Gas-dynamic effects of the interaction between a pulsed laser-ablation plume and the ambient gas: analogy with an underexpanded jet

Bulgakov, Alexander V.; Bulgakova, Nadezhda M.

doi:10.1088/0022-3727/31/6/017

Cited by 140 publications

(88 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The transient evolution of the Mach disk dimensions and the near-nozzle shock structure of both methane and hydrogen jets are comparable with the recently published schlieren observations of Rogers et al [54]. This type of behaviour normally occurs when a low density gas is issued into a high density environment or a cold gas is injected into hot ambient [56][57]. This feature of enhanced turbulent mixing through developing However, the initial sign of tip vortex formation appeared earlier for the jet with higher NPR.…”

Section: Transient Shock Dynamics and Jet Developmentsupporting

confidence: 86%

Gas dynamics and flow characteristics of highly turbulent under-expanded hydrogen and methane jets under various nozzle pressure ratios and ambient pressures

Hamzehloo

Aleiferis

2016

International Journal of Hydrogen Energy

View full text Add to dashboard Cite

The current study used large eddy simulations to investigate the sonic and mixing characteristics of turbulent under-expanded hydrogen and methane jets with various nozzle pressure ratios issued into various ambient pressures including elevated conditions relevant to applications in direct injection gaseous-fuelled internal combustion engines. Due to the relatively low density of most gaseous fuels such as hydrogen and methane, DI requires high injection pressures to achieve suitable mass flow rates for fast in-cylinder fuel delivery and rapid fuel-air mixing. Such pressures typically form an under-expanded fuel jet past the nozzle exit. Test cases of hydrogen injection with nozzle pressure ratio (NPR) of 10 issued into quiescent air with pressure P ∞ ≈1, 5 and 10 bar were simulated. Direct comparison between hydrogen and methane jets with NPR=8.5 and P ∞ ≈1 was also made. The effect of ambient pressure on features of transient development of the nearnozzle shock structure and tip vortices (vortex ring) was investigated. It was observed that at constant NPR, higher ambient pressure resulted in slightly faster formation of the Mach reflection and shorter Mach disk settlement time. Different mechanisms were observed between hydrogen and methane with regards to transient formation of their initial tip vortex rings. It was found that the initial transient tip vortices of hydrogen jets may also contribute to the flow instabilities at the boundary of the intercepting shock and, unlike for methane, promote fuel-air mixing before the Mach reflection. It was also shown that the nearnozzle shock structure was only affected by NPR regardless of the ambient pressure. Furthermore, no flow recirculation zone was found just downstream of the Mach disk, a finding comparable to all previous experimental investigations. Also, it was observed that a locally richer mixture was created for jets with higher NPR or with higher ambient pressure at constant NPR. Based on the results of the current study, correlations were proposed for the shock cell spacing and jet tip penetration of highly under-expanded jets issued from millimetre-size circular nozzles.

show abstract

Section: Transient Shock Dynamics and Jet Developmentsupporting

confidence: 86%

Gas dynamics and flow characteristics of highly turbulent under-expanded hydrogen and methane jets under various nozzle pressure ratios and ambient pressures

Hamzehloo

Aleiferis

2016

International Journal of Hydrogen Energy

View full text Add to dashboard Cite

show abstract

“…It should be noticed that plasma plume narrowing (focusing) was first found in [30] in laser deposition experiments for ns laser pulses. Later it was explained by the analogy with the dynamics of underexpanded jets that assumes transverse oscillations of the plume with distance from the target [31]. As shown in [32], the effect connected with the transverse oscillations of the ablation plumes upon its focusing in the presence of an ambient gas can also be observed at fs laser ablation regimes that calls for further studies.…”

Section: Figurementioning

confidence: 98%

“…To evaluate the additional heating of the target due to plasma radiation, the spherical model of laser plume expansion was exploited [22,31] as the second stage of modeling. The model allows to simulate ionization/recombination dynamics of the plasma and its energy balance and, hence, to evaluate the temporal dynamics of plasma radiation.…”

Section: Plasma-assisted Ultradeep Ablationmentioning

confidence: 99%

“…The complicated hydrodynamics of the ablation plume with formation of shock waves and vortical structures brings ablated particles back to the irradiated surface [19,31,89,90]. During mixing with air, ablated particles can experience oxidation and form clusters.…”

Section: Backward Deposition Of Ablation Productsmentioning

confidence: 99%

“…Vortical structures were also obtained in a number of modeling attempt to describe laser-induced plume expansion in an ambient atmosphere [31,90,[92][93][94]. Due to complexity of hydrodynamics, the most of attempts are based on the Euler equations and does not take into account interdiffusion and mixing of the ablation products with the ambient gas.…”

Section: Backward Deposition Of Ablation Productsmentioning

confidence: 99%

See 2 more Smart Citations

Impacts of Ambient and Ablation Plasmas on Short- and Ultrashort-Pulse Laser Processing of Surfaces

et al. 2014

View full text Add to dashboard Cite

Abstract:In spite of the fact that more than five decades have passed since the invention of laser, some topics of laser-matter interaction still remain incompletely studied. One of such topics is plasma impact on the overall phenomenon of the interaction and its particular OPEN ACCESSMicromachines 2014, 5 1345 features, including influence of the laser-excited plasma re-radiation, back flux of energetic plasma species, and massive material redeposition, on the surface quality and processing efficiency. In this paper, we analyze different plasma aspects, which go beyond a simple consideration of the well-known effect of plasma shielding of laser radiation. The following effects are considered: ambient gas ionization above the target on material processing with formation of a "plasma pipe"; back heating of the target by both laser-driven ambient and ablation plasmas through conductive and radiative heat transfer; plasma chemical effects on surface processing including microstructure growth on liquid metals; complicated dynamics of the ablation plasma flow interacting with an ambient gas that can result in substantial redeposition of material around the ablation spot. Together with a review summarizing our main to-date achievements and outlining research directions, we present new results underlining importance of laser plasma dynamics and photoionization of the gas environment upon laser processing of materials.

show abstract

Mechanisms of Pulsed Laser Ablation of Biological Tissues

Vogel

Venugopalan

2003

ChemInform

View full text Add to dashboard Cite

show abstract

Gas-dynamic effects of the interaction between a pulsed laser-ablation plume and the ambient gas: analogy with an underexpanded jet

Cited by 140 publications

References 40 publications

Gas dynamics and flow characteristics of highly turbulent under-expanded hydrogen and methane jets under various nozzle pressure ratios and ambient pressures

Gas dynamics and flow characteristics of highly turbulent under-expanded hydrogen and methane jets under various nozzle pressure ratios and ambient pressures

Impacts of Ambient and Ablation Plasmas on Short- and Ultrashort-Pulse Laser Processing of Surfaces

Mechanisms of Pulsed Laser Ablation of Biological Tissues

Contact Info

Product

Resources

About