50 research outputs found
Non-stationary resonance dynamics of weakly coupled pendula
In this paper we fill the gap in understanding the non-stationary resonance
dynamics of the weakly coupled pendula model, having significant applications
in numerous fields of physics such as super- conducting Josephson junctions,
Bose-Einstein condensates, DNA, etc.. While common knowledge of the problem is
based on two alternative limiting asymptotics, namely the quasi-linear approach
and the approximation of independent pendula, we present a unified description
in the framework of new concept of Limiting Phase Trajectories (LPT), without
any restriction on the amplitudes of oscillation. As a result the conditions of
intense energy exchange between the pendula and transition to energy
localization are revealed in all possible diapason of initial conditions. By
doing so, the roots and the domain of chaotic behavior are clarified as they
are associated with this transition while simultaneously approaching the
pendulum separatrix. The analytical findings are corrobo- rated by numerical
simulations. By considering the simplest case of two weakly coupled pendula, we
pave the ground for new opening possibilities of significant extensions in both
fundamental and applied directions.Comment: 7 pages, 7 figure
Stationary and non-stationary resonance dynamics of the finite chain of weakly coupled pendula
We discuss new phenomena of energy localization and transition to chaos in the finite system of coupled pendula (which is a particular case of the Frenkel-Kontorova model), without any restrictions on the amplitudes of oscillations. The direct significant applications of this fundamental model comprise numerous physical systems. In the infinite and continuum limit the considered model is reduced to integrable sine-Gordon equation or certain non-integrable generalizations of it. In this limit, the chaotization is absent,
and the energy localization is indicated by the existence of soliton-like solutions (kinks and breathers). As for more realistic finite models, analytical approaches are lacking, with the exception of cases limited to two and three pendula. We propose a new approach to the problem based on the recently developed Limiting Phase Trajectory (LPT) concept in combination with a semi-inverse method. The analytical predictions of the con-ditions providing transition to energy localization are
confirmed by numerical simulation. It is shown that strongly nonlinear effects in finite chains tend to disap-
pear in the infinite limit
Non-stationary resonance dynamics of the harmonically forced pendulum
The stationary and highly non-stationary resonant dynamics of the harmonically forced pendulum are described in the framework of a semi-inverse procedure combined with the Limiting Phase Trajectory concept. This procedure, implying only existence of slow time
scale, permits one to avoid any restriction on the oscillation amplitudes. The main results relating to the dynamical bifurcation thresholds are represented in a closed form. The small parameter defining the separation of the time scales is naturally identified in the ana-
lytical procedure. Considering the pendulum frequency as the control parameter we reveal two qualitative tran-
sitions. One of them corresponding to stationary instability with formation of two additional stationary states, the other, associated with the most intense energy drawing from the source, at which the amplitude of pendulum oscillations abruptly grows. Analytical
predictions of both bifurcations are verified by numerical integration of original equation. It is also shown that
occurrence of chaotic domains may be strongly connected with the second transition
Non-conventional phase attractors and repellers in weakly coupled autogenerators with hard excitation
In our earlier studies, we found the effect of non-conventional
synchronization, which is a specific type of nonlinear stable beating in the
system of two weakly coupled autogenerators with hard excitation given by
generalized van der Pol-Duffing characteristics. The corresponding synchronized
dynamics are due to a new type of attractor in a reduced phase space of the
system. In the present work, we show that, as the strength of nonlinear
stiffness and dissipation are changing, the phase portrait undergoes a
complicated evolution leading to a quite unexpected appearance of difficult to
detect repellers separating a stable limit cycle and equilibrium points in the
phase plane. In terms of the original coordinates, the limit cycle associates
with nonlinear beatings while the stationary points correspond to the
stationary synchronous dynamics similar to the so-called nonlinear local modes
Semi-Inverse Method in the Nonlinear Dynamics
The semi-inverse method based on using an internal small parameter of the nonlinear problems is discussed on
the examples of the chain of coupled pendula and of the forced pendulum. The efficiency of such approach is
highly appeared when the non-stationary dynamical problems are considered. In the framework of this method
we demonstrate that both the spectrum of nonlinear normal modes and the interaction of them can be analysed
successfully