  We study the hydrodynamics of relativistic fluids with several conserved
global charges (i.e., several species of particles) by performing a
Kaluza-Klein dimensional reduction of a neutral fluid on a N-torus. Via
fluid/gravity correspondence, this allows us to describe the long-wavelength
dynamics of black branes with several Kaluza-Klein charges. We obtain the
equation of state and transport coefficients of the charged fluid directly from
those of the higher-dimensional neutral fluid. We specialize these results for
the fluids dual to Kaluza-Klein black branes.
