Penetration of the Flame Into the Top-Land Crevice - Large-Eddy Simulation and Experimental High-Speed Visualization

2015 ◽  
Author(s):  
Peter Janas ◽  
Mateus Dias Ribeiro ◽  
Andreas Kempf ◽  
Martin Schild ◽  
Sebastian A. Kaiser
Keyword(s):  
Large Eddy Simulation ◽  
High Speed ◽  
Eddy Simulation ◽  
Large Eddy

RANS and Large Eddy Simulation of Internal Combustion Engine Flows—A Comparative Study

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Xiaofeng Yang ◽  
Saurabh Gupta ◽  
Tang-Wei Kuo ◽  
Venkatesh Gopalakrishnan
Keyword(s):  
Large Eddy Simulation ◽  
High Speed ◽  
Combustion Engine ◽  
Flow Analysis ◽  
Partial Geometry ◽  
Computational Domain ◽  
Mean Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Rans Simulations

A comparative cold flow analysis between Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) cycle-averaged velocity and turbulence predictions is carried out for a single cylinder engine with a transparent combustion chamber (TCC) under motored conditions using high-speed particle image velocimetry (PIV) measurements as the reference data. Simulations are done using a commercial computationally fluid dynamics (CFD) code CONVERGE with the implementation of standard k-ε and RNG k-ε turbulent models for RANS and a one-equation eddy viscosity model for LES. The following aspects are analyzed in this study: The effects of computational domain geometry (with or without intake and exhaust plenums) on mean flow and turbulence predictions for both LES and RANS simulations. And comparison of LES versus RANS simulations in terms of their capability to predict mean flow and turbulence. Both RANS and LES full and partial geometry simulations are able to capture the overall mean flow trends qualitatively; but the intake jet structure, velocity magnitudes, turbulence magnitudes, and its distribution are more accurately predicted by LES full geometry simulations. The guideline therefore for CFD engineers is that RANS partial geometry simulations (computationally least expensive) with a RNG k-ε turbulent model and one cycle or more are good enough for capturing overall qualitative flow trends for the engineering applications. However, if one is interested in getting reasonably accurate estimates of velocity magnitudes, flow structures, turbulence magnitudes, and its distribution, they must resort to LES simulations. Furthermore, to get the most accurate turbulence distributions, one must consider running LES full geometry simulations.

scholarly journals Large Eddy Simulation of Microbubble Drag Reduction in Fully Developed Turbulent Boundary Layers

2020 ◽  
Vol 8 (7) ◽  
pp. 524
Author(s):  
Tongsheng Wang ◽  
Tiezhi Sun ◽  
Cong Wang ◽  
Chang Xu ◽  
Yingjie Wei
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Drag Reduction ◽  
High Speed ◽  
Streamwise Velocity ◽  
Burst Frequency ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Good Agreement

Microbubble drag reduction has good application prospects. It operates by injecting a large number of bubbles with tiny diameters into a turbulent boundary layer. However, its mechanism is not yet fully understood. In this paper, the mechanisms of microbubble drag reduction in a fully developed turbulent boundary layer over a flat-plate is investigated using a two-way coupled Euler-Lagrange approach based on large eddy simulation. The results show good agreement with theoretical values in the velocity distribution and the distribution of fluctuation intensities. As the results show, the presence of bubbles reduces the frequency of bursts associated with the sweep events from 637.8 Hz to 611.2 Hz, indicating that the sweep events, namely the impacting of high-speed fluids on the wall surface, are suppressed and the streamwise velocity near the wall is decreased, hence reducing the velocity gradient at the wall and consequently lessening the skin friction. The suppression on burst frequency also, with the fluid fluctuation reduced in degree, decreases the intensity of vortices near the wall, leading to reduced production of turbulent kinetic energy.

scholarly journals Large-Eddy Simulation of Light-Round in an Annular Combustor With Liquid Spray Injection and Comparison With Experiments

2017 ◽  
Author(s):  
Théa Lancien ◽  
Kevin Prieur ◽  
Daniel Durox ◽  
Sébastien Candel ◽  
Ronan Vicquelin
Keyword(s):  
Large Eddy Simulation ◽  
Flame Propagation ◽  
High Speed ◽  
Complex Geometry ◽  
Numerical Study ◽  
Ignition Process ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Annular Combustor

A combined experimental and numerical study of light-round, defined as the flame propagation from burner to burner in an annular combustor, under perfectly premixed conditions has previously demonstrated the ability of large-eddy simulation (LES) to predict such ignition processes in a complex geometry using massively parallel computations. The present investigation aims at developing light-round simulations in a configuration closer to real applications by considering liquid n-heptane injection. The large-eddy simulation of the ignition sequence of a laboratory scale annular combustion chamber comprising sixteen swirled two-phase injectors is carried out with a mono-disperse Eulerian approach for the description of the liquid phase. The objective is to assess this modeling approach to describe the two-phase reactive flow during the ignition process. The simulation results are compared in terms of flame structure and light-round duration to the corresponding experimental images of the flame front recorded by a high-speed intensified CCD camera. The dynamics of the flow is also analyzed to identify and characterize mechanisms controlling flame propagation during the light-round process.

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