Physics, Instrumentation and Sensing

Optical diagnostics in hypersonic flows and in the upper atmosphere

Results on Flow Visualization using Electron Beam Fluorescence in the R5 Mach 10 Windtunnel

Density mesurements are quite easy in a low density gas (up to 1015 molecules/cm3) where the intensity of fluorescence is directly proportional to the density. For higher densities, collisional non radiative desexcitation sets a non-linear relationship between fluorescence intensity and density, where other parameters like temperature are involved. Nevertherless, qualitative density variation can still be useful to assess better understanding of flow structure, pointing out for instance shock waves. This is usually done by sweeping the beam to illuminate a sheet of the flow, which provides spectacular images of vizualization.

Figure 1 shows an example of interaction of shock waves between two models placed in a Mach 10 flow (ONERA R5 wind tunnel). Densities are here too high (> 1016 molecules/cm3) to allow accurate density mesurements by this technique, but this kind of visualization helps to configurate the models and to choose the right type of interaction for more accurate measurements by other techniques (CARS for instance).

Figure 1 - Shock interactions in ONERA R5 Wind Tunnel

Mars sample Return Orbiter in aerocapture phase

Double cone for SWBLI studies

ESA EXPERT balistic reentry model for basic reentry studies

Holow cylinder for SWBLI studies

Last Update: 8 January 2007 - © ONERA 2009 - Terms of use