Effects of Gas Flowing around the Energy Release Zone during Laser Combustion Wave Propagation

The reasons for the observed propagation velocities of stationary laser-supported combustion (LSC) waves in laser plasmatron scheme in argon and air to exceed the calculated ones in assumption of heat-conductive propagation mechanism are considered. Earlier obtained analytical solution of the hydrodynamic problem of flowing around model low density heated gas volume with step-like spherical boundary is used for interpretation experimental results. It is shown that when laser power is 2–3 times above LSC threshold power heat-conductive mechanism with correction factor predicted by the model gives satisfying description of the LSC wave velocities observed. At higher laser power radiative heat transfer factor should be taken into account. It is shown that flowing around spherical hot gas boundary model can also be applied to describe gas flow in thermal gravitational convection around continuous optical discharge (COD). An estimate is given for the pulsation frequency of the convective plume from COD, leading to the similarity relation common for optical discharges and flickering flames.