Imaging of an underexpanded nozzle flow by UV laser Rayleigh scattering

Optimization of supersonic nozzle flow for titanium dioxide thin-film coating by aerosol deposition

“…2a. The UV-laser-Rayleigh-scattering images from Dam et al (1998) in Fig. 2b shows how four periodic diamond structures form within 26 mm downstream; the white rectangle is the nozzle exit.…”

Free underexpanded jets in a quiescent medium: A review

“…The total diameter of the jet will diminish due to momentum exchange, caused by the entrainment of the ambient fluid, leading to a very long plume. Typically, this corresponds to an exit pressure ratio 3 4 e η − ≲ [57,43] or to a total pressure ratio 7 0 η ≥ [35].…”

“…A slipstream (marker 7) then emanates from this point: this is an embedded shear layer separating the flow behind the Mach disk (which is subsonic) from the flow downstream of the reflected shock (which is supersonic). Typically, this corresponds to an exit pressure ratio 2 4 e η ≲ ≲ [30,34,38,[56][57][58][59][60][61]43,54] or to a total pressure ratio 4 5 7 0 η − ≲ ≲ [62][63][64][65]35,38,59,13]. Very highly (extremely) underexpanded jet (see Fig.…”

Rayleigh Scattering Density Measurements, Cluster Theory, and Nucleation Calculations at Mach 10

“…Later subsonic studies over model wing surfaces increased signal levels using ultraviolet excimer lasers [5]. Two-dimensional images were acquired in air in supersonic flows [6], at Mach 1.5 [7], at Mach 2.5 [8], and in hypersonic flow at Mach 6 [9][10][11]. Most attempts at density measurements were frustrated in supersonic and hypersonic flows by clusters or condensation that overwhelmed molecular LRS signals.…”

“…At cooling rates of 10 6 K=s encountered in hypersonic nozzles, molecules of air attain cryogenic temperatures and agglomerate, forming clusters that can grow in size along the nozzle and test section. Eventually, the LRS signal from these clusters exceeds the LRS signal from air molecules, preventing quantitative density measurements [9].…”