Accretion Disk

Reynolds = Inertia Fources / Viscous Fources = FlowLength * FlowVelo / Viscosity

Reynolds » 1.00 :

• Viscosity is dynamically unimportant
• Viscosity plays essentially no role
• TLUSTY Viscosity = sqrt(GMR) / Reynolds

Reynolds « 1.00 :

• Viscous force dominates the flow
• TLUSTY Viscosity = alpha-disk model with GR

Reynolds > 10^{2-3} 程度になると乱流が起こる
降着円盤モデルでは基本的にReがかなり大きい
乱流を取り入れた降着円盤のalpha-modelがShakura-Sunyaev (1973)

標準モデルによるTurbReynoldsを考える
TurbReynolds = (FlowS/DiskH) * (AzimV/SoundV) / alpha = 10^{2-3} / alpha

The relation between alpha and Reynolds (Kriz & Hubeny 1986; Idan et al. 2010)
alpha = (KeplerianV/SoundV)^{2} / Reynolds = (RadialDist/Height)^{2} / Reynolds = 0.01 - 1.0 (order unity)