Scientists from the Samara branch of the Physical Institute of the Russian Academy of Sciences received a revolutionary data simulation of shock waves in non-equilibrium gas phase, that they believe will significantly advance plasma aerodynamics.
Emerged a few years ago, plasma aerodynamics (the term was proposed by Russian scientists) studies the interaction of the plasma with a subsonic or supersonic gas flow. One of the main issues, most researchers are interested in right now — is a shock wave in a non-equilibrium gas-plasma medium. It is a surface discontinuity moving with respect to the gas. At its intersection pressure, density and temperature of the medium have a sharp jump, with changes and its own speed.
Even more difficult to study shock waves in a magnetized plasma, since the passage of the wave front there is an abrupt change in the characteristics of the magnetic field. Although the laws that occur such drastic transformation for conventional (equilibrium) media are known, with nonequilibrium until such clarity is.
We recall the important problems of such research is the creation of the "plasma membrane" of the aircraft — the layer artificially generated plasma on the wing controlled by the magnetic field and reduces wind resistance, while reducing the likelihood of flow separation from the wing. According to preliminary estimates, this shell will reduce fuel consumption at cruising at 40-50%.
NE Molevich at the Third European Conference for Aerospace Sciences (3 EUCASS) (here and below illustrate LPI-inform).
As long as such operations are conducted purely by experiment that resembles a spaceship trying to collect at random, blindfolded and without a blueprint. If the experiments and give some effect, then come out too expensive to justify it. In short, despite the serious efforts both abroad and in this country, over the last two decades trying to create something similar with acceptable performance with no success. Obviously, we need a deeper theoretical developments. And there is something to offer the group, led by Professor Nonna Molevich, head of the theoretical sector Samara branch of the Physical Institute. Russian Academy of Sciences (SB LPI).
Created by Russian physicists model acoustically active nonequilibrium gas qualitatively explains the possible causes of the acceleration of the shock wave, the broadening of the transition region behind the front, splitting the waves and the formation of shock-wave pulse. This model, according to NE Molevich satisfactorily described and previously observed in other modes gaz-plasma experiments of shock and acoustic waves. "We have shown for the first time, — says scientist — that in a nonequilibrium medium of a shock wave can actually be very different from the equilibrium. Steady-state waves of four different types of shock waves with an increase in the density and pressure of the rupture of the waves with the decrease of these values, in the form of Autowave momentum, in the form of self-sustained wave of detonation non-zero asymptote. For all of these models of nonequilibrium heat-medium evolution of waves of small amplitude can be described by a single nonlinear equation. "
Previously, the view was that the dynamics of the shock wave can be described by dividing its spectrum into high and low frequency region. The model proposed by a group of Mrs. Molevich, deals with the whole frequency spectrum of perturbations that can more adequately describe the behavior of waves at different points in time.
Physicists still do not know which concludes the acoustic instability of the environment, because of its nonlinear structure was explained on the basis of either low-frequency or high-frequency models, with the postulated a priori impossibility of holistic analysis once for all frequencies. SB LPI group was able to show that this approach is incorrect. According samartsy, stationary wave structure is formed as a result of the nonlinear energy transfer from unstable to stable low-frequency and high-itself has a wide range. It is therefore correct to describe it was only when the received acoustic generalized equation for the low and high frequencies.
In addition, the physics of the first to show that, depending on the degree of nonequilibrium of the medium, the critical velocity of shock waves. They may only be sold at velocities above this critical value. Of shock waves with an initial velocity of less than critical, the methods of numerical simulation revealed that they will eventually accelerate and break up the sequence avtoimpulsov or autowaves with a non-zero asymptote detonation type. Later, these findings were confirmed by experiments. The parameters of these self-sustained structures are completely determined by the properties of the non-equilibrium environments.
Finally, it was determined one of the possible mechanisms of action of precipitation-viscous properties of nonequilibrium gas environment on the structure of the shock wave. The acoustic properties of this environment lead to qualitative and quantitative changes in the structure of shock waves. It is shown that these structures can be formed in different types and models of nonequilibrium relaxation, not only in technical applications, but also in natural environments. The latter may occur even brighter due to its large size, and therefore more suitable for forming the stationary mode. An example of this kind can serve as a model of interstellar gas.
The proposed Molevich Nonna and her colleagues shock wave transformation model has allowed to confirm the hypothesis of Constantine Krasnobaeva of the Space Research Institute of the observed fiber structure of the interstellar gas, in which the structure of shock waves in the interstellar gas may be associated with an acoustic instability of the fuel temperature. Numerical modeling undertaken by the Federation Council on the LPI-art models of the interstellar medium, showed the possibility of spontaneous decay of the shock to the system of individual self-sustained waves that form the fiber.
Above: The results of the numerical simulation of the splitting of the front of a plane shock waves in non-equilibrium environments and experimentally obtained images of the shock wave. Below: The fibrous structure of shock waves in the interstellar gas.
"For the development of the idea of the" plasma membrane ", and plasma aerodynamics in general to detailed understanding of the mechanisms that lead to the transformation of the structure of a shock wave in a non-equilibrium gas-plasma and reactive environments to classify these modifications, — concludes NE Molevich. — That is why the experiments investigate the behavior of shock waves in a simple model conditions for ignition discharge of various types. Physicists have observed effects, such as increased acceleration and shock waves, changing the structure of the front and its splitting, the generation of precursor in the form of a pulse front of the shock wave. But the theoretical basis of these phenomena yet. So, scientists are "blind". We hope that our work will make a difference. "