A small-scale Mach 5 blowdown wind tunnel has been developed to generate steady-state nonequilibrium flows. The wind tunnel uses transverse nanosecond pulse discharge, overlapped with transverse dc discharge, to load internal energy modes of N 2 and O 2 in plenum. The stable discharge is operated at high plenum pressures, at energy loadings of up to ∼0.1 eV=molecule in nitrogen, generating nonequilibrium nitrogen and airflows with run time of 5-10 s, translational/rotational temperature of T 0 ∼ 300-400 K, and N 2 vibrational temperature of up to T V0 ∼ 2000 K. Internal energy-mode disequilibrium is controlled by injecting O 2, NO,H 2, or CO 2 into the subsonic flow between the discharge and the nozzle throat. Flow over a cylinder model in a Mach 5 test section is visualized by schlieren imaging and NO planar laser-induced fluorescence imaging, using a burst-mode laser operated near 226 nm, at a pulse-repetition rate of 10-20 kHz. NO planar laser-induced fluorescence images on two single-line NO(X; v′ = 0 → A; v″ = 0) transitions are used to infer rotational temperature distributions in NO-seeded nitrogen flows in the supersonic section, with and without discharge. Single-lineNOplanar laser-induced fluorescence images on a NO(X; v′ = 1 → A; v″ = 1) transition are used to infer the NO vibrational temperature in a nitrogen Mach 5 flow excited by the discharge and seeded with NO. The results are compared to three-dimensional nonequilbrium flow modeling calculations, showing good agreement.
Bibliographical noteFunding Information:
The present research is supported by the U.S. Air Force Office of Scientific Research Aerothermodynamics Program. The support and guidance of Eswar Josyula of the U.S. Air Force Research Laboratory is gratefully acknowledged.