International audienceTransverse secondary gas injection into the supersonic flow of an axisymmetric convergent-divergent nozzle is investigated to describe the effects of the fluidic thrust vectoring within the framework of a small satellite launcher. Cold-flow dry-air experiments are performed in a supersonic wind tunnel using two identical supersonic conical nozzles with the different transverse injection port positions. The complex three-dimensional flow field generated by the supersonic cross-flows in these test nozzles was examined. Valuable experimental data were confronted and compared with the results obtained from the numerical simulations. Different nozzle models are numerically simulated under experimental conditions and then further investigated to determine which parameters significantly affect thrust vectoring. Effects which characterize the nozzle and thrust vectoring performances are established. The results indicate that with moderate secondary to primary mass flow rate ratios, ranging around 5 %, it is possible to achieve pertinent vector side forces. It is also revealed that injector positioning and geometry have a strong effect on the shock vector control system and nozzle performances

Recent studies have shown atmospheric plasma discharges to be an effective means of air flow control. If in subsonic conditions the plasma's effect is explained by a transfer of momentum from the charged particles to the neutral ones, in supersonic conditions it seems that the effects are mainly of thermal origin but some authors think that this effect is not the only one to act. This paper presents experimental results of stagnation pressure, spectroscopic emission and drag performed in a rarefied Mach 2 flow over a flat plate model with a half-wedge leading edge. Changes caused by a negative dc discharge located on the upper surface of the flat plate are investigated in two cases. In the first case the negative potential is applied on the upstream electrode and in the second case it is applied downstream. The second electrode is grounded. The measurements carried out indicate two opposite effects depending on the localization of the negative potential.

International audienceThis paper describes experimental and numerical investigations focused on the shock wave modification induced by a dc glow discharge. The model is a flat plate in a Mach 2 air flow, equipped with a plasma actuator composed of two electrodes. A weakly ionized plasma was created above the plate by generating a glow discharge with a negative dc potential applied to the upstream electrode. The natural flow exhibited a shock wave with a hyperbolic shape. Pitot measurements and ICCD images of the modified flow revealed that when the discharge was ignited, the shock wave angle increased with the discharge current. The spatial distribution of the surface temperature was measured with an IR camera. The surface temperature increased with the current and decreased along the model. The temperature distribution was reproduced experimentally by placing a heating element instead of the active electrode, and numerically by modifying the boundary condition at the model surface. For the same surface temperature, experimental investigations showed that the shock wave angle was lower with the heating element than for the case with the discharge switched on. The results show that surface heating is responsible for roughly 50 % of the shock wave angle increase, meaning that purely plasma effects must also be considered to fully explain the flow modifications observed

A quasi-steady sliding discharge at atmospheric pressure is generated by combining a surface dielectric barrier together with a DC corona discharge in a three-electrode geometry. The discharge extends along the whole side-length of the electrodes (150 mm) and covers the full inter-electrode gap (30 mm). It is found that this discharge is composed of repetitive streamers that are uniformly distributed along the whole electrode length and that propagate along the inter-electrode gap with an average velocity of ∼2 × 10 7 cm s −1 , and with an average electric field of ∼120 kV cm −1 and a total particle number of ∼5 × 10 8 at the streamer head. Assuming that the electron distribution function reaches an equilibrium value with the electric field, an electron temperature of 9 eV at the streamer head is obtained. The streamer frequency is around 5 × 10 4 Hz for a well-developed sliding discharge regime, and the time-averaged electron density amounts to 1.5 × 10 7 cm −3 .