The aerodynamic
instability of profiles equilibrium states
V.I.Vanko
The Lyapunov's instability condition of
equilibrium states for arbitrary profiles in air flow, is used for
investigations of
instability of circular profiles systems.
The hypothesis about the additivity
of aerodynamical characteristics has been formulated
for special systems of bad-streamlined profiles. This hypothesis was examined
by experiments in a wind tunnel of Zhukovsky Central Aerodynamical Institute. The calculation method of
aerodynamical characteristics is given (for example,
the cooling systems tubes for atomic reactors, the bundle conductors of
over-head electrical lines). The aerodynamical instability's domains about attack's angles
are determined
It is known, that the main condition of aerodynamical profile's instability is Glauert
- Den-Hartog condition (a necessary condition). The
inequality is obtained by consideration of a stalled profile with one degree of
freedom: autorotation about fixed axis; galloping across a wind. Before the
mechanical model of the bad-streamlined profile with viscoelastic
constrains has been considered. Considered model had three degrees of freedom
and moved in its plane: displacements along Ox,
Oy axises and rotation about a centre-of-mass. The sufficient
condition of Ljapunov's instability was obtained for
possible equilibrium states at any wind velocities.
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