Fast tides in slow stars: The efficiency of eddy viscosity

Turbulent viscosity is believed to circularize and synchronize binary orbits and to damp stellar oscillations. Older binaries appear to be circular out to longer periods, which indicates that circularization proceeds during the main-sequence phase. It is also believed that when the tidal period is shorter than the turnover time of the largest eddies, turbulent viscosity is partially suppressed. The degree of suppression, however, is disputed. We reexamine both of these beliefs via (1) direct perturbative calculations, linearizing the fluid equations on a turbulent background; and (2) numerical integration of a chaotic dynamical system subject to periodic forcing. We find that dissipation of rapid tides is severely suppressed. Even when we disregard this suppression, we conclude that some mechanism other than turbulent convection circularizes solar-type binaries.