Russian physicists have studied structure of impact waves in non-equilibrium environment. Among other applications, these studies can help lower negative effects of impact waves on supersonic flying vehicles. Impact waves usually form around bodies of “iron birds”, when they travel in the atmosphere.

An impact wave or shock wave is a thin transition region, travelling with supersonic speed, in which matter density, temperature and pressure abruptly increase. Such waves are frequent guests during explosions, supersonic movement, and powerful electric discharges. When an aircraft or a rocket move with supersonic speed, shock waves form around their bodies and have powerful effect on ascension force and resistance of flying vehicles. Moreover, vehicles, flying in the atmosphere, are usually heated by air friction. However, an interesting phenomenon exists – in non-equilibrium environments negative effects of shock waves and air frictions are miraculously lower. Russian physicists decided to understand the nature of this phenomenon.

Well, this research group isn’t pioneers in studying structure of shock waves in non-equilibrium environments. First experimental studies of that subject started in 1980s in Soviet Union and then continued in the United States. These studies gave a rise to a new science – plasma aerodynamics, which now actively developing all around the world.

In 2005 a student of Samara State Aerospace University named after Korolev joined the group in Moscow. The talented young man found out and classified all existing profiles of impact waves, depending on wave speed and degree of environment’s non-equilibrium. The student also showed how new acoustic properties of non-equilibrium environment changed shock wave structure. This work brought the student the medal of Russian academy of sciences.

 

 

As a non-equilibrium environment, physicists took vibrationally excited gas. Studies of its behaviour revealed that shock wave structure in non-equilibrium environment was totally different from that in equilibrium gas. Researchers also discovered that when weak shock waves break down, they form a sequence of pulses, which, being in laser environment, for instance, could have had a great effect on quality of laser radiation. Another interesting factor, discovered by Russian physicists and affecting resistance during supersonic movement, is that pressure behind shock front in non-equilibrium gas was much weaker than that in equilibrium gas (given that speed was the same in both environments).

Scientists hope to understand all details of changes in resistance and structure of shock waves, because it is an important step towards creation of “plasma shell” of a new hypersonic aircraft. “Plasma shell” means a technology of creating artificial flow of non-equilibrium plasma around aircraft’s wing. Controlling this flow by means of magnetic field can help controlling the aircraft, but we need to create plasma flow with given parameters in given place. Current research can make “plasma shell” more real.

Researchers currently study structure of an impact wave in chemically active mixtures, and at the same time, develop a unified approach towards disturbances in various non-equilibrium environments. This approach is also applicable to no-equilibrium interstellar gas, therefore, physicists can learn more about nature of some astrophysical phenomena.

Source: The Institute of Physics

Kizilova Anna