  We investigate, by means of two-dimensional incompressible
magnetohydrodynamic (MHD) numerical simulations, the fast collisional magnetic
reconnection regime that is supported by the formation of plasmoid chains when
the Lundquist number $S$ exceeds a critical value (at magnetic Prandtl number,
$P_m = 1$). A recently developed characteristic-Galerkin finite-element code,
FINMHD, that is specifically designed for this aim in a reduced visco-resistive
MHD framework, is employed. Contrary to previous studies, a different initial
setup of two repelling current channels is chosen in order to form two
quasi-singular current layers on an Alfv\'enic time scale as a consequence of
the tilt instability. If $S < 5 \times 10^3$, a subsequent stationary
reconnection process is obtained with a rate scaling as $S^{-1/2}$ as predicted
by the classical Sweet-Parker model. Otherwise, a stochastic time-dependent
reconnection regime occurs, with a fast time-averaged rate independent of $S$
and having a normalized value of $0.014$. The latter regime is triggered by the
formation of two chains of plasmoids disrupting the current sheets with a
sudden super-Alfv\'enic growth following a quiescent phase, in agreement with
the general theory of the plasmoid instability proposed by Comisso et al.
[Phys. Plasmas 23, 100702 (2016)]. Moreover, the non-monotonic dependence of
the plasmoid growth rate with $S$ following an asymptotically decreasing
logarithmic law in the infinite $S$-limit is confirmed. We also closely compare
our results to those obtained during the development of the coalescence
instability setup in order to assess the generality of the mechanism. Finally,
we briefly discuss the relevance of our results to explain the flaring activity
in solar corona and internal disruptions in tokamaks.
