Development of a Mach 5 nonequilibrium-flow wind tunnel

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.