  The steady state properties of an interface in a stationary Couette flow are
addressed within the framework of fluctuating hydrodynamics. Our study reveals
that thermal fluctuations are driven out of equilibrium by an effective shear
rate that differs from the applied one. In agreement with experiments, we find
that the mean square displacement of the interface is strongly reduced by the
flow. We also show that nonequilibrium fluctuations present a certain degree of
universality in the sense that all features of the fluids can be factorized
into a single control parameter. Finally, the results are discussed in the
light of recent experimental and numerical studies.
