LES/FMDF of Mixing in Turbulent Jet in Cross-Flows

2014 ◽  
Author(s):  
Mostafa Esmaeili ◽  
Asghar Afshari
Keyword(s):  
Velocity Profile ◽  
Numerical Scheme ◽  
Mass Density ◽  
Cross Flow ◽  
Mixing Enhancement ◽  
Complex Flow ◽  
Mixing Condition ◽  
Eddy Simulation ◽  
Jet Velocity ◽  
Flow Configurations

In this study, an Eulerian-Lagrangian computational methodology is utilized for large eddy simulation (LES) of mixing phenomena in jet in cross-flows. A high-order multi-block algorithm is used to solve Eulerian equations in a generalized coordinate system. The composition is formulated based on the filtered mass density function (FMDF) and its equivalent stochastic Lagrangian equations, which is solved by Lagrangian Monte-Carlo method. Parameters influencing mixing enhancement including jet velocity profile, and jet pulsation are investigated. A good consistency between Eulerian and Lagrangian components of the numerical scheme is established. In jet in cross-flow (JICF) simulations, the vortical structures and flow features are predicted with the current numerical scheme. The results also show that the jet velocity profile affects both trajectory and mixing condition and the jet pulsation can enhance mixing depending on the Strouhal numbers. The obtained results including concentration distributions are in good agreement with available experimental data ensuring the performance and reliability of LES/FMDF methodology to study mixing in relatively complex flow configurations such as JICF.

Large-Eddy Simulation of Turbulent Mixing of a Jet in Cross-Flow

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Mostafa Esmaeili ◽  
Asghar Afshari ◽  
Farhad A. Jaberi
Keyword(s):  
Large Eddy Simulation ◽  
Velocity Profile ◽  
Turbulent Mixing ◽  
Mass Density ◽  
Cross Flow ◽  
Vortex Pair ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Jet In Cross Flow ◽  
Large Eddy

An Eulerian–Lagrangian mathematical/computational methodology is employed for large-eddy simulation (LES) and detailed study of turbulent mixing in jet in cross-flow (JICF) configuration. Accurate prediction of mixing in JICF is crucially important to the development of advanced combustion systems. A high-order multiblock finite difference (FD) computational algorithm is used to solve the Eulerian velocity and pressure equations in a generalized coordinate system. The composition field, describing the mixing, is obtained from the filtered mass density function (FMDF) and its stochastic Lagrangian Monte-Carlo (MC) solver. Our simulations are shown to accurately predict the important flow features present in JICF such as the counter-rotating vortex pair (CVP), horseshoe, shear layer, and wake vortices. The consistency of the FD and MC parts of the hybrid LES/FMDF model is established for the simulated JICF in various conditions, indicating the numerical accuracy of the model. The effects of parameters influencing the jet penetration, entrainment, and turbulent mixing such as the jet velocity profile, and jet pulsation are investigated. The results show that the jet exit velocity profile significantly changes the trajectory and mixing of injected fluid. The jet pulsation is also shown to enhance the mixing depending on the flow Strouhal number. The LES/FMDF results are shown to be in good agreement with the available experimental data, confirming the reliability of LES/FMDF method for numerical simulation of turbulent mixing in complex flow configurations.

LES/FMDF of turbulent reacting jet in cross-flow

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mostafa Esmaeili ◽  
Asghar Afshari
Keyword(s):  
Mass Density ◽  
Cross Flow ◽  
Combustion Efficiency ◽  
Content Type ◽  
Eddy Simulation ◽  
Jet In Cross Flow ◽  
Large Eddy ◽  
Flow Features ◽  
Hybrid Solver ◽  
Good Agreement

Purpose This study aims to numerically investigate the flow features and mixing/combustion efficiencies in a turbulent reacting jet in cross-flow by a hybrid Eulerian-Lagrangian methodology. Design/methodology/approach A high-order hybrid solver is employed where, the velocity field is obtained by solving the Eulerian filtered compressible transport equations while the species are simulated by using the filtered mass density function (FMDF) method. Findings The main features of a reacting JICF flame are reproduced by the large-eddy simulation (LES)/FMDF method. The computed mean and root-mean-square values of velocity and mean temperature field are in good agreement with experimental data. Reacting JICF’s with different momentum ratios are considered. The jet penetrates deeper for higher momentum ratios. Mixing and combustion efficiency are improved by increasing the momentum ratio. Originality/value The authors investigate the flow and combustion characteristics in subsonic reacting JICFs for which very limited studies are reported in the literature.

Numerical Simulations of Two-Phase Turbulent Combustion in Spray Burners

2007 ◽  
Author(s):  
Zhaorui Li ◽  
Murat Yaldizli ◽  
Farhad A. Jaberi
Keyword(s):  
Turbulent Combustion ◽  
Mass Density ◽  
Droplet Size Distribution ◽  
Energy Coupling ◽  
Computational Method ◽  
Spray Angle ◽  
Two Phase ◽  
Eddy Simulation ◽  
Flow Configurations ◽  
Liquid Combustion

The complex interactions among turbulence, combustion and spray in liquid-fuel burners are modeled and simulated via a new two-phase Lagrangian-Eulerian-Lagrangian large eddy simulation (LES) methodology. In this methodology, the spray is modeled with a Lagrangian mathematical/computational method which allows two-way mass, momentum and energy coupling between phases. The subgrid gas-liquid combustion is based on the two-phase filtered mass density function (FMDF) that has several advantages over “conventional” two-phase combustion models. The LES/FMDF is employed in conjunction with non-equilibrium reaction and droplet models. Simulations of turbulent combustion in a spray-controlled double-swirl burner are conducted via LES/FMDF. The generated results are used for better understanding of spray combustion in realistic turbulent flow configurations. The effects of spray angle, mass loading ratio, fuel type, droplet size distribution, wall and inflow/outflow conditions on the flow and combustion are investigated. The LES/FMDF predictions are shown to be consistent with the experimental results.

Large eddy simulation of a pulsed jet in cross-flow

2012 ◽  
Vol 695 ◽  
pp. 1-34 ◽  
Author(s):  
Axel Coussement ◽  
O. Gicquel ◽  
G. Degrez
Keyword(s):  
Large Eddy Simulation ◽  
Cross Flow ◽  
Sine Wave ◽  
Navier Stokes ◽  
Pulsed Jet ◽  
Eddy Simulation ◽  
Characteristic Boundary ◽  
Jet In Cross Flow ◽  
Large Eddy ◽  
Flow Configurations

AbstractThis study quantifies the mixing that results from a pulsed jet in cross-flow in the near jet region. By large eddy simulation computations, it also helps to understand the physical phenomena involved in the formation of the pulsed jet in cross-flow. The boundary conditions of the jet inlet are implemented via a Navier–Stokes characteristic boundary condition coupled with a Fourier series development. The signals used to pulse the jet inlet are a square or a sine wave. A new way of characterizing the mixing is introduced with the goal of easily interpreting and quantifying the complicated mixing process involved in a pulsed jet in cross-flow flow fields. Different flow configurations, pulsed and non-pulsed, are computed and compared, keeping the root mean square value of the signal constant. This comparison not only allows the characterization of the mixing but also illustrates some of the properties of the mixing characterization.

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%.

Large Eddy Simulation of a Supercritical Fuel Jet in Cross Flow using GPU-Acceleration

2016 ◽  
Author(s):  
Kalyana C. Gottiparthi ◽  
Ramanan Sankaran ◽  
Anthony M. Ruiz ◽  
Guilhem Lacaze ◽  
Joseph C. Oefelein
Keyword(s):  
Large Eddy Simulation ◽  
Cross Flow ◽  
Gpu Acceleration ◽  
Eddy Simulation ◽  
Jet In Cross Flow ◽  
Fuel Jet ◽  
Large Eddy

On LES Methods Applied to Seal Geometries

2012 ◽  
Author(s):  
James Tyacke ◽  
Richard Jefferson-Loveday ◽  
Paul Tucker
Keyword(s):  
Maximum Error ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Final Solution ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy ◽  
Rans Models ◽  
Flow Through

Nine Large Eddy Simulation (LES) methods are used to simulate flow through two labyrinth seal geometries and are compared with a wide range of Reynolds-Averaged Navier-Stokes (RANS) solutions. These involve one-equation, two-equation and Reynolds Stress RANS models. Also applied are linear and nonlinear pure LES models, hybrid RANS-Numerical-LES (RANS-NLES) and Numerical-LES (NLES). RANS is found to have a maximum error and a scatter of 20%. A similar level of scatter is also found among the same turbulence model implemented in different codes. In a design context, this makes RANS unusable as a final solution. Results show that LES and RANS-NLES is capable of accurately predicting flow behaviour of two seals with a scatter of less than 5%. The complex flow physics gives rise to both laminar and turbulent zones making most LES models inappropriate. Nonetheless, this is found to have minimal tangible results impact. In accord with experimental observations, the ability of LES to find multiple solutions due to solution non-uniqueness is also observed.

Large Eddy Simulation of Cross Flow in Pipe Junction

2018 ◽  
Author(s):  
Jiajun Chen ◽  
Yue Sun ◽  
Hang Zhang ◽  
Dakui Feng ◽  
Zhiguo Zhang
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Exciting Force ◽  
Navier Stokes ◽  
Pipe Network ◽  
Eddy Simulation ◽  
Large Eddy

Mixing in pipe junctions can play an important role in exciting force and distribution of flow in pipe network. This paper investigated the cross pipe junction and proposed an improved plan, Y-shaped pipe junction. The numerical study of a three-dimensional pipe junction was performed for calculation and improved understanding of flow feature in pipe. The filtered Navier–Stokes equations were used to perform the large-eddy simulation of the unsteady incompressible flow in pipe. From the analysis of these results, it clearly appears that the vortex strength and velocity non-uniformity of centerline, can be reduced by Y-shaped junction. The Y-shaped junction not only has better flow characteristic, but also reduces head loss and exciting force. The results of the three-dimensional improvement analysis of junction can be used in the design of pipe network for industry.

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