  We have studied a bulk electrolyte, and polyelectrolyte solutions with
surfactants or multivalent salt with the explicit presence of counterions and
solvent molecules by means of the mesoscopic dissipative particle dynamics
(DPD) method in the Grand Canonical ensemble. The electrostatic interactions
are calculated using the Ewald sum method and the structure of the fluid is
analyzed through the radial distribution function between charged particles.
The results are in very good agreement with those reported in the literature
using a different method for the calculation of the electrostatic forces, and
with those obtained using DPD in the canonical ensemble. We also studied the
salt dependent conformation of polyelectrolyte solutions as a function of the
solvent quality, and analyzed the electrostatic interaction strength dependence
of dilute flexible polyelectrolytes in solution. For the complex systems
mentioned above, the electrostatic interactions and the solvent quality play a
key role in understanding phenomena that do not occur in noncharged systems.
