Investigation of Rayleigh–Taylor turbulence and mixing using direct numerical simulation with experimentally measured initial conditions. II. Dynamics of transitional flow and mixing statistics

2009 ◽  
Vol 21 (1) ◽  
pp. 014107 ◽  
Author(s):  
Nicholas J. Mueschke ◽  
Oleg Schilling
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Initial Conditions ◽  
Transitional Flow

Direct Numerical Simulation of Partial Fuel Stratification Assisted Lean Premixed Combustion for Assessment of Hybrid G-Equation/Well-Stirred Reactor Model

2021 ◽  
Author(s):  
Chao Xu ◽  
Muhsin Ameen ◽  
Pinaki Pal ◽  
Sibendu Som
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Initial Conditions ◽  
Operating Conditions ◽  
Premixed Combustion ◽  
Lean Premixed Combustion ◽  
Fuel Stratification ◽  
Stirred Reactor ◽  
Lean Premixed ◽  
Flame Structures

Abstract Partial fuel stratification (PFS) is a promising fuel injection strategy to stabilize lean premixed combustion in spark-ignition (SI) engines. PFS creates a locally stratified mixture by injecting a fraction of the fuel, just before spark timing, into the engine cylinder containing homogeneous lean fuel/air mixture. This locally stratified mixture, when ignited, results in complex flame structure and propagation modes similar to partially premixed flames, and allows for faster and more stable flame propagation than a homogeneous lean mixture. This study focuses on understanding the detailed flame structures associated with PFS-assisted lean premixed combustion. First, a two-dimensional direct numerical simulation (DNS) is performed using detailed fuel chemistry, experimental pressure trace, and realistic initial conditions mapped from a prior engine large-eddy simulation (LES), replicating practical lean SI operating conditions. DNS results suggest that conventional triple flame structures are prevalent during the initial stage of flame kernel growth. Both premixed and non-premixed combustion modes are present with the premixed mode contributing dominantly to the total heat release. Detailed analysis reveals the effects of flame stretch and fuel pyrolysis on the flame displacement speed. Based on the DNS findings, the accuracy of a hybrid G-equation/well-stirred reactor (WSR) combustion model is assessed for PFS-assisted lean operation in the LES context. The G-equation model qualitatively captures the premixed branches of the triple flame, while the WSR model predicts the non-premixed branch of the triple flame. Finally, potential needs for improvements to the hybrid G-equation/WSR modeling approach are discussed.

Direct numerical simulation of transitional flow in the nasal cavity during a sniff

2020 ◽  
Vol 2020.31 (0) ◽  
pp. 1C13
Author(s):  
Keiichiro YOSHIOKA ◽  
Shuta MIURA ◽  
Shinya KIMURA ◽  
Toshihiro SERA ◽  
Kenji Ono ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Nasal Cavity ◽  
Transitional Flow

The Analysis of Direct Numerical Simulation and Experiment in Critical Point of Transitional Flow

2014 ◽  
Vol 1046 ◽  
pp. 196-199
Author(s):  
Jun Wang ◽  
Guang Sheng Du ◽  
Yong Hui Liu
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Critical Point ◽  
Transitional Flow ◽  
Viscous Force ◽  
Wall Region ◽  
Flow State ◽  
Transitional Area ◽  
Simulation And Experiment

In order to study the lower critical point in transitional area of pipe, we used the method of direct numerical simulation to simulate fluid flow and contrasted it with experiment. The result showed that the flow state is close to laminar. Along the pipe axis, the change of pressure is not obviously. The changing rate of axial velocity U near wall region was significantly greater than in the mainstream area, it proved the important role of viscous force.

scholarly journals Direct numerical simulation of transitional flow in a stenosed carotid bifurcation

2008 ◽  
Vol 41 (11) ◽  
pp. 2551-2561 ◽  
Author(s):  
Seung E. Lee ◽  
Sang-Wook Lee ◽  
Paul F. Fischer ◽  
Hisham S. Bassiouny ◽  
Francis Loth
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Carotid Bifurcation ◽  
Transitional Flow

Numerical Simulation of Turbulent Transport and Structures in Temporally Developing Plane Mixing Layers

2013 ◽  
Vol 367 ◽  
pp. 57-62
Author(s):  
Thangam Natarajan
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Computational Model ◽  
Simulation Study ◽  
Initial Conditions ◽  
Turbulent Transport ◽  
Turbulence Models ◽  
Mixing Layers ◽  
Turbulent Structures

The investigation on the sensitivity of the flows to the initial conditions was carried with varying grid resolutions, turbulence models and perturbations. The Direct Numerical Simulation study of Pantano and Sarkar [1] was taken as the reference study and the computational model used in this study was built with a similar configuration of theirs except for the perturbations used. Important results were arrived pertaining to the effect of initial conditions on the turbulent properties and the turbulent structures of the flow.

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