Application of the absorption spectroscopy for time resolved hypersonic flow field measurements using the D2-transition of seeded atomic rubidium

Kurzfassung

In an ongoing effort to better understand and characterise high enthalpy gas flows, a diode laser based absorption lineshape diagnostic has been applied to the HEG facility in which the atomic rubidium 5S1/2 - 5P3/2 (780.2nm) resonance transition was used. Atomic rubidium (Rb) was still present in the flow after seeding RbNO3 (2-3µg) into the test gas at the shock tube end. The absorption technique has been used to determine the change in kinetic temperature and gas velocity during the first millisecond test time in HEG using a lineshape analysis. Depending on the particular flow condition, the measured temperatures were foundto be in the range 900-1400 K and the velocities in the range 3900-6200 m/s. These values supply important information for a better understanding of the free stream and model gas flows produced in HEG. It has been shown that this techique is a reliable instrument for performing optical measurements in the free stream flow of high enthalpy facilities