DOI: https://doi.org/10.32347/2410-2547.2019.102.121-138

### Oscillations of aerodynamic constructions: safe speed band

#### Abstract

The article deals with the shock waves regularities interaction with the flutter angular speed of the aerodynamic surfaces control are established basing on the analysis of Bernoulli’s equation for compressible gas, the evaluation of changes of the supersonic flow characteristics in the Prandtl-Meyer expansion fan and the aerodynamic profile “dynamic curvature” hypothesis. The established regularities explain the cause of the disturbing forces and hinge moments of the supersonic aircraft aerodynamic surfaces control and aerospace systems at transonic flight speeds.

The mathematical models of estimation of the disturbing forces and the disturbing hinges magnitudes of the aerodynamic surfaces control are obtained basing on the established regularities of shock waves with interaction the flutter angular velocity of the aerodynamic surfaces control.

The dangerous range of Mach number flight is determined basing on a quantitative analysis of the obtained mathematical models and it is shown that the genesis of transonic flutter of supersonic aircraft and aerospace systems is possible in a narrow range of the Mach numbers flight.

Moreover, the range of the Mach numbers flight, in which there is an increase in the disturbing hinge moments of the aerodynamic surfaces control and in which the planes stay in the phase of flight speed reducing from supersonic to subsonic, is more than three times the range of the Mach numbers flight, in which the planes stay in the phase of the flight speed increasing from subsonic to supersonic. This result permits to explain one of the possible reasons why the transonic flutter occurrence of the supersonic aircraft is more often observed in the phase of flight speed reducing from supersonic to subsonic.

The obtained results can be used for a preliminary assessment of the transonic flutter characteristics of the supersonic aircraft aerodynamic surfaces control and aerospace systems, as well as the recommendations developing for flight personnel on the piloting features of supersonic aircraft at transonic flight speeds.

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