Digital holographic interferometry at F4-ONERA hypersonic wind tunnel

Abstract

The feasibility of digital holographic interferometry using a CW laser @ 532 nm and a Photron APX camera is demonstrated in the F4-ONERA hypersonic wind tunnel. This optical technique is used to point out the possible combustion of a small hydrogen jet in the shock layer developed on the model. The optical technique generates in the field under analysis, interference micro-fringes which are used as carrier spatial frequency. The field of optical thickness is obtained with a FFT2D post processing. Then, if the flow is assumed to be twodimensional, the map of the refractive index can be estimated. The adjustment of the optical bench is easy to implement and the results obtained with this technique can be used for several interesting comparisons: from the phase difference maps, the holographic images and schlieren images in the x and y directions can be recalculated, which is not possible with a conventional schlieren optical setup. In addition, if the characteristics of the ionized gas are well known, the value of the gas density upstream and in the shock layer can be estimated.

Scramjet Powered Vehicle Tests in the ONERA F4 Hotshot Wind Tunnel. Comparison to Numerical Simulations

“…1, 2 These developments were qualified during preliminary test campaigns in 2011 and 2012, including test of simple hydrogen combustion configuration and new optical diagnostics implementation. 3,4 In 2013, within the LAPCAT 2 European project, 5 two scramjet models have been tested in representative conditions and combustion processes have been evidenced and characterized. 6 The model tested here is a small-scale wave-rider designed by ESTEC and manufactured by DLR in the frame of the LAPCAT 2 European program 7-9 (see figure 1).…”