation for the simulation determining the filling ratio (FR) and subsequently the heat transfer coefficients (HTCs) in the piston cooling gallery.

Comparison of Partially Averaged Navier–Stokes and Large-Eddy Simulations of the Flow Around a Cuboid Influenced by Crosswind

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Siniša Krajnović ◽  
Per Ringqvist ◽  
Branislav Basara
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Better Than ◽  
Good Agreement ◽  
Near Wall

The paper presents a partially averaged Navier–Stokes (PANS) simulation of the flow around a cuboid influenced by crosswind. The results of the PANS prediction are validated against experimental data and results of a large-eddy simulation (LES) made using the same numerical conditions as PANS. The PANS shows good agreement with the experimental data. The prediction of PANS was found to be better than that of the LES in flow regions where simulations suffered from poor near-wall resolution.

scholarly journals Jet Noise in Airframe Integration and Shielding

2020 ◽  
Vol 10 (2) ◽  
pp. 511
Author(s):  
Saman Salehian ◽  
Reda Mankbadi
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Jet Noise ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Complex Geometries ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

This paper reviews and presents new results on the effect of airframe integration and shielding on jet noise. Available experimental data on integration effects are analyzed. The available options for the computation of jet noise are discussed, and a practical numerical approach for the present topic is recommended. Here, it is demonstrated how a hybrid large eddy simulation—unsteady Reynolds-averaged Navier-Stokes approach can be implemented to simulate the effect of shielding on radiated jet noise. This approach provides results consistent with the experiment and suggests a framework for studying more complex geometries involving airframe integration effects.

scholarly journals Numerical Investigation of Fluid Flow and Performance Prediction in a Fluid Coupling Using Large Eddy Simulation

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Wei Cai ◽  
Yuan Li ◽  
Xingzhong Li ◽  
Chunbao Liu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Performance Prediction ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Comparison Results ◽  
Large Eddy ◽  
Hydraulic Coupling ◽  
And Performance

Large eddy simulation (LES) with various subgrid-scale (SGS) models was introduced to numerically calculate the transient flow of the hydraulic coupling. By using LES, the study aimed to advance description ability of internal flow and performance prediction. The CFD results were verified by experimental data. For the purpose of the description of the flow field, six subgrid-scale models for LES were employed to depict the flow field; the distribution structure of flow field was legible. Moreover, the flow mechanism was analyzed using 3D vortex structures, and those showed that DSL and KET captured abundant vortex structures and provided a relatively moderate eddy viscosity in the chamber. The predicted values of the braking torque for hydraulic coupling were compared with experimental data. The comparison results were compared with several simulation models, such as SAS and RKE, and SSTKW models. Those comparison results showed that the SGS models, especially DSL and KET, were applicable to obtain the more accurate predicted results than SAS and RKE, and SSTKW models. Clearly, the predicted results of LES with DSL and KET were far more accurate than the previous studies. The performance prediction was significantly improved.

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