  The nonequilibrium hydrodynamic correlations of a
Multiparticle-Collision-Dynamics (MPC) fluid in shear flow are studied by
analytical calculations and simulations. The Navier-Stokes equations for a MPC
fluid are linearized about the shear flow and the hydrodynamic modes are
evaluated as an expansion in the momentum vector. The shear-rate dependence and
anisotropy of the transverse and longitudinal velocity correlations are
analyzed. We demonstrate that hydrodynamic correlations in shear flow are
anisotropic, specifically, the two transverse modes are no longer identical. In
addition, our simulations reveal the directional dependence of the frequency
and attenuation of the longitudinal velocity correlation function. Furthermore,
the velocity autocorrelation functions of a tagged fluid particle in shear flow
are determined. The simulations results for various hydrodynamic correlations
agree very well with the theoretical predictions.
