Introductory FLUENT Notes Fluent User Services cente ANSYS LUENT v6. 3 December 2006 wwfluentusers. com FLUENT Is the flow turbulent? External flows where Re PUL x≥5000 along a surface L L=x.d,、d,.etc Re>20000 around an obstacle Other factors such as free-stream turbulence. surface conditions and disturbances may cause transition Internal flows to turbulence at lower reynold Re,≥2,300 numbers Natural Convection Ra where Ra βgL△Tp2CD阝gD△7 is the rayleigh number P μ k a k is the Prandtl number C 2006 ANSYS. nc All ANSYS, Inc. Proprietar© 2006 ANSYS, Inc. All rights reserved. 6-3 ANSYS, Inc. Proprietary Fluent User Services Center www.fluentusers.com Introductory FLUENT Notes FLUENT v6.3 December 2006 Is the Flow Turbulent? External Flows Internal Flows Natural Convection Rex  500,000 along a surface around an obstacle where where Other factors such as free-stream turbulence, surface conditions, and disturbances may cause transition to turbulence at lower Reynolds numbers Re  2,300 dh Re d  20,000 is the Rayleigh number   = U L Re L , , ,etc. d dh L = x k g L T Cp g L T     =    = 3 2 3 Ra 9 10 Pr Ra  k Cp =   Pr = is the Prandtl number