Laser-induced breakdown is a versatile means of depositing energy in a gas and seeding ignition of a combustible mixture, and it offers multiple advantages over conventional approaches. To analyze the laser-generated flow and ensuing ignition dynamics, direct numerical simulations are conducted in several configurations: a quiescent gas, a temporally evolving shear layer, and a model gas-gas rocket combustor. Consistent with experimental observation, it is shown that ignition is possible even when energy is deposited in a non-flammable region of the flow, due to a laser-generated vortex of hot, radical-rich gas. In contrast to directly depositing energy in a premixed region, this mode of ignition crucially depends on the reacting vortex and its thermochemistry as it interacts with local mixture and flow gradients. It is also shown that ignition is critically mediated by turbulent fluctuations: changing the instantaneous pre-ignition flow alone, while preserving all statistics exactly, can be sufficient to produce different ignition outcomes.
