Interesting physics and chemistry can happen in LSD wave, including a number of unknown phenomena. As it is impossible to take into account all the phenomena occurring in the process of laser-absorption heating, a numerical simulation needs appropriate assumptions. In this simulation four chemical reactions (elastic collision, inelastic collision, bremsstrahlung and inverse bremsstrahlung) are considered for simplicity. It is also assumed that the laser light is focused spherically and all the physical quantities are solved by one-dimensional spherical coordinate. The propellant gas used here is Argon, while the source laser is CO2 (wave length λ = 10.6μm).
The problem is described by the two governing equations; the laser intensity equation and Euler equation. Once LSD wave is formed, large discontinuity appears at the shock front, so that several devices are required in order to delete the stiffness. The temperature of electron is separated from that of heavy-particle. Another device is the time-splitting technique: As chemical reaction is very stiff, it is separated from the flow-field. To control the time step, the characteristic time of each phenomenon is evaluated and accurate comparison is always made.
In addition, the cutoff effect of plasma is considered and as a result we could simulate “galloping” phenomena.
In this simulation the structure of LSD wave, the interaction between the two waves and the effect of the plasma cutoff are analysed.
