On the relevance of subcritical hydrodynamic turbulence to accretion disk transport

摘要: Hydrodynamic unstratified Keplerian flows are known to be linearly stable at all Reynolds numbers, but may nevertheless become turbulent through nonlinear mechanisms. However, in the last ten years, conflicting points of view have appeared on this issue. We revisited problem numerical simulations shearing sheet limit. It turns out that effect Coriolis force stabilizing flow depends whether is cyclonic (cooperating shear and rotation vorticities) or anticyclonic (competing vorticities); anticyclonic. obtained following results:
i/ The does not quench turbulence subcritical flows; however, more efficient, much easily found, than ones.
ii/ number/rotation/resolution relation has been quantified problem. In particular we find resolution demand, when moving away from marginal stability boundary, severe for ones. Presently available computer resources do allow codes reach regime.
iii/ efficiency transport directly correlated number transition Rg , such a way Shakura-Sunyaev parameter $\alpha\sim 1/Rg$. This correlation nearly independent cyclonicity. expected basis generic physical arguments.
iv/ Even most optimistic extrapolations our data show would too inefficient by several orders magnitude astrophysical purposes. Vertical boundary conditions play role issue although no significant was found preliminary tests.
v/ Our results suggest Keplerian-like Taylor-Couette settings largely affected secondary flows, as Ekman circulation.