Dynamics Evolution of Shock Waves in Laser-Material Interaction

2008 ◽  
Author(s):  
Sobieslaw Gacek ◽  
Xinwei Wang
Keyword(s):  
Shock Wave ◽  
Wave Front ◽  
Shock Wave Front ◽  
Structural Evolution ◽  
Md Simulations ◽  
Background Gas ◽  
Supersonic Shock ◽  
Kinetics Of ◽  
Material Interaction ◽  
Insight Into

In this work, the dynamics of the shock wave in laser-ablated argon plume with its evolution through the background gas is explored at the atomic level. Molecular Dynamics (MD) simulations have been conducted which give the insight into atomistic scale interaction and correlation effects of the propagating shock wave in the background medium. The supersonic shock wave front carries inherent sharp increase in density, temperature, and pressure. These thermodynamic parameters of the expanding shock wave are evaluated with emphasis on the kinetics of the shock wave front. The position of the shock wave front has been defined and determined over nanoseconds. Extensive research is elaborated upon to study the inside structural evolution of the shock wave and the effect of optical absorption depth.

Shock Waves in Pulsed Laser Material Interaction: Internal Structure and Mass Penetration

2008 ◽  
Author(s):  
Lijun Zhang ◽  
Xinwei Wang
Keyword(s):  
Shock Wave ◽  
Wave Front ◽  
Shock Wave Front ◽  
Picosecond Laser ◽  
Mixing Length ◽  
Momentum Exchange ◽  
Laser Material ◽  
Ambient Gas ◽  
Background Gas ◽  
Material Interaction

This work pioneers the atomistic modeling of the shock wave in picosecond laser-material interaction by simulating the material that is irradiated with a picosecond laser pulse (11.3 ps FWHM) in a 0.25 MPa background gas. The dynamic structure and mutual mass penetration between the plume and background gas are investigated in detail. In the shock wave the compressed ambient gas region has a very uniform temperature distribution while the temperature decreases from the front of the plume to its end. The group velocity of atoms in the shock wave front is much smaller than the shock wave propagation speed and experiences a fast decay due to momentum exchange with the ambient gas. Strong decay of the shock wave front temperature and pressure is observed while its density features much slower attenuation. An effective mixing length is designed to quantitatively evaluate the mutual mass penetration between the plume and background gas. This effective mixing length grows at a rate of ∼ 60 m/s. This fast mixing/mass penetration is largely due to the strong relative movement between the plume and the background gas. The MD results agree well with the analytical solution in terms of relating various shock wave strengths.

Kinetics of ionization and excitation of mercury atoms in the relaxation flow zone behing the shock wave front

1971 ◽  
Vol 35 (6) ◽  
pp. 419-420 ◽  
Author(s):  
G.K. Tumakev ◽  
T.V. Zhikhareva ◽  
V.R. Lazovskaya
Keyword(s):  
Shock Wave ◽  
Wave Front ◽  
Shock Wave Front ◽  
Flow Zone ◽  
Kinetics Of

The theory of inoizing shock waves in a magnetic field. Part 1. Skew and oblique shock waves, boundary conditions and ionization stability

1981 ◽  
Vol 26 (1) ◽  
pp. 29-53 ◽  
Author(s):  
M. A. Liberman ◽  
A. L. Velikovich
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Shock Waves ◽  
Electric Field ◽  
Boundary Conditions ◽  
Wave Front ◽  
Shock Wave Front ◽  
Neutral Gas ◽  
Supersonic Shock ◽  
Photo Ionization

The general theory of ionizing shock waves in a magnetic field has been constructed. The theory takes into account precursor ionization of a neutral gas ahead of the shock wave front, caused by photo-ionization, as well as by the impact ionization with electrons accelerated by a transverse electric field induced by the shock front in the incident flow of a neutral gas. The concept of shock wave ionization stability, being basic in the theory of ionizing shock waves in a magnetic field, is introduced. An additional equation for the electric field in the shock wave is obtained. This equation, together with the investigation of the singular point in the downstream flow behind the shock wave front, provides all the information required for solving the problem. For example, this provides two additional boundary conditions for the shock waves of type 2, determining the value and direction of the electric field in the incident flow. One additional boundary condition determines a relation between the value and direction of the electric field for supersonic shock waves of type 3. There are no additional boundary conditions for supersonic shock waves of type 4. The electric field ahead of the shock front has two degrees of freedom. As well as for shocks of other types, its value is less than that of the transverse electric field at which an ionization wave could be emitted by the shock wave front (the ionization stability condition). The additional relationship for supersonic waves of type 4 determines the onset of an isomagnetic (viscous) jump in the structure of the shock wave front. The boundary conditions and ionizing shock wave structures, considered earlier by the authors of the present paper in the ‘limit of electrostatic breakdown’, as well as the structural determination of the electric field, considered earlier by Leonard, are limiting cases in the theory developed here. The ionizing shock wave structures are shown to transform from the GD regime at a low shock velocity to the MHD regime at an enhanced intensity of the shock wave. The abruptness of such a transition (e.g. the transition width on the Mach number scale) is determined by precursor photo-ionization.

Numerical Simulation of Air Flow in the State of Thermal and Chemical Nonequilibrium behind a Shock Wave Front

2021 ◽  
pp. 94-111
Author(s):  
A.I. Bryzgalov
Keyword(s):  
Shock Wave ◽  
Shock Front ◽  
Wave Front ◽  
Shock Wave Front ◽  
Reaction Rate ◽  
Vibrational Temperature ◽  
Pure Oxygen ◽  
Published Data ◽  
Calculation Results ◽  
Temperature Nonequilibrium

We used the model of a five-component air mixture flow behind the front of a one-dimensional shock wave to compute the flow parameters for shock front temperatures of up to 7000 K, taking into account the variable composition, translational and vibrational temperatures and pressure in the relaxation zone. Vibrational level population in oxygen and nitrogen obeys the Boltzmann distribution with one common vibrational temperature. We consider the effect that temperature nonequilibrium has on the chemical reaction rate by introducing a nonequilibrium factor to the reaction rate constant, said factor depending on the vibrational and translational temperatures. We compared our calculation results for dissociation behind the shock front to the published data concerning temperature nonequilibrium in a pure oxygen flow behind a shock wave front for two different intensities of the latter. The comparison shows a good agreement between the vibrational temperature, experimental data and calculations based on the experimental values of vibrational temperature and molality. We computed the parameters of thermodynamically nonequilibrium dissociation in the air behind the shock wave front, comparing them to those of equilibrium dissociation and calculation results previously published by others. The study demonstrates that the molality values computed converge gradually with those found in published data as the distance from the shock front increases. We list the reasons for the discrepancy between our calculation results and previously published data

The thermal wave before a shock wave front in metals

1975 ◽  
Vol 9 (3) ◽  
pp. 378-380 ◽  
Author(s):  
V. F. Nesterenko ◽  
A. M. Staver ◽  
B. K. Styron
Keyword(s):  
Shock Wave ◽  
Wave Front ◽  
Shock Wave Front ◽  
Thermal Wave
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