Shock Propagation in a High Temperature Gas Discharge Initiated by Ultraviolet Laser-Induced Breakdown
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2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Characterization of freestream flow properties and variability is of critical importance to wind tunnel testing and the development of high fidelity ground test capability. In particular, the free-stream velocity, temperature and Mach number are of interest both in low and high enthalpy facilities. In this work, an accessible, non-intrusive diagnostic known as Thermal Acoustic Wave (TAW) thermometry has been demonstrated for temperature measurement in high-temperature, low-pressure, and non-equilibrium gas environments relevant to arc jet facilities. Temperature measurements are inferred by tracking Shock Wave (SW) propagation initiated by Ultraviolet Laser-Induced Breakdown (LIB) using a zero-dimensional modified blast wave model. Considering the real gas composition of the arc jet freestream, methane (CH4), nitrogen (N2), and argon (Ar) mixtures have been employed to study the molar mass and ionization potential effect on the laser breakdown process and temperature measurement accuracy. An in-house test-bed provides the high-temperature (up to 1500 K) and low-pressure conditions targeting on the realistic environment of the arc jet freestream. The current work has been performed at a constant gas number density (9.661017cm-3) with temperature ranging from the room temperature (295 K) up to 900 K. The zero-dimensional modified Sedov-Tayler SW model has been applied and shown to yield a temperature accuracy of 50 K with an uncertainty of 10 %.
