  We study the dynamics of confinement-deconfinement (C-D) phase transition in
the context of relativistic heavy-ion collisions within the framework of
effective models for the Polyakov loop order parameter. We study the formation
of $Z(3)$ walls and associated strings in the initial transition from the
confining (hadronic) phase to the deconfining (QGP) phase via the so called
Kibble mechanism. Essential physics of the Kibble mechanism is contained in a
sort of domain structure arising after any phase transition which represents
random variation of the order parameter at distances beyond the typical
correlation length. We implement this domain structure by using the Polyakov
loop effective model with a first order phase transition and confine ourselves
with temperature/time ranges so that the first order C-D transition proceeds
via bubble nucleation, leading to a well defined domain structure. The
formation of $Z(3)$ walls and associated strings results from the coalescence
of QGP bubbles expanding in the confining background. We investigate the
evolution of the $Z(3)$ wall and string network. We also calculate the energy
density fluctuations associated with $Z(3)$ wall network and strings which
decay away after the temperature drops below the quark-hadron transition
temperature during the expansion of QGP. We discuss evolution of these
quantities with changing temperature via Bjorken's hydrodynamical model and
discuss possible experimental signatures resulting from the presence of $Z(3)$
wall network and associate strings.
