Three-dimensional rainbow schlieren measurements in underexpanded sonic jets from axisymmetric convergent nozzles

Three-dimensional reconstruction of a microjet with a Mach disk by Mach–Zehnder interferometers

“…The first divergence of the slip streams leads to the rapid density rise after the density jump by a Mach disk because of the aerodynamic effect of the subsonic flow behind a Mach disk. The waveform with the two significant bumps behind a Mach disk also appears in the density profile obtained from the rainbow schlieren deflectometry by Takano et al (2016) as illustrated later in figure 12. Additionally, the similar waveform just downstream of a Mach disk can be observed in the velocity profile along the jet centreline obtained by PIV of André et al (2014).…”

“…To obtain density data on shock-containing free jets, various non-intrusive experimental techniques have been presented in the past, including rainbow schlieren deflectometry (Satti et al 2007;Kolhe & Agrawal 2009;Takano et al 2016), background oriented schlieren (Venkatakrishnan 2005;Van Hinsberg & Rösgen 2014;Nicolas et al 2017), moiré schlieren (Tabei, Shirai & Takakusagi 1992) (Nicolas et al 2017), D e = 22 mm RSD (Takano et al 2016), D e = 10 mm MZI (Nakamura & Iwamoto 1996), D e = 10 mm Moire schlieren (Tabei et al 1992), D e = 6 mm FIGURE 12. Comparison among centreline density profiles of underexpanded sonic jets obtained by various optical diagnostics for NPR = 4.0.…”

“…Figure 12 shows a comparison between the density profiles along the jet centreline obtained using the various quantitative flow visualization methods for underexpanded sonic jets emitted from axisymmetric convergent nozzles under the same nozzle operating condition (NPR = 4) with different exit diameters. The density profiles normalized by the ambient density ρ b from Tabei et al (1992), Nakamura & Iwamoto (1996), Takano et al (2016) and Nicolas et al (2017) are superimposed on our measurement (indicated by the blue line) using the Mach-Zehnder interferometer and the numerical result (indicated by the red line) from the RANS simulation with the SST k-ω turbulence model. In order to make it easier to view, the precision error bars are removed from our experimental result and the theoretical density rise by a normal shock wave is also included as a reference.…”

Optical Measurements of Shock Waves in Critical Nozzles at Low Reynolds Numbers

“…The Reynolds number employed in the present paper was varied from 7. filter is contained in the paper by Takano et al [7].…”

Two-dimensional quantitative visualization of isolator shock trains by rainbow schlieren deflectometry

“…Yamamoto et al [6] measured the density fields in the correctly expanded supersonic jets issued from an axisymmetric convergent-divergent nozzle with a design Mach number of 1.6. Takano et al [7] measured the density field of an underexpanded sonic jet by the rainbow schlieren deflectometry combined with the computed tomography. However, almost all the studies by rainbow schlieren deflectometry have been applied for free jet issued from nozzles.…”