Subgrid Two-Phase Mixing and Combustion Modeling for Large-Eddy Simulations

1998 ◽  
Author(s):  
Suresh Menon ◽  
Sreekanth Pannala
Keyword(s):  
Molecular Diffusion ◽  
Combustion Model ◽  
Small Scale ◽  
Liquid Droplets ◽  
Two Phase ◽  
Combustion Modeling ◽  
Droplet Vaporization ◽  
Eddy Simulation ◽  
Subgrid Model ◽  
Large Eddy

A subgrid scalar mixing and combustion model originally developed for gas phase combustion has been extended to include the liquid phase. This approach includes a more fundamental treatment of the effects of the final stages of droplet vaporization, molecular diffusion, chemical reactions and small scale turbulent mixing than other LES closure techniques. As a result, Reynolds, Schmidt and Damkohler number effects are explicitly included. This model has been implemented within an Eulerian-Lagrangian two phase large-eddy simulation (LES) formulation. In this approach, the liquid droplets are tracked using the Lagrangian approach up to a pre-specified cut-off size. The evaporation of the Lagrangian droplets and the evaporation and mixing of the droplets smaller than the cutoff size is modeled within the subgrid using an Eulerian two-phase model. The issues related to the implementation of this subgrid model within the LES are discussed in this paper along with some preliminary results that demonstrate its capabilities.

scholarly journals Prediction of a Small-Scale Pool Fire with FireFoam

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Camilo Andrés Sedano ◽  
Omar Darío López ◽  
Alexander Ladino ◽  
Felipe Muñoz
Keyword(s):  
Numerical Results ◽  
Pool Fire ◽  
Flame Height ◽  
Combustion Model ◽  
Small Scale ◽  
Average Temperature ◽  
Eddy Simulation ◽  
Fire Experiment ◽  
Large Eddy ◽  
Good Agreement

A computational model using Large Eddy Simulation (LES) for turbulence modelling was implemented, by means of the Eddy Dissipation Concept (EDC) combustion model using the fireFoam solver. A small methanol pool fire experiment was simulated in order to validate and compare the numerical results, hence trying to validate the effectiveness of the solver. A detailed convergence analysis is performed showing that a mesh of approximately two million elements is sufficient to achieve satisfactory numerical results (including chemical kinetics). A good agreement was achieved with some of the experimental and previous computational results, especially in the prediction of the flame height and the average temperature contours.

Subgrid Scale Combustion Modeling Based on Stochastic Model Parameterization

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
William H. Calhoon ◽  
Andrea C. Zambon ◽  
Balu Sekar ◽  
Barry Kiel
Keyword(s):  
Large Scale ◽  
Turbulent Flame ◽  
Time Model ◽  
Strain Effects ◽  
Combustion Modeling ◽  
Eddy Simulation ◽  
Model Parameterization ◽  
Subgrid Model ◽  
Large Eddy ◽  
Linear Eddy Model

A new modeling formulation for turbulent chemistry interactions in large-eddy simulation (LES) is presented that is based on a unique application of the linear-eddy model (LEM) that includes large scale strain effects. This novel application of the LEM may be used to predict turbulent flame extinction limits due to both small and large scale strain effects. Statistics from this modeling formulation may be used to generate an inexpensive run-time model for LES predictions. This paper presents the LEM modeling formulation and demonstrates the capabilities of the approach for augmenter conditions. A methodology is also presented for formulating an LES-linear-eddy model (LES-LEM) subgrid model based on the simulation data.

Combustor and Augmentor Combustion Modeling for LES Based on Stochastic Model Parameterization

2011 ◽  
Author(s):  
William H. Calhoon ◽  
Andrea C. Zambon ◽  
Balu Sekar ◽  
Barry Kiel
Keyword(s):  
Large Scale ◽  
Turbulent Flame ◽  
Time Model ◽  
Strain Effects ◽  
Combustion Modeling ◽  
Eddy Simulation ◽  
Model Parameterization ◽  
Subgrid Model ◽  
Large Eddy ◽  
Linear Eddy Model

A new modeling formulation for turbulent chemistry interactions in large eddy simulation (LES) is presented that is based on a unique application of the linear-eddy model (LEM) that includes large scale strain effects. This novel application of the LEM may be used to predict turbulent flame extinction limits due to both small and large scale strain effects. Statistics from this modeling formulation may be used to generate an inexpensive run-time model for LES predictions. This paper presents the LEM modeling formulation and demonstrates the capabilities of the approach for augmentor conditions. A methodology is also presented to formulate a LES subgrid model based on the simulation data.

Large-Eddy Simulation of turbulent, cavitating fuel flow inside a 9-hole Diesel injector including needle movement

2016 ◽  
Vol 18 (3) ◽  
pp. 195-211 ◽  
Author(s):  
Felix Örley ◽  
Stefan Hickel ◽  
Steffen J Schmidt ◽  
Nikolaus A Adams
Keyword(s):  
Large Eddy Simulation ◽  
Fluid Model ◽  
Immersed Boundary ◽  
Small Scale ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features ◽  
Two Fluid Model ◽  
Liquid Flows

We investigate the turbulent multiphase flow inside a nine-hole common rail Diesel injector during a full injection cycle of ISO 4113 diesel fuel into air by implicit large-eddy simulation (LES). The simulation includes a prescribed needle movement obtained from a one-dimensional multi-domain simulation. The injector geometry is represented by a conservative cut-element-based immersed boundary method with subcell resolution, which has been developed for the application in the context of cavitating liquid flows. We employ a barotropic two-phase two-fluid model, where all components (i.e. air, liquid diesel, gaseous diesel) are represented by a homogenous mixture approach. The cavitation model is based on a thermodynamic equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics. The analysis of the turbulent flow field reveals that the opening and closing phase are dominated by small-scale turbulence, while in the main injection phase large vortical structures are formed in the needle volume and reach into the nozzle holes. Violent collapse events of cavitation structures are detected during the closing phase in the nozzle holes and after closing in the sac hole region. A comparison with LES results with a fixed injector needle at different lift positions shows a good agreement for large needle lifts, while the needle movement has significant effects on important flow features at low needle lifts.

scholarly journals Cavitation of Multiscale Vortices in Circular Cylinder Wake at Re = 9500

2021 ◽  
Vol 9 (12) ◽  
pp. 1366
Author(s):  
Fadong Gu ◽  
Yadong Huang ◽  
Desheng Zhang
Keyword(s):  
Circular Cylinder ◽  
Large Scale ◽  
Volume Fraction ◽  
Small Scale ◽  
Cylinder Wake ◽  
Two Phase ◽  
Phase Volume Fraction ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Approximate Frequency

Cavitation characteristics in the wake of a circular cylinder, which contains multiscale vortices, are numerically investigated via Large Eddy Simulation (LES) in this paper. The Reynolds number is 9500 based on the inlet velocity, the cylinder diameter and the kinematic viscosity of the noncavitation liquid. The Schneer–Sauer (SS) model is applied to cavitation simulation because it is more sensitive to vapor–liquid two-phase volume fraction than the Zwart–Gerber–Belamri (ZGB) model, according to theoretical analyses. The wake is quasiperiodic, with an approximate frequency of 0.2. It is found that the cavitation of vortices could inhibit the vortex shedding. Besides, the mutual aggregation of small-scale vortices in the vortex system or the continuous stripping of small-scale vortices at the edge of large-scale vortices could induce the merging or splitting of cavities in the wake.

scholarly journals Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

2021 ◽  
Vol 11 (15) ◽  
pp. 7167
Author(s):  
Liang Xu ◽  
Xu Zhao ◽  
Lei Xi ◽  
Yonghao Ma ◽  
Jianmin Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Wall Temperature ◽  
Target Surface ◽  
Impinging Jets ◽  
Small Scale ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Large Eddy

Swirling impinging jet (SIJ) is considered as an effective means to achieve uniform cooling at high heat transfer rates, and the complex flow structure and its mechanism of enhancing heat transfer have attracted much attention in recent years. The large eddy simulation (LES) technique is employed to analyze the flow fields of swirling and non-swirling impinging jet emanating from a hole with four spiral and straight grooves, respectively, at a relatively high Reynolds number (Re) of 16,000 and a small jet spacing of H/D = 2 on a concave surface with uniform heat flux. Firstly, this work analyzes two different sub-grid stress models, and LES with the wall-adapting local eddy-viscosity model (WALEM) is established for accurately predicting flow and heat transfer performance of SIJ on a flat surface. The complex flow field structures, spectral characteristics, time-averaged flow characteristics and heat transfer on the target surface for the swirling and non-swirling impinging jets are compared in detail using the established method. The results show that small-scale recirculation vortices near the wall change the nearby flow into an unstable microwave state, resulting in small-scale fluctuation of the local Nusselt number (Nu) of the wall. There is a stable recirculation vortex at the stagnation point of the target surface, and the axial and radial fluctuating speeds are consistent with the fluctuating wall temperature. With the increase in the radial radius away from the stagnation point, the main frequency of the fluctuation of wall temperature coincides with the main frequency of the fluctuation of radial fluctuating velocity at x/D = 0.5. Compared with 0° straight hole, 45° spiral hole has a larger fluctuating speed because of speed deflection, resulting in a larger turbulence intensity and a stronger air transport capacity. The heat transfer intensity of the 45° spiral hole on the target surface is slightly improved within 5–10%.

scholarly journals A Fractal Dynamic SGS Combustion Model for Large Eddy Simulation of Turbulent Premixed Flames

2016 ◽  
Vol 188 (9) ◽  
pp. 1472-1495 ◽  
Author(s):  
Katsuhiro Hiraoka ◽  
Yuki Minamoto ◽  
Masayasu Shimura ◽  
Yoshitsugu Naka ◽  
Naoya Fukushima ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Premixed Flames ◽  
Combustion Model ◽  
Turbulent Premixed Flames ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbulent Premixed
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