Experimental study of a co-flowing jet in ONERA’s F2 research wind tunnel by 3D background oriented schlieren

Abstract

This paper describes the first application of 3D density reconstruction from a limited number of background oriented schlieren (BOS) images in a large research-type low speed wind tunnel. The tested flow is an ad hoc co-flowing hot jet generated at the wingtip of a simplified airfoil. Ray deviation maps captured by 12 synchronized cameras are combined to reconstruct the three dimensional density field of the jet, in the line of the direct 3D BOS technique described in Nicolas et al (2016 Exp. Fluids 57 1–21). A comparison with thermocouple sampling shows consistent results and highlights the efficiency of this new method for thermal measurement of a low speed convective flow. Finally, we underline the new possibilities for fluid dynamic characterization offered by combining stereo particle image velocimetry and 3D BOS measurements.

Flow over an espresso cup: inferring 3-D velocity and pressure fields from tomographic background oriented Schlieren via physics-informed neural networks

“…In addition to the refractive index and the density, temperature field or other quantities can be further inferred by analysing the BOS images (Tokgoz et al 2012). In the past two decades, the BOS technology has been applied to various applications in fluid mechanics (Venkatakrishnan & Meier 2004; Goldhahn & Seume 2007; Nicolas et al 2017; Grauer et al 2018). However, despite the substantial improvements of the hardware (e.g.…”

Quantitative density measurement of wake region behind reentry capsule (Improvements in accuracy of 3D reconstruction by evaluating the view-angle of measurement system)

“…In this study, we determined the number of cameras from the maximum number that can be installed on the same plane in the ballistic range. Nicolas et al(2016Nicolas et al( , 2018 and Hirose et al(2018) also used twelve cameras. Fig.…”

“…These reports have focused on the reconstruction of steady flow, reproducible unsteady flow or axially symmetrical unsteady flow because the data captured simultaneously from multiple directions are necessary for 3D reconstruction. Nicolas et al(2016Nicolas et al( , 2018 proposed the method to measure the 3D density field of unsteady jet flow from BOS measurement. They focused on jet flow and used a YAG laser to illuminate the monochrome background.…”

Tomographic background oriented schlieren using plenoptic cameras

“…This information can in turn be used to determine other flow field quantities such as temperature and density. Tomographic BOS algorithms take several forms including: a two-step method [1][2][3][4][5][6][7][8][9][10], a two-step wavefront distortion method [11], a direct reconstruction method [12][13][14][15][16][17], and most recently, a unified method [18]. b = 1 n 0 ˆ∇n ds.…”