Internal energy excitation and dissociation of molecular nitrogen in a compressing flow

Prediction of the radiative heat-flux to the surface of a spacecraft entering a planetary atmosphere strongly depends on the completeness and accuracy of the physical model used to describe the non-equilibrium phenomena in the flow. During an atmospheric entry, the translational energy of the fluid particles drastically rises through a shock. Depending on the intensity of the shock, different physico-chemical processes may take place, such as excitation of the internal energy modes, dissociation of the molecules, ionization of the atoms and molecules. These non-equilibrium phenomena are strongly coupled to each other. For re-entry velocities>10 km/s, a significant portion of the heating experienced by the heat shield can be due to radiation and is highly influenced by the shape of the internal energy distribution function. Understanding thermo-chemical non-equilibrium effects is also important for a correct interpretation of experimental measurements in flight and in ground wind-tunnels. Concentration of the gas species and distribution of their internal energy level populations can be estimated by means of either multi-temperature models (Park 1990) or collisional radiative (CR) models (Laux 2002; Bultel et al. 2006; Magin et al. 2006; Panesi et al. 2009)

Non-thermal atmospheric pressure plasmas for aeronautic applications

Dielectric barrier surface discharges (DBD) have the potential to act as flush mounted flow control devices for separation control and other aeronautic applications. A pulse-sustained plasma with the ions driven by a DC bias voltage is proposed for optimum performance. While characterizing these devices, it was found that their performance is severely limited by surface charge build-up. That charge builds up rapidly and remains for as long as hours. Work in this paper shows that the surface charge can be mitigated by using a reversing DC bias potential or by using a constant DC bias potential with a partially covered electrode