Visualization of a filamentary plasma objects in supersonic airflow

Summary form only given, as follows. Analyses and discusses results of the flow visualization in frames of the last experimental works the influence of non-uniform plasma formation on the characteristics of streamlined bodies in high-speed airflow. Very often plasma generation occurs in a non-homogeneous manner. It provides an energy release to airflow as well as change of gas-kinetic and electro-magnetic properties of the medium. Application of a special organized electrical discharge allows us to significantly decrease a required energy input for a drag reduction of bodies in high-speed airflow. Special interest is in electrodeless and single-electrode plasma due to the possibility of energy release into a defined zone without additional hardware and, prospectively, electronic control of plasma location. The work is provided in the framework of the Advance Flow/Flight Control (AFFC) concept. The dynamics of an individual plasma filament in a high-speed airflow is studied intensively. The HF plasma filaments have a specific appearance at relatively high static pressure P=100-200 Torr. The typical diameter of the plasma structure at the initial stage is in a range 0.1-1 mm and the velocity of moving is about the velocity of airflow. At the same time the level of airflow disturbances in an external airflow can be relatively large in respect of the integral phase change on a light beam. The scheme of a direct shadow device and a Schlieren scheme have been used for visualization of such plasma objects. A light source was a surface spark with discharge duration not more than 1 ms. Different schemes of a registration system have been tested. Appropriate photos are presented. Simulation of optical pictures for different cases has been provided. An analysis of a parasitic turbulence influence has been done. On a base of the calculations the optical scheme has been optimized for a specific conditions of a filamentary HF discharge.