Control of the Spectrum of Unstable Acoustic Waves in a Supersonic Channel of Experimental Setup

We propose an approach for selecting the optimal characteristics of an experimental setup for studying the char-acteristics of supersonic flows o f n onequilibrium g as a nd the formation of a system of shock waves and shock-wave pulses in an unstable gaseous medium. The influence of local bends in the form of caverns and protrusions on the surface of an annular cylindrical channel on the spectrum of sound waves generated in a supersonic gas flow iss tudied. G as flow at a supersonic speed near these local inhomogeneities leads to expansion/compression of the flow and the generation of sound waves that form two wave packets propagating along the flow and against it. The velocity of the gas flow, t he shape and dimensions of these caverns/protrusions affect both the frequency and the amplitude of the generated acoustic waves, forming a certain sound spectrum in the annular cylindrical channel. The amplitude of the generated acoustic waves depends on the transverse geometric characteristics of the caverns/protrusions and the velocity of the supersonic gas flow (Mach number). The frequency of these acoustic waves is determined by the longitudinal sizes of the caverns/protrusions and Mach number in the supersonic flow. T he results of a series of computational hydrodynamic experiments provided a relationship between the parameters of local bends of the surface of an annular cylindrical channel and the spectrum of the generated sound at a given flow velocity. This can be the basis for effective control of the spectrum of sound waves generated in the annular cylindrical channel of the experimental setup for studying the nonlinear dynamics of acoustic instability in a nonequilibrium chemically active gas.