Gas Dynamics of Sublimed Carbon Nano-Clusters in High Fluence Time-Resolved Laser-Induced Incandescence

2013 ◽  
Author(s):  
F. Memarian ◽  
K. J. Daun
Keyword(s):  
Shock Waves ◽  
Gas Dynamics ◽  
Direct Simulation Monte Carlo ◽  
Analytical Models ◽  
High Fluence ◽  
Time Resolved ◽  
Back Flow ◽  
Model Predictions ◽  
Laser Induced Incandescence ◽  
Simulation Monte Carlo

High fluence time-resolved laser-induced incandescence (TiRe-LII) measurements show a discrepancy between experimental observations and model predictions. Several hypotheses have been proposed to explain this discrepancy, including the possibility of back flow of sublimed species and the possibility of formation of shock waves. This is the first study that uses transient Direct Simulation Monte Carlo (DSMC) to investigate the abovementioned effects in high fluence TiRe-LII. This study verifies that back flow of sublimed species occurs, and must be included in analytical models. On the other hand, shock waves were not observed for the fluences and predetermined temperature curves used in this study.

Prompt Transient Heat Transfer Effects in Low-Fluence Laser Induced Incandescence

2012 ◽  
Author(s):  
F. Memarian ◽  
K. J. Daun
Keyword(s):  
Experimental Studies ◽  
Direct Simulation Monte Carlo ◽  
Recent Time ◽  
Direct Simulation ◽  
Transient Effects ◽  
Time Resolved ◽  
Laser Induced Incandescence ◽  
Simulation Monte Carlo ◽  
Heat Transfer Effects ◽  
Particle Cooling

Recent time-resolved laser-induced incandescence (TiRe-LII) experimental studies have revealed anomalies in particle cooling rates that cannot be explained using steady-state conduction models. This is the first study to use Direct Simulation Monte Carlo (DSMC) to investigate possible transient effects in heat conduction between the laser-energized particle and surrounding gas. While the DSMC results reveal an increased cooling rate shortly after the laser pulse, this effect is small relative to experimentally-observed anomalous cooling.

Nanoparticle Detachment Using Shock Waves

2005 ◽  
Vol 219 (3) ◽  
pp. 91-102 ◽  
Author(s):  
D Zhou ◽  
A. T. J. Kadaksham ◽  
M. D. Murthy Peri ◽  
I Varghese ◽  
C Cetinkaya
Keyword(s):  
Shock Waves ◽  
Direct Simulation Monte Carlo ◽  
Rolling Resistance ◽  
Nanoparticle Interactions ◽  
Gas Molecule ◽  
Resistance Moment ◽  
Discrete Nature ◽  
Frequency Excitation ◽  
Gas Molecules ◽  
Simulation Monte Carlo

The fundamentals of nanoparticle detachment at the sub-100nm level using pulsed laser-induced plasma (LIP) shock waves are investigated in the current study. Two detachment mechanisms based on rolling resistance moment and rolling by resonant frequency excitation are identified as possible detachment mechanisms for nanoparticles. The gas molecule-nanoparticle interactions are studied using the direct simulation Monte Carlo method to gain knowledge about the nature of the detachment forces and moments acting on a nanoparticle in the LIP shock wave field. The discrete nature of the gas molecules colliding with the particle on the sub-100 nm length scale is linked to the stochastic transient moment experienced by the particle. Both experimental and computational findings of the current study indicate that nanoparticle detachment at the sub-100 nm level is possible by LIP shock waves.

Effect of Selective Accommodation on Soot Aggregate Shielding in Time-Resolved Laser-Induced Incandescence Experiments

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
K. J. Daun
Keyword(s):  
Direct Simulation Monte Carlo ◽  
Monte Carlo Analysis ◽  
Shielding Effect ◽  
Time Resolved ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Accommodation Coefficients ◽  
Dynamics Simulations ◽  
Gas Surface Interactions ◽  
Scattering Kernel

Time-resolved laser-induced incandescence is an emerging diagnostic for characterizing primary particle size distributions within soot-laden aerosols. This measurement requires an accurate model of heat conduction between the laser-energized soot and the surrounding gas, which is complicated by the fractal-like structure of soot aggregates since primary particles on the aggregate exterior shield the interior from approaching gas molecules. Previous efforts to characterize aggregate shielding through direct simulation Monte Carlo analysis assume a Maxwell scattering kernel, which poorly represents actual gas/surface interactions. This paper shows how selective thermal accommodation into the translational and rotational modes of the gas molecule influences the aggregate shielding effect using the Cercignani–Lampis–Lord kernel and thermal accommodation coefficients derived from molecular dynamics simulations.

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