scholarly journals Three-dimensional direct numerical simulation of turbulent lean premixed methane combustion with detailed kinetics

2016 ◽  
Vol 166 ◽  
pp. 266-283 ◽  
Author(s):  
A.J. Aspden ◽  
M.S. Day ◽  
J.B. Bell
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Three Dimensional ◽  
Methane Combustion ◽  
Lean Premixed ◽  
Detailed Kinetics

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 Drops in Three Dimensional Viscoelastic Simple Shear Flows

2001 ◽  
Author(s):  
Shriram B. Pillapakkam ◽  
Pushpendra Singh
Keyword(s):  
Numerical Simulation ◽  
Shear Flow ◽  
Direct Numerical Simulation ◽  
Viscoelastic Fluid ◽  
Simple Shear ◽  
Polymer Concentration ◽  
Three Dimensional ◽  
Simple Shear Flow ◽  
Splitting Technique

Abstract A three dimensional finite element scheme for Direct Numerical Simulation (DNS) of viscoelastic two phase flows is implemented. The scheme uses the Level Set Method to track the interface and the Marchuk-Yanenko operator splitting technique to decouple the difficulties associated with the governing equations. Using this numerical scheme, the shape of Newtonian drops in a simple shear flow of viscoelastic fluid and vice versa are analyzed as a function of Capillary number, Deborah number and polymer concentration. The viscoelastic fluid is modeled via the Oldroyd-B model. The role of viscoelastic stresses in deformation of a drop subjected to simple shear flow and its effect on the steady state shape is analyzed. Our results compare favorably with existing experimental data and also help in understanding the role of viscoelastic stresses in drop deformation.

Three-dimensional direct numerical simulation of flow induced by an oscillating sphere close to a plane boundary

2021 ◽  
Vol 33 (9) ◽  
pp. 097106
Author(s):  
Samayam Satish ◽  
Justin S. Leontini ◽  
Richard Manasseh ◽  
S. A. Sannasiraj ◽  
V. Sundar
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Three Dimensional ◽  
Plane Boundary ◽  
Oscillating Sphere

scholarly journals Modelling of the processes of impact of a projectile with elements of individual defence

2019 ◽  
Vol 221 ◽  
pp. 01021
Author(s):  
Aleksandr Kraus ◽  
Evgeny Kraus ◽  
Ivan Shabalin
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Heterogeneous Media ◽  
Three Dimensional ◽  
Stationary Problem ◽  
Heterogeneous Structure ◽  
Plate Steel ◽  
Two Dimensional ◽  
Human Bones ◽  
Armor Plate

A two-dimensional and three-dimensional non-stationary problem of the interaction of a homogeneous impactor and a heterogeneous structure made of steel and ceramics and placed in a Kevlar pocket is considered. The model of the human body is a plate of gelatine with cylindrical inserts-imitators of human bones. The results of numerical simulation using different approaches for describing heterogeneous media are compared. On the basis of direct numerical simulation, it is shown that the gradient armor plate (steel + B4C) has the best weight and size parameters.

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